EVALUATION OF A CENTRAL BULL TEST STATION

by

STANLEY MACK YOUNG, B.S

A THESIS

IN

ANIMAL BPJ:EDING

Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for

the Degree of

MASTER OF SCIENCE

Approved

^jy^A. n' OjmA. Chairniin of the/t:o'^ittee

'H,v\>

-^U^/v^vU- 0 . (|-<,.c-.U-.>

Accepted

Dean of

August, 1976

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ACKNOWLEDGEMENTS

I am most grateful to Dr. C. Boyd Ramsey for directioi

of this thesis and his encouragement during m.y graduate

study. The assistance and guidance provided by the other

members of my committee. Dr. Robert C. Ablin and Dr.

Frank A. Hudson, are also appreciated.

I am especially grateful to Dr. Dale W. Zinn who

served as my graduate committee chairman during the eairly

part of my graduate studies. Appreciation is also ex­

pressed to Dr. Charles T. Gaskins whose friendship, guid­

ance and assistance with the statistical analysis were

most helpful.

11

v_

TABLE OF CONTENTS

ACKNOWLEDGEMENTS ii

ABSTRACT V

LIST OF TABLES vii

LIST OF FIGURES viii

I. INTRODUCTION 1

II. REVIEW OF LITERATURE 2

III. RESULTS AND DISCUSSION 5

Summary 5

Introduction 6

Methods and Materials 7

Results and Discussion 8

On Test Weight 11

Weight Gains 11

Sale Price 12

Weight Effects 12

Fat Thickness 14

Height and Length Measurements 18

Selected Correlations 22

Length of Test Period 2 4

LITERATURE CITED 27

111

•T.- VTT:

APPENDIX TABLES

A. Composition of the Bull Test Diets 29

B. Components of Indices 30

C. Distribution of Bulls within Year and Breed by Fat Thickness over the Ribeye 31

D. Least Squares Means for Body Length and Height of Bulls On and Off Test - 1971 33

IV

ABSTRACT

Selected traits were analyzed for 708 bulls tested at

the Texas Tech University Center at Amarillo from 1967 to

1975. The trend for these traits indicated little change

in ADG and weight per day of age (WDA) over the years.

Weight on test was influenced by age on test (r = .66).

Younger bulls either maintained or increased their WDA

during the test period.

ADG and WDA were increased slightly by the introduction

of the larger, later-maturing European breeds and their

crosses. The larger breeds also exhibited less fat thick­

ness over the ribeye.

A more detailed analysis of the 80 bulls tested in

1970-71 showed that Angus and Hereford bulls fattened at a

greater rate than the Simmental crosses. Length and height

measurements revealed that the longer and taller bulls were

heavier both on and off test and were less fat.

The bull's index was most highly related to sale price

(r = .62) and was followed by off test weight (r = .54) and

ADG (r = .47). Off test age and fat thickness over the rib­

eye influenced buying decisions very little. Because the

index was heavily influenced by weight and gain, buyers

obviously selected the larger, faster-gaining bulls.

^

Simple correlation coefficients between variables at

the 112- and 140-day test periods were .97 for weight, .89

for total weight gain and .95 for fat thickness. These

results indicate that the 140-day test period could be

shortened to 112 days with only a small loss of information.

VI

y " ' ^

LIST OF TABLES

1. Number of Bulls by Breeds by Years 9

2. Least Squares Means for the Effects of Year on Selected Traits 10

3. Simple Correlation Coefficients for Height and Length Measurem.ents with Selected Traits 21

4. Simple Correlation Coefficients Betv/een Selected Traits 23

5. Simple Correlation Coefficients Between Final Weight or Total Gain while on Test with Weight or Total Gain at Each 28-Day Weigh Period 25

APPENDIX TABLES

A. Composition of the Bull Test Diets 29

B. Components of Indices 30

C. Distribution of Bulls within Year and Breed by Fat Thickness over the Ribeye 31

D. Least Squares Means for Body Length and Height of Bulls On and Off Test - 1971 33

Vll

LIST OF FIGURES

1. Off Test Weight by Years and Breeds 13

2. Off Test Fat Thickness by Years for All Bulls 15

3. Off Test Fat Thickness per 45 kg of Live Weight by Years and Breeds 17

4. Fat Thickness per 45 kg of Live Weight by Time on Feed and Breeds - 1970-71 19

5. Final Fat Thickness Distribution of Bulls 20

Vlll

CHAPTER I

INTRODUCTION

Cattlemen recently have had to reevaluate their busi­

ness and plan for increased efficiency and productivity

because of an unfavorable economic climate. Perform.c.nce

records are a vital tool for improving productivity of a

beef herd. The performance of a potential herd sire is an

important record for herd improvement. Central bull test­

ing stations play an important role in evaluating the per­

formance of potential herd sires or the progeny of existing

herd sires. During 3 5 years of performance testing, a

standardized 140-day testing period has been established.

More of the emphasis in the bull's final index generally has

been placed on average daily gain (ADG) during the test than

any other trait measured.

This study was planned to evaluate the bull testing

program at the Texas Tech University Center at Amarillo.

The objectives were to determine the feasibility of shorten­

ing the test period from 14 0 days, the trends in production

characteristics and the interrelationhip of bull traits and

selling price.

»

CHAPTER II

REVIEW OF LITERATURE

The selection of a herd sire is one of the most impor­

tant decisions an animal breeder must make. Hazel and Lush

(1942) theorized that using an index to express the net

breeding value of an animal would produce more genetic im­

provement than selection for a single trait or selection

for several traits with independent culling levels. Wilson

et al. (1963) calculated selection indexes involving wean­

ing weight, initial (on test) conform.ation, final (off

test) conformation and ADG. They concluded that final con­

formation was the least important trait and that ADG was

the most important trait in determining theoretical genetic

progress for selection.

Swiger et al. (1963) studied the heritability of wean­

ing weight, 396-day weight and 550-day weight. They con­

cluded that increased accuracy should be achieved in

predicting genotypes for final weight from weights taken at

an earlier age if gains were measured while the cattle were

fed a high energy diet.

Selection for conformation score at 396 days and at

550 days was equally effective in improving conformation.

The selection for weight at 396 days was, as a pooled esti­

mate, 81% as effective as the selection at 550 days.

y ^ — • — \ > g - .. - --

3

Cundiff et al. (1964) reported that selection for growth

rate would lead to increased muscular development, improved

carcass grade and a slight increase in carcass fatness.

Growth rate was more highly correlated genetically with

muscular development than with fat deposition.

Shelby et al. (1955) reported heritability estimates

of 60% for gain in the feedlot, 84% for final weight at the

end of the feedlot period and 38% for thickness of fat.

They stated that selection for most growth characteristics

should be based on the individual's record, while selection

for carcass traits must be based on sib or progeny tests.

A similar conclusion was reached by Warwick and Cartwright

(1955) after they studied the results of the gain test at

the Blue Bonnett Farm. They concluded that a high herita­

bility estimate for gain (54%) lent overwhelm.ing support to

the conclusion that selection for rate of gain would be

effective when the individual's record was used. They

observed that the use of a gain ratio eliminated differences

due to year, breed or cross, sex and ration.

In other studies involving selection criteria for re­

placement breeding animals, high positive correlations

between the rate and efficiency of gain have been reported

by Winters and McMahon (19 33), Black et al. (19 36), Knapp

et al. (1941), Stanley and McCall (1945), Kohli et al.

(1951), Grizzle and Kincaid (1954) and Carter and Kincaid

(1959). Shelby et al. (1963) concluded that selection for

ADG or final weight would be moderately successful and that

final weight was a slightly superior selection criterion

to ADG.

CHAPTER III

RESULTS AND DISCUSSION

Summary

Selected traits were analyzed for 708 bulls tested at

the Texas Tech University Center at Amarillo from 1967 to

1975. The trend for these traits indicated little change

in ADG and weight per day of age (WDA) over the years.

Weight on test was influenced by age on test (r = .66),

Younger bulls either maintained or increased their WDA

during the test period.

ADG and WDA were increased slightly by the introduc­

tion of the larger, later-maturing European breeds and

their crosses. The larger breeds also exhibited less fat

thickness over the ribeye.

A more detailed analysis of the 80 bulls tested in

1970-71 showed that Angus and Hereford bulls fattened at a

greater rate than the Sinmiental crosses. Length and height

measurements revealed that the longer and taller bulls were

heavier both on and off test and were less fat.

The bull's index was most highly related to sale price

{t: = .62) and was followed by off test weight (r = .54) and

ADG (r = .47). Off test age and fat thickness over the rib­

eye influenced buying decisions very little. Because the

index was heavily influenced by weight and gain, buyers

obviously selected the larger, faster-gaining bulls.

Simple correlation coefficients between variables at

the 112- and 140~day test periods were .97 for weight, .89

for total weight gain and .94 for fat thickness. These

results indicate that the 140-day test period could be

shortened to 112 days with only a small loss of information.

(Key Words: Bull Test, Testing Period, Fat Thickness.)

Introduction

The selection of the herd sire can be one of the most

important decisions that a cattleman is required to make.

Studies have determined the factors which are important in

that decision and some of the heritabilities of live animal

and carcass traits. In one of the earlier studies. Hazel

and Lush (194 2) concluded that the use of an index would

provide more improvement than . selection for a single trait.

Also, it has been determined that selection for final weight

can be moderately successful in increasing that trait.

Since selection is so important, this study was undertaken

to determine the feasibility of shortening the 140-day test

period to reduce testing costs, the trends in production

characteristics, and the relationship of bull traits to

selling price.

Methods and Materials

The data were obtained from 7 08 bulls which were tested

at the Texas Tech University Center at Amarillo from 1967 to

1975. These bulls were owned by 94 different cooperators

and were placed on test during the fall of each year, usu­

ally in October. They were sold at auction in March after a

140-day feeding period.

The bulls were acclimated to the diets (Appendix Table

A) and surroundings during a 14-day adjustment period before

the official test began. They were weighed every 28 days

while on the test. Other data obtained on the bulls were

205-day adjusted weaning weight, age and an ultrasonic

estimate of fat thickness over the ribeye at the end of the

test. Other variables which were calculated at the end of

the test included ADG on test, total gain on test, WDA, grade

and index. The same index was not used every year (Appendix

Table B). It was changed at the request of the majority of

the breeders. The index will be discussed in this study

only in relation to sale price to determine if the buyers

were using it as a tool for selection of bulls to purchase.

During the 1970-71 test a more detailed study was con­

ducted. In addition to the data previously mentioned, other

data obtained were an ultrasonic estimate of subcutaneous

fat thickness at the 12th rib after every 28-day period and

three linear measurements—height at the shoulders, length

8

from the point of the shoulder (lateral condyle of the

humerus) to the hooks (tuber coxa of the ilium) and length

from the hooks to the pins (posterior extremity of the

ischium). The linear measurements were taken with calipers

at the beginning and at the end of the 14 0-day feeding test.

Data were analyzed by the method of least squares

(Harvey, 1960). Duncan's New Multiple Range Test was used

to determine differences between means when a significant

difference was found in the main effect. Simple correla­

tion coefficients were calculated between selected variables

on an overall basis.

Results and Discussion

Distribution of the 708 bulls among breeds and crosses

within years is shown in Table 1. Angus and Hereford bulls

comprised 63% of the total number and were tested all 9

years. No other breed was tested more than 5 years. The

crossbred bulls were one-half blood of the sire breed

except in 1974 and 1975 when 7 and 15 of the Simmental were

of three-fourths blood of the sire breed, respectively.

Least squares means for selected traits of the bulls are

given in Table 2. The effect of year was significant

(P<.05) for all of the traits except WDA. Thus, environment

(weather, dam's milk production, range conditions, etc.) and

the variation in the cooperators from year to year accounted

for a large portion of the variation among bulls.

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On Test Weight

On test weight averaged 299.6 kg and was positively

correlated (r = .66) with off test age (average of 413.8

days), indicating that age accounted for about 44% of the

variation in on test weight. The age-weight relationship

decreased only slightly during the test period (r = .62

between off test weight and age). A tendency was found for

younger and lighter bulls to be placed in the 1974 and 1975

tests than in the previous 4 years. A negative association

(r = -.58) between off test age and WDA indicated that younger

bulls tended to have a higher V7DA. This result agrees with

a previous report by Schalles and Marlowe (19 67).

Weight Gains

ADG while on test varied .28 kg among years (P<.05).

The trend was upward since 1972. This trend can be attrib­

uted to an increasing number of bulls of the larger, later-

maturing, faster-growing European breeds or crosses being

placed on test. These data show that improvement in ADG

occurred only when new breeds or crosses were introduced

to the test. The lowest ADG (1.15 kg) was found in 19 72

when the winter weather was unusually severe. A greater

than normal rainfall produced more mud, and the wet condi­

tions probably reduced gains. No significant differences

in ADG were found between 1968 and 1971. The gains in 1967

and 1973 were nearly identical (1.32 vs 1.33 kg).

12

VIDA showed only a .10-kg range among the years. Differ­

ences between years were not significant at the 5% level of

probability. A need obviously exists for more selection

pressure to be focused on this trait to obtain the desired

improvement.

Sale Price

Sale price of the bulls reflected the slaughter cattle

market trends. The upward range of the m arket was reflected

in the high prices received for the bulls in the 1973 and

1974 tests. The break of the market in the spring of 1974

apparently affected the sale price of the 1975 bulls, which

showed a decrease of about 50% in market value when compared

to the previous year.

Weight Effects

Weight differences by breeds and crosses among years

(Figure 1) showed that Hereford, Angus and Santa Gertrudis

bulls were lighter (P<.05) than the Charolais or the

Simmental crosses. Weight differences between years within

the breeds were due in part to the variation in cooperators

who consigned bulls to the test across years. Final weight

of the Angus bulls apparently was affected more severely by

the abnormally wet and cold weather of the 1972 test than

was the weight of the other breeds. The weight of the

Simmental cross in 1973 was disregarded because only one

13

Off t e s t weight , kg

540

520

500

^SiiJ^-^s'X^^t^- •

480 Santa Gertrudi

460

440

420

400

380

360

1967 1968 1969 1970 1971 1972 1973 1974 1975

Year

Figure 1, Off test weight by years and breeds.

14

bull was tested. The Charolais showed only small variations

in final weight during the 5 years they were tested. The

uniformity of breeders consigning Charolais may be the

reason for this small variation. However, the Santa

Gertrudis showed wide ranges in weight among years. Santa

Gertrudis bulls in 1972 were consigned by a single coopera-

tor who only tested in the 197 2 test. Santa Gertrudis in

1969, 1973, 1974 and 1975 were consigned by several differ­

ent breeders and the bulls tended to have a lighter final

weight than in 1972. Hereford bulls had less variation in

final weight than Angus. They also comprised the largest

percentage of the bulls in the test each year except 1975

and probably are a more representative sample of the popula--

tion than the other breeds.

Fat Thickness

Least squares means of a single ultrasonic estimate of

subcutaneous fat thickness over the 12th rib are plotted in

Figure 2. The distribution of fat thicknesses among breeds

within years is shown in Appendix Table C. Differences

among years were great (P<.01). However, the differences

between years were not significant from 1972 to 1975. Part

of the year differences are due to the introduction of the

crossbred bulls, which were sired by the less fat European

breeds. Most of the differences in mean fatness between

c

10.0 Fat thickness, mm

1970 1971 1972 1973 1974 1975

Year Figure 2. Off test fat thickness by years

for all bulls.

16

years in Figure 2 were due to differences of bulls in each

breed or cross and not to a great decline in fatness within

breeds over the years.

The first year in which fat thickness was estimated,

the fattest bull had 20 mm of subcutaneous fat and brought

the highest price in the sale. However, such a fat-price

relationship has not been found since that time. Fat thick­

ness was incorporated into the index in 197 2 as an estimate

of fatness of the bulls; however, it was removed in 1973

due to the desires of the cooperators.

The Hereford and Angus bulls were fatter per 4 5 kg of

off test weight (P<.01) than the Simmental crosses, Santa

Gertrudis and Charolais (Figure 3). Differences between

years within breeds were as small as .04 mm/45 kg for the

Simmental cross bulls and as large as .29 mm/45 kg for the

Angus bulls. The Angus bulls were fatter than the Herefords

in 1972, 1973 and 1974, but little or no difference was

found between these breed samples in the 1970, 1971 and

1975 tests. The Hereford and Santa Gertrudis exhibited

essentially the same variation in fatness among years v;ith

a range of .13 and .14 mm/45 kg, respectively. Simmental

cross and Charolais bulls showed little change in fat thick­

ness expressed as a proportion of body weight, indicating

that the fatness of the bulls probably has not changed

during the last several years of testing.

17

1.0

.9

8

.6

.5

.4

.3

.2

.1

Fat thickness/45 kg, mm sm

Angus

Santa Gertrudis

• Simmental crosses'***.

1970 1971 1972 1973 1974 1975

Year

Figure 3. Off test fat thickness per 45 kg of live weight by years and breeds.

18

In a more detailed study in 1971, the fattening pat­

tern (Figure 4) was determined every 28 days during the 140-

day feeding test. Angus and Hereford were fatter per 4 5 kg

of live weight coming on test and they fattened at a faster

rate than the Simmental crosses while on test. Angus and

Hereford groups fattened at a similar rate with both having

an increase in fat thickness of .5 mm/45 kg during the test.

The two groups attained nearly identical final fat

thicknesses.

Figure 5 shows the distribution of all bulls of all 6

years among fat thicknesses. Angus and Hereford bulls

showed a near normal distribution with the greatest number

of bulls having 7.5 mm of fat thickness. However, the dis­

tribution of fat thickness of all other breeds combined was

skewed greatly to the left, indicating considerably less

fat. The greatest number of these other breeds had 2.5 mm

of fat thickness. Some of these bulls probably had less

than 2.5 mm of fat, the lowest measurement recorded.

Height and Length Measurements

Table 3 contains simple correlation coefficients of

the height and length measurements on and off test with

selected traits for the 1971 test. The means for these

traits are shown in Appendix Table D. The longer-bodied,

taller bulls were heavier both on test and off test. On

19

F a t t h i c k n e s s / 4 5 kg , mm !!" jarais;

fi'-':r^,-'\ ^aSE^E«SSgiilE}3

0 28 56 84 112 140

Days on feed

Figure 4. Fat thickness/45 kg of live v/eight by time on feed and breeds.

20

90

80

70

60

50

40

30

20

10

Number of bull

:* ^ N

SS:-:-:- k^

itt

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^ '

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f

i ^ Angus and Hereford

• Other breeds

^ g ^

12.5 15 17,5 20

Fat thickness, mm

Figure 5. Final fat thickness distribution of bulls.

21

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22

test height and lengths were more highly related to on test

weight than to off test weight. However, off test linear

measurements, with the exception of shoulder to hooks length,

were similar in their relationship to on test and off test

weights. Structural dimensions were associated with 50% or

less of the variance in weight. The on test height measure­

ment account for 36% of the variation in on test fat thick­

ness. The taller bulls were the least fat and this

relationship was only slightly lower (r = -.53) at the con- .

elusion of the test. Total gain while on test was most

highly associated with the shoulder to hooks length at the

end of the test with the longer-bodied bulls gaining at a

slightly faster rate (r = .28). The height at the shoulders

and length from the hooks to the pins showed practically no

correlation with total gain on test. The off test shoulder

to hooks length measurement accounted for the largest amount

of the variation in both grade (r = .34) and index (r = .40).

Therefore, the graders tended to give the longer-bodied bulls

a higher grade. About 7 0% of the index was composed of

weight variables and the remaining 30% was composed of grade.

Thus, the longer-bodied bulls which gained more and received

a higher grade tended to be indexed higher.

Selected Correlations

Table 4 contains simple correlation coefficients be­

tween selected traits. Sale price was most highly associated

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with index (r = .62) and 140-day weight (r = .54). ADG and

grade accounted for 22 and 18%, respectively, of the vari­

ance in sale price. Fat thickness, off test age and 205-

day adjusted weaning weight were associated with less than

3% of the variation in sale price. However, Marlowe and

Marlowe (1965). and Swaim et al. (1966) found higher associa­

tions for both fat thickness and off test age with sale price

Buyers of bulls apparently considered the index, final

weight, ADG and grade more than the other traits when

selecting bulls. Off test age and fat thickness had very

little influence on sale price. Gain, rather than composi­

tion of gain, obviously was more important to the buyers.

Index was most highly associated with ADG (r = .76).

This association is due to the fact that the indexes used

over the years emphasized measures of weight—either WDA,

ADG or 365-day adjusted yearling weight (Appendix Table B).

Grade, which was a subjective composite measure given by

three persons, was positively associated with index (r =

.70) but negatively associated with fat thickness (r = -.57),

Therefore, the graders tended to give the fatter bulls a

lower grade. The heavier and older bulls tended to be

fatter coming off test.

Length of Test Period

Simple correlation coefficients between final weight

of total gain while on test with weight or total gain after

25

each 28-day weigh period are contained in Table 5. The cor­

relations of weight at each weigh period with the 140-day

TABLE 5- SIMPLE CORRELATION COEFFICIENTS BETWEEN FINAL WEIGHT OR TOTAL GAIN WHILE ON TEST WITH

WEIGHT OR TOTAL GAIN AT EACH 28-DAY WEIGH PERIOD^

Weigh period, days

Off test weight

.84**

.89**

.92**

.96**

.97**

Total gain after 140 days

0

28

56

84

112

46**

82**

89**

N=7 08.

Value for 28 days was not calculated.

* * P<.01.

weight were significant (P<.01). On test weight accounted

for 71% of the variation in final weight; this percentage

increased throughout the test: 79% at 28 days, 85% at 56

days, 92% at 84 days, and 94% at 112 days. The correla­

tions indicate that final weight could be predicted at each

interval during the test with reasonable accuracy and that

the accuracy increased with each successive weigh period.

The correlations between weight gains were not as high as

the correlations between weights at the weigh periods.

Twenty-one percent of the variation in total gain during

26

140 days was associated with gain at 56 days, but the rela­

tionship increased greatly to 67% at 84 days and 79% at 112

days.

In the 1971 study, the simple correlation of fat thick­

ness at 112 days with fat thickness at 140 days was .94.

Therefore, with these high correlations, the test could be

concluded before 14 0 days with only a small loss of produc­

tion information. If the tests had been concluded after

112 days, 21% of the variation in total gain, 12% of the

variation in fat thickness (1971 data only) and 8% of the

variation in live weight at 140 days would have been un­

explained. Concluding the test at 84 days would have

resulted in a further reduction of 12% in 140-day total

gain predictability, only a 2% reduction in 140-day weight

predictability, and a 17% reduction in 140-day fat thick­

ness predictability.

These data suggest that feeding tests should be termi­

nated at 112 days. Relatively small losses in information

occur when the standard 14 0-day test is reduced in length

by 28 days. Additionally, bull testing would become less

expensive and the bulls would become less fat, possibly

causing fewer reproductive problems. The shorter feeding

period would more nearly match that presently used with

steers, which would allow more realistic comparisons of

steer and bull half-sib data.

LITERATURE CITED

Black, W. H., Bradford Knapp, Jr. and A. C. Cook. 1936. Correlation of body measurement of slaughter steers with rate and efficiency of gain and with certain characteristics. J. Agr. Res. 56:465.

Carter, R. C. and C. M. Kincaid. 1959. Estimates of genetic and phenotypic parameters in beef cattle. J. Anim. Sci. 18:331.

Cundiff, L. A., Doyle Chambers, D. F. Stephens and R. L. Willham. 1964. Genetic analysis of some growth and carcass traits in beef cattle. J. Anim. Sci. 23:1133.

Grizzle, J. E. and C. M. Kincaid. 1954. The relationship between body weight, daily gain, and efficiency of feed utilization in beef cattle. J. Anim. Sci. 13: 959 (Abstr.).

Harvey, Walter R. 1960. Least Squares Analysis of Data with Unequal Subclass Numbers. U.S.D.A., A.R.S. Bull. 20-8.

Hazel, L. N. and Jay L. Lush. 1942. The efficiency of three methods of selection. J. Hered. 33:393.

Knapp, Bradford, Jr., A. L. Baker, J. R. Quesenberry and R. T. Clark. 1941. Record of performance in Hereford cattle. Mont. Agr. Exp. Sta. Bull. 397.

Kohli, M. L., A. C. Cook and W. M. Dawson. 1951. Relations between some body measurements and certain performance characters in milking Shorthorn steers. J. Anim. Sci. 10:352.

Marlowe, G. A. and T. J. Marlowe. 1965. Some factors that influence the sale price of Virginia performance tested bulls. Livestock Research, 1964-65 Progress Report. Va. Agr. Exp. Sta.

Schalles, R. R. and T. J. Marlowe. 1967. Factors affecting test performance of beef bulls. J. Anim. Sci. 26:21.

Shelby, C. E., R. T. Clark and R. R. Woodward. 1955. The heritability of some economic characteristics of beef cattle. J. Anim. Sci. 14:372.

27

o 8

Shelby, C. E., W. R. Harvey, R. T. Clark, J. R. Quesenberry and R. R. Woodward. 1963. Estimates of phenotypic and genetic parameters in ten years of Miles City R.O.P. steer data. J. Anim. Sci. 22:346.

Stanley, E. B. and Ralph McCall. 1945. A study of perfor­mance in Hereford cattle. Ariz. Agr. Exp. Sta. Tech. Bull. 109.

Swaim, J. R. ill, c. B. Ramsey and J. B. McLaren. 1966. Somacope estimates of fatness and muscling of bulls at Ames Plantation. Tennessee Farm and Home Science Progress Report No. 58.

Swiger, L. A., K. E. Gregory, R. M. Koch, W. W. Rowden, V. H. Arthaud and J. E. Ingalls. 1963. Evaluating post-weaning gain of beef calves. J. Anim. Sci. 22: 514.

Warwick, Bruce L. and T. C. Cartwright. 1955. Heritabil­ity of rate of gain in young growing beef cattle. J. Anim. Sci. 14:363.

Wilson, L. L., C. A. Denkel, D- E. Ray and J. A. Minyard. 1963. Beef cattle selection indexes involving con­formation and weight. J. Anim. Sci. 22:1086.

Winters, Lawrence M. and Harry McMahon. 1933. Efficiency variations in steers. Minn. Agr. Exp. Sta. Tech. Bull. 94.

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APPENDIX TABLE D. LEAST SQUARES MEANS FOR BODY LENGTH AND HEIGHT OF BULLS ON AND OFF

TEST - 1971

Trait Mean, cm

On test

Height at shoulders 105.6

Length

Shoulder to hooks 93.3

Hooks to pins 43.3

Off test

Height at shoulders 119.1

Length

Shoulder to hooks 107.4

Hooks to pins 46.4

^N=81.