Methods of increasing beef production in hot climates

r 'TOr£ Division of Agricultural Sciences UNIVERSITY OF CALIFORNIA Methods of Increasing Hot Climates H, R. ITTNER T. E. BOND C R KELLY IM...

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r

'TOr£

Division

of

Agricultural Sciences

UNIVERSITY OF CALIFORNIA

Methods of Increasing

Hot Climates

H, R. ITTNER T. E.

BOND

C

R KELLY

IMER RATIONS

ZALIFORNIA AGRICULTURAL BULLETIN 761

EXPERIMENT STATION

COMFORTABLE CATC Fifty-one per cent of the cattle in the United States, representing

7%

where the average above 75° F. Because many of these areas are close to important markets, have plentiful supplies of water and high quality feeds, cattlemen have for a long time been interested in improving their beef production in such hot areas, notably the desa cash value of

billion dollars, are in areas

summer temperature

is

'

erts of California.

Experience and experiments have shown that beef production drops considerably in hot summers as cattle become uncomfortable and eat less.

Since 1946 the Animal Husbandry and the Agricultural Engineer-

1

ing departments of the University of California in cooperation with the United States Department of Agriculture have been conducting

experiments at the University experiment station in El Centro, California, to study the effect of different hot weather environments on beef cattle. The goal of the experimenters has been to devise means whereby cattlemen could make their beef animals more comfortable

-

during the hot months and carry out profitable year-round operations. The experiments have resulted in a number of practical applications which may be carried out by farmers at minimum expense. The steps to be taken to maintain animal comfort and production revolve around five key factors Shade Water Air Movement Radiation Feed. SHADE . . . Properly designed shades will reduce the radiation heat load on cattle up to 50 per cent. Most shades in the desert areas are from 16 to 20 feet wide and up to several hundred feet long. Experi| ments indicate that 10 to 12 feet is the best height for a cattle shade. I

I

.

.

.

.

.

.

.

.

.

.

.

.

.

How

roofing materials and coolers

influenced average daily gain

£1.5 HAY OVER WET GALVANIZED

ALUMINUM AND WET GALVANIZED IRON

IRON

BURLAP

[2]

ENCLOSED SHADE WITH COOLER

.

OW

BETTER DAILY GAINS IN WEIGHT

Although east-west orientation is best from the standpoint of reducing radiation heat load, experimenters found that shades oriented north and south, so that the sun would cover the entire area for part

improved sanitary conditions. The experimenters used galvanized steel sheets, aluminum sheets, boards and hay as roof material. Hay proved to be the coolest of all of the day,

materials tested although

it

provides problems of replacement, pro-

from wind and damage when wet by rain. Hay should be held together by two layers of wire net to reduce blowing. It was also found that by painting the top side of metal white, the radiant heat load under the shade could be reduced considerably. Painting the underside of a metal roof black also was found to be an aid in reducing radiant heat load on the animals because the dark paint absorbed radiation from the ground rather than reflecting it tection

back onto the animals. Although tests were not conducted to ascertain the shade space requirement per head, it is believed 60 square feet per head is adequate. The important thing to remember is to avoid crowding during summer months. A complete summary of shade experiments may be found on page 32. WATER . . • Experiments were conducted to increase animal gains by using water to wet the cattle in pens and by cooling drinking water. The use of sprays, hoses and other methods of wetting animals was not too successful unless the animals were wetted to the skin. Investigators believe that the humidity increase occasioned by the use of water may slow the evaporation of moisture from the cattle, and in fact make it more difficult for them to retain thermal balance.

How 3.0

corral

air

movement, water temperature and

construction influenced daily gains

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They do however feel that such programs may be of value in areas humid than the location of the experiment station. The cooling of drinking water on the other hand did appreciably increase animal comfort and production. By keeping drinking water

less

at

about 65°

F.,

noticeable gains were reported. While mechanical

refrigeration costs are probably too high for commercial programs,

other methods of cooling were suggested. Evaporative water towers helped keep water cool. By using underground pipes from wells where the water was already at a low temperature, experimenters to obtain cool water at little or no extra cost. By keeping water in shallow tanks so that cool water could not be reached by the cattle and by covering tanks except for small drinking holes low temperatures were maintained. Shaded drinking tanks also proved val-

were able

uable but shades should not be large enough to allow animals to stand

under them. page 50.

AIR

A

complete summary of experiments with water

MOVEMENT

. . .

is

on

Increased air movement has proven to be of

great benefit to cattle. Either mechanical or natural

means can be

utilized to increase the circulation of air in cattle pens.

Without incurring extra expense cattlemen can take advantage of natural conditions to increase circulation by proper corral construc-

Wire or cable corrals offer little resistance to natural air movement and during tests resulted in significant gains compared to cattle penned in wooden corrals. Proper orientation of corrals to take

tion.

advantage of air movement in the area is also important. The experimenters successfully employed large fans, operating either full or part time, to increase air movement over penned cattle. Even though penned in wooden corrals, cattle subjected to mechanical air movement made better gains than animals in wooden corrals without fans. Experimenters feel that the gains more than offset

the cost of operating fans.

Although

cattle are not

indicate that they

studies

considered to be sweating animals, recent may lose a large amount of moisture

through the skin and that increased air movement speeds up evaporation of the moisture and brings about more rapid cooling. A complete summary of air movement experiments can be found on page 66. RADIATION . . . The sky, the ground, the corral, nearby buildings, literally everything in sight, radiates heat onto the cattle. Reducing this radiation is a complex but not insoluable problem. Corral construction, which plays an important role in promoting important in controlling radiation. absorbing or reflecting heat, has proven much better than wood for this purpose. The fences in a wooden corral absorb a great amount of heat and increased air circulation,

Wire or

radiate

it

cable, because

directly

it

is also

offers relatively little area for

back onto the penned

cattle.

Buildings, hay stacks, large farm machines and other obstacles

which would radiate heat should not be located near

corrals. This

permit free circulation of the air. If at all possible cattle pens should be located near growing crops. Cattle in pens in such surroundings showed much better gains than will also

[4]

animals subjected to radiation from the bare earth, roads or other Air temperatures in the vicinity of growing crops were

surfaces.

significantly lower.

Experiments with special electronic equipment revealed that the north sky usually is cooler than the rest of the sky. The temperature of

was measured. Orientation of shades and fences so that animals can be exposed to this cool area of the sky is another factor in promoting animal comfort. A summary of radiation experiments the sky

can be found on page 75. FEED . . . The proper ration for hot weather is extremely important in beef production. Care should be taken not to supply high fibre diet during hot months. Such feeds produce a high "heat increment" which must be dissipated by the body, a difficult task in hot weather. In general, a summer ration should be good quality roughages and grains.

In general, cattle in the desert with proper shade, corrals, water and

can be expected to gain two pounds per day or more. However, it was advisable to bring cattle into the desert area before the mid-summer heat so the animals could become accustomed to the high temperatures of that period gradually. Best results were obtained if the animals were brought to top finish in the spring or fall, rather than in the heat of the summer. A complete summary of feeding experiments may be found on page 78. diet

experimenters found that

How

roofing material influenced temperature

of various shade structures 150-

AUGUST

JUNE 25 1:35

P.M.

11:10

gioo CO

o a

50

U_l

en

o o CJ3

(2) [5]

19

A.M.

AUGUST 22 NOON

12:00

CONTENTS Reasons for Study

7

High temperatures and production Basic

9

approach

10

Shades

Cattle

18

Summary

of

shade

32

tests

Water as a Cooling Agent

Summary Air

34

of water tests

50

Movement and Temperature

Summary

of air

52

movement and temperature

66

tests

67

Radiation

Summary Rations for

Summer

Summary

75

of radiation tests

Production

76

of feeding tests

78

Costs and Power Consumption

78

Summer Water Requirements

80

THE AUTHORS: N.

R.

Ittner

was

Specialist

in

Animal Husbandry, Imperial Valley

Field

Station,

El

Centro

(deceased).

USDA,

T. E.

Bond

is

Agricultural Engineer,

C.

Kelly

is

Professor of Agricultural Engineering

F.

Davis.

and Agricultural Engineer

Station, Davis.

APRIL

1

958

in

the Experiment

METHODS OF INCREASING BEEF PRODUCTION in HOT CLIMATES* N.

R.

ITTNER

T.

E.

BOND

C.

F.

KELLY

Introduction Why, how, and when

the studies

described here were conducted

Reasons for Study The heat load on animals

high during the summer in the Imperial Valley, Coachella

Valley,

is

Palo Verde

Valley,

and other desert areas of California. Environmental studies to determine ways and means of making livestock more comfortable during the hot weather have been in progress at the University of California's Imperial Valley Field Station since 1946.

Heat in this area is generally of the dry type although there are about six weeks every summer when a humid condition develops from moist air blowing in from the Gulf of California.

(Ota, Garver, and Ashby, 1953), and with beef cattle at the Imperial Valley

Field Station (Ittner and Kelly, 1951). All of these investigations have

shown

that the depressive effects of heat begin

low temperature around 75° F.f This is known as the critical temperature and can be defined as the air temperature beyond which cattle begin to have a higher than normal body temperature. ^ There are many areas in the world where high temperatures are a problem in livestock production. Here in the United States the 75° isotherm (fig. 1) divides the country into two parts: All to be felt at a relatively level,

The adverse effects of a hot environment on livestock are more pronounced

of the area

than those of a cold environment. Vari-

July,

ous studies have shown the effect of

parts of the country, except along the

heat on livestock, with dairy cattle at the University

of Missouri

(Ragsdale,

Brody, et al., 1948) and California (Regan and Richardson, 1938), with swine at the University of California (Heitman and Hughes, 1949), with poultry at the Beltsville (U.S.D.A.) Research Center

south of the line has an average temperature above 75° during

which

is

Pacific Coast,

the hottest

where August

The region south

is

in all

hotter.

of the isotherm con-

tains 51 per cent of

and calves and dairy *

month

all

the beef cattle

cattle

(including

Submitted for publication April, 1957. temperatures in this bulletin are on the Fahrenheit scale.

[7]

f All

Statistics,

of Kenya, the N'dama in French Guinea, or the Criollo cattle of Venezuela. Con-

1953). Their 1953 value in farm and ranch was over 7Vs billion dollars, out of a total for the country of 16% billion

improvement can be, and has been made through selection, but this method has its limitations and progress

dollars.

is slow. New improved types can be developed faster by crossing these indigenous types with one of the more produc-

heifers over try

In

two years old) of

(U.S.D.A.

many

Agriculture

this coun-

parts of the world,

work

is

more productive animals that are adaptable to their particular hot climated In the southern part in progress to develop

of the United States

much

of this

work

being done with Brahmans or Brahmans crossed with the exotic breeds and with the Charolais cattle of France. The King Ranch in Texas has developed the Santa Gertrudis breed by crossing the Brahman and Shorthorn (Rhoad, 1955) In our country we usually think of the is

Brahman

as the only heat-tolerant ani-

mal, but there are a

number

of other

areas that have heat-tolerant, indigenous

types of cattle, such as the Boran cattle

Fig. 1.

75° F isotherm for average July

value of livestock

in

air

siderable

tive breeds. South Africa is using the Africander with the Hereford and Short-

horn

to get a

more

desirable beef type

adaptable to their conditions.

Much

pro-

being made along these lines, but all are long-range programs which no doubt will eventually provide the hot regions of the world with more producgress

is

tive types of animals.

'

A more immediate approach to this problem was needed for our desert areas since more and more cattlemen are operating on a year-round basis. The environment project described herein was

temperature

in

the United States,

areas north and south of isotherm (U.S.D.A., Agric.

Climate and Man, U.S.D.A. Yearbook, 1941.)

[8]

and number and

Statistics).

(Isotherm from

established to find

ways of reducing the

heat load on animals, and the results of the last ten summers' experiments are

Some

discussed in this bulletin.

of the

methods tested have proved to be very helpful, while others have not proved to be too practical.\The results of these experiments will be discussed and illus-

animal with a large skin area per unit is desirable. These characteristics are found in the small Nguni breed of South Africa.

weight

Many

livestock

men and

scientists

throughout the world have noted that when European breeds of cattle are

moved away from

the cool climatic con-

rigorous condi-

home and placed environment they show marked distress and low productivity. Some of this distress and low productivity is undoubtedly due to the plane of nutrition,

made

the parasitic condition of the animals,

with Hereford cattle since they seem to

and management practices, all of which, more often than not, are quite different

and methods of application to a livestock program will be recommended. Many of the methods are also applicable

trated

to heat-tolerant animals since they per-

form better under

less

tions^ Nearly all of the tests were

be the most heat-tolerant of the European breeds and are the popular breed in the west.

ditions of their native in a hot

from what they have been accustomed to. Internal and external parasites are usually

Effect of

High Temperatures

on Production Heat tolerance

is

more

severe in a hot,

humid

the term applied to

the year,

and the parasitic problems are

the animal's ability to escape the adverse

not serious. Anaplasmosis

consequences of a hot environment. Just what constitutes heat tolerance in an animal is not definitely known, but all the evidence points to the fact that it is a

site that

complex entity. It is known that tropical cattle have a higher heat tolerance than temperate-zone cattle, and among the European cattle some breeds have more heat tolerance than others.

Body

tem-

one way of checking heat tolerance (Rhoad, 1944). Bonsma (Bonsma and Pretorius, 1943) in South Africa has done a great deal of work with cattle in tropical environments and has shown that short-haired cattle have a lower body temperature and grow faster than those with woolly coats. He has also perature

is

shown that light-colored cattle reflect more solar heat than those with dark hair.

An

vironment

animal's suitability to an enis

indicated by heat tolerance,

growth, feed efficiency, high

fertility,

and

low incidence of disease. The indigenous cattle found in the semi-arid subtropics are usually rather large-framed animals like the Africander. In the

heat dissipation

is

most

humid difficult

climate

than in a hot, dry climate. California's desert areas are hot and dry most of

tropics

so an

time.

is one parahas been a problem from time to

With the increasing numbers of

animals, parasites are likely to become

more of a problem. However, it should be remembered that sanitation is the answer to many disease problems and good hot sunlight is one of our best disinfectants.

Except for the summer heat, this reis an ideal place to feed cattle. There is an abundance of feed, such as alfalfa, sudan, barley, and milo. There is also plenty of cheap irrigation water and very little rain to create a mud problem for the cattle. Last but far from least, is the region's proximity to the growing Los Angeles market. Heat in this area is severe enough to materially reduce the daily gain of beef cattle, and dairy cattle have more than a normal drop in milk production. When the body temperature rises, usually at air temperatures of 75°-80° F for European and 95° F for Indian cattle, the animals lose appetite and reduce feed intake; this reduces their metabolic rate and keeps them cooler, but it also region

[9]

duces daily gain and milk production (Worstell and Brody, 1953). Cattle in this region show little loss of production with daytime temperatures of 110° to 115° F if the night temperature drops to around 60° F. When the

maximum temperature is 105° F and the minimum is 80° F for two or three days, is an immediate drop in food consumption and reduction in daily gain. Most of the environmental studies reported herein have used summer gains and feed efficiency of beef cattle as indices for testing different feeds and management practices. Cartwright (1955)

there

reports that

summer

gains are sufficiently

high in heritability (19 per cent) to be useful in selecting breeding animals.

Although

considerable

information

has been gathered throughout the world

on the reactions of

cattle

to

thermal

stress, there is still a great deal that is

not

known concerning

the fundamental

physiology of temperature regulation in cattle, as well as the anatomical differences responsible for their adaptability to heat.

is

transferred between an animal and

its

environment.

Convection: By convection an animal can lose heat to, or gain heat from, air circulating around it, depending on whether this air is cooler or warmer than the animal surface. The amount of heat exchanged is controlled according to the relationship:

Q c = CAV Here heat,

n

-t 2 )

(t 1

Q is the convective exchange of V is the air velocity, A is the animal c

surface area,

-

(t x

t2 )

is

difference between air

the temperature

and animal

sur-

and C is the convection constant. The amount of heat exchanged varies linearly with animal surface area and with the temperature difference between animal surface and air. It varies nonlinearly with air velocity (wind). The value of the coefficient C is dependent upon the characteristics of the surface (in the case of cattle the length and thickness of hair, how much hair, and whether curly or straight). The value C also depends upon the direction of air face,

flow with respect to the surface.

A

Approach to the Problem Basic

An

animal

Evaporation: For each pound of moisture evaporated, about 1050 Btu of heat

continually producing

is

heat from the feed

only a part of this

consumes. Since feed energy is utilized it

and fat, and for body maintenance, the excess must be disposed of. For an animal to be thermally comfortable there must exist a balance between the energy added to it and that utilized by, or removed from it. The problem of keeping livein the production of milk, meat,

stock cool during hot weather

is

essen-

one of aiding the animal to maintain a proper energy balance. It is quite possible to control or modify most of the tially

factors affecting this balance.

stand better

how

plished and to the problem,

the four

this

form

it

To under-

may be accom-

a basic approach to

is essential to

modes by which

consider

heat, or energy,

are exchanged.

The

rate of energy ex-

changed between the surrounding

air

and

an animal's surface can be described by an equation of the type,

Q e = KAV Here

Q e is V is

change,

the

n

A(p s -p)

evaporative

the air velocity,

animal surface area, A

is

heat

ex-

A

the

is

the latent heat

of vaporization of water, (p s - p) is the difference in partial pressure of the water

vapor at the animal surface and in the surrounding air, and K is the evaporative constant, which, like the convective coefficient is affected

and

its

flow of air. is

The

of surface

relationship to the

air velocity exponent, n,

similar to that in the convection equa-

tion

[10]

by the type

directional

above which means that evaporative

and convective exchanges of heat are similarly affected by wind. In the case of beef cattle, as with most livestock, moisture is also removed from the respiratory areas, and the amount of heat exchanged by this method is greatly affected by the rate and extent of respiratory activity. Radiation: All surfaces radiate, aband reflect energy (heat) in sorb, amounts dependent upon the temperature and character of the surface. Any two surfaces, then, are continually exchanging heat at a rate defined by the equation,

Q = AaF a F e r

(T 1 4 -'iY)

Here

Q

A

the area of one surface, a

is

is

r

the radiation heat exchange,

Stefan-Boltzman constant, F a

is

is

the

a factor

that allows for the relationship of one to another (sometimes called "shape" or "seeing" factor), and T 1 and

surface

T2

are the absolute temperatures of the

two surfaces. The factor F e allows for the radiation characteristics, emissivity*

and absorptivityt, of the two surfaces. Conduction: Heat is transferred by conduction through an object if there is a temperature gradient present, or from a

warm

surface in contact with a cooler

surface,

determined by the

a rate

at

equation,

Conduction

is

perhaps the least impor-

modes by which heat is exchanged externally by an animal. There is also some exchange of heat with surrounding air by conduction. Treatment of these four modes of heat exchange has been highly simplified for sake of illustration. Also, they have been treated as being independent. For inanimate objects independent treatment is often possible for an animal it is not. For example, environmental temperature

tant of the four



surface temperature of animals so that any change in environmental temperature is accompanied by a change in surface temperature. The equations given above show that each mode of heat exchange is affected by the respective levels of these two temperatures (in the evaporation equation the vapor pressure is a function of temperaaffects the

ture). All

other factors affecting heat

exchange are equally interdependent so that approaching the problem of cooling livestock solely on a theoretical basis is highly illogical. The other approach is experimental.

The four equations point out

all

the

factors affecting thermal comfort of ani-

mals. Since any improvement of the thermal comfort of an animal must be made through some modification or control of these factors, these are listed be-

Q k = UA(t 1 -t1 Here

Qk A

ferred, is

)

is

the conductive heat trans-

is

the area through which heat

transferred,

(t x

-

is

t2 )

the tempera-

low and they define what areas can and should be investigated to provide thermal relief for animals in a hot environment. This was the approach that guided the research reported in this bulletin.

ture gradient through the object or be-

tween two surfaces, and

U

is

the over-all

A. Air

Temperature Humidity

heat transfer coefficient of the system.

Velocity *

Emissivity:

the

ratio

of

the

intensity

of

Direction

radiation of any given wavelength emitted from unit area of a surface to the intensity in the

same wavelength from unit area body at the same temperature.

of a

B.

black

Animal

ation absorbed by a substance. At any wave-

Surface Surface Surface Surface

length and temperature the absorptivity of an opaque substance is equal to its emissivity or

Breed Feed

t Absorptivity

to

one minus

:

its

the fraction of incident radi-

Water

reflectivity.

[11]

temperature area characteristics

evaporation

C. Surroundings

Temperature Radiation

characteristics

surrounding

of

surfaces

Location with respect to animals Solar and sky radiation

Since these experiments are primarily a study of the heat exchange between the

Cooperative Nature of Study

to continue to expand. This study has

cooperators,

the

Animal

its environment, many engineering instruments have had to be used in order to measure heat flow both to and

animal and

Cooperative programs in research are imperative if scientific information is three

and the United States Department of Agriculture. All three have contributed men, money, and materials for the development of this program. sity of California

of surrounding surfaces

Hus-

bandry Department and the Agriculture Engineering Department of the Univer-

from the animal. Evidence

is beginning accumulate that the gaining ability of cattle in a hot environment is directly related to its comfort and heat tolerance.

to

The Climate Factors that

make beef

difficult in

Air Temperature,

Wind

Velocity

from the ground

and Relative Humidity Two

raising

the desert area

to radiate into the

upper

stratosphere.

Warm, humid

terms used for the classification

climates are character-

summer weather are "hot dry" and "warm humid." These two conditions

ized

occur in nature, but quite often any one

vegetative cover which reduces the radia-

of

by clouds and moist

move some

air,

which

of the solar radiation,

re-

and

heat load from the ground. Air

place will have variations or combina-

tion

two types of weather during the summer. Death Valley in California is an example of a hot, dry area, while the states bordering on the Gulf of Mexico have warm, humid summers. A hot, dry environment is characterized by high air temperatures, low humidity, and dry ground with little or no vegetation. Such conditions provide very few clouds or moisture vapor in the air to remove the intense rays of the sun. These high temperatures and direct solar

temperatures in these climates are mod-

tions of these

radiation are bad, but there

is

also the

intense reflection of the sun's radiation

from the dry ground. However, there are two factors operating here which prevent these conditions from becoming unbearable: one is the dry air which facilitates evaporation of water, and the other is the clear sky which allows considerable heat

erate

and seldom above the animal's skin

temperatures, but the evaporation of water is

very slow. Most people find the wet,

sticky condition

of the skin distinctly

uncomfortable in these regions. Increas-

humid area aids and makes life more comfortable to human beings. High winds with high temperature and a ing air

movement

in a

in the evaporation of water

low humidity can be most uncomfortable because of their drying effect on the body. Imperial Valley, Coachella Valley, and Palo Verde Valley are, in many respects, typical of a hot, dry region, but for about six

weeks every summer these valleys

become hot and humid. This phenomenon is brought about by a prevailing wind from the south, bringing moisture

[12]

from the Gulf

of California. During the remainder of the year the prevailing wind is from the west. This six-week period also has a number of tropical thunder showers, usually local and at times quite destructive. Relative humidity readings are usually below 40 per cent during the heat of the day and more often than not range betwen 15 and 35 per cent. When the noon humidity is 30

human beings become uncomfortable. Fortunately, excessively high temperatures do not usually prevail

per cent or above,

during this humid period; maximum temperatures range between 100° and 105° F. However, minimum tempera-

become excessive, seldom dropping below 70° F. Furthermore, they are seldom below 80° F for more than four hoursiyThe moisture-laden air from the Gulf radiates the heat back to the earth instead of letting it dissipate in the upper atmosphere. Since the ground cannot cool, night temperatures rise and the mean temperature for the 24-hour period goes well above the critical temperature for cattle (75-80° F) with a consequent drop in production. XThere are periods when the night temperature does not drop below 80° F for 15 to 20 days at a tures

were conducted each summer between June 21 and September 27. Weather records were kept every summer, and table 1 shows the average maximum, minimum, and mean air temperatures and relative humidities for the test period of 1947 to 1956 inclusive. Although the Imperial Valley and surrounding areas have a humid condition during part of the summer, the humidity is still lower than that of the states around the Gulf of Mexico. Figure 3 shows average diurnal air temperatures and relative humidity at the Imperial Valley Field Station, California, Baton Rouge, Louisiana, and Corpus Christi, Texas, from July 6 to September 14, 1955. Air temperatures at the Field Station averaged 102° F during the heat of the day, while the relative humidity was 20 per cent. At Corpus Christi and Baton Rouge air temperatures average around 87° F and relative humidity about 60 per cent during the middle of the day.

90

115

Hot dry day Aug. 3, 1955 Hot humid day Aug. 9,1955

time.

These desert areas have a mean monthly temperature above 75° F for about six months of the year for nearly four months it exceeds 85° F and for two months it is 90° F. Figure 2 shows the ;

temperature and humidity for a typical hot, dry day and a hot, humid day for the Imperial Valley. Air movement during the summer is negligible, although for an hour or so winds may reach velocities of 40 to 50 miles per hour. The average wind velocity during the summer is around 2.5 miles per hour 3 feet above the ground.

With very

little

air

movement, high temand very few

perature, high humidity,

clouds, a few days each year are almost

unbearable.

Fig. 2. Diurnal air

temperature and relative

humidity for a hot, dry day and a hot, humid

Environmental studies reported herein

day

[13]

at the Imperial Valley Field Station.

Table

1

—Weather During Feeding Periods

Data for Imperial Valley Field Station During Test Periods, 1947 to 1956 Inclusive

Air relative humidity (%)

Air temperature (F.)

Year

Period of feeding

trial

1947 1948 1949

July 23 to September 15 July 28 to September 20

1950f 1951 1952 1953 1954 1955 1956

June 21

July 12 to September 16

.

.

.

.

.

.

.

.

.

September 9 July 3 to September 27 ... July 2 to September 11 ... June 30 to September 22 June 24 to September 16 July 6 to September 14 ... June 27 to September 5. to

.

.

.

.

.

*

The mean

t

One group was

.

.

.

.

.

Ave.

Ave.

Max.

Min.

Mean

105.7

74.7

90.2

108.1

74.7

91.4

73.4

88.9

74.8

89.9

103.7

71.8

87.7

106.7

77.7

91.8

105.5

77.1

91.3

61

103.6

76.4

90.0

67

19

103.2

78.3

90.3

80

102.4

74.2

88.3

68

23 17

3.

As

34 25 31 39 36 26 24 28 29 22

46 33 44 47 50 40 36 39 46 36

24 28 29 26

Corpus

California,

Christi,

Texas, Baton Rouge, Louisiana, and Tallahassee, Florida.

Mean

daily air tem-

peratures are about 90°

F for the California Station and between 80° and 85° for the other three stations.

Rainfall during June, July, August, is rather heavy in the Gulf Coast States, averaging 11 inches for Corpus Christi, 20 inches for Baton Rouge, 26 inches for Tallahassee, and only 0.7 inch for El Centro. Air movement in these Gulf Coast States varies some, but the average ranges between 5 and 12 mph, while in the Imperial Val-

mph

summer months. Air movement was taken

3

feet

because of their summer heat.

Solar and Sky Radiation

As

will

be discussed

later

(page 18),

a large part of the heat load on an animal is

due to radiation from its surround. solar and sky radiation influences,

The

or indirectly, the thermal environment of entire areas and is dependent, at any particular time, upon altitude, directly

and air moisture, and dust content. The United States Weather Bureau has for many years used Eppley pyrheliometers to observe solar and diffuse sky radiation throughout the country. These measurements indicate a higher than avlatitude, cloud cover,

erage radiation intensity in the Imperial Valley as compared with other sections of the country at the

same

latitude.

For

instance, the July, 1955, isolines for this

for the

area show a daily average solar radiation

at the

of about 600 langleys, whereas the southeastern part of the United States aver-

above

the

aged about 500 langleys.

ground. Climatic conditions are these four areas, but

similar problems in livestock production

gas,

and September

averages around 2.5

same as those shown.

a further

perature for the Imperial Valley Field

station

Mean*

17

fed from June 14-September 5 and weather data are almost the

comparison of the difference between a "hot dry" and a "warm humid" climate, figure 4 shows the mean daily air tem-

it

19

104.3

Noon

relative humidity is the average of all 2-hr. readings throughout the period.

are not included in figure

ley

26

105.1

is about the same as Baton Rouge, Louisiana; but the data

F

Ave.

Min.

67 55 71 76 78 66

Tallahassee, Florida,

Station,

Ave.

Max.

all

different

in

have somewhat

Much of this difference can be attributed to the greater cloud cover in the

[14]

no

105

>/^^

100

100

^^N \

Temperature

95

^

90

J jf

/ /

\

UJ cr

h-

<

/An

a: UJ a.

2

^

<

85

80

UJ 1-

'

s\/ /



70 ,> N

Temperature

V.o

^s.

*••..

\s

**

«''. 6

••.

..'

\

*

Relative humidity

...•**

p* ,^

/\

/

\

..-•*'"

- 90

/

...<**

\\V/

/

\V

u_



>»^ ^N*»«^

/ V^

- -.^

V

2

jt

>
*-o...



#

_ 60 -

°''

t

EE

<

/ /

75 —

/



"

- 50 o

<

70 -

40

/

Corpus

/

v

65

Baton Rouge, La.

30

_^y^^

^s^

Texas

Christi,

Imperial Valley Field

Station, California i

1

1

.

1

1

,

1

i

1

1

i

1

<

.

.

1

1

.

i

1

I

10

12

N

2

4

6

8

10

12

M

TIME Fig. 3.

Average diurnal

air

temperature and relative humidity at four points south of the 75°F

isotherm from July 6 to September 14, 1955. (Out-of-State data from the U. S. Department of

Commerce Weather

more

easterly

Bureau.)

sections.

The

average

cloudiness during June, July, August,

and September, Corpus

is,

4.2 for

New

on the

Christi,

to

10 basis,

Texas, 5.2 at

Orleans, Louisiana, 5.3 at Apala-

chicola, Florida, but at

Yuma, Arizona,

50 miles east of El Centro, California, only 1.3 (U. S. Department of Commerce, 1956). No continuous records of solar and sky radiation are available for the Imperial Valley, but observations by the authors with the portable instruments

Fig. 4.

Mean

June, July,

daily air temperature during

August, and

Tallohassee, Floridi Elevation +64 feet

September at four

points south of the 75°F isotherm. (Out-of-state

data from the U.

S.

Department of Commerce

I 1

I

M

5 IOI5

Weather Bureau.)

[15]

I

I

I

2025305

JUNE

I

I

I

I

I

2025 JULY

10 15

31

I

I

I

I

15 2025 AUGUST

5 10

I

I

I

I

>

I

I

202530 SEPTEMBER

31 5 10 15

many days during July and August with noon halfspace radiation intensities on a horizondescribed on page 17 indicate

surface of 425 to 475 Btu/hr. sq. ft. measured by a total energy radiometer and of about 300 Btu/hr. sq. ft. as measured by an Eppley pyhrheliometer. tal

as

Experimental procedures

trials

good many feeding are reported in this bulletin, and to

eliminate repetition the standards used are discussed in this section. All animal weights, unless otherwise

noted, are after a 10-hour stand in a dry corral without feed or water. In most cases weights were taken every 28 days.

The wooden

corral pens were 50 x 50 by a 6-foot fence constructed of four 2 x 10-inch planks. Each pen had a hay or aluminum shade 10 feet above ground. All wire pens were made of ordinary fence wire and all have hayfeet enclosed

at least

10 feet high.

Water consumption was measured by calibrated water meters on the water inlets. is

Since the accuracy of these meters

highest

when

recorders kept a continuous record of the temperature of the water near the top of

ers.

results of a

covered shades

full flow was obtained whenever the water level in the tank dropped 1 inch. The water meters were read at least once a day; and on some days hourly observations were made. Pen

water valve so that

the tanks.

and instruments The

switch were arranged with a solenoid

a full stream of water

is

flowing through them, a float and micro-

Not

all lots

had

these record-

Feeding was by hand and

all lots

were fed twice a day. The instruments used for defining the environment were for the most part portable, so that they could be moved from pen to pen, or from pen to open area. A continuous record of air temperature and relative humidity was, however, obtained by a Friez hygrothermograph located in a standard Weather Bureau shelter about 600 feet from the main corrals. In recent years some wind-velocity data have also been collected at this location. The Friez cup-type anemometer used for measuring wind velocity was only 3 feet above the ground, a little more than half the height of a standing cow. As new instruments became available they were used in the project, so that the same types of instru-

ments were not necessarily used throughout the period covered by this report. The portable instruments were of two general types: those for measuring the air temperature and velocity, and those for measuring radiation. Air temperature and velocity: Small portable weather stations were used where a continuous record of air temperature and velocity was required at a particular location over periods of sev-

weeks or months. These have been and detail by Schultz in Brooks (1956). A 4-pen clock-operated recorder allowed 24-hour or 7-day records to be obtained. One pen recorded air temperature as sensed by a fluid-filled capillary tube, another ground temperature, and a third globe-thermometer temperature. The latter was 8 inches in diameter. The fourth pen was used to eral

described

Fig. 5.

Portable "spot" climate recorder. The

4-pen clock-operated recorder provides 24-hour records of air and ground temperatures, globethermometer temperature, and wind velocity.

record impulses from a Friez cup-type

[16]

and DunThe

anemometer, at the rate of one impulse for each 1/12 mile. A view of one of the

kle,

portable or "spot" climate recorders

sensing element of this instrument

shown

is

Other devices used to measure air temperature were small copper-constantan thermocouples shielded with metal

mercury thermometers,

etc.

The Alnor Velometer, a vane-type

ane-

mometer, was also used

to indicate air

velocities.

Radiation: Since such a large part of was related to protecting the animals from solar radiation, special attention was given to radiation measuring instruments. To measure total spherical radiation (both sky and ground), globe thermometers either 6 or 8 inches in diameter were used. These give, by means of the internal temperature of a black, hollow copper sphere, the result of the combined effects of air temperature, spherical radiation, and air velocthe experiment

ity.

By

.

is

a

was indicated by a Leeds and Northrup No. 8662 semi-precision potentiometer in field observations, and by a Brown recording electronic potentiometer in stationary use. A view of the instrument on



calculation,

mean

the

radiant

tripod in the field

its

6.



1951, for complete description)

thermopile, whose electromotive force

in figure 5.

cylinders,

California, Berkeley. (See Gier

This instrument

ure

all

is

is

shown

in figure

designed to meas-

upon a

radiant energy falling

horizontal surface, including both long

and short wave-lengths. There

is

no cover

of glass or other material to act as a ter,

fil-

and the receiving surface has a high

absorptivity for

all

wave-lengths.

Another instrument sometimes used to measure half-space radiation was the Eppley pyrheliometer, described by Lee (1953). Because its sensing element is covered with glass, it measures only the solar and diffuse energy, and screens out most of the long-wave atmospheric ra-

temperature of the entire surround may then be obtained with varying accuracy,

diation.

depending upon the rates

which the

Gier and Dunkle was used at times for

air temperature, radia-

measuring half-space radiation (solar and diffuse), its response being similar to the Eppley pyrheliometer. It consists

climatic factors tion,

and



air velocity

at

— are changing.

A

complete discussion of this instrument has been given by Bond and Kelly (1955). Recently the "spherical radiometer" was developed for this project and has been used especially for checking the

The "Solarimeter"

as

developed by

mean

radiant temperatures as measured by globe thermometers. This instrument consists of two 2-inch-diameter spheres, one of polished silver, the other black.

The spheres contain heating elements by which the sphere temperatures can be maintained equal and convection losses compensated for. The current used is a measure of the spherical radiation (Dunkle and Gier, 1954). To measure half-space radiation, or the energy falling on a flat horizontal surface, use was made of the total energy plate radiometers developed by the Illumination

Laboratory,

University

of

Fig. 6. Flat-plate

mounted

[17]

radiometer and solarimeter

for portable field use.

of

two thermopiles encased in a

plastic

radiosity of a smaller area or object, one

two instruments was used



cover, one painted white, the other black

of

(figure 6).

Gier directional radiometer or a Hardy dermal radiometer. These have been de-

Brooks (1951) has stated that the and diffuse radiation amounts to about 60 per cent of the total sky radiation as measured by the total energy radiometer. Since an animal's surface absorbs both short and long-wave energy, it seems that the total energy radiometer would Be a better indicator of radiation heat load upon an animal than would an instrument of the type of the Eppley pyrheliometer. Where it was desired to determine the solar

either a

scribed in detail by Kelly, Bond, and Lorenzen (1949) and by Hardy (1934). The sensing elements of both instruments are blackened thermopiles. The Gier radiometer has a cone opening of 16°, the Hardy dermal radiometer one of 12°. They were used to obtain radiosity and temperature of cattle surfaces, shade and corral materials, ground cover, and effective sky temperatures in selected locations.

The Experiments Studies of different materials

and techniques for cooling animals Providing a comfortable environment summer can

fer

by

for livestock during the hot

in the

be considered as a problem in heat transThere are four avenues of heat transfer available to the animal for cooling

three

fer.

itself:

Radiation, convection,

evapora-

and conduction. These four methods do not operate alone, and their effects on cattle are always changing. To study one of these methods of heat transtion,

itself

is

impossible, since cattle

open are also affected by the other

means

same methods are operat-

of heat transfer at the

time. Since all four

ing together most of the time, this study

has been broken

down

into five cate-

gories: cattle shades, water as a cooling

movement, radiation of an animal's surrounding, and rations for high summer temperatures. agent, air

CATTLE SHADES Shades will reduce the radiation heat load from the sun and sky by more than 50 per cent. There are a number of factors that cause the effectiveness of any given shade to vary. For a more detailed discussion of these factors and their effect on thermal design of shades see Kelly, Bond, and Ittner (1950). An animal in the sun receives radiant energy from three sources: (a) sun and sky, (b) unshaded ground, and (c) horizon, actually a. band extending about 10 degrees above the horizon which is separated from the remainder of the hemis-

phere in calculations because

it

at a greater rate as a result of

back radi-

ation

from moisture

radiates

in the heated air

near the ground.

On

a typical August day at the Im-

perial Valley Field Station the total ra-

diant heat load on an animal in the sun 2 was 244 Btu per hour ft. (of animal surface), as determined from blackglobe thermometer readings. Under a shade the radiant heat load was 167 Btu 2 per hour ft. Shade reduces radiant heat load from the sun and sky, and substitutes shaded area for part of the hot

[18]

ground, but it adds a new source of energy, the shade material itself. In this instance the total effect

was nevertheless

a reduction of the radiant heat load on

from 244

the animal, 2

to reducing the i

to

167 Btu per hour

of animal surface. This

ft.

ture*

of

the

mean

animal's

is

equivalent

radiant temper a-

surround from

153° to 98° F.

Shade Material Several different types of shade ma-



and two heights of shade 7 feet and 12 feet were tested during the summers of 1947, 1948, and 1949. In 1947 the weighing facilities and the number of animals involved in the tests were interial



adequate, but a considerable

number

of

radiation readings were taken through-

out the summer. Four shades were tested during the summer of 1947; each was 16 x 24 feet and 10 feet high at the eaves. The roofs are gable with about an 18inch rise. A brief description of each follows:

I.Wood

slat

shade. The roof

is

constructed of 1 x 10 inch boards spaced 1

inch apart.

west.

The

The cracks run

east

and

floor is dirt.

2. Hay covered shade. The roof is about a 6-inch layer of coarse hay held in place between two layers of wovenwire fencing. The floor under the shade is

concrete.

3.

Aluminum shade. The

roof

is

4. is

Galvanized iron shade. The

old,

roof

corroded corrugated galvanized

sheet iron,

and the

floor is dirt.

In June, 1947, before animals were available for the experiment, the inten-

under each shade was compared with that from the unshaded sky and sun by means of a flat-plate radiometer. The instrument was held 3 feet above the ground, and readings were made on both the upper and lower hemispheres. The observations covered a pesity of radiation

riod of several hours during the hottest

When measuring

part of the day.

the

radiation under a shade, the instrument the center of the shadow.

was held

at

From 10

A.M. to 2 p.m. the radiation

from the upper hemisphere was reduced 65 per cent by the solid shades (galvanized iron, aluminum, and hay covered), and 55 per cent by the wood-slat shade. This agrees well with the findings of workers in Africa (Reinerschmid, 1943) There was a slight difference in the amount of energy reaching the flat-plate under the various shades. For instance, at 12 noon, when the air temperature was 99° F, the energy incident on the instrument under the hay shade was 181 2 Btu per hour/ft. under the aluminum shade, 190; under the galvanized shade 193; and under the wood slat shade, 223. At this time the total solar and sky radiation, including incoming long-wave atmosphere radiation, amounted to 527 2 Btu per hour/ft. In other words, the hay covered shade cut off 1.7 per cent more of the solar energy than did the aluminum shade, 2.3 per cent more than the galvanized iron, and 8 per cent more ;

.

commercial 5-V Crimp aluminum sheets. The floor is concrete and has a 2-inch drain in one corner. Overhead, down the center of the shade, are several spray

heads which may be used to produce a fine spray under the shade. Although this shade was equipped with the sprinklers, it was tested without the sprinklers with the radiation instruments. *

Mean

radiant temperature: that tempera-

ture of a uniform enclosure (usually designated

than the

,

black to eliminate reflection) with which a body would exchange the same amount of energy by radiation as in the actual environment.

[19

wood

slat

shade.

was found that shades also reduced the radiation from the lower hemisphere, or the ground, although not as much. At 12 noon, when the ground radiation in the sun, amounted to 242 Btu per hour/ 2 ft. the ground radiation under the solid shades averaged about 173 Btu per hour/ 2 ft. a reduction of 28 per cent. Again there was a slight difference noted in It

,

various shades. The hay and aluminum shades reduced the ground

of radiation

radiation 28 per cent, the galvanized iron

as

effect of the

27 per

cent,

and the wood-slat shade 22 should be noted that the

from the zenith and from

several angles below the zenith, as well

from several angles

isphere, were

in the lower

made with

a

hem-

Hardy dermal

sprays were not in operation under the

radiometer. This instrument included in its view an angle of only 12°, rather than

aluminum shade

the entire hemisphere, as did the

per cent.

It

at the

time of these ob-

and that the ground or floor under all shades was dry. Some of the differences in ground radiation, howservations,

ever,

may

be attributed to differences in

floor material.

In August quantitative measurements

plate

radiometer.

"scanning"

The

results

of

flat-

the

hemispheres are shown in figure 7 for each of the shades. As with the flat-plate radiometer, the instrument was held about 3 feet above the ground, at the center of the shadow. of

the

Galvanized Iron

Spaced

Boards

-Hay Aluminum

Fig. 7.

Radiation from shade, unshaded sky, and ground at center of shadow, at noon, under

four shades at the Imperial Valley Field Station. Observations

[20]

made August

22, 1947.

The

air

View

of the hay-covered

shade

temperature was 95° F.

The

Fig. 8.

sprays under the aluminum shade were cut

off,

but the concrete floor was wet.

As shown by indicated the

solar

(d)

(right).

original data are given in table 2 along with the emissive power as ob-

tained by the

The value

Hardy radiometer. of each shade material in

wood slat, and The heifers under

and sky radiation was by the reactions of cattle sheltered under them. Between July 23 and September 15, 1947, three Hereford heifers were placed in the pens surround-

a slightly different

order of

namely,

radiation,

aluminum, (b) hay,

and the slatted-wood shade

The

figure 7, this instrument

efficiency of the several shades in cutting off

(left)

(a)

(c)

galvanized iron. hay-covered shade

cutting off solar also determined

and wood-slat

ing each of the four experimental shades,

shade are shown in figure 8. While the animal standing in the shadow of a shade is protected from the

consumption, and weight gains were observed. They were fed fair quality al-

direct rays of the sun,

receiv-

falfa hay, a little cottonseed meal, salt,

ing and giving energy to and from the

and water. Although the length of time was short, the number of animals small, and most differences between pens not

the

it

is still

surroundings, depending on

temperature

and

its

emissivity,

surface

and

the

temperature and emissivity of the surroundings. The roof of the shade is usually above the air temperature, during August, times when the air temperature was about 100° F, the temperature of the underside of the El Centro shades (the side the

daytime.

Observations

in

1947, indicated that at midday,

at

radiating to the animals standing in

its

shadow) averaged for the galvanized iron, 26° above air temperature; for the

aluminum shade, 10°; for the wood shade, 9°; and for the hay shade, 5°.

and

their physiological reactions,

statistically significant,

almost

feed

all differ-

ences followed the same pattern; that

is,

those animals under the hay and alumi-

num shades appeared cooler and more comfortable than those under the woodslat and galvanized iron shades. The normal body temperature of a cow is between 101° and 102°, while the comfort zone for respiration rate is between 20 and 50 breaths per minute. Between July 23 and September 3, with a mean air temperature of about 90° F, 31 sets of

[21]

body temperatures were taken on these

heifers. Unfortunately, there

was a wild

diant temperature of the surround. Both shades had double roofs, spaced about 3 feet apart. In the first shade, a sub-

heifer under the galvanized iron shade,

and only a few body temperatures were taken on this group. Body temperature

roof of burlap sacks was kept wet by four sprinklers spaced evenly above it.

averages were as follows: hay roof, 103.0° F; aluminum roof, 103.3° F; and

wood

slat roof,

in respiration rates of the four pens

negligible,

all

Surplus water dripped from the burlap

103.5° F. The difference

to a drained concrete floor, usually wet-

somewhat in the process. The burlap sub-roof (21 x 21 ft. in size, compared with 16 x 24 ft. for the upper aluminum roof) was 7 feet above the pavement (fig. 9). The second shade had a water-cooled sub-roof of galvanized iron (16 x 24 ft.)

was

ting the cattle

averaging about 90 per

minute.

The average rate of gain for all animals was poor, being 0.48 pound per day for the 55-day test period, but the animals under the hay and aluminum shades again did a little better than those under the other two shades. Feed consumption

sloping to one side to carry surplus water

followed the same pattern as the rates of gain. Salt consumption

upper roof was of hay and of the same size. The plain galvanized iron shade mentioned previously was used as a check for these two cooled shades. In August, 1948, comparisons were made on the basis of (a) air temperature beneath the shades, (b) temperature of

was normal.

Cooling Shade Surfaces

by Evaporation Animals may lose

heat by radiation

by

to the surround, as well as to the air

convection and evaporation,

when

The

to a drain, leaving the floor dry.

the

roof surfaces next to the

less

perature of ground beneath the shades,

than that of the animal's surface. In 1948, water was used to cool the surface

and (d) amount of solar, sky, and ground radiation cut off by the shades. The average figures from a series of readings on a typical day, which had a

radiosity

the

of

surroundings

is

of two shades in order to lower their temperature (by evaporation), which thereby lowered that portion of the ra-

Table 2

maximum

air

tem-

cattle, (c)

temperature

of

109° F,



Temperature and emissive power of under surfaces of shades covered with hay, wood, galvanized iron, and aluminum, at Imperial Valley Field Station

Date (1947)

Hay

Wood

Galv. iron

Aluminum

covered

covered

covered

covered

Mr temp.,

Time

deg. F.

Temp., deg. F.

June 25

E*

Temp., deg. F.

E*

104 106

Temp., deg. F.

E*

Temp., deg. F.

E*

112

122

2:30p.m

100 98

101 104

Aug. 19

ll:10a.m 2:40p.m

102 108

107 114

174 160

112 115

190 181

139 125

194 180

127 124

172 166

Aug. 22

12:00 noon

95

101

167

110

174

128

187

118

156

1:35 p.m..

.

120

* Emissive power (Btu/hr/sq. ft.) as determined by Hardy radiometer. NOTE: Air temperature obtained by No. 30 BS gage shielded copper constantan thermocouple and surface temperatures by touch thermocouple of same size wire.

[22]

Table 3



Average environmental conditions under the three shades on August 6, 1 948. Between 1 1 :00 A.M. and 1 :00 P.M. Galvanized iron check shade

Comparison

Average outside air temperature (°F.) Air temperature under shade (°F.) Temperature of underside of roof (°F.) Temperature of ground in shadow (°F.) Radiation from sun and sky cut off by shade (%) Lowering of ground radiation by shade (%) .

.

.

and a minimum of 84° F, are given

in

table 3.

The temperatures

of the undersides of

the roof surfaces were markedly different.

The

wet, shielded, galvanized iron

shade at times was 36° cooler, and the wet burlap was 45° cooler than the uncooled galvanized iron roof. Cooling the sub-roof had little effect upon air temperature. Beneath both cooled shades the air averaged about 2° cooler than outside. The check shade showed no lowering of air temperature.

The wet pavement beneath the burlapcovered shade was as much as 10° lower than the ground below the check shade. The ground beneath the cooled galvan-

Fig. 9.

.

.

.

Burlap roof cooled by

Galvanized

sprinklers

iron cooled by sprinklers

103.5

103.5

103.5

104.0

101.5

101.5

127.5

89.0

92.0

107.5

97.2

100.0

56 27

62 31

61 37

was 3° cooler than that under the check shade on the average, and 7° cooler during the hottest part of

ized iron shade

the day.

This lowering of the radiosity of the surround with shades will decrease the radiant-heat load on the animals from 176 Btu per hr. per sq. ft. of animal surface with the uncooled check shade, to 165 with the wetted galvanized iron shade, and to 157 with the wetted burlap shade. In other words, a 700-pound steer with a surface area of about 42 sq. ft. exposed to radiation would receive 462 Btu per hr. less under the wetted galvanized iron shade than under uncooled surface shade, and 798 Btu per hr. less under

Shades with surfaces cooled by evaporation of water used

has burlap sub-roof; right hand shade galvanized iron sub-roof.

in

1948

tests.

Shade

at

left

the wetted burlap shade. This calculation

based upon observations made at 11:30 A.M., September 1, 1948, when the ambient air temperature was 101° F. The effect of the two cooled shades and the galvanized iron check shade was evaluated by a 54-day feeding trial. On July 28, 17 good quality Hereford steers and 6 good Braford steers were divided is

among

the three pens.

Throughout the

period these animals were fed

test

all

good alfalfa hay they would consume, and during the last 27 days they received, in addition, 1 pound of barley per head daily. The data on weights and gains are shown in table 4. Two Brafords were the

assigned to each shade. All gained at approximately the same rate. Their greater heat tolerance apparently made

them of

less sensitive to differences in

shades.

made

it

Inclusion

of

types

these animals

impossible to ascertain the feed

consumption

of

the

Herefords.

The

weight-increase data in the table are for the Herefords only. During the

test, one Hereford in the pen with the galvanized iron roof died from an undetermined cause, and this animal is not included in the results. The Herefords under the hay and galvanized iron roofs gained at the most rapid rate, 0.89 pound per head daily, and those under the plain galvanized iron shade gained the least, 0.69

Table 4

daily gains of 0.80 pound. However, one

animal under the wet burlap shade was most of the experiment, and if he is eliminated from the calculations, sick during

the rate of gain would be 0.90 pound.

Drip from the wet burlap roof kept damp, and they seemed to be more comfortable than the animals in the other pens. The concrete floor under this shade had to be cleaned several times a week and sanitation was a problem. The animals under the plain galvanized iron shade suffered the most, as evidenced by increased panting, driveling, and smaller gains. the animals

On

a particularly hot day,

when

the

3:00 P.M. was 118° F and the relative humidity 15 per cent, the average respiration rates per minute under the three shades were: galvanized iron, 116; double roof with galvanized iron, 105; and double roof with burlap, 80. Brafords usually had about as many respirations per minute as the Herefords, air temperature at

but their breathing was

On

this

much

shallower.

very hot day the Brafords aver-

aged a few respirations more per minute than the Herefords, but their degree of suffering

All

was much less. measurements taken during show the two wetted shades to

the

this test

provide a cooler environment for the

—Comparison

of weights and gains of Hereford steers with three different types of shade materials (July

Type

pound per head daily. The animals under aluminum and burlap roofs made

the

of

shade

28-September 20, 1948)

Number of

Herefords

Galvanized iron roof

5

Aluminum and burlap roof ... Hay and galvanized iron roof.

6

5J

Average*

Average

initial wt.

final wt.

daily

lbs.

July 28

Sept. 20

gain

gain

(lb.)

(lb.)

(lb.)

(lb.)

0.69

1230 1266 1091

Average*

430 429 420

467 472 468

0.80 0.89

Feed/100t

* Average weight and gains are only for the Herefords since there was no significant difference between the Brafords. t Feed per 100 pounds of gain includes feed eaten by the Brafords. t One Hereford died.

[24]

The steers under these two shades were more comfortable, gained about 0.20 pound more than the check pen, had lower respiration rates, and did less steers.

!

driveling. Nevertheless, the increases in

gain do not seem to be enough to compensate for the higher cost of constructing double-roofed shades and the extra

work of keeping the pens

.

*€-

-.

sanitary.

High and Low Shades, 1948-1949 At another corral were two shades, one was 7 feet high to the underside of the roof, while the other was 12 feet high. Both were 18 x 36 feet and were covered with hay supported by wire (fig. 10) A group of animals on pasture had access to these shades and showed a decided preference for the 12-foot one. Measurements with a flat-plate radiometer showed that the high shade cut off 64 per cent of the total solar and sky radiation at noon as compared to 61 per cent for the low shade. In 1949, the experiment with the low and high shades was repeated, but the corral was rebuilt so that the exit to the pasture was the same distance from each shade, and a water tank placed in line with each. A manger for hay was set up between the two, so that it did not cast a shadow in either of the shaded areas. Thus, the two shades were equally convenient. Eight Hereford steers averaging 650 pounds used these shades. They were fed about 13 pounds of alfalfa hay per head daily along with the alfalfa pasture, and gained 1.57 pounds per head daily during the test period (July 12-September 16) The high shade was used almost exclusively. Observations in 1948 under several experimental shades showed that the type of shade has very little effect on the air temperature under the shelter, unidentical except for height;

.

.

less

water

is

evaporated into the air

from sprays or from urine and feces. A more complete test was made in 1949 with the 7-foot and 12-foot shades. Using a 16-point recording potentiometer,

a

Fig. 10.

Hay-covered shades, one 7 feet and

the other 12 feet high to the underside of the roof.

continuous record of air temperature

at

was obtained under these two hay-covered shades for 48 hours. Thermocouples of 30-gauge copper-constantan wire were supported from the roofs at heights of 1, 3, and 6 feet under the low shade and at 1, 3, 6, 9, and 11 feet under the high shade. The supports were moved hourly so that the bottom thermocouple was always close to the center of the shadow. At night all junctions were left directly under the center of the shade. While there was some eviseveral levels

dence of stratification at higher elevations, at the 1-

and 3-foot

levels, occu-

pied by the animals, there was

little dif-

ference between the two shades. Most of the benefit, as far as animal comfort

is

concerned, should be ascribed to a lowering of the radiation heat load.

Louver Shade

A louver shade was also tested in 1949. The louvers were set at such an angle that a solid shadow was cast on the ground but allowed almost

total

exposure

of the animals to the colder north sky (fig.

11).

The angle and spacing

of the

were calculated for the latitude of El Centro at slats

(1 x 10-inch boards)

The over-all size was 13% x 22 feet. At first this shade was 6 feet above the ground, but later it was raised to 9 feet. This noon of

the longest day.

of the shade

[25]

'

shade was compared with the galvanized iron shade and the hay-covered shade with a sub-roof of galvanized iron, but no water was used for cooling. Animal preference was used as an indicator of the effectiveness of these three

The test animals included eight Hereford and eight Braford steers, averaging about 650 pounds each. They had access to pasture and, in addition, were

shades.

fed an average of 6.4 pounds of good alfalfa

made

per head daily. The Herefords an average daily gain during the

period (July 12 to September 16) of 1.20 pounds, while the Brafords averaged 2.13 pounds. The cattle came in from pasture about

66-day

test

7 a.m. and went out again between 4 and 5 p.m. Gates of the corrals were left open, giving all the animals free choice of the shades. Their preferred resting place was the double-roofed shade.

The

galvanized iron shade was never used

and

shade only occasionally, although both were more conthe

louvered

veniently located relative to feed.

About

halfway through the test, the louvered shade was raised from 6 to 9 feet, but the preference of the steers remained the same.

A

comparison of the energy incident flat surface was made by means of a hemispherical radiometer at noon on

on a

Fig.

1

1.

Louver shade.

August 24 when the air temperature was 106° F. The double-roof shade cut out 58 per cent of solar and sky radiation the center of the shadow;

at

the galvan-

ized iron shade, 54 per cent; and the louvered shade, 53 per cent. The south

end of the louvered shade cut

off even energy (51 per cent). By the use of

less

a directional radiometer, traversing from the north horizon through the zenith

down that

to the south horizon,

the

high-intensity

it

was found was

radiation

energy reflected from the top side of the down onto the steers. A person standing under the shade could feel the concentration of energy on the face and body from the north side. Raising the shade to 9 feet gave the same effect, although intensity was less at cow level. louvers

Trees for Shade Trees have been suggested

as provid-

ing the "ideal" shade. Because of their irregular shape, their comparative value is difficult

to measure.

A

limited

number

of observations at Davis indicate that their radiosity may be somewhat less than for a flat aluminum shade. A large black walnut tree averaged 138 Btu per hr. sq. ft. when viewed from the shadow beneath it; a smaller catalpa tree averaged 141 Btu, and an aluminum shade, 170 Btu. At this time the air temperature was 83° F, with a slight breeze. One distinct advantage of trees is the fact that, because of their thickness of mass of leaves, their shadow is always larger

than the vertical projected area, giving a larger low-temperature ground area with a given exposure to cool sky than is

possible with a thin shade. Disadvan-

tages of trees are that in

shadow

is

many

cases the

not solid because of openings

between leaves, and that they do not fit into practical farming practice where it is

desired to rotate pastures frequently.

Painted Shade Materials Certain materials, such as white paint, are highly reflective (low absorptivity) to

short-wavelength radiation and are

12.

Fig.

Three 8 x 8 x 4-feet-high

shades set up over a

test

mometers at center of each shadow and

in

very good emitters (high emissivity) of long-wave radiation at their normally low temperatures. In the study described below,

white-painted

aluminum

sheets

were as much as 15° cooler than unpainted aluminum sheets when exposed to the sun. White-painted galvanized iron

much as 50° cooler than unpainted ones. While the characteris-

sheets were as

tics of the

top surface greatly influence

the temperature of the shade material, is

it

the emissivity of the bottom surface

that influences the quantity of energy,

due

to

this

temperature, that will be

emitted to the animal. The reflectivity of the bottom surface determines the quantity of incident

energy, from the ground,

that will be reflected back

down

to the

animal.

To study

the thermal effects of changes

in radiation characteristics induced

on

the surfaces of various shade materials

by painting,

field

tests

of several

ma-

were conducted during the summers of 1952 and 1953. Three flat, portable shade frames, 8x8x4 feet high, were covered with the materials tested. The frames were collapsible so that they could be easily moved (fig. 12). One frame was always covered with plain corrugated embossed aluminum roofing to serve as a check shade.

terials

dirt field.

Note black-globe

ther-

sun.

The

real thermal

comparison of two

shades should be based on the relative

comfort of animals under them. To obtain such comparisons, one 6-inch blackglobe thermometer was placed under each of three shades and kept in the center of the shadow. A fourth globe was placed in the sun to serve as a basis for comparison. The temperatures of the shade materials were obtained with thermocouples attached to the undersurface of the shades. Temperatures of both the globes and the thermocouples were continuously recorded by a 16-point recording potentiometer. The quantity of radiant energy from the shade surface and from different parts of the surround was measured with a Hardy radiometer. The upper left-hand section of figure 13 shows the radiant heat load on the globes under three shades covered with corrugated embossed aluminum roofing.

One was Fuller's

left

unpainted.

Two

coats of

Myratic No. 1520 white paint

were applied to the top surface of the remaining two, and the bottom surface of one of these was painted with two coats of Fuller's Myratic No. 1518 velvet black paint. The lower set of curves shows the surface temperatures of these three shades.

[27]

White paint and the unpainted

alu-

mmum

sheet

amount of

reflect

about

the

same

ferences must be attributed to a rcduc of reflected energy under the blackpamted shade. The undesirable effect (greater emission by the black surface) was less than the desirable effect (re-

solar energy

(about 75 per cent), but the emissivity of the white paint at ordinary shade material tern-

perature,

is

much

ban

greater (about 0.89)

duced

(0.11 to 0.20). The white-painted surtace consequently maintained a lower temperature because of better radiation exchange with the cold sky. Since the radiation characteristics of the bottom surfaces were identical, the radiant heat load under the white-painted shade was

considerably

the same as that and yet the radiwas as much as

ant heat load under it 13 Btu per hr. ft.* less. Since the uppersurface radiation characteristics of these two were the same (white paint) the dif-

incident

energy)

from the

rate

temperature rise of

The surface temperatures of the painted shades were at times 15° lower than that of the unpainted shade. The radiant heat load under the white and Wack shade was as much as 18 Btu per U " " tha der tHe un P ai "ted " shade

Hay has

invariably proved "cooler"

I

f\

White top - Black bottom

Aluminum

Fig. 73.

uncW *l ^°« Z^lJlZt** ""^ T ^^ W

Radiant heat loads

shade was determined from •he shade materials are also

8 y

ft

v

><

t

.

° fu' f sh " d °

shewn

[28]

by

radiation to the cool shadow. Furthermore, convection cooling would tend to prevent an excessive the black surface.

of the third

shade, painted white on top and black underneath, was about of the white-top shade,

of

unshaded ground than did he unpamted surface, but at the same bme it lost heat at a greater

less.

The surface temperature

reflection

The black surface absorbed more radii ion

-

Surf

'° ad

""^

each temperatures of

than most other shade materials. One of was covered with a 4-inch

the shades

were compared with the unpainted and the white and layer of hay,

and

results

black aluminum shades. this

test

are

shown

in

The curves

for

The radiant heat load under the hay shade was much lower than that under the other two shades. Here, the hay temperature (bottom surface) remained very close to that of the air, and as much as 25° lower than the surface temperature of the plain aluminum shade. The very uneven char-

hay surface evidently acts as a black surface and absorbs most of the irradiation on it from the hot ground, acter of the

reducing the energy reflected back down to the animal. We do not know what the surface convection coefficient for the hay is, but, because of the uneven character of the surface, it is probably very high. The hay presumably lost much of its heat to the air by convection. Also, because of the insulating thereby

value of the 4-inch layer of hay, the

bottom surface did not receive much heat from the top surface by conduction. Although hay has excellent thermal properties, it does have limitations as a shade material, for it must be replaced periodically and does not provide a permanent and weatherproof structure. Painted galvanized iron roofing sheets

were compared similarly and the same beneficial effects of paints were noted. White paint applied to the top surface of galvanized iron caused a reduction of as

much it

as 50° in

perature

of

white-painted

The addition

sheets.

the

temperature, bring-

its

within a few degrees of the tem-

galvanized

iron

aluminum

of white paint to sheet

made

it

a

may be many the

affecting

The combined

desirable

top

on an animal under a

minum

The

White-painted Metal Buildings During the summer of 1955 a study was made of the influence of white paint on the thermal environment within a metal building. The building was 60 x 32 with the long dimension oriented

feet,

north and south. The exterior of the south end and the south 20-foot section

and roof) were painted with (fig. 14). The middle 20-foot section was painted with white paint supplied by the building manufacturer. The north section and north wall were left unpainted. Temperatures of the different building sections were meas(sidewalls

a

flat

white paint

ured with thermocouples attached to the inside surfaces. Surface temperatures for a 24-hour period are 15.

Maximum

among

and

red at 1:00 P.M.

when

in figure

the air tempera-

ture outside the building

and

inside,

was

little

was 100.0° F

102.5° F. These reductions were: west wall, 25.0° F; west roof, 42.6° F; and east roof, 41.0° F. There difference in the surface tem-

peratures of the two ends even though the south end

White paint

was

in the sun all day.

effectively put the south

"in the shade." There was

little

end

difference

two types of white

white did show a advantage over the building manubut the

flat

facturer's paint (fig. 15).

Since only

the different

shades shown in the curves (fig. 13) will not always be of the same magnitudes.

shown

surface temperature re-

ductions, due to the white paint, occur-

slight

difference in radiant heat load

shade of alu-

aid in increasing an animal's comfort.

paint,

surface temperature

flat

or galvanized iron and should

in the effect of the

it.

of

effects

surface

greatly in reducing the radiant heat load

"cooler" shade material than plain alu-

load beneath

shades,

and blackpainted undersurface were shown to help white-painted

minum,

establishing a lower radiant heat

less or greater,

environmental such as wind velocity, air temperature, radiation from the sun and sky, and ground cover. factors

the right-hand

section of figure 13.

ing

These differences depending upon

one building with both

painted and unpainted surfaces was used, it

[29]

was not possible

to directly

compare

Fig. 14.

Corrugated galvanized

tion painted flat white,

north section

60x32

feet.

South end and south 20-foot sec-

and north end unpainted.

Fig. 15. Inside surface

building

steel building,

middle 20-foot section painted with building manufacturer's white paint,

shown

in

temperatures over a 24-hour period of the walls and roof of the metal

figure 14.

160

[30]



Air temperatures in white-painted and unpainted Table 5 corrugated galvanized steel building, 60' x 32', Imperial Valley Field Station, 1955 Inside Air Temperatures, °F.

Time

Date

1:00 p.m 2:00p.m 2:00 p.m

6/25 6/25 6/26

painted and unHowever, by theoretical considerations it was possible to show what the air temperature of a wholly unpainted building would have to be when heat was transferred to the in-

air

temperatures

painted

in

buildings.

White

Unpainted

Temperature

(measured)

(theoretical)

difference

102.5

130.5

28.0

100.0

116.8

16.8

102.5

119.8

17.3

side air at the

same

rate as in the white-

painted building, based on actual temperatures of the painted and unpainted

and with no was done and the retemperatures are shown in

sections at a particular time ventilation. This

sulting air

table 5 for three different sets of surface

temperature values.

To show



Table 6 Radiosity (Btu/hr/ft ) of outside surfaces of metal barn and surrounding ground, 2:30 P.M., Imperial Valley 2

Field Station, West

1955 side

of barn (sun)

Surface

East side of barn (shade)

the

ability

painted surfaces to

of

white-

the

"lose" heat

more

readily than the unpainted surfaces,

and

thereby remain at a lower temperature,

was measured with directional radiometer. One set of these readings is shown in table 6. The white surfaces in the shade gave off the radiosity* of these surfaces

more

heat, indicating a greater emission

from the unpainted sursun the greater amount of energy from the white surfaces indicated both greater reflectivity and greater emissivity than the unpainted surfaces very of energy than

Unpainted Manufacturer's white Flat white

Ground

231

172

311 315 275

179 184 179

faces. In the



desirable characteristics in heat-load conditions for buildings.

*

The

Radiosity radiosity

surface,

and

—the

total quantity of radiant

energy leaving a surface per unit time per unit area. energy initially emitted by a surface, to energy reflected from the energy transmitted through the surface.

may be due to

to

[31]

that

THE TESTS

SHOWED

Measurements

in

good shade

will

reduce the heat load as much as 50 per cent, and will increase gains

the tests indicated

could lose

effectiveness

its

that properly designed shades will reduce

shadow outside the corral

the radiation heat load on an animal 50

the day.

by casting

its

much

of

for

per cent or more. Since sky temperature,

Higher shades receive sun under them

and

for a longer time during the day than do

other factors are never constant, no one shade can be best for all conditions.

lower shades, thus keeping the area drier. Moisture under a shade serves to lower the ground temperatures, but keeping just the right amount of moisture under a shade would be very difficult. It is probably more practical to plan on keeping this area on the dry side. Shades betwen 10 and 12 feet high seem to be most practical. Men on horseback can ride under such shades without difficulty, cleaning equipment can be used, and the animals have a good opportunity to be exposed to the cool sky. Shades higher than 12 feet must make more allowances for strong winds. This makes them more expensive to construct and keep in repair. Shade Material. Hay, galvanized

solar

radiation,

temperature,

air

Size of Shade. Most shades in this area vary from 16 to 20 feet in width

and up to several hundred feet in length, depending upon the need. Wide shades cut down on the amount of cool sky radiating to the animal, although the larger

shadow

results in less radiation

from the

ground. The net result in cooling effect is about the same for both wide and narrow shades; however, wider shades reduce the drying effect from solar radiation, and unsanitary conditions may develop more easily.

Orientation. Most shades

in the area

are constructed with a north-south orientation.

This usually allows enough sun-

shine under the shade to keep

promote

sanitation.

tion allows

East-west

more animals

ground the day.

is

little

to be

orienta-

tested

as roofing material for shades.

Hay

the coolest material tested to date.

east-west orienta-

tion decreases the radiant heat load

the animals, north-south orientation it

on is

pro-

motes better sanitary conditions.

Height. Raising the height of a shade shadow a greater exposure to the cool sky and tends to increase the cooling effect. Cattle were found to prefer a shade 12 feet high rather than one 7 feet high. Although shadow size is not affected by height, the higher the shade the faster the shadow moves during the day. A high shade gives the animal in the

and boards have all been

sheets,

exposed

shaded for a greater part of

preferred by cattlemen because

aluminum

spaced

lower because the

Even though

iron sheets,

dry and

and ground tem-

to the cool north sky,

peratures are a

it

A

is

2-inches

apart

hay has an insuand heat from the top does not penetrate through and radiate onto the cattle. Very little heat is reflected back to the animals from the underside of the shade. The underside of a hay roof stays 4- to 6-inch layer of

lating effect,

very close to air temperature, thus reducing the radiant heat load. However, using

hay as a shade roof does have lems. Unless

it

is

its

prob-

held together between

two layers of wire, it tends to blow away. In a wet country hay can absorb a great amount of water during rainy periods and thus tends to break down the shade support unless

it is

well built.

Even

well-

constructed hay shades must have the

hay replaced periodically. Bamboo, palm

[32]

fronds,

etc.,

give the

same cooling

effect

as hay.

Galvanized steel sheets provide the exposed to the sun were found to have a temperature 20 to 30° higher than air temperature. The underside radiates this heat

down onto

the cattle.

By

paint-

ing the upper side white with a good

chalking white paint

lem

can

be

sheets

steel

aluminum

of

as well as galvanized steel

sheets.

much

reduced; then

come

of this prob-

the

galvanized

close

to

hay-

covered shades in the resulting cooling effect on the animals. Galvanized steel and other metal sheets have the advan-

more permanent than hay, and they shed rain during the wet season. Aluminum sheets were found to be good shade material. They reflect much of the solar radiation. White paint was found to improve the reflecting qualities tage of being

Wood makes

a good shade material,

but leaving a crack between the boards fall directly on the catThis produces a hotter environment than a solid shade. Cracks appeared to reduce the fly population under a shade, but all the experiments to date show that

allows the sun to

tle.

shade is definitely cooler. Figs. 16 and 17 show two types of shades that

a solid

may

be used in this area.

Although no tests have been conducted on the shade required per animal, a check of the shades used year after year indicate that 60 sq. ft. of shade per aniis practical. Many feeders provide between 40 and 50 sq. ft. of shade, but animals should not be crowded during the summer months.

mal

' ::' .

Fig. tical

in

wooden roofed shade

prac-

Fig. 17. This 11-foot

areas where small whirlwinds tend to

by cables and the hay

16. This

is

destroy hay covered shades. Cracks between

two layers of

boards should be kept to a minimum.

fences.

[33]

light

hay shade is supported is sandwiched between

fence wire. Note the cable

WATER AS A COOLING AGENT Water

an ideal cooling agent; it cheap and abundant, and it can be economically transported to the animals; it is noncorrosive and nontoxic it has the highest heat capacity of any of the common liquids (1 Btu per pound/ F) and also the highest latent heat of evaporation (1050 Btu per pound at 70°) This discussion covers tests over the period 1947-1955 that used water as a cooling agent in four different ways: (a) spraying the animals, (b) cooling the air, (see page 52), (c) cooling the shade surfaces, (see page 22), and (d) cooling the drinking water. usually

is

is

;

.

made in 1946, when some preliminary studies were conducted with

in tests

cattle. At an about 109° F and a 18 per cent, wetting hose reduced body

dairy

temperature of humidity of cows with a garden temperature about air

relative

1.5° and slowed respiration rates by about 20 breaths per minute. The spray tests reported herein were conducted each summer, from 1947 to 1952 inclusive, except for 1948. The results are

summarized

in table 7, together

with the number and breed of animals

and their initial weights. Water temperature at the nozzles varied from 85° to 95° F in

all

the

tests.

Following are brief

Spraying the Animals

descriptions and results of the studies, by

Spraying dairy cattle with water has been investigated by Seath and Miller (1948). The effect of wallows and rain on water buffalo, Zebu cattle, and sheep was studied in India by Minett (1947). European- and Indian-evolved cattle lack sweat glands as they are found in man. However, they do lose moisture and are cooled by the evaporation of water from the skin, more so than originally thought. Kibler and Brody (1952) have shown that at temperatures above 75° F

year:

Jersey and Holstein dairy cattle will lose

about two-thirds of their insensible (latent) heat of metabolism through the skin and only one-third by way of the lungs. This evaporative cooling of the body is not enough to prevent discomfort when environmental temperatures are above the critical range (75° to 85° F). At air temperatures of 105° F all heat

produced was dissipated by evaporative cooling. Cattle

sprayed

with

water

will

be

cooled by the evaporation of the water

from

their skin

and by conduction when

the water temperature

skin temperature. This

is

lower than the

was

first

shown

In 1947 three Hereford heifers were housed under a 16 x 24-foot aluminum shade equiped with three shower heads giving a fine spray. The spray heads were 8 feet above the ground. Water pressure at the heads was 30 pounds per sq. in. A concrete slab under the shade carried the waste water to a drain.

made

little

The animals

use of the sprays, got only the

ends of the hairs wet (not their skins), and did not seem to be getting any measurable benefits. One spray head, with the mcn to wet the anihole enlarged to mals to the skin, was then lowered to 6 feet above the ground, cutting down the drift. When the animals were also wetted

%

down with them the

a hose several times, to

benefits of standing

show

under the

shower, they began to make greater use of the spray. By the end of the summer one animal was standing under the shower about three hours per day. Occasionally, even though the shadow movement left the showering animal exposed to the sun, it nevertheless stood under the shower even when the air temperature was 109° F (fig. 18).

[34]

-ill

Fig.

18. Yearling Hereford standing in sun, with air

advantage

temperature at 109°F,

in

order to take

of spray.

Suovto Stall

/Vaohetic To \>Ateq Supply^

SuovtR MCAD

Duoto Clectqic Cell Belay

Dlan Fig. 19. Single

shower

stall,

Sei^tkmh Tmdu Smover

shower head controlled by photoelectric

cell relay.

Plan shows relation between

shade, and pasture. Section indicates position of relay with respect to shower

and animal.

[35]

stall

Wetted animals usually had body temperatures 2° or 3° lower than those of dry animals, and lower respiration rates by 20 or more breaths per minute. These animals never used the sprays at night; even when the night temperature did not go below 80° F, they preferred standing in the open, exposed to the cooler sky. The continuous operation of the showers used excessive amounts of water and created unsanitary conditions under the shade, even though the floor was con-

Weight records and feed records were too meager in 1947 to indicate any advantage between the spray and check

crete.

1949

(there were

no spray

tests in

1948) an inexpensive photo-electric cell relay ($30) and an electric solenoid water valve were used to control the water flow to a single coarse shower head (fig. 19) so that the shower operated only when an animal entered the stall. The shower was installed over an irrigation ditch so that waste water went directly into the ditch. The shower, with standing room for only one animal, was situated between shade and irrigated alfalfa pas-

was anticipated that the cattle would wet themselves at frequent intervals when passing to and from the pasture. It

them into the stall. In spite of this, the average daily gain of the test pen during the 66-day feeding period (July 12-

September 16) was 0.37 pound per animal greater than the gain of the unsprayed, check

gain

cattle.

This difference in

may have been

influenced by the

wood

the

In

6

to

in

Shower

use

in

stall,

tests

located over irrigation

of 1950.

Water flow

controlled by photoelectric cell relay.

is

in a

950

1

at

corral.

feet,

the shower stall

was widened

three shower heads were in-

and the number was reduced to four so stalled,

of test animals

that all would have equal opportunity to shower. All animals used the spray a great deal of the time during the day. They received all the alfalfa and barley hay they wanted

but

made

little

use of the pasture.

They

enjoy the water and were definitely more comfortable than the unshowered check animals. The check steers were also in a wire pen, had access to

seemed

test Fig. 20.

was

wire pen and the check animals were

pasture,

ditch,

The

let

corrals since the shower group

pens. In

ture, thus increasing grazing time.

8 check animals were at the wood corral and had access to pasture. Feed records were not kept on these animals. Several of the 8 test cattle (table 7) used the shower very little, partly because they never learned its comfort and partly because "boss" cows would not

to

and were fed the same

as the

group. The average daily gain during

the 80-day feeding trial (June 21-Sep-

tember 9) was 0.22 pound greater than the gain of the check animals (table 7). Because of a shortage of irrigation water the showers were not operated during three or four days of each month. A view of the

shower

stall in

operation

is

shown

in figure 20.

In

1951

a test using very fine mist

sprays was conducted in a feeding

trial

with 5 Shorthorns (2 steers, 3 heifers). The check pen had 4 Shorthorns (2 steers, at the

lots were fed from July 3 to Sep-

2 heifers), and both

wooden

corrals

tember 27. These spray nozzles, known as "foggers," have been used with some success in California to prevent the death of

s

fe

Sol*

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laying hens confined in cages during hot weather (Wilson and Hillerman, 1952). Although mists did not prove successful in 1947, it was thought that the extremely fine mist produced by these nozzles might prove more efficient in cooling, simplify the spraying equipment, cut down the amount of water needed, and increase sanitation under the shade. Monarch No. H-61 nozzles were used, delivering 1 gallon of water per hour under a pressure of 20 pounds per sq. in.

(manufacturer's rating)

conditions.

The average

daily gain was good for and check animals (table 7), but the "fogged" animals gained only 0.06 pound per day per animal more than the check animals, which was not significant. However, the feed consumption per 100 pounds of gain was slightly less with the fogged group. The animals under the foggers appeared uncomfortable and particularly avoided getting their heads in the moisture. Their hair was seldom wet enough to be plastered down to their test

8,

1952, with

F and

humidity 17 per cent. Some of the nozzles were always in shadow.

Ten Herefords were used ing

trial,

for the feed-

with 10 similar animals in an

unfogged corral as checks. The test was run from July 2-September 11. All 20 animals had their drinking water cooled to 65° F. (See discussion below on cooling drinking water).

Time

of spray op-

eration was as before, from about 8

A.M. P.M. The sprayed animals with cool drinking water gained 0.10 pound per animal per day less than unsprayed cattle with 4

until

Six nozzles, 6 feet above the ground and out of reach of the animals' backs, were arranged under the same 16 x 24foot shade used in 1948, in two rows of three nozzles each. Nozzles were 8 feet apart in the rows, and the rows 7 feet apart. The concrete slab was enlarged by 3 feet all around to improve the sanitary

both

1:15 P.M. on September

at

the air temperature at 109°

to 5

cool drinking water (table 7)

.

Later tests

have indicated that 10 head may have crowded the animals a little too much and not allowed as many square feet of shade per animal as is necessary. (See page 33.)

During the same summer a short trial was made with a commercial mechanical "fogger" a whirling wire brush, driven by (not a feeding experiment)



%-HP

motor, that dispersed atomized water from its periphery by centrifugal a

force

(fig. 22). Droplet size could be adjusted by varying the rate of water

When

flow.

same

droplet size appeared about

as that produced

skins. In fact, the beads of moisture sometimes appeared to cause the long

by the fogger was lowered from 110° to 95° F as far as 10 feet from the wheel. The animals were not wetted appreciably and avoided getting their

hair to stand out from the skin, thus

heads

actually

increasing

insulation

heat transfer from skin to

air.

against

These

animals received some grain in their

ra-

which may have masked benefits from the fogging. In 1 952, therefore, fogging was tried again, with hay as the only ration. The number of nozzles was increased to 18 and the concrete slab again increased, this time to 30 x 40 feet. The arrangement of nozzles, shade, and slab is shown tion,

in figure 21,

and

relative

along with air temperature humidity observations made

the

nozzles, the air temperature

seemed

in

the

moist

clouds,

but

they

to like the lowering of the air

temperature and the air movement duced by the rapidly whirling brush.

in-

The cooling

effect of sprays on anidue to several different mechanisms. Wetting the animal to the skin produces cooling by conduction when

mals

is

water temperature

is

lower than skin

temperature; the amount of the

differ-

ence in temperature and the rate of water flow determine the amount of cooling. Further cooling will result from the evaporation of water that does not run

[38]

AIR DRIFT

NOZZLES 8'-0"o.c.



103'

=fc\V^ !

im& 55'-0"

Fig. 21.

Arrangement

of fogger nozzles under 16

isotherms are for September 8, 1952, at 1:10 p.m.,

off the

cooling tailed

animal. (This will be the greatest if

the rate of water flow

is

cur-

by a limited water supply) Part .

the heat for evaporation will

come

of di-

from the animal by conduction, and part from sensible heat of the air. Cooling of air may or may not be of benefit, depending upon the opportunity the cooled air has of circulating back around the animal. The rate of heat loss from the animal surface (by convection, radiation, and evaporation) will vary directly with changes in the surface temperature of the animal due to wetting. As rectly

shown

in figure 23, the animal-surface

temperature may be expected to decrease through the evaporation of water. This can only decrease the rate of heat loss from the animal's surface by convection to the air and by radiation to the surround. At higher environmental temperatures the direction of heat flow

modes may

by these

actually be reversed, with

heat flowing from the environment into the animal surface. further

The heat balance is by the animal's

complicated

physiological reaction to a lowered skin

temperature.

Internal

body heat flows

toward the surface at an increased rate, by conduction through the body tissues

x

24-ft.

when

shade

in

1952

tests.

outside temperature

Air temperature

was 109°F.

A lowered skin temperature change that part of heat-transfer rate established by blood flow. The literature is not clear on peripheral circulation of blood and vasomotor activity of cattle when subjected to high temperatures. Some work has shown that in contrast to man, the pulse rate of nonand

liquids.

will also

sweating animals

is

higher in a comfort-

environment than in a hot one (Worstel and Brody, 1953). Recent

able

22.

Fig.

stalled

mals

Whirling-brush

under shade

all

face

in

1952

away from

fogger device test.

fogger.

Note that

in-

ani-

2:10

2:20

UQ

230

Fig. 23.

in sun and in shade, before and and globe-thermometer temperature in sun.

work by Beakley and Findlay (1955) with 4-month-old Ayrshire bull calves showed an increase in heart rate with environmental temperatures above 68° F and with increasing humidity above a temperature of 86° F. How-

increasing

ever, even less information

on the effect of blood flow.

A

number

artificial

is

available

wetting upon

of cattle under one set of

sprays will increase by evaporation the

humidity already present from water droplets in the air. This may cause discomfort to adjacent animals by decreasing evaporation from their wetted surfaces. If the dry-bulb

temperature of the

above 85° F,

this increased hu-

air is

(PA.)

Surface temperature of Brown Swiss cow

with air temperature

midity will decrease heat loss from ad-

330

320

3-10

3:00

2:50

TlAE

air temperatures,

may

in trying to cool cattle

after wetting

be the weak link by this method.

Wetting the animals with heavy sprinkling has seemed more effective than the foggers, but this is expensive and creates the problem of keeping the yards sanitary where large numbers of cattle are involved. High humidity not only reduces the cooling effect from evaporation, but high humidity with high air temperature (75°-100° F) causes a decided increase in rectal temperature and respiration rates of dairy cattle (Kibler

and Brody, 1950). These plain

why

the

facts

sprinklers

may

ex-

and misty

sprays were not too effective, since the

animals were under them during most of the day.

jacent unwetted animals also, as recently

shown with dairy cows by Thompson, Worstell, and Brody (1953). This increase in humidity, in the area where cattle are under sprays with high

Cooled Drinking Water The methods

of cooling beef cattle dis-

all depended directly upon evaporative cooling

cussed so far have or indirectly

[40]

effects.

was thought that cooling the

It

drinking water might indirectly increase evaporative cooling by increasing water

consumption, thus providing more water

and lungs. At the same time there would be some direct cooling by transfer of body heat to the for loss through skin

cool water in establishing a heat balance in the body fluids. In Imperial Valley livestock drinking

due to conduction the

water, supplied mostly ditches,

as 90°

may F

from

irrigation

reach temperatures as high

in the ditch

and 100° F

in the

drinking troughs. Experiments have been carried on with cooled drinking water for five years,

In

1

1950 through 1955 (table 8).

950 two groups

of Herefords, in-

cluding 3 steers and 1 heifer each, averaging 840 pounds in weight, were used to

measure the effect of cool drinking waBoth groups were fed a ration containing 75 per cent alfalfa hay and 25 per cent barley hay. The two groups were ter.

made an average

daily

gain

of

1.46

pounds per day, those in the warm water pen gained 1.07 pounds. This difference in daily gain of 0.39 pound is significant at the 5

In

per cent

level.

1951 a small evaporative cooling

tower (fig. 24) was used to cool the water in an attempt to reduce costs in comparison with the mechanical refrigeration system. According to Perry (1945), the performance of such towers depends upon tower design, wind velocity,

water-circulation rate,

and heat

load.

A

well-designed tower will give a final water temperature within 5° of the wetif wind velocity is as mph. The tower constructed

bulb temperature little

as 1

had eight 30 x 40-inch trays, spaced 8 inches apart, of ^-inch mesh hardware cloth. Water circulation was at the rate of 6 gal/min. Water consumption of four animals was estimated as 60 gallons per day. The heat load to cool this amount

placed in separate wooden corral pens,

each pen provided with a circular concrete water tank 30 inches high and 36 inches in diameter. The tank in the cool water pen was insulated with commercial insulation and the top covered with 2inch planks, except for a small opening for the cattle to drink through. The water 2° in this tank was maintained at 65° by a horsepower mechanical refrigeration unit with direct expansion coils

Fig.

ter in 1951.

±

%

immersed

in the water.

A

small

pump

at

the bottom of this 110-gallon tank pro-

vided agitation and kept the cold water

from settling to the bottom. The mean air temperature and humidity for the test period (June 14-September 5) are shown in table 1. The lowest reading recorded was 54° F and the highest 118° F. Only 29 days of the pe-

had minimum readings below 70° Average water temperature for the warm water pen was 88.2° F. riod F.

Table 8 gives the rates of gain, food consumption, and feed per 100 pounds of gain for each group of animals.

four

Herefords

receiving

cold

24.

Small

evaporative cooling tower

used for lowering temperature of drinking wa-

The

water

[41]

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of water from 95° to 70°

F was

cal-

culated to be 12,500 Btu. This was dou-

water, and 1.58 pounds for the

water. Feed consumption and

warm

economy

allow for estimated reheating

of gain were almost identical (table 8).

through the warming of the tank by radi-

High humidity during this summer was a definite factor in the result of this test. Humidity prevented the cool water from being cooler, and it has been shown

bled, to

and convection. The resulting heat load of 25,000 Btu would have to be handled during the period when most of the water is drunk about 9 hours during the daytime. The rule of thumb stating that 1 sq. ft. of screen area is needed

ation



for each 10 Btu to be dissipated per min-

was then applied. The average water temperature maintained by the tower for the 86-day summer feeding period (July 3 to September 27) was 75.4° F, an average cooling of ute

around 9°

to about 3°

above the average

daily wet-bulb temperature. tion

pump was

The

circula-

operated from 8 A.M. to

4 or 5 P.M. However, there were 35 days when the water averaged 78.5° F, and 21 days when it averaged 70.8° F. Of these 21 days, 10 came after September 3. During humid days evaporative cooling was very poor and water temperatures ran around 80° F, but on dry days temperatures dropped as low as 66° F.

Weather data in table 1 shows that 1951 was the coolest year in respect to temperature, but it had the highest relative humidity of any of the 10 years that these tests were run. Water in the warm water tank had an average temperature of 84.2° F, so the average difference between these two watemperatures was only 8.8°.

animals in surroundings of high temperature and high humidity are under more thermal stress than animals exposed to high temperature and low humidity. The grain diet did give the steers a lower increment of heat, and they all

that

made

fairly

1952

In

good

gains.

experiments

repeated

the

1950 test with the water cooled to 65° F by mechanical refrigeration, and the animals were fed hay. This refrigeration unit had a 3-ton capacity and is shown in figure 25. Ten Hereford steers averaging 764 pounds were put on a 71-day feeding trial (July 2 to September 11), with 10 similar Herefords receiving uncooled water as a check. Uncooled drinking water averaged 89.6° F and ranged from 70° to 102° F. Table 8 shows the results of this test.

The

difference in daily gain

between the cold and

warm

water

lots

was 0.26 pound in favor of cold water and was not significant. Ten animals per pen may have been too many, especially in the cold water lot which had only 41 square feet of shade per animal. These shades might have been adequate if some animals had not had to stand near the

ter

hot fence. Individual data also indicate

Shorthorn steers were used in 1951, since they were available and are considered less heat tolerant than Heref ords. The steers were in very good condition and averaged 842 pounds at the beginning of the experiment. Five steers were in the cool water pen and four in the warm water pen, and they occupied the same pens in the wooden corral as the cool and warm water steers in 1950. Instead of feeding alfalfa hay, they were given a ration of hay and grain. Both groups of steers gained the same, 1.56 pounds per head per day for the 75° F

that the "boss" animals

may have

se-

lected the cooler spots for themselves.

(See page 33 for further discussion of

square

the

feet

of

shade needed by

animals).

1953 tests clarification the In was sought concerning the relationship between hay and grain rations and between warm and cold water. For these four pens each, with seven Hereford averaging 871 pounds, received the following treatments during an 84day test period (June 30 to September (a) cold water and hay, (b) cold 22) tests

steers

[44]

:

water and hay plus grain, (c) uncooled water and hay plus grain, and (d) uncooled water and hay. The average daily gains for this test were: cold water-hay, 1.51 pounds; cold water-hay plus grain,

pounds; warm water-hay plus 1.57 pounds; and warm waterhay, 1.18 pounds. As for the hay- and grain-fed animals, the average daily gain of those on cooled water was 0.44 pound greater than that of animals on uncooled water. With hay-fed animals, cooled water produced 0.33 pound greater daily gain than did the uncooled water (table 8). Analysis of this study shows no significant interaction between feed and water effects furthermore, each of the main 2.01

grain,

;

effects (feed

and water)

the 1 per cent level.

is

significant at

(See page 76 for

further discussion on feed effects in hot

climates).

In

the 1954

tests,

since 65°

F

drink-

ing water seems to be a significant factor in

heat-regulatory

the

cattle, it

was decided

mechanism

of

to increase the salt

would drink more cool water and thus gain even

in the ration to see if they

faster.

In recent years a salt-and-concen-

mixture has been used extensively in the range country to control the concentrate intake of animals self-fed on pasture. This high-salt diet has nearly doubled the animals' water requirements trate

(Riggs, Colby, and Sells, 1953). In the

four previous experiments

it is

interest-

ing to note that animals with cool drink-

ing water consumed slightly

than those with the

warm

less

water

water, (table

9).

In order to get the animals to con-

sume excessive amounts

of salt, two pelwere prepared. Both contained the following: 35 per cent alfalfa hay, 15 per cent oat hay, 35 per cent barley, and 15 per cent molasses-dried beet pulp. Ten per cent salt was added to one lot of pellets and none to the other lot. All lots had block salt in their pens. Seven Hereford steers, averaging 814 pounds, were placed in each of four wooden pens and given the following treatments: (a) 65° F water plus pellets, (b) 65° F water plus pellets with 10 per leted

cent

diets

salt,

(c)

warm

water plus

pellets,



Table 9 Comparison of consumption of cooled and uncooled water, and cooling effects calculated Av. daily water consumption per animal

Daily Av. temp. uncooled

of

Water cooled

1950 1952 1953

difference in cooling

water

effect

(°F)

per animal*

to 65°

Uncooled water

(gal.)

(gal.)

15.4

16.6

88.2

13.4

15.0

89.6

(Btu)

Hay ration

13.6

t

89.2

Grain ration

11.3

13.0

89.2

1954

No salt

12.6

14.1

86.3 1

Salt

20.3

19.5

1955

60° water 70° water

10.9 §

12.4

86.3| 87.7

n.o§

12.4

87.7

2831 2348

2084 2030 3718 1583 1446

* Based on raising daily consumption of water of the two different temperatures up to estimated body temperature of 103°. t Water consumption not measured. t Unshaded first month of test then shaded. § Water temperature as shown under year.

[45]

Fig. 25.

1952

Mechanical refrigeration equipment and controls used for cooling drinking water from

to 1955.

Fig. 26.

The tower

is

for cooling

condenser water.

Large evaporative cooling tower mounted above 4 x 4 x 4-foot metal water tank.

[46]

and (d) warm water plus pellets with 10 salt. During the first 28 days of the test all lots developed an appetite for the wooden mangers and corral fences, per cent

pound tendency was

but with the addition of 1

hay per day

this

of oat

elim-

inated.

Daily gains, food consumption, and of gains are shown in table 8.

economy

Although the daily food consumption was higher in the salt pens than in the others, each animal ate 1.7 pounds of salt per animal per day. This means that their daily food intake was less. Water consumption by the salt-fed animals did not double, but it increased about 40 per cent in the warm-water pen and 60 per cent in the cool water pens (table 9). Average daily gain for animals with salt pellets and cooled water was 0.03 pound greater than that of animals on warm

Two

cattle

tank was available to the aniEach day the tank was refilled during the time the pump was operating. These operations were controlled by a time clock and a solenoid valve. Water was circulated during the early morning hours because the air temperature was ter in the

mals.

at its lowest;

although relative humidity

was higher, the dew point was

at

its

lowest for the 24-hour period, which

would bring the water temperature of the tank to the lowest possible

level.

Louvers in the cooling tower were removed during the month the fan was operated. Another set of louvers was placed at the surface of the water in the tank to protect the surface from daytime radiation and to gain the benefit of nocturnal cooling by radiation of the water

65° F drinking water produced 0.19 daily gains than the un-

surface to the cold sky. Fan operation was from 7 P.M. to 7 a.m. and was regulated by the time clock. Water was added

pound greater cooled water.

The greater water consumption, due to seem to give

the salt in the diet, did not

added comfort, nor did the show any detrimental effect on aver-

when the fan started to operate. The average water temperature

the steers any

cooling

salt

months of the

test

during the

month

age daily gain, efficiency of feed tion,

or dressing percentages.

lots did show a decrease when compared to the

(Meyer,

utiliza-

The

in carcass

salt

grade

low-salt groups

1955). mechanical refrigeration of drinking water is expensive, two cheaper methods were tested during the summer of 1954. For the first two months a larger evaporative cooling tower (4 x 4 x 14 feet) was used to cool the water. The last month water was cooled by a 36-inch fan placed horizontally 6 feet above a 4 x 4 x 4-foot insulated metal water tank. This cooling tower was much larger than the one used in 1951 and was mounted above the water tank as shown in figure et al.,

Since

26.

drinking cups

were fitted to the outside, close to the bottom of the tank so that the coolest wa-

steers receiving block

water. salt,

With the

for three days.

A

% HP pump circulated water over

the tower between 2 A.M.

and 5 A.M. The

tank held enough water to supply seven 816-pound Hereford steers with water

tower last

during

the

was 70.2° the fan

for the

first

two

F, while

was used

the water temperature averaged 71.3° F.

The cooling tower lowered

the water tem-

perature in three hours, while with the it took 12 hours for the water to reach about the same temperature. On

fan

days with low humidity, water temperature was as low as 50° F and on humid days the water averaged around 79° F. Water in the tank had a gradual 4° to 5° increase in temperature during the day. The pen with the cooling tower was wire, and the animals were compared to another group of steers in a wire pen with drinking water at 81.4° F. Both groups of Herefords were in a cooler environment and the 10° difference in water temperature did not produce a significant difference in gain. Cattle with

from the cooling tower made an average daily gain of 2.03 pounds and

the water

[47]

the other lot gained 1.94 pounds. feed, treatment,

and

these two groups are

The

effect of

The

cooled to a constant temperature of 60°, 65°, or 70° F. For the period, the aver-

efficiency of gain of

shown

wire pens

is

age superiority in daily gain per cooledwater animal was 0.36 pound exclud-

in table 10.

discussed



more

"Natural Air

fully in the section entitled

ing the 1951

Movement." In

1955

the evaporative

when salt was used in the ration. As shown by the average rate of water con-

was conducted to check the effect of 60°, 70° F, and warm drinking water for cattle. The three pens each contained seven Hereford steers, which were fed grain and alfalfa hay and had adequate shade. These animals were tested in the heavy wooden corrals. Water temperature for the warm pen averaged 87.7° F. This experiment ran from July 6 to September 14, and the steers in the check pen gained 1.29 pounds per head per

F

when

cooling tower cooled the water only to an average of 75.4° F, and the 1954 test

a further test with cool water

day, while those receiving 60°

test,

sumption in table 9, this superior weight increase cannot be due to increased water consumption, since actually the animals always drank less of the cooled water. Compared to the total metabolism animals, the cooling effect of

of the

cooled water was very small, never

total-

more than 2,831 Btu per animal per

ing



day (for animals without salt) about 4 per cent of the average daily heat production (table 9) This figure is also low when compared with the estimated lightening of heat load by shade, 1,344 Btu per hour at 100° F as reported above.

drink-

ing water gained 1.69 pounds per head

.

per day, and the animals with the water

70° F gained 1.79 pounds per head per day. A 10° difference in water temperature did not make a significant difat

A

report by Bligh (1955) shows that

ference in daily gain, but both the cool

the temperature of the blood leaving the

water pens gained significantly faster

left

than the check

lower than the rectal temperature of the

lot (table 8)

of the heart

is

only slightly

animal. This would indicate that

Results from the six years' tests were uniformly in favor of drinking water

Table 10

side

changes

in

rectal

upward

temperature in

—Average weights, daily

gains, and food consumption of seven Hereford steers in a wooden corral and seven Herefords in a wire corral (June 24-September 16, 1954)

Item

Av.

initial

weight

Av. final weight

Wooden

Wire

corral

corral

corral cool water

Lb.

Lb.

Lb.

815 942

814 977

816 986

Av. daily gain

Oat hay Feed per 100 lb. gain Oat hay = 35%

*

16.8

16.4

1.1

1.1 (pellets)

barley,

15%

867 56

1085 72

molasses dried beet pulp,

[48]

Wire

1.94

1.51

Av. daily feed (pellets)

* Pellets

re-

35%

alfalfa hay,

and 15% oat hay.

2.03 17.4 1.1

860 53

sponse to external heat stress indicate changes of a similar magnitude in "deep body temperature." Since body temperature is a good index of the external heat stress on an animal, a series of body temperatures was taken on four Hereford steer calves to study the effect of cold (60° F) and hot (87° F) drinking water on the body

|E CO

v?-o

te "73

w-^

is

TO

c

o*?

Nw Tiro

c o

S.fe

s

>

o

2

W

O

a

probably other physiological reasons besides heat loss which account for the increased gains due to the cool drinking water. These experiments demonstrate the significance of drinking water as a part of the heat-regulatory

mechanism

Ttf"

fe & O®

co o ^ o o tH tH

Tji

UP **

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io CO CO

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tjJ

tjJ

r-l

to p.m. p.m.

iter

tion of

cooling effect on the animals, there are

tf)

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amed

reduced temperatures 1.55°. Although the cool water has a decided

q (N o o tH tH

o o tH tH

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test

body temperature for the warm water was 0.35°, while the cold water

"^ CO ^" CO

t-J

^ o o tH tH

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summer show

of time. In this case the average reduc-

rH id

t-H

q q id o o tH

» CO

«o «o

and others run during the that there is some reduction in body temperature when either hot or cold water is consumed. Cold water has more effect on body temperature than warm water and for a longer period

q ih «* ^ o o tH tH

fa o

cated in table 11.

This

o o tH

CO tH IO id

CO*-*

temperatures. Getting the calves to drink

about the same amount of water and to behave alike was a problem. On September 1, 1955, with air temperature at 108° F at 2:00 p.m., a very good test was conducted with all parties cooperating. At 7:30 a.m. the four calves were fed alfalfa hay in a corral without water but with shade. Then at 12:15 p.m. all four calves were tied up in the shade and their body temperatures recorded; they were then allowed to drink, and a series of body temperatures was taken as indi-

*

2-°

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o

p

00

c o „

fe.

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2 ho© oo

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.

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£

ofc

of

Perhaps the cool water cools the food mass in the rumen so that the heat of digestion is slowed down, or it may cool the thermoregulatory section of the brain, with the cooled blood bringing the whole body closer to thermal neutrality

cattle.

Pci

o

t00

M

^-v

fa

O

O CO,

CD CD

ts

for several hours. eS

is

[49]

tH CN CO

2o

THE TESTS

Practical use of is a definite

SHOWED

water

aid in beef production

Water

number

liquid as well as the highest latent heat

Although they enjoy the water and in most cases gain slightly more than the check animals, the increases in gain do not have the significance found in other methods of cooling. For four tests where

methods of using

weight-gain data are available, the aver-

water for cooling livestock were tried.

age increase in daily gain has been 0.14 pound. Theoretically, water has many

as a cooling agent has a

of advantages;

able

it

by ditch or

is

cheap, easily avail-

pipeline,

and has the

highest heat capacity of any of evaporation. Several

common

Sprays

fine attributes as a cooling agent, but

Five different experiments were con-

cooling animals by sprays has not proved

ducted in which sprinklers or sprays in various ways. Wetting beef

too satisfactory in the tests conducted to

were used cattle

with water definitely reduces their

body temperature some 1.5° and their respiration rate some 20 or more respirations per minute. Animals have to be educated to the use of a shower by playing a garden hose over

them.\When

have been provided where they pass through from drylot to pasture, "boss" animals seem to take over and the other animals do not get sufficiently shower

stalls

moist to be benefited./ Animals appear to receive more benefit from coarse sprays than from foggers.

Fig. 27.

courage

A

date.

So

far, the

for this

is

only logical explanation

the rise in humidity which

comes from the sprays themselves and from the evaporation of water from the surface of the cattle. Sanitation would also be a real problem if sprinklers were used on a large number of animals in a feedlot. Figures 18 and 20 show two methods of using sprays to cool cattle.

Cooling Shade Surfaces Tests were run to of shade

compare two types

— one with a sub-roof of galvan-

ized iron

which was kept wet with water,

concrete drinking tank with shade. The shade should not be large enough to en-

cattle to stand

near tank for shade.

[50]

the other with a sub-roof of burlap kept

wet with a system of sprinklers (fig. 9). Instrument recordings showed these two

environments to have a cooler surrounding, roof and ground, than did the check shade, but the increases in animal gain were not significant enough to justify the high construction cost; furthermore, the burlap sub-roof left much to be desired as to sanitation. Here again, humidity may have had an influence on the gains

ground and not used as part of the corral. This does not cool the water from the ditch, but it does keep it from getting any hotter. Shade over the water tank will

keep water 2° to 3° lower than

that held in tanks in the direct sunlight.

This shade should run east and west, shading the tank for most of the day,

and should be

animals

away from

Cooled Drinking Water

Much

of the water used for drinking

comes from the Colorado River. During the

summer

the temperature of drinking

water from this source

is

about 90° F.

Since the water was so warm, nine ex-

periments were conducted to see cooled to 65°

F by

if

refrigeration

help the animals keep cool.

Two

water

would

of these

were complicated by other factors, but seven tests gave an average increase

tests

in daily gain of 0.36

pound

for the cool-

water group; four of these experiments

were significant at the 1 per cent level; one was significant at the 5 per cent level. The range ran from 0.19 to 0.50 pound increase in gain.

made with both 60° and F water and resulted in no differ-

Tests were

70°

ence in gain between the two tempera-

tures/Cooling of water by refrigeration may be too expensive for the average feedlot, but there are several inexpensive ways to provide cooler water for cattle.^

Water pipes should be kept under-

[51

enough

shade

to

vide enough shadow for a few of the

"boss"

of the cattle.

just large

the tank. Larger shades sometimes pro-

who keep

the water.

the

others

Tanks with

false

bottoms that hold only 8 to 10 inches provide cooler water, since the water cooled by surface evaporation does not sink out of reach of the animals when it cools. Figure 27 shows one of these tanks. In this case the pressure system is shaded, which is also a help. Shallow tanks are easier to keep sanitary and do not leave much water in the corral when it is cleaned. Deeper tanks, however, have the advantage of providing water for a longer time if the water system should break down. The tests have shown that cooler water is a definite benefit to cattle, so whatever can be done toward keeping water cooler should be a benefit. The reason for cool water increasing daily gains is not definitely known, but it does keep body temperatures a degree or two lower for several hours after a drink. Animals do not drink more cold water than warm; in fact, in most cases they drank a gallon or two less per day.\Salt used with feed to increase water consumption did not result in greater weight gains.

AIR

MOVEMENT AND TEMPERATURE

Air has a complex influence on the comfort of animals. The evaporative exchange of heat between an animal and air is influenced by both rate of air

movement and condition perature and humidity)

exchange

controlled

is

movement and

.

(tem-

of air

ence between animal surface and

by

is

affected indirectly

movement and temperature

air

air.

be-

cause of the influence these have on ani-

to the

velocity

Even though the relationship between and the several modes of heat trans-

fer is

air

wind

rative cooling.

by

of

the greater

there exists a greater potential for evapo-

air

rate

With

animal.

Convective heat

the temperature differ-

Radiation exchange

exchange from the surroundings

complex, air can be used effectively

for cooling beef cattle. results

of

Some

investigation

this

of the best

were ob-

tained by lowering the air temperature

and increasing

its

velocity

over

the

animals.

mal surface temperatures. Little

is

known

rate of moisture

of the vaporization

from beef

cattle.

Studies

with dairy cattle at the University of

Missouri (Thompson, Yeck, et al., 1954) that under conditions of in-

indicate

creased air movement, convective cooling

primary. The use of water sprays

is

and shower baths (page 34) was an

at-

tempt to increase the evaporative exchange of heat. As long as air temperature is lower than the surface temperature of an animal, air has a potential convective cooling effect (page 10). The surface temperature of an animal increases with increasing air temperature but at a slower rate so that the temperature differential that

controls

creases

For

as

dairy

air

convective

cooling

temperature

cattle

increases.

(Thompson,

Animal heat

loss can, of course,

be

in-

creased by lowering air temperature and increasing air velocity, thus increasing

by convection. Cooling by water evaporation is economical and feasible in hot, dry climates. Most commercial evaporative coolers pass air through wetted excelsior pads. The sensible heat of air and unevaporated water is changed to latent heat of evaporation, the fraction lost air

thereby reducing the dry-bulb temperature of the air to a few degrees above

the wet-bulb temperature.

Gordon and

Perry

(1942) have described application of the evaporative or "desert cooler" to the air conditioning of

homes

in Cali-

deFig. 28.

Three-sided 16 x 24-ft. shade cooled

with 2500-cfm evaporative air cooler installed et

al.,

temperature differential is zero at an air temperature of about 103° F. When air has a temperature greater than this it then has a potential convective heating effect. To offset this decreasing temperature differential, when cooling is most needed, the velocity of the air can be increased. However, an increase in air velocity tends to reduce the animal-surface temperature and again reduce the temperature differential between air and animal surface. With a lower surface temperature there

1954)

Evaporatively Cooled Air

this

exists a greater potential for radiation

on south end. North end

is

open.

additional

An

fornia. Tavernetti (1940) studied the cooling of poultry houses by this means.

cooler with a rated capacity of 2500

Desert coolers applied to cooling beef

was

cattle

pose a special problem under Cali-

fornia methods of management, for the structure

must be open enough for

in-an-out

movement

free

of the cattle.

In 1948, an evaporative cooler was used under a 16 x 24-foot shade, with the area enclosed except for the north

28). The walls were of hay between woven-wire fencing nailed to both sides of 6 x 6-inch posts. side

(fig.

packed

The roof was aluminum

sheets laid over

insulation.

installed

evaporative

cfm

under the south end of the

shade, near the roof line.

A

galvanized

iron shade, 16 x 24 feet and 10 feet high,

was used as a check on performance. The evaporative cooler, usually operated from 9 a.m. to 5 p.m., provided approximately one air change per minute. Continuous records were obtained for air temperatures and relative humidities, inside and outside (four hot days, shown in fig. 29).

The dry-bulb temperature

of

was reduced 15° to about 5° above

the air at the fan outlet

20° by the cooler,

boards, with a 3-foot layer of hay sup-

to

ported on woven wire beneath

the wet-bulb temperature of the outside

12

M

Aug.lG Fig. 29. Air

12

A\

it

for

I2M

I2A\

Au^3l

I2M Sept.

12 A\ 1

12

N

Sept. 2

temperature and relative humidity outside and inside of 3-sided shade cooled with in 1948. Vertical grid indicates periods of fan operation. Recording instruments

"desert" cooler

were located at center

of shade, 3 feet

above ground.

[53]

air.

However,

since

this

quickly mixed with the

cooled

warm

27 days they received daily 1 pound of ground barley per head in addition. For the Herefords (429 pounds average ini-

air

under the shade and received heat from the walls and cattle, the inside temperature was rarely as much as 10° cooler than the outside temperature, and never more than 10° cooler. It will be noted in figure 29 that the greatest reduction in air temair

tial

weight) average daily gain per ani-

mal was 1.05 pounds under the cooled shade and 0.69 pound under the galvanized

shade,

iron

a

difference

pound which may be

of

0.36

attributed to the

perature occurred at the hottest time of

cooler air or to the increased air move-

the day.

ment. The Brafords showed no significant difference in gains (table 12).

Fan-induced air motion within the shade increased heat loss by convection when the air temperature was below 102° to 105° F. (Above this temperature the surface temperature of a shaded animal may be below air temperature.) The air velocity was about 850 fpm at the fan outlet and 300 to 500 fpm at the shade center 3 feet above the ground. Near the shade walls and toward the open end, it varied between 50 and 100 fpm. The cattle preferred standing where the air velocity

was

greatest,

Both Herefords and Brafords entered shade as soon as the cooler was started in the morning, leaving only occasionally to eat and drink, usually between 1 and 2 P.M. About 4 p.m. or later on extremely hot days, the animals would leave the cooled shade and lie in its shadow, where they were exposed to the the

cool sky, for greater radiation heat loss.

by Refrigeration

Air Cooled

which of

In 1953 a small building was con-

course was also the region of lowest air temperatures.

(14x16

structed

feet)

and insulated

with bales of hay and building paper

Ten Herefords and four Brafords used

(fig.

in a 54-day feeding trial (July

28 to September 20) were divided into two groups equal in numbers and breed proportions: seven animals under shade constructed and cooled as described above, and seven under an uncooled, galvanized iron shade. Both lots received all the good alfalfa hay they would eat, in mangers outside the shade. During the last

A

30).

frigeration

mechanical air-cooled re(about 3 tons) was

unit

used to cool this room and was set to cool it to 65° F. However, because of the high summer temperatures the room temperature usually only cooled down to 70° or 75° F.

An

electric clock started the

cooler at 2 A.M., and at 6 A.M. the four

840-pound Hereford steers were put in the room and fed alfalfa hay. The ani-



Table 12- Comparison of weights and gains of Hereford steers cooled with a desert cooler (July

28-September 20, 1948)

Number Type

of

shade

of

Herefords

Galvanized iron roof Desert cooler

Average*

Average

Feed per f

initial

final

daily

weight

weight

gain

100 pounds gain

(lb.)

(lb.)

(lb.)

(lb.)

0.69

1230 1158

Average*

430 428

5 5

467 485

1.05

* Average weight and gains are only for the Herefords since there was no significant difference between the 2 Brafords in each pen. f Feed per 100 pounds of gain includes feed eaten by the Brafords.

[54

Fig. 30. Air-cooled shelter

used for night cooling of four Hereford

steers, Imperial

Valley Field

Station.

mals were left here until 10 A.M. when they were locked out of the house but had plenty of shade in the corral. Previous observations had indicated that cattle will do well, even though daytime temperatures are 110° F or more, if they can cool off at night for a few hours with temperatures around 65° F. This test ran from June 30 to September 22, and the cattle only gained 0.93 pound per day while the check steers gained 1.18 pounds. A hygrothermograph in the house showed the average temperature in the house to be 74° F

and the

relative humidity 59 per cent during the time the animals were in the structure. This is about the point where

body temperature of crease. Although the

cattle cattle

begins to

in-

enjoyed the

cool house, the capacity of the refrigera-

was not large enough to animals sufficiently to be of benefit. Apparently the heat load posed on the cooler by the four

tion unit

the

pound

cool

any im840-

Natural Air

When

the

daily

gain

increased daily gains of beef steers. Differences in daily gains were

convenience,

animals entered the house.

moved [55

in

were first noticed between cattle fed in heavy wooden corrals and those fed in wire pens, these differences were thought to be due primarily to the radiant heat load from the corral fences. Black-globe thermometer readings indicated heat loads of as much as 10 Btu per hr. per ft." of animal surface less in the wire pens, benefiting the animals about as much as lowering the air temperature 4° (comfort equation, Raber and Hutchinson, 1947). Since the air temperature was about 2° lower in the wire pens to start with, and with a lower heat load, the animals were in an environment that was in effect 5.5° to 6° less. Later data have shown that wire pens have greater air movement than wooden corrals, and mechanically increasing the air movement has proved to be very beneficial in

was too much, as the temperature began to rise as soon as the steers

Movement differences

first

noticed in 1953 when, as a matter of

one

lot

of

to a wire

pen

at

7 steers was some distance

Fig. 31. Picture

the wire pen used

on in

left

shows the construction of the main

corral, while the right picture

from the main corral

(fig.

31).

was

It

Five other animals, not included in

1953 experiment, were fed hay and warm water at the main corral, and it was difficult to keep them on feed as soon as they were moved to the wire pen (July 28 to August 24) their food consumption increased, each consuming 11.2 pounds of concentrate per day, as compared to only 9.3 and 7.1 pounds for lots receiving cold water and warm water in the heavy wooden corral.

not realized at the time that the differ-

this

ence in environment would be enough to

grain with

During the month of July made a daily gain of 1.76 pounds, but when they were moved back

affect gains.

these steers

to the

main

corral all animals lost a

little

same weight for the month of August. The month of September was cooler and all lots made good or remained the

daily gains. Fig.

shows

these environmental studies.

32A. Shades and corrals used

in

the

test. This

corral.

':/%

[56]

;

picture shows

aluminum shade

in

wooden

groups of Hereford steers were fed pen during the summers of 1951 and 1952. Gains were 2.42 pounds for some rather thin steers averaging

each pen. The tank in the wooden corral was not shaded during the first month, but was shaded during the remainder of the test. Shade was provided for the

800 pounds, and 1.79 pounds for some rather fleshy 1,000-pound steers. The dates of these tests were July 2 to September 12 and July 10 to September 3.

tank in the wire pen throughout the

Instrument readings, as noted above, indicated a comfort advantage for the wire pen due to differences in air tempera-

tank in the wooden pen. The other wire

Two

in this wire

ture

and velocity and

to differences in

radiation from surrounding surfaces.

An

experiment was designed to check and run during the summer of 1954. In the spring two wire

these observations

test.

This tank had a false bottom, holding only 8 inches of water (28 gallons).

There were 110 gallons of water in the pen had the cooling tower for drinking water, discussed on page 47. One wire pen and the wooden corral had a microweather station continuously recording air temperatures and wind velocities. The temperature-sensing elements for the recorders were installed near the centers

pens, 35 x 60 feet, were constructed in

of

an irrigated alfalfa field near the wooden corral. In each pen there was an 18 x 35 foot hay-covered shade. The wooden corral was 50 x 50 feet with an aluminum

painted white, with anemometers on top

The floors of all three Each pen provided 90 sq. ft. of shade per animal, which was felt to be more than adequate. Views of the wood and wire pens and their shades are shown in figure 32. Circular concrete drinking-water tanks 30 inches high and shade 18 x 35

feet.

corrals were dirt.

36 inches

Fig.

in

diameter were installed in

the

corrals

in

two small

shelters,

(fig. 5). This instrument shelter was about 30 inches above the ground. Seven Hereford steers averaging 814 pounds were placed in each pen and fed a pelleted diet consisting of 35 per cent alfalfa hay, 15 per cent oat hay, 35 per cent barley, and 15 per cent molassesdried beet pulp. During the first 28 days of the test both lots developed an appe-

wooden mangers and

corral

fences, but with the addition of 1

pound

tite

for the

32B. This picture shows a hay-covered shade located

alfalfa field.

[57]

in

a wire pen surrounded by a green

of oat

hay per day

level. The cattle gains in the wire pen with the cool water were not

tendency was

this

per cent

eliminated.

Weather data for the summer of 1954 1. Recorded temperature extremes were 60° and 117° F. Temperatures fell below 70° F on 17 nights. The mean temperature for the 84day feeding period was 90° F and the mean relative humidity was 39 per cent. There was one period of 15 days when

when compared

significant

to the daily

gains of the animals in the other wire

are presented in table

pen.

Average diurnal temperatures for the period of the experiment (June 24 to September 16) for an outside weather station,

wooden

corral,

and the

relative

humidity

and wire pen, weather

at the

the night temperature did not drop be-

station are presented in figure 33. Aver-

low 80° F.

age temperature was 90.0° F at the outside weather station, 89.5° in the wood corral, and 85.7° in the wire corral. In

Daily gains, food consumption, and

economy of gain are shown in table 10. The animals in the wood corral had an

the morning, temperatures at the

average daily gain of 1.51 pounds while

corral ran

made

those in the wire corral

dif-

ferences between the wire pens and the

wooden

corral are significant at the 1

60

110

105

—\

'

\ 100

wood

higher than at the

little

weather station, but were lower in the afternoon. Temperatures at the wire pen, from 7 to 9 a.m., were the same as the outside weather station, but were somewhat lower for the remainder of the day.

a gain of

1.94 pounds, and those in the wire corral

with cool water 2.03 pounds. These

a

\



Wood (

^^

corral

per2

j^>-

1)

"Weather

°^^

/ /

statioi?

^temperature



55



50

u 45

g95

^ l

Q.90

e Relative

t 85

^"Veatfeer 80

staTioi?

H551 a 30

ia

\

75

70

\/ \, \ /\ / \^^Ov M,

l?urr2idiTy

at

-r-

1

ii-ii

i

6 Fig. 33. Air

1

12

temperatures

in

J

mVi

i

Moor wood and

Vire pen 1

6

i

i

i

(

i



2)^*

pen.

i.i

i

12

i

i

25

20

Aid.

wire corrals and at outside weather station. Relative

humidity at outside weather station.

[58]

Wire-pen temperatures averaged 4.3° lower than at the weather station and 3.8° lower than in the wooden corral. Aver-

only cover the

wooden corral during the third month. Average wind velocity for the third month at the wire pen was 1.79 mph. The animals

.

Average diurnal wind velocity is presented in the upper section of figure 34. The wooden corral had an average wind velocity of 1.11 mph while the wire pen had 2.43 mph. The greatest difference usually came around 5 p.m., with an air

in the wire

pen had a

cooler environment from lower radiation

from lower air temperature and greater air velocity. Radiation measurements at the center of the shadows, made with globe thermometers on August 28 and 29, indicated that the radiation heat load was less in the wire pen as well as

mph for the wooden cormph for the wire pen, a

velocity of 1.34

and 3.36

first

in the

but only 20 per cent during the hottest

ral

period, as

test

age relative humidity at the weather station ranged between 20 and 60 per cent part of the day (usually around 3 p.m.)

mph. These records two months of the the wind recorder broke

difference of 2.02

3.5

3.0

>25

Wire pen

5

I

I

I

I

Vood

u 90

o

(

I

I

I

I

I

per2 2)

I

I

I

>^

corral (pert

I

1

I

^Nv

Water 'supply

Q.

E I-&5

u^*

^r

"

^N*.

^^^



L.

2 >ao

j?---^';'

75

111

1

Wire per2(per2

1-

1

1

1

1

I

I

!2Noor2 Fig. 34.

Upper: Average diurnal

drinking-water temperature

in

1

6

i

K^

i

i

i

i

1

i

i

i

i

l2Aid.

wood and wire corrals. Lower: Average diurnal and temperature of water supply.

air velocities in

the two pens

I

>*v

2)

[59]

by as much as 9.5 Btu per

hr, per sq.

ft.

of animal surface. Radiation

and reflection from the wooden fence were high. At noon a horizontal reading with a directional radiometer pointed north in-

dicated a radiation intensity of 212 Btu 2

per hr. per

compared If the

ft.

wooden

in the

corral, as

wire pen.

summer thunder showers. These experiments show definitely that proper equipment for cattle can reduce thermal heat load and increase daily absence of

gains significantly.

radiation and air-temperature

effects are

combined

into a single rep-

environmental

resentative

mean

(average of

and

in the

163

to

Weather during the summer of 1954 was cooler than average, and the humidity was a little lower because of an

radiant temperature

air temperature),

Mechanical Air Movement Since there was a difference in air

temperature

then the repre-

movement

of 1.32 mph, between wooden and wire pens, and the difference in daily

sentative environmental temperature in

gain could be attributed to either in-

was about 5° less. Similar comparisons of environment during the late summer of 1953 (but at a different location than the 1954 test) showed the environmental temperature in a wire pen

creased air

the wire pen

to be 5.5° to 6° lower than that in a

movement

or to a reduction

in radiation heat load,

visable to

wind on

it

was

felt

ad-

study the cooling effect of

cattle

by mechanically

increas-

ing the air movement.

the effects of corral construction upon

During the summers of 1955 and 1956 trials were conducted with Hereford steers for 70-day periods, from July 6 to September 14, 1955, and June 27 to September 5, 1956. Seven steers were fed in each of two similar pens, except the pen without the fan had only five steers in 1956. Two steers were lost to

radiation heat load showed even greater

the experiment at the very beginning.

wooden

feeding

corral.

Radiation

observations

were

rather late in the season on days the

97°

made when

maximum air temperature was only F (as compared with a season's

average of 103.6° F)

differences

.

It is

most

during

probable that

of

the

test

period.

The drinking-water temperatures for shown in the lower section of figure 31. The wooden corral had the two pens are

an average daily water temperature of 86.3° F, while that of the wire pen was 81.4° F, and the wire pen with the cool-

The average weight of animals at the start of the test was 670 pounds in 1955 and 651 pounds in 1956. Both pens were about 50 x 50 feet, and each had a 17 x 32-foot shade that was 10 feet high (about 78 sq.

ft.

of shade per animal).

by evaporation, and

The drinking water was uncooled (about 87° F). The animals were fed twice daily and were given all they would clean up between feedings. One pen each year served as a check pen that is, a pen with no artificial movement of air through it. For the second pen, a 42-inch barn-ventilating fan (17,000 cfm capacity) was mounted on

the cool water in a shallow tank remains

top of the 6-foot board fence along the

ing

tower

averaged

70° F. Tap-water

temperatures did not vary much throughout the 24-hour period or through the period of the experiment, staying very close to 93° F.

Air movement with low humidity cools the drinking water

available to the cattle because

it

cannot



side of the corral

sink out of reach. However, part of the

vailing

differences in water temperature shown here can be attributed to the shallow tank

first

being located in a cooler environment (wire pen).

wind blew

from which the (fig.

pre-

35). In 1955 the

fan ran 12 hours during the day the 21 days, then continuously for the test. In 1956 the fan ran continuously. The center of the air

remainder of the

[60]

Fig. 35. This 42-inch barn-ventilating

fan (17,000 cfm capacity) was used to cool the cattle by

convection.

stream was directed down into the corral at about the center of the shade. Air velocity on the animals at the center of the shade was about 350 fpm or about

4 mph. In 1955,

at the center of

each

mph), while at the weather station movement was 1.75 mph. Figure 37 shows the diurnal wind velocity for these three locations. There was no dif(3.7

the air

ference

in

relative

humidity

between

pen, at animal level, there was a wire

these two pens; the relative humidity at

pen enclosing a small weather station (fig. 5). These were not used in 1956. These portable weather stations recorded

The average

the air temperature, air velocity, rela-

the weather station

pens and

was 46.4 per

cent.

air temperatures in the

two

weather station, over the entire period, were 87.5°, 88.8°, and at the

humidity, and black-globe thermometer temperatures at animal level. As shown by the chart, (fig. 36) the distribution of air was quite good and air movement was increased over prac-

tive

tically the entire pen.

When

these air-

velocity readings were

made, the average velocity of air in the check pen was 50 fpm. Animals naturally stayed under the shade most of the day and so were exposed to a good breeze all day. Since the weather records were not kept for the two pens in 1956, the records reported are for the 1955 test, but weight gains, feed consumption, and weather station records are reported here for both years.

Over the entire 70-day period (1955) the air velocity at the center of the shade

pen was 55 fpm (0.63 mph) In the fan or windy pen it was 325 fpm of the check

Fig.

36.

Air velocity distribution

in

windy

pen, Imperial Valley Field Station, 8:30 a.m.,

June 30, 1955.

[61]

45

40 Fan pen

v^ £U 3.0

2 2.5

UJ 2.0

> <

Weather station

1.5

Fig.

37.

Diurnal air

velocity in the fan

1.0

Check pen

pen

and the no-fan pen and at the weather station.

1

I

1

I

I

1

I

I

1

I

I

1

1

4

I2M

10

TIME

90.3°

F

pen,

and weather

Figure 38

station.

shows these differences for the three cations. In the

lower temperatures are more marked during the hours of darkness. The tem-

windy

respectively for check,

perature in the fan pen was only about 2° lower than at the weather station.

lo-

morning there was very

On August

11, 1955, and September Hereford calves were used to check the cooling effect a fan has on body temperatures. Air temperatures at 2 P.M. were 103° and 106° F, humidity

difference in air temperature, but

little

from noon

8 A.M.

until approximately

differences of 1° to 5° are noted,

11, 1956, four

and

they are lower at the corral in the check

pen than

weather station. These

at the

-

105

/y'~"m"~'~'\\

-

/y U.

A

~ 95 -


^Fan pen ture,

\\ \


'0\ *

II ;

v

70

XX

\ '•.

if :

5:

Fig. 38. Air

v\ \ \

II

TEMPERATURES

AIR

\

\

•'

*. *•

S

i

X

85

//

y

^ >v

\

/

^V

**•.

/^.^

/»•/

>

/

/

75 _

••...„.

'••*

/

\

RELATIVE HUMIDITY

\

Weother stotion-;.^

- 30

1

1

1

1

1

1

10

1

1

1

1

!

I

1

i

i

i

i

i

I2N

TIME

[62]

I

i

i

i

i

I

temperahumidity

the fan pen,

in

the

no-fan pen, and at the

weather 60

2 80 —

5

relative

station.

26 and 18 per cent respectively. At about 9 :00 A.M. all four calves were tied in the shade without any air movement, and body temperatures were taken at 9:30 A.M. Right after this two calves were moved under the shade where the fan was blowing, and body temperatures were taken as shown in table 13. Both shades and pens were identical. Body temperatures were definitely lower for the calves under the fan. During the time the body tempera-

Table 13

were being taken in 1955, skin temperatures were also measured. Each skin-temperature figure shown in table tures

14

is

an average of six readings. Air

velocity during this test averaged

fpm

in the

windy pen and 20 fpm

pen without the

As long

400

in the

fan.

as air temperature

is lower than the surface temperature of an animal, wind has a potential convective cooling effect. If, however, the air is

warmer than the

—Body temperature

surface, the effect re-

differences of Hereford steers

with and without a fan* August

11,

1955 f Body temperatures,

Calf

Calf

No.

weight

°F.

9:30 a.m.J 10:00 a.m. 10:45 a.m. 12:15 p.m. 2:30 p.m.

Fan

1

2

602 621

Average

No fan

3

4

600 554

Average

104.3

104.0

103.7

103.8

104.4

104.2

104.8

104.2

103.9

104.2

104.25

104.40

103.95

103.85

104.30

104.6

104.8

104.7

105.6

105.8

103.8

104.6

104.8

104.8

105.1

104.20

104.70

104.75

105.20

105.45

September

11,

1956f Body temperatures,

Calf

Calf

No.

weight 9:30

Fan

5

6

754 692

Average

No fan

7

8

Average * Air

587 690

a.m.:}:

°F.

10:00 a.m. 11:00 a.m. 12:00 noon 1:00 p.m.

2:00 p.m.

103.8

104.4

104.8

104.4

104.4

104.6

102.9

103.6

103.8

103.3

103.5

104.3

103.35

104.00

104.30

103.85

103.95

104.45

102.4

103.4

103.0

103.7

104.0

104.1

104.4

106.2

105.8

105.2

106.2

106.1

103.40

104.80

104.40

104.45

105.10

105.10

movement averaged around 400 fpm

in the fan pen

and about 20 fpm

in th 8

no fan pen during the

tests.

p.m. air temperature 103°, humidity 26 per cent; Septemb er 11, 1956, 2 p.m., air temperature 106° humidity 18 per cent. t Right after their body temperatures were taken at 9:30 a.m. two calves were moved to the shade in the fan pen, the other two stayed under the shade in the no fan pen. t

August

11, 1955, 2

[63]

Table 14



Skin temperature difference of Hereford steers with and without a fan (August 11, 1955)

C Air temperature F.

Air velocity

(ft.

per minute)

Time *

t

20

400

Difference

(°F)

(°F)

(°F)

9 :50 a.m

92.9

92.5

98.9

96.1

2.8

10:30 a.m

94.3

95.6

102.6

96.8

5.8

12:30 p.m

97.0

98.4

102.7

101.2

1.5

2:10 p.m..

99.0

103.5

104.4

101.8

2.6

* Air temperature in low air velocity pen. t Air temperature in high air velocity pen.

Table 15

—Cooling

effect of

(July

a fan on Hereford steers

6-September

14, 1955)

(June 27-September 5, 1956)

1956

1955

Fan

Number of animals Av.

initial

weight

Av. final weight

(lbs.)

(lbs.)

Fan

7

7

7

669 831

669 759

645 813

Check

5

657 788

2.32

1.29

2.40

1.87

Barley

5.07

4.23

4.65

4.73

M.D.B.P.* Alfalfa hay Oat hay

2.33

1.92

2.32

2.37

12.07

9.12

9.86

9.07

1.94

1.91

2.35

2.19

Total

21.41

17.18

19.18

18.36

hay Oat hay

219 100 521 84

327 149 706 148

193 97 410 98

253 127 485 117

Total

924

1330

798

982

Av. daily gain

(lbs.)

Av. daily feed

(lbs.)

Feed per

100-lb. gain

Barley

M.D.B.P Alfalfa

*

Check

Molasses dried beet

pulp.

[64]

verses so that there

is

potential convec-

bers at

chamthe University of Missouri have

shown

that the surface temperature of

tion heating

from wind. Studies

in

mean

air

temperatures for 1956 were

the lowest during the 10 years of testing.

dairy cattle increases with an increase

Mean relative humidity was 36 per cent, was close to the lowest of the 10 years. There were 21 days in the 1956 period

in air temperature, but at a slower rate

with

so that the surface temperature

is

always

above air until both come together at about 103° F. Whether this 103° F holds good under natural conditions is not known, but there could be a variation from this point depending on relative humidity, velocity of air movement, and the

amount

of moisture lost through the

and 14 show body temperatures and skin

skin of cattle. Tables 13 that both

temperatures of the calves were lower in the pen feet

where

air velocity

averaged 400

per minute.

Water consumption during these two years did not vary much. Fan-pen ani-

mals in 1955 and 1956 drank 13.8 and 11.9 gallons per head per day, while the low-air-movement-test animals drank 12.4 and 12.2 gallons respectively.

Weather data for the test periods of 1955 and 1956 are shown in table 1. Although the mean temperature of 90.3° F in 1955 was not the highest during the 10 years of these tests, the average minimum of 78.3° F was higher than any other year. Only five nights had a minimum temperature less than 70° F. In 1955, one of the more humid years, the mean humidity was 46 per cent. Average maximum, average minimum, and

night temperatures lower than 70°F. The average daily gain for the

animals in the check pen in 1955 was 1.29

pounds per day per animal, and

they consumed 1,330 pounds of feed for

each 100 pounds of gain. Animals exposed to the additional wind from the fan gained 2.32 pounds, and it took only 924 pounds of feed per 100 pounds of gain. In 1956 the differences were not as great; the check pen gained 1.87 pounds per head per day and the fan group gained 2.40 pounds. Economy of gain for the fan pen and check lot was 798 and 982 pounds respectively. Both years' differences were significant at the 1 per cent level. The feed intake of the fan pens was higher than the check pens

during both years (table 15). Animals were weighed every 14 days in 1956, but the weight gains

and

air

much correlahumid weather in

temperature do not show

However, the 1955 no doubt raised the night temperature and probably accounts in part for the very low daily gains of the check-pen animals. Lower temperatures and lower humidity in 1956 probably are factors in

tion.

higher daily gains of the animals in the

check

[65]

lot.

THE TESTS

SHOWED

That mechanical or natural air movement aids thermal comfort

Air movement can be increased in two ways. The

crease of 0.43

pound

in daily gain

when

method is to allow the natural air currents and wind free access to the corral area by constructing

to animals in a

39 shows

this airy type of construction.

the pens with wire, cable, sucker rods,

Working

corrals should be built with

pipe, etc.

first

The second method

is to

use

fans to increase the air flow around the

animals. Both have given a larger in-

the animals in a wire pen were

wooden

compared

corral. Figure

wood, since there is enough stretch in wire and cable to allow animals to escape if they become crowded and excited.

crease in daily gain than most other cool-

Mechanical Air Movement

ing methods so far tested.

Natural Air Natural creased by

Movement

air movement can be inmore than 1 mile per hour in

the Imperial Valley construction.

One

Fig. 39.

by proper corral showed an in-

test

Mechanical air movement by the use two summers; the fan resulted in an increase in daily gain of 1.03 pounds the first summer, and 0.53 pound the second summer. Both pens used in the test were built of wood. of fans has been tested

Fence corner showing one type of cable corral construction.

[66]

air movement in the pen with a fan averaged 3.7 mph, while that in the check pen averaged 0.63 mph (air movement checked first year only). The fan ran continually and was placed on the south

The

side of the corral so as to assist the pre-

wind (fig. 35). Further work needs to be done to determine if the fans need to be run only part of the day, the differences in gain

fan and cattle without a fan have shown the ones with the fan to have a lower

body temperature. This type seems

Cooling Air by Evaporation

A

vailing

a fan will

make

in a wire or cable corral,

and the velocity of

air

movement most

keeping the animals cool. Recent studies by Kibler and Brody (1950) have shown that European cattle lose a considerable amount of water effective for

through the skin even though they are not classified as sweating animals like the horse or man. Increasing the air movement around the cattle may facilitate the evaporation of this skin moisture which would carry away excess body heat. Several tests in which body temperatures were taken of animals under a

of cooling

to be quite effective.

"desert cooler" under a shade with

(fig. 27) was tested with Hereford and Braford beef cattle.

three sides enclosed

The Brafords did not show a

significant

difference in gain, but the Herefords un-

der the cooled shade gained 0.36 pound

more than

the check animals.

The

in-

crease in gain was good, but the cost of

construction and maintenance of shades of this type

coolers"

is

and the cost of the "desert

higher than some other cool-

ing methods tested. Temperatures in the

shed were rarely

than 10 degrees

less

cooler than the outside air temperature.

As

experiments have shown, the inmovement may actually have been of more benefit than the 10° cooler later

creased air

air.

RADIATION An

exposed to radiation from everything "within sight." The sky is an important source of radiation because

animal

it is

is

so large. Parts of the sky, how-

North Sky Directional

means

of

radiation

the

tensity at the surface of the earth

ever, are cooler than an animal's surface

areas of the sky.

and may be used advantageously

the sky,

as a

provide

radiometers

obtaining

Many

from horizon

a in-

from

traverses over

to horizon, with

cold sink to absorb radiation from an

a Gier directional radiometer indicate

animal. Corral fences, because they are

that azimuth orientation has

so close, influence the radiant heat lost

upon sky radiosity throughout the hot part of the day if the instrument opening receives no direct-beam energy from the sun, and if the sky is free of clouds. Angle of elevation above the horizon is

or gained by the animal. The ground surrounding an animal is important both because it is close to the animal and is such an extensive source of radiation. These three surfaces sky, corral fences, and surrounding ground are nearly al-





important

—an

angle of 60°

little effect

is

usually

the coldest.

ways "within sight" of the animal, so

In figure 40 a series of traverses with

they are potentially important in influ-

the

encing the radiation heat load on an animal.

south and east-west orbits

directional

radiometer is

in

north-

shown

for

three different times on a cloudless day.

[67]

At 12 noon, when the radiometer target was 60° above the north horizon, the

been plotted against air temperatures obtained simultaneously 42 inches above

made

observations

the ground. All observations were

radiosity.

between 10:00 A.M. and 5:00 P.M. on cloudless days (less than 10 per cent cloud cover), during the months of July to September. A linear regression curve has been fitted to these points. Its equation is: t s =-81.9 + 1.5 t a where t s is the temperature of the sky and t a the temperature of the air. A difference of about 28° between air and sky is available as a cooling sink at an air temperature of 100° F and of about 22° at 110° F. The extent of cloud cover is the main factor controlling north-sky temperatures in the Imperial Valley. Data obtained from the Naval Air Station near El Centro indicate that during the hottest month, August, there were at least 15 days, throughout the period of 1949 to 1954, which averaged less than 10 per cent cloud cover at 2:00 p.m. It has been observed also that even when the south hemisphere may be fairly cloudy, the north sky may be clear because the

indicated the lowest sky This area had a somewhat higher intensity at 10 and 2 o'clock. The same inference can be drawn from the east-west traverse, shown in the lower section of the figure. To cool a building

by direct long-wave radiation to the sky, it would seem desirable to have all openings designed to have the greatest shape factor or seeing angle with respect to this

area in the north sky about 60°

above the horizon. By using an emissivity for the sky of 1.0, the effective sky temperatures can be calculated. In figure 41 a series of 116 north-sky temperatures, observed with the Gier directional radiometer, has

,

clouds appear to form in the area wards the Gulf of California.

The

large

number

to-

of cloud-free days

indicates a fairly reliable sink for radia-

which should be exploited

tion cooling,

in the design of livestock shelters for hot

climates.

Corral Materials In the section "Natural Air Movement" (page 66) results of feeding trials were shown to indicate that animals in a corral enclosed by a wire fence gained more rapidly than animals in a corral surrounded by a heavy wooden fence. This greater rate of gain was attributed to a more comfortable environment in the wire-fence corral. The better environment within the wire-fence corral was ,

Fig. 40.

meter

in

Traverses of Gier directional radio-

north-south (top)

tom) directions.

and east-west

(bot-

due

to:

(b)

greater

a

(a)

lower air temperature,

wind

velocity,

and

less radiation in the pen. Just

(c)

to

how much

each of these factors contributed to the unknown. In tests previ-

test results is

[68]

1

1

u 1

'

^^



"^100

o

O o o o

o o

o

o

o

90

(T LU a.

2 UJ H

o o

^r

>^

aoo

O

«°

*

v^C

_,

00

^0

/x

00

000

/

o

^r

o



o

o

/

yo

o

S^

o

/^

/

< 7n

60

50

/\v

temperature at ground

/

1



/

1

90

80

70

/

Line of equal

OBSERVED SKY TEMPERATURE Fig. 41. Relation of air

/

/

/

/

^ temperature

1/

1

1

1

40

30

/

/

/

/

/

/

»

o

y'

80

O

r

o



o

'

s^

00

o

3 H <

o

0/^

or

Oog fcftr dfir aoo

o

LU cr

Je

'

000 00

^rt>

o

o

Ll.

«/





1 1

1

to effective north sky

100

(°F) temperature 60° above

horizon.

ously described, wherein the effect on

animal weight gains of each of these three factors was considered separately (air temperature page 55, wind page 52,

ments were made with a directional radiometer to determine the intensity of energy radiated from different sources and objects in and around the wire-fence and

wooden fence 42 show

and radiation page 67), the benefits from wind were greatest, and from lower radiation, least. However, this should

was

not be considered as an evaluation of

times as

the contribution each

made

of these factors

figure

in

less

corrals.

the

much

The curves

of

that the radiant heat load

wire-fence

corral



at

2

10 Btu/hr. ft. less. Also, the air temperature in the wireas

improving the climatic environment. The levels of differences between the control and test pens, for each of these factors, were unrelated, making comparison difficult. It is somewhat more difficult to comprehend and measure radiation differences between two locations than wind in

velocity or air temperature differences.

For

this reason

made

in

1953

a detailed study was

to investigate the radia-

tion difference between wire-fence

wooden fence

corrals.

globe thermometers

Six-inch

were kept

and

blackat

the

center of the shadows of the shades in

two pens shown in figure 31. These were used to measure the radiant heat load to which an animal standing in that spot would be exposed. Radiation measure-

Fig.

Comparison of and air velocity

42.

perature,

radiation, air tem-

within the

wooden-

fence and wire-fence corrals, August 31, 1953.

[69]

Reflectivity of the boards for solar energy was determined by measuring the quantity of solar energy irradiating them

and the amount given off by them. These measurements were made with a solarimeter selective for wavelengths below 3 microns. Reflectivity of the boards was found to vary from 54 to 90 per cent, with an average value of 70 per cent. Such high reflectivity makes the board fences good potential heat sources. Solarenergy reflectivity of the ground was found to be about 47 per cent lower than for the boards. This 47 per cent reflectivity would represent the reflectivity of the wire fence comparable to the 70 per cent reflectivity of the boards be-

EAST

~^*^^^

"-^2- Wire

o





AVERAGE OF J 7

I

8

I

I

9

10

II

N.,S.,E.,aW. I

I

I2N

RADIATION I

cause animals inside a wire enclosure

L

I

TIME

Comparison of radiation from four the wooden-fence and wire-fence August 31, 1953.

Fig. 43.

directions corrals,

in

fence corral was

less,

averaging about

2° lower.

would be exposed to ground instead of the wooden fence. The high reflectivity of the ground inside the corral probably accounts for the greater radiation from the south fence (ground reflection rereflected by the boards) even though the south boards were in the shadow of the

Radiation within the two corrals was by taking a series of readings with a directional radiometer. With

sun.

the receiver of the radiometer at a height

from the spaces between the boards, as well as from the boards themselves. The actual radiation from the boards, and from the spaces between the boards, was measured in a separate series of observations. The radiation from the boards was found to be considerably greater than the radiation from the spaces between the boards. The spaces would represent

The horizontal

also studied

of 24 inches

shadow of

and

at the center of the

the shade, a series of hori-

zontal readings

was taken

to

determine

the effect of the corral material on the

radiation coming from each direction. The results of one series of reading is shown in figure 43. During most of the period shown there was less radiation,

from the wire fence. During the morning the radiation from the wooden fence on the west was highest; in the afternoon it was highest from the wooden fence on the east. The position of the sun affects the amount of energy radiated from the boards the boards became hotter, and more solar energy was reflected from them, as the sun became more normal to the boards. This was why the west boards radiated more in the morning and the east boards in every direction,



radiated

more

in the afternoon.

directional radiometer

readings of figure 43 include radiation

the effect of a wire fence because the actual radiation

from the wire

itself

would

be insignificant.

The

corral-fence

material

actually

does have an influence on the amount of radiation an animal in the corral receives. To reduce the radiant heat load on an animal a wire or cable fence

should be used for penning animals.

Surrounding Crops Ground temperature and radiation are important to the problem of animal com-

[70]

warm

fort in

climates.

The

flat-plate ra-

an instrument that measures the total radiant energy falling on it from the hemisphere above. Measurements with this instrument facing both upper and lower hemispheres indicate that energy from the lower hemisphere may be as much as 40 to 60 per cent (ratio of lower hemisphere radiation to diometer

is

upper, table 16)

as great as

from the

upper hemisphere, depending on the type of ground surface. The lower hemisphere radiation is comprised of low-temperature radiation, due primarily to the temperature of the ground surface, and reflected

energy influenced by the radiation

characteristics of the surface. Table 16

indicates

some

ferences

between

and

of the characteristic dif-

unvegetated

ground

alfalfa.

Lower hemisphere radiation was considerably less over the alfalfa field than

over bare ground. The solarimeter measures only the short-wave energy between

When

0.295 and 3.0 microns.

down

the sola-

measures lower hemisphere short-wave energy only and, consequently, only energy reflected from the ground surface. A comparison of the incoming short-wave energy from the lower and upper hemispheres indicates the reflectivity of the ground surface. rimeter

faced

is

it

Table 16 shows that the reflectivity of the alfalfa is considerably lower than that of the bare ground. Over two adjacent 200ft.-square plots the air temperature over alfalfa averaged 5° lower at mid-day than over plowed ground. At this same time the lower hemisphere radiation from the alfalfa was 30 per cent of the upper hemisphere radiation, and from the plowed field 40 per cent. While it would be impractical to maintain green vegetation under and immediately adjacent to an animal shade, except while pasturing, it may be possible to increase an animal's comfort by selection of the proper type of unvegetated ground surface. Ground surfaces vary in temperature by reason of differences in thermal conductivity, density, and other characteristics. Measurements with a touch thermocouple in the Imperial Valley in August, 1947, showed a variance in ground-surface temperatures between areas only a few feet apart. At 11 :00 A.M.

temperature was only 89° F, temperatures were observed in the sun:

when

air

following

the

Hard ground, tramped by Hard ground,

124°F

cattle

in road

129°F

Soft ground, not tramped by cattle. ,132°F

Dry rotted manure

148°F

in feed lot



Upper and lower hemisphere radiation over bare ground and over an alfalfa field as measured with a flat plate radiometer (total radiation) and a solarimeter (short wave radiation), Imperial Valley, 1954

Table 16

Upper hemisphere radia-

Lower hemisphere radiation

Reflectivity,

Btu/hr/ft 2

per cent

tion, Btu/hr./ft»

Time Short wave

Ground

9:55

a.

m

10:10a.m 1:00 a.m

Short wave

Total

Total

409 411 447

253 282 272

[71]

259 268 277

Alfalfa

201 199 198

Ground

Alfalfa

94 79 62

68 66 25

Ground

Alfalfa

37 28 22

27 23 9

During the summer of 1949 tempera-

O

00 P5 t» ff oi id oc (O 00 CC
0} fr-

ee hi

H

o

N O

tures of several types ot surfaces were

measured

)

(table 17)

to

show the great

variation that can be expected. 9

h q o w CO OS OS CD O 00 iH rH tH

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A o

i-H

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diant heat load at each location. Addi-

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tional black-globe thermometers

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effect of radiation

horizon, unshaded ground, and

upon the mometer

total radiation the

receives.

The

from

shadow

globe ther-

radiosity

(in-

cludes both temperature radiation and

from each part of the surround was measured with a Hardy radiometer. These values, for one day, reflected energy)

shown in table 18. The cloudless sky is the coolest part of the surround and has the same radiosity with respect to both shades. The radiosare

CD

Sg §1 J-

O C

OS «# lO
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ity for the

§

the shade over the plowed field

a

than for those surrounding the shade over green pasture, with the exception


43

o


other four parts surrounding

1 CO

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an integrated

each part of the surround, sky, shade,

o

a

is

•? •3

ft

T3

The radiant heat load measure of the

^

a

lo-

field.

P

CC >

10

c

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CO

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were

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During the summer of 1951 two iden12' x 12' portable shades were located in separate fields, one in an alfalfa field and the other in a plowed field to determine the effect of ground cover on environment. Black-globe thermometers were kept at the center of the shadow of each shade, at a height 12 inches above ground, to measure the ratical

CC t-

oi

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0>

r-l



of the horizon.

The

is

greater

radiosity of the hori-

*"

£

lm

3

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zon would be expected to be about the same over both fields because it includes trees, etc., that are equally on the horizon of both shades. The influence of these greater

radiosities

higher

radiant

is

in

the

over

the

reflected

ea

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ft

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heat

loads

plowed field as determined from blackglobe thermometer measurements (table 19).

A

ground cover reduce the magnitude of this source of heat. Also, ground temperature influences the temperature of the air over it, so it should be as low as possible; this is evident in the air temperatures over "low-temperature"

will help to

[72]

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Table 19 Radiant heat load determined from black globe thermometer readings, El Centro, September 11 and 12, 1951

Air temperature °F.

Time

Radiant heat load under shade

Radiant heat load over open field

Btu/(hr.)

Btu/(hr.) (sq.

(sq.

ft.)

ft.)

Grass

Dirt

Grass

Dirt

Grass

Dirt

10 a.m..

85.0

85.5

153.5

156.2

238.4

254.7

11a.m.. 12 noon

84.0

86.0

159.5

166.4

248.1

251.6

85.5

85.5

156.3

170.0

230.2

244.4

lp.m.. 2 p.m.. 3 p.m.. 6 p.m..

86.0

86.5

156.3

165.0

251.8

263.3

86.5

88.0

157.1

158.5

239.0

257.0

86.0

87.5

156.1

157.4

226.9

242.7

80.5

80.0

135.0

141.2

135.3

146.8

59.5

60.5

125.0

127.2

119.2

122.0

66.5

66.0

137.0

138.6

202.3

204.7

9/11/51

9/12/51 la.m.. 7 a.m..

shown in table 19. Air temperature 12 inches above the plowed field averaged 0.6° higher for the period shown than over the green field. During

the two fields as

the hotter part of the day this difference

was

1.5°. Direction of air

such that

it

passed

first

movement was over the green

field so the increase in air

Fig. 44.

temperature

moved over 45 feet Nearby "low-tempera-

occurred as the air of the dirt field.

ture" covers, such as clover or alfalfa,

can be very beneficial in keeping down both heat load on an animal and the air temperature. Animals on pasture have this advantage over animals held in a dry lot.

View of a feed yard using hay shades and cable fences which reduces radiation and

allows for greater air movement.

>*-*-,.

,

,„

,,

,;

^

THE TESTS

That considering radiation

SHOWED

from surrounding areas

pay off

within a wire pen to be as much as 10 2 Btu/hr. ft. less than in a wooden-fence

Reduction of Radiation



I

Three surfaces sky, corral fences, and surrounding ground are nearly always "within sight" of cattle in the feed yard and influence the radiation heat load on the animals^ Tests reported in this bulletin show that^here are practical ways of reducing this heat load...

A



corral, indicating the effect of corral

ma-

on radiation. Wind velocity in the wire corral was always greater, and the air temperature averaged about 2° lower. terial

total effect was a reduction in environmental temperature within the wire pen of 5° to 6°.

The

summer sky

^Corrals, or cattle pens, should be con-

radiosity observations taken during the

structed of wire or cable to permit free

years shows that the north sky (about 60° above the horizon) has an average temperature of 20° to 30° lower

radiation heat load on animals and the

North Sky.

series of

last ten

than ground-air temperature.

Any

cloud

cover will materially reduce the difference between north sky temperature and

ground/ How-

air temperature near the

Imperial Valley has a large

ever, the

number

of cloud-free days

which make

the north sky a fairly reliable source of

radiation cooling.

sky

is

Even when

the south

fairly cloudy, the north sky

clear because clouds appear to

may be

form

to-

ward the Gulf of California. The louver shade, discussed earlier, was one attempt to use the north sky as a cold body to which animals might radiate heat. Even though this test was not successful,

method in 1

will

better gains

in

the

authors

feel

that

this

air

air

designing livestock shelters for hot

Corral Material. The better environment in wire or cable corrals was the

to aid in reducing the

temperature in the pen. Also, build-

ings, haystacks, or

and might be

area

animals,

to

eliminate

reflected

corrals

The

made toward improving the environment was not de-

contribution each of these

termined, but each does contribute to

animal comfort. Tests

showed the radiant heat load

the

is

necessary for the roads and

but a crop planted in the vicinity of the feed yard will tend to reduce the alleys,

temperature and radiation. Figure 44 shows a feed yard that has

air

provided cattle with a cooler environment. The hay shades are about 11 feet high, which reduces radiation from the sun and still allows animal exposure to the cool north sky.

radiation.

that

Surrounding Crops. Bare ground radiate more heat than an area planted to a crop. Also, air moving over bare ground tends to become warmer than air moving across a green field. A certain amount of bare ground around

made

less

to

will

wind

and

radiation

from them

if-

result of lower air temperature, greater

velocity,

any major obstacle

should be kept away from a corral to permit free air movement through the

of cooling should be considered

climates.

movement and

The

corral fence

is

which reduces fence radiation and allows for free air movement. Haystacks and buildings are away from the corrals. Although the photo does not show it, there is a crop planted around of cable,

the feed yard.

[75]

RATIONS FOR SUMMER PRODUCTION effect of food is much ruminants than in animals with a single stomach. One of the chief maintenance requirements for animals in a cold climate is heat to keep the body warm. Roughages have a much higher relative value for heating the body than they do for productive purposes. For instance, idle horses can be wintered on rather poor quality roughage alone because of the heat produced through its

The calorigenic

greater in

digestion and assimilation.

By

the

same

token, a roughage diet during the sum-

mer would tend hotter at a time

to make the animals when they are having

balance between the produced and rate of heat

difficulty getting a

rate of heat lost.

Heat produced

in the

body following

the consumption of food

"heat increment." This

is

is

known

duced in the body by digestion and similation of food.

as

the heat pro-

As noted

as-

above, this

warm the body but cannot be used for any other purpose since the body is unable to convert heat into other forms of energy. Even with such easily

heat will

digested feed as barley, about one-third of the total energy in the digested nutri-

and hay and straw are much larger (60 per cent for wheat straw.) A summary of several tests, some conducted during the summer and others during the winter, with some groups receiving a hay concentrate ration and ents

is lost

in the increment of heat,

the losses with



Comparative gains and estimated gains of summer and winter feeding trials with Hereford steers*

Table 20

Number of animals Av. length of trials (days) Av.

initial

weight

Av. final weight

(lbs.)

(lbs.)

Av. daily gain

(lbs.)

Av. daily feed

(lbs.)

.

.

.

Alfalfa

Alfalfa

Hay Summer

Hay Summer

Warm

65

Water

Water

21 77 814 890

20 77 810 909

0.97

°F.

1.27

Alfalfa

Alfalfa

Alfalfa

Grain

Grain

Alfalfa

Hay

Summer

Summer

Grain Winter

Winter

11 131 662 890 1.74

Warm

65

Water

Water

21 75 732 849

21 75 740 877

1.58

°F.

16

84 810 1004

1.83

2.31 6.7

Barley

4.4

5.1

M.D.B.P.§ Alfalfa hay Oat hay

2.2

2.4

2.8

18.4

19.4

16.0

9.9

10.2

10.6

1.7

1.8

1.8

2.0

2.3

1.9

Total

20.1

21.2

17.8

18.5

20.0

22.0

TDNf DCP|

10.26

10.82

9.07

11.10

12.09

2.14

2.26

1.88

1.69

1.80

1.99

1.50

1.70

1.50

1.70

2.00

2.20

Estimated gain

13.66

* All summer feeding was done in the warm environment of the wooden corrals during July, August and first part of September. Winter feeding was done from January through most of May. Each test includes at least three feeding tests. f Total digestible nutrients. t Digestible crude protein. § Molasses dried beet pulp.

the

[76]

others only a

hay

diet, indicates the

low

using a hay and grain

Summer

diet.

more feed

make

productivity of cattle on a roughage diet

gains usually require

during the summer. Possibly the heat increment of a roughage ration is only a partial explanation of these differences

100 pounds of gain, and daily food consumption is also down during the summer. It is just a little more difficult to keep animals on feed during hot weather. Although summer diet seems to be a factor in producing faster gains, cattle still present a difficult problem to feeders trying to improve their production in hot weather. Cattle have a high rate of heat production, as shown by the basal metabolism of a 765-pound Guernsey cow 48 hours after feeding, which was 62 m/hr., while a 35-year-old Cal./sq. woman only produced 37 Cal./sq. m/hr. (Worstell and Brody, 1953). Along with this high heat production, cattle have a low loss of heat through moisture vaporization. Cattle seem to react to low temperatures more as arctic species do while

in daily gain.

table 20.

These

Each group

tests are is

shown

in

the average of at

least three experiments. All of the

sum-

mer feeding was done in the warm environment of the wooden corrals, which produced lower daily gains than would be the case from animals in the cooler environment of an airy wire corral. Summer tests were conducted from the first part of July to about the middle of September, while the winter tests ran from January through most of May. Animals in these tests were all Hereford steers. Animals made poor daily gains (0.97 pound) on a hay ration during the summer. Cool water increased these gains to 1.27 pounds and also increased food consumption, but the expected gain based on the food consumption (TDM and DCP) shows that they should actually be gaining about 0.5 pounds more per day. With a hay and grain diet, the daily gains are 1.58 and 1.83 pounds for warm and cool water respectively; only about 0.15

pound less than the expected gain. During the winter when temperature is not a factor, daily gain for alfalfa hay is 1.74 pounds and 2.31 pounds for the grain-hay ration. These gains are a little above the expected daily gain based on the daily food intake. With a cooler environment than the wooden corrals most animals will make better than 2.00 pounds gain with a concentrate roughage ration. If two animals are receiving 20 pounds of feed a day and one animal gets one-third of this as grain and the other only hay, the one receiving hay and grain would have about 20 per cent less energy to dissipate as heat and 20 per cent more energy to use for productive purposes than the animal on the hay diet.

The animal's

efficiency of gain is

terially increased

ma-

during the summer by

to

man's reactions are like those of tropical species, and there is definitely a basic incompatibility between high productivity and high environmental temperatures for these larger non-sweating animals. surprising to note that cows,

It is

when

kept in constant-temperature rooms with the heat slowly increased

from 80°

to

100° F, will show a decline in heat production of 30 to 40 per cent. Part of this is due to a decline in feed consumption and milk production, which may amount to 25 per cent of the total heat produced. The remainder may be

decline

due

to a decline of thyroid activity since

non-sweating animal, have a lower

rats, a

thyroxine production at high temperatures which decreases their basal metab-

olism

(Kibler,

Brody,

and

Worstell,

1949).

At high temperatures,

cattle are

hard

pressed to keep body function going, but at the

mean temperature

of 90°

F during

July and August in the Imperial Valley

they are definitely more productive on a hay and grain ration than on a straight hay diet, and this is partly due to heat increment.

[77]

THE TESTS

A

That the proper summer diet will help cattle maintain thermal comfort

SHOWED

high in fiber will produce con-

In these desert areas of California 2.00

siderable energy that will have to be dis-

pounds of gain per day or better can be expected during the summer months if

diet

sipated as heat from the animal's body.

This phenomenon

dence

in

is

much more

in evi-

ruminants than in singleanimals. Although the heat

stomach produced in the body following the consumption of food is very valuable to cattle

during cold winters,

detriment in the

it

is

a decided

summer when animals

are having difficulty reaching a balance

between heat produced and heat lost. Our tests have shown that using grain and good quality roughages (low in fiber) will

allow cattle to

make

satisfactory

gains during the summer. Even ration

is

composed

of just

when

the

good quality

proper precautions are taken as to

Even

diet,

food consumption and efficiency of gain are lower when compared to winter production. Some consideration should also be given to having cattle acclimated before summer comes; that is, bringing them into the area before summer starts so they water, corrals, and shade.

so,

can gradually become accustomed to the heat. It is also desirable to plan a live-

stock

program so

that cattle do not reach

a high degree of finish during the middle of

summer.

It

would be

better to finish

the fattening period just before

summer

have considerably lower daily gains than would be ex-

weather begins or during the early fall. A heavy layer of fat reduces the animal's

pected.

ability to rid itself of excass heat.

roughage they tend

to

Costs and Power Consumption Results indicate that most

investments

In obtaining results reported in this

in

cooling

was good, and upkeep of the equipment offset

cost

were considered, but they were garded as criteria for evaluating sults. The tests reported were all mental and the basic objective

the value of the increased gains.

find

re-

the re-

Costs must often be rationalized care-

experi-

fully to obtain a true evaluation of ex-

was

perimental results. Cattle drinking cooled water in a hot environment did gain sub-

to

the effect of different treatments.

However, records of costs were kept, and analysis will show that most of the treatments, even as applied experimentally on a small scale, increased the producer's net income.

One treatment

off

the increase in weight gains

bulletin, costs of the different treatments

not

pay

that did not

show an increased return, as applied experimentally, was cooling drinking water by mechanical refrigeration. Although

stantially

more than

cooled water.

cattle

Practical

drinking un-

application

of

does not necessarily require the large equipment investment used in the experimental tests. Other methods of this result

cooling water by evaporation (page 41)

and nocturnal radiation (page 47) were tried. In some cases the problem may not

[78]

',

be to cool water, but to keep it cool. One producer in the Palo Verde Valley, interested in applying these results, was able to get 70° F water from his well, store it in an insulated tank, and pipe it under-

ground to cool. With

would stay additional cost, he was

his corrals so little

it

able to supply his cattle with cool drink-

ing water.

Using a fan

to increase the air flow

could very easily be justified by the

in-

creased returns from greater production. Even here, the costs involved are not entirely relevant to the value of the results.

The

tests

air flow

proved the benefit of increased fan was only a means of

—the

increasing the air flow.

Where

location

and surrounding structures can be planned and arranged to utilize natural wind, there may be no of the enterprise

over beef cattle during hot weather pro-

extra cost involved in applying results of

moted increased daily animal gains. In this case the cost of the fan and its operation, even on an experimental basis,

the fan tests.

Table 21

equipment

If

— Power use

is

installed to cool the

cool the drinking water, or to in-

air,

of

equipment Electric

power use

—KW Hr.

Cattle treated

For season

Per animal day

Per day

Cooling air with desert cooler

1948

88

7

Evaporative cooling tower

1951 1954

1.63

0.233

pump

5

129

1.50

7

89

1.49

0.300 0.213*

2.98

0.426f

Evaporative cooling tower fan

1954

76

7

Refrigerated drinking water

1952

20

1953

13

1954 1955

14

1131 786 846 996

14

Fans 1955 1956

17.14

0.857

9.36

0.720

10.07

0.719

14.23

1.0161

in corral §

974 1207

7 7

13.91

1.987

17.24

2.463

Pump

used to circulate water for first half of 1954 season. Fan used to cool water during second half of 1954 season. Includes energy for cooling extra water consumed by steers on salt water experimei it. § During 1955 fan was on 12 hours per day for 21 days and continuously for 49 days Fan was on continuously for 70 days in 1956. * t

j

.

[79]

crease the air flow, the equipment cost

cooler to 2.45 kw. hr. for the fan, Aver-

and maintenance

age power costs on Cailfornia farms are 1% cents per kw. hr., so the power costs in our tests would have ranged from 0.345 cents per animal per day to 3.675 cents. This lat-

will generally

be the

largest item of the cost increase for cool-

ing beef cattle for

—but

tests the

all

sumed

less

not always. While

"cooler" animals con-

feed per unit of weight in-

crease, their total food

consumption was

greater than that of the "uncooled ani-

mals. Increased cost for additional feed

may

actually be greater than

equipment

cost.

The

is power, if it is however, is generally small. Actual power used in the tests des-

third cost item

required.

This,

is shown in table The power used varied from 0.23 kw.

cribed in this bulletin 21.

hr. per

animal per day for the desert

usually considered to be

ter

cost

is

perhaps excessive, but this

was for power to run the fan that ran continuously, which was probably unnecessary. Also, the fan probably would have cooled 30 animals instead of 7. Table 21 also shows how much less power was needed to cool water by evaporation than by mechanical refrigeration. The value of "cooling" beef cattle is greatly influenced by the relationship between beef prices and feed cost.

Summer Water Requirements Cattle with cool water or less

thermal

A

daily record of water consumption

was kept on many of these test animals, especially on the cold drinkingwater lots and check groups. Some of by

lots

these data have already been presented,

but a more detailed accounting is desirable since water is such an important part of the animal's body. The engineer is

also interested in the water require-

ments of

cattle

during the summer.

Many

of these data are presented in table 22

and show both the average daily water consumption and average daily water consumption per 100 pounds of live weight by periods. In most cases those animals with cool water, or under less thermal stress, drank less

water than steers with

in

a

warm water

or

warmer environment. As noted

above, the use of

salt in the ration in-

creased water consumption in both the

warm-and cold-water fits

of

pens, but no bene-

could be ascribed to the

Brahmans was

salt.

fed during the

One pen summer

stress

drank

less

water

(1950) and their water consumption was than the Herefords even when it

less

was calculated on the basis of gallons consumed per 100 pounds of live weight. A detailed investigation was made of the times when water was consumed by the cattle during 1950 and has been checked with data collected in

later years.

The general trend has been the same. All groups of animals drank more water on the warmer days than they did on cooler days. This

is

especially true of the

warm-water Herefords. As a further check on this, the average water consumption on about 20 days, with a mean air temperature of 83° F or less, was

compared with the average water consumption on about 20 days with a mean air temperature of 88° F or more. In all cases the water consumption

was greater

on the hotter days. The warm-water Herefords drank 2.23 gallons per day per head more on the hot than on cool days; the Brahmans 1.30 gallons more; and

[80]

under controlled conditions of

the cold-water Herefords only 0.49 gal-

tained

lon more. Several sets of hourly read-

their

ings of water consumption were taken

Thompson, Worstell, and Brody (1950) found that Braham cows consumed less water per 100 pounds weight below a

test. Most of the water was consumed by the Herefords in two

throughout the

4-hour periods during the day, 7 a.m. to 11 A.M., and 4 p.m. to 8 P.M. This coincides with the times of feeding, 7:30 A.M. and 5 p.m. Both groups of Here-

Climatic

Laboratory.

constant temperature of 90° F.

F upward

the

Ragsdale,

From 85°

Brahmans increased water

tion of water intake with atmospheric

consumption rapidly and exceeded, with one exception, the Jerseys and Holsteins. One Jersey consumed huge quantities at high temperatures and kept up her production. The other Holsteins and Jerseys tended to decline in water consumption at high atmospheric temperature. These high temperatures were constant temperatures and exceeded those experienced here in Imperial Valley. Water consumption varies considerably from one animal to another, and individual reactions may be significant. A recent study by Winchester and Morris (1956) gives the water requirements of cattle under a wide range of conditions and diets. They point out that water consumption remains rather constant between air temperatures of 10° and 40° F. As air temperatures increase to 100° F, consumption increases rap-

temperature variation in this study con-

idly.

under field conditons, the results reported by the Missouri workers as ob-

double with a change in air temperature from 40° to 90° F.

fords drank approximately 1.1 gallons

per hour per head during the 4-hour morning period and 1.7 gallons per hour per head in the evening. During the heat of the day, 11 a.m. to 4 p.m., only about 0.4 gallon per hour per head was consumed, and, during the night, when the water was fairly cool, the animals drank only 0.3 gallon per hour per head. The Brahmans drank less than these amounts but followed the same trend. The water consumption reported in 1950 is roughly double the observed consumption of cool water (50° ± 10°) by non-lactating dairy cows under temperate conditions (data cited by Thompson, Worstell, and Brody, 1949). Thus, the high water intake and the high correla-

firm,

[81]

Water consumption

will

more than

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BIBLIOGRAPHY Beakley, W.

Bligh,

R.,

The

and

J.

D. Findley

environmental temperature and humidity on the frequency of the heart beat of Ayrshire calves. Jour, of Agr. Science, 45:461-468.

1955.

effect of

John Comparison of

1955.

Bond, T.

rectal

and deep body temperature

and C. F. Kelly 1955. The globe thermometer

in the calf. Nature, 176:402-405.

E.,

Bonsma,

in agricultural research. Agricultural Engineering, 36:251-255.

C, and A.

J. J. Pretorius 1943. Influence of color and coat cover on adaptability of

cattle.

Farming

in So. Africa, 18-

101-121.

Brooks,

F. A.

Thermal processes

1951.

Cartwright, T. C. 1955. Responses

in micro-climotology. Syllabus, University of California.

of beef cattle to high

ambient temperatures. Journal of Animal Science, 14:

350-361.

Dunkle, R. V., and J. T. Gier 1954. The two-ball (total spherical) radiometer. Agricultural Engineering, 35:738. Gier,

and R. V. Dunkle Total hemispherical radiometer. Transactions American Institute of Electrical Engi-

J. T.,

1951.

neers, Vol. 70.

Gordon, H. 1942.

Hardy, 1934.

S., and R. L. Perry Air conditioning for houses in California. Calif. Agr. Exp. Sta. Circular 351.

J.

D.

The

radiation of heat from the

human

body. Journal of Clinical Investigations, 13:593-

598.

Heitman, Hurert, Jr., and E. H. Hughes 1949. The effect of air temperature and relative humidity on the physiological well being swine. Journal of Animal Science, 8:171-181.

of

Ittner, N. R., and C. F. Kelly 1951. Cattle shades. Journal of Animal Science, 10:184-194.

Kelly, C. 1949.

F.,

T. E. Bond, and C. Lorenzen, Jr.

Instrumentation for animal shelter research. Agricultural Engineering, 30:297-304.

Kelly, C. F., T. E. Bond, and N. R. Ittner 1950. Thermal design of livestock shades. Agricultural Engineering, 31:601-606. S. Brody, and D. M. Worstell Environmental physiology. IV. Influence of temperature, 50° to 105 °F., on heat production and cardiorespiratory activities in dairy cattle. Mo. Agr. Exp. Sta. Res. Bui. 435.

Kibler, H. H., 1949.

Kibler, H. H., and S.

Brody

1950.

Environmental physiology. X. Influence of temperature 5° to 95 °F on evaporative cooling from the respiratory and exterior body surfaces in Jersey and Holstein cows. Mo. Agr. Exp. Sta. Res. Bui. 461.

1952.

Environmental physiology. XIX. Relative efficiency of surface evaporative, respiratory evaporative and non-evaporative cooling in relation to heat production in Jersey, Holstein, Brown Swiss, and Brahman cattle 5° to 105°F. Mo. Agr. Exp. Sta. Res. Bui. 497.

Lee, D. H. K. 1953.

Meyer, 1955.

of field studies on the heat tolerance of domestic animals. Food and Agriculture Organization of the United Nations.

Manual J.

H.,

The

W. C. Weir, N. R. Ittner, and J. D. Smith influence of high sodium chloride intakes by fattening sheep and cattle. Journal of

Animal Science, 14:412-418. Minett, F. C. 1947.

Effect of artificial showers, natural rain,

animals. Journal of

and wallowing on the body temperature of

Animal Science 6:35-49.

[84]

Ota, Hajima, H. L. Garver, and Wallace Ashby 1953. Heat and moisture production of laying hens. Agr. Eng. 34:163-167. Perry, R. L. 1945.

Characteristics of small atmospheric cooling towers for dairy farms. Univ. of Calif.,

Mimeograph.

Davis.

Raber, B. F., and F. W. Hutchinson 1947. Panel heating and cooling analysis. John Wiley and Sons,

New

York.

Ragsdale, A. C, S. Brody, H. J. Thompson, and D. M. Worstell 1948. Environmental physiology. II. Influence of temperatures 50° to 105° F on milk production and feed consumption in dairy cows. Mo. Agr. Exp. Sta. Res. Bui. 425.

Ragsdale, A. C, H. J. Thompson, D. M. Worstell, and S. Brody 1950. Environmental physiology. IX. Milk production and feed and water consumption responses of Brahman, Jersey and Holstein cows to changes in temperature, 50° to 105 °F and 50° to 8°F. Mo. Agr. Exp. Sta. Res. Bui. 460.

Regan, W. M., and G. A. Richardson 1938.

Reaction of the dairy cow to changes in environmental temperature. Journal of Dairy Science, 21 :73-79.

Reinerschmid, G. 1943.

The amount of solar radiation and its absorption on the hairy coat of cattle under South African and European conditions. Journal So. African Medical Assn., 14:121-141.

Rhoad, A. O. 1944. The Iberia heat-tolerance

test for cattle.

Trop. Agric. Trim, 21 162-164. :

Rhoad, A. O. (Edited by) 1955.

Riggs,

Breeding beef cattle for unfavorable environments (a symposium presented Ranch Centennial Conference) Austin. University of Texas Press.

J. K.,

1953.

W. Colby, and

R.

The

at the

King

L. V. Sells

effect of self-feeding salt-cottonseed

meal mixture

to

beef cows. Journal of Animal

Science, 12:379-393.

Seath, D. M., and G. D. Miller 1948. Effect of water sprinkling with and without nal of Dairy Science, 31:361-366. Schultz, H. 1956.

A

B.,

air

movement on cooling dairy cows. Jour-

and F. A. Brooks

spot climate recorder. Bui.

American Meteorological

Tavernetti, J. R. 1940. Poultry house cooling. Univ. of

Calif.

Society, 37:160-165.

Mimeograph.

and D. M. Worstell, and S. Brody 1949. Environmental physiology. V. Influence of temperature, 50° sumption in dairy cattle. Mo. Agr. Exp. Sta. Res. Bui. 436.

Thompson, H.

J.,

to

105°F, on water con-

J., D. M. Worstell, and S. Brody Environmental physiology. The effect of humidity on insensible weight loss, total vaporization moisture, and surface temperature in cattle. Mo. Agr. Exp. Sta. Res. Bui. 531.

Thompson, H. 1953.

Thompson, H. 1954.

U.

S.

Department of Agriculture

1953.

U. S.

J., R. G. Yeck, D. M. Worstell, and S. Brody Environmental physiology and shelter engineering. The effect of wind on evaporative cooling a surface temperature in dairy cattle. Mo. Agr. Exp. Sta. Res. Bui. 548.

Agriculture Statistics. Table 442 and 535.

Department of Commerce

1956.

Climatological Data, National

Summary.

Winchester, C. F., and M. J. Morris 1956. Water intake rates of cattle. Journal of Animal Science, 15:722-739. Wilson, W. O., and John Hillerman 1952. Methods of cooling laying hens with water. Poultry Science, 31 :847-850. Worstell, D. M., and 1953.

S.

Brody

Environmental physiology and shelter engineering. Comparative physiological reactions of European and Indian cattle to changing temperature. Mo. Agr. Exp. Sta. Res. Bui. 515.

[85]

ACKNOWLEDGMENTS The authors

gratefully acknowledge the council and assistance of the following: H. R. Guilbert, H. B. Walker, W. C. Rollins, J. H. Meyer, G. P. Lofgreen, H. H. Cole, Roy Bainer, H. B. Schultz, and C. Barbie University of California and Wallace Ashby, and Harry Garver (AERD) United States Department of Agriculture. Also to Phil Trask and Delbert Gaskin, herdsmen, and to Robert Combe, superintendent of buildings and grounds, for his help with the refrigeration and electrical equipment, and Vincent J. Galindo, who made all of the drawings for the F. A. Brooks,

manuscript.

10m-2,'58(C6932)JD

.

:c^

^S£*

$y»ujL*j^

"stunt". This

is

.

probably the world's largest plow



an acre in four and one-quarter minutes.

it

was

A

swath 60 feet wide was turned

built about 1910. It

under by 55 bottoms, pulled by three oil-burning

was

built in sections

Impractical?

and assembled for several

...

tractors.

test

plowed

The monster plow

runs in the midwest.

no!

This "stunt" yielded new knowledge about hitches cultural engineers have used in designing

many

.

.

.

knowledge that

of today's

agri-

farm implements.

For more than 40 years agricultural engineering has offered opportunity

young men

i

of mechanical bent with an interest in agriculture.

And

to

as

mechanization increases on farms, opportunities in agricultural engineering

expand

Many Davis. its

.

.

.

with the

GOOD JOBS going to those who are WELL TRAINED.

leaders in the field were trained at the University of California at

The

staff at

Davis

is

recognized nationally and internationally for

accomplishments in teaching and in research. The Department of Agri-

cultural Engineering is accredited ... a graduate is eligible for

tion for a Professional Engineer's license, or he

may

examine

*,

continue study toward

a master's or doctor's degree. The growing College of Letters and Science

on the same campus broadens the student's educational and

social back-

grounds.

For further information ... about courses and careers in agricultural engineering, write Mr. Roy Bainer, Chairman, Department of Agricultural Engineering, University of California, Davis.

See the College Entrance Advisor Advisor.

in

the office of yoor local Farm