^^^/Jy^

Ag84Te

United States

Department of

Agriculture

Agricultural

Research

Service

Composite Breeds To Use

Heterosis and Breed

Differences To Improve

Efficiency of Beef Production

Technical

Number 1875 If) cooperatJon with the Institute of

October 1999 Agriculturs and Natural Resources,

University of Nebraska-Lincoln
United States

Department of

Agriculture

Agricultural

Research

Service

Technical

Bulletin

Number 1875

October 1999

Composite Breeds To Use

Heterosis and Breed

Differences To Improve

Efficiency of Beef Production

In cooperation with the Institute of

Agriculture and Natural Resources,

University of Nebraska-Lincoln

K.E. Gregory, LV. Cundiff, and R.M. Koch

Gregory is a research geneticist and Cundiff a research leader, U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U.S. Meat

Animal Research Center, Clay Center, NE 68933. Koch is a professor emeritus.

University of Nebraska, Department of Animal Science, Institute of Agriculture

and Natural Resources, Lincoln, NE 68583-0908.
Abstract

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1999.

Composite Breeds To Use Heterosis and Breed

Differences To Improve Efficiency of Beef Production. U.S. Department of Agriculture Technical

Bulletin No. 1875, 81 pp.

This report is a summary of results from a long-term

experiment of 15 years conducted with beef cattle at

the Roman L. Hruska U.S. Meat Animal Research

Center. The study estimated the retention of heterosis for major bioeconomic traits in composite populations (established with contributions by four or

five purebreeds) and evaluated the potential of using

these composite populations to achieve and maintain

optimum performance levels and to maintain high

levels of heterosis. At least 13 scientific papers were

published from this project, resulting in numerous

conclusions, presented here.

This publication will be of use to scientists, students,

and extension specialists interested in beef cattle

breeding and genetics; beef cattle breeders; and

others with interests in the beef cattle industry.

Keywords: beef cattle breeding, breed composition,

breeding, calves, cattle, crossbreeding, composite

breeds, genetics, genotype, heritability, heterosis,

heterosis retention, heterozygosity, inbreeding,

phenotype

While supplies last, single copies of this publication

may be obtained at no cost from Keith Gregory,

USDA-ARS, Roman L. Hruska U.S. Meat Animal

Research Center, P.O. Box 166, Clay Center, NE

68933.

Copies of this publication may be purchased from

the National Technical Information Service, 5285

Port Royal Road, Springfield, VA 22161; telephone

703-605-6000.

The United States Department of Agriculture

(USDA) prohibits discrimination in all its programs

and activities on the basis of race, color, national

origin, gender, religion, age, disability, political

beliefs, sexual orientation, and marital or family

status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program

information (Braille, large print, audiotape, etc.)

should contact USDA's TARGET Center at 202-

720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA,

Director, Office of Civil Rights, Room 326-W,

Whitten Building, 14th and Independence Avenue,

SW, Washington, DC 20250-9410 or call 202-720-

5964 (voice or TDD). USDA is an equal opportunity

provider and employer.

Issued October 1999
Contents

Executive summary iv

Rationale for development of composite breeds iv

Conclusions from experimental results iv

Introduction 1

Experimental procedure 2

Populations 2

Mating procedure 5

Management of heifers and cows 6

Feeding of young heifers and young bulls 7

Data collection 7

Growth, feed efficiency, and carcass and meat data of castrate males 7

Analysis of data 9

Results and discussion 9

Heterosisand heterosis retention 9

Differences among parental breeds 23

Inbreeding coefficients 49

Genetic and phenotypic variances 49

Heritabilities 49

Genetic correlations 55

Phenotypic correlations 67

Adjustment factors for age of dam 67

Composite breed formation c 67

References 72

Glossary 73

111
Executive Summary

Rationale for Development of Composite Breeds

1. Heterosis (hybrid vigor) for major bioeconomic

traits, including reproduction, calf survival,

maternal ability, growth rate, and longevity of

beef cattle is important. Heterosis can be used to

increase weight of calf weaned per cow exposed

to breeding by 20 percent. Crossbred cows

remain in the herd 1.3 yr longer and have a 30

percent greater lifetime production than straightbred cows.

2. Large differences exist among breeds of beef

cattle for major bioeconomic traits, including

growth rate and size, composition of gain, milk

production, dystocia (calving difficulty), age at

puberty, and climatic and nutritive adaptability.

These are traits where the optimum is determined by production environment and by

market requirements.

3. About 55 percent of the cows in the U.S. beef

breeding herd are in units of 100 or fewer cows.

This involves about 93 percent of the farms and

ranches that have beef cows.

4. Crossbreeding systems can achieve high levels

of heterosis. However, optimum crossbreeding

systems are difficult to adapt in herds that use

fewer than four bulls.

5. Fluctuation in breed composition between

generations in rotation crossbreeding systems

can result in considerable variation in level of

performance among cows and calves for major

bioeconomic traits unless breeds used in the

rotation are similar in performance characteristics.

6. Use of breeds with similar performance characteristics restricts the use that can be made of

breed differences to optimize average genetic

merit for major bioeconomic traits. This includes traits such as growth rate and size,

carcass composition, milk yield, and age at

puberty.

7. Composite breeds offer the opportunity to (a)

use high levels of heterosis on a continuing

basis if population size in seedstock herds is

sufficiently large or if periodic introduction of

new genetic material is made to avoid inbreeding, (b) achieve and maintain optimum breed

(additive genetic) composition needed to match

performance characteristics of different composite breeds to each of a wide range of production

situations and to different market requirements,

and (c) achieve and maintain uniform performance levels from one generation to the next.

Conclusions From Experimental Results

1. High levels of heterosis were observed for

growth rate, reproduction, and maternal traits,

including milk production.

2. Heterosis differed among composite populations

for some major bioeconomic traits. Results

suggest that specific cross heterosis is important, that is, the level of heterosis for traits may

vary among breed crosses.

3. Generally, retained heterosis in advanced

generations was equal to or greater than expected based on retained heterozygosity in the

three composite populations.

4. Results suggest that although there is generally

a high relationship between retained heterosis

and retained heterozygosity, the relationship is

not linear for all situations, that is, for some

traits and in some breed combinations, retained

heterosis may be greater or less than expected

based on retained heterozygosity.

5. Even though results suggest that specific cross

heterosis is of some importance, it is not feasible to have estimates of F^ heterosis and of

heterosis retained in advanced generations of a

large number of specific breed combinations in

order to choose breeds as contributors to specific composite populations (breeds). Thus, the

IV
use of average values for F^ heterosis and of

retained heterosis based on genetic expectation

in advanced generations of inter se mated

composite populations is suggested for Bos

taurus breeds.

6. These results, generally, support the hypothesis

that heterosis in cattle can be accounted for by

dominance effects of genes. Thus, heterosis in

breed crosses involving Bos taurus breeds can

likely be accounted for by recovery of accumulated inbreeding depression that has occurred in

breeds since their formation.

7. Estimates of genetic standard deviations and

phenotypic coefficients of variation were similar

for parental purebreds combined and for composite populations combined for most

bioeconomic traits. Estimates of heritability

were similar for parental purebreds and composites. Thus, no increase in genetic variation was

observed in composite populations relative to

contributing purebreeds. The similarity of

genetic variation for composites and contributing purebreds is believed to result from the large

number of genes affecting major bioeconomic

traits. Composite populations (breeds) have a

high degree of uniformity both within and

between generations.

8. Composite populations (breeds) offer an alternative breeding system that is generally competitive with crossbreeding for using heterosis and

is easier to manage regardless of herd size.

9. Composite populations (breeds) offer a procedure that is more effective than continuous

crossbreeding for using genetic differences

among breeds to achieve and maintain optimum

performance levels for major bioeconomic traits

on a continuing basis. This includes traits such

as growth rate and size, composition of gain,

milk production, climatic and nutritive adaptability, and age at puberty.

10. Large differences among parental breeds were

observed for growth rate and size; dystocia; age

at puberty; scrotal circumference; maternal

traits, including milk production; and carcass

composition.

11. Composites were generally intermediate to

parental breeds for carcass composition and

more nearly approached the optimum carcass

composition, for example, Hereford, Angus, and

Red Poll (British breeds) had more carcass fat

than is optimum, whereas the continental breeds

tended to have less carcass fat than is optimum

to meet current market requirements in U.S.

beef production systems.

12. There is limited opportunity to select among or

within breeds to achieve high levels of marbling

or high levels of fat in the longissimus muscle

simultaneously with achieving a high percentage of retail product in the carcass. These results

suggest that the most logical approach to resolution of the genetic antagonism between favorable carcass composition and less favorable

carcass quality grade (that is, marbling) is to

form composite breeds with breed contributions

organized to achieve a balance between favorable carcass composition and desirable carcass

quality grade at optimum slaughter weights.

13. Factors favoring the use of composite breeds are

(a) it is a simple procedure that results in high

levels of retained heterosis, (b) it is a highly

effective procedure that makes use of breed

complementarity, (c) it achieves a relatively

high level of uniformity both within and between generations, and (d) it makes use of high

levels of heterosis and breed complementarity

simultaneously, regardless of herd size.

V
Introduction

Heterosis achieved through continuous crossbreeding can be used to increase weight of calf weaned

per cow exposed to breeding by 20 percent (Gregory

and Cundiff 1980). Heterosis can also increase

longevity of cows by 1.3 yr and can increase the

total calf weight weaned per cow by 30 percent over

the life span of a dam (Cundiff et al. 1992).

Comprehensive programs of breed characterization

revealed large differences among breeds for most

bioeconomic traits (Gregory et al. 1982; Cundiff et

al. 1986). Optimum crossbreeding systems are

difficuh to adapt in herds having fewer than four

bulls (Gregory and Cundiff 1980). Further, fluctuation in breed composition between generations in

rotational crossbreeding systems can result in considerable variation among cows and calves in the

level of performance for major bioeconomic traits

unless breeds used in the rotation are of similar

biological type. Use of breeds with similar performance characteristics restricts the use that can be

made of breed differences in average genetic merit

for bioeconomic traits to meet requirements for

specific production and marketing situations (Gregory and Cundiff 1980). The potential of composite

breeds as an alternative to continuous crossbreeding

for using heterosis and for using genetic differences

among breeds (that is, breed complementarity) to

achieve and maintain a more optimum additive

genetic (breed) composition needed to be investigated in a comprehensive experiment. Retention of

initial (Fj) heterozygosity after crossing and subsequent random (inter se) mating within crosses is

proportional to (n-l)/n when n breeds contribute

equally to the foundation (Wright 1922; Dickerson

1969, 1973). When breeds used in the foundation of

a composite breed do not contribute equally, the

percentage of F^ heterozygosity retained is proportional to 1 - SPJ^ , where P. is the fraction of each of

n contributing breeds to the foundation of a composite breed. This loss of heterozygosity occurs between

the Fj and F^ generations, and, if inbreeding is

avoided, further loss of heterozygosity in inter se

mated populations does not occur (Wright 1922;

Dickerson 1969, 1973).

The large differences that exist among breeds for

most bioeconomic traits are the result of different

selection goals in different breeds. Results from the

Germplasm Evaluation Program at the U.S. Meat

Animal Research Center (Cundiff et al. 1986)

provide evidence that genetic variation between

breeds is similar in magnitude to genetic variation

within breeds for many bioeconomic traits. The

heritability of breed differences approaches 100

percent, whereas the heritability of differences

within breeds for major bioeconomic traits varies

from less than 10 percent to about 50 percent,

depending on the trait. The heritability of breed

differences approaches 100 percent because estimates of breed differences are based on the means of

a large number of individuals from a representative

sample. This tends to average within-breed genetic

variation. Estimates of the heritability of differences

within breeds are generally based on single observations of individuals for a specific trait. Thus selection among breeds is much more effective than

selection within breeds.

Breed differences in bioeconomic traits are an

important genetic resource and can be used to

achieve and maintain performance levels that are

optimum for different production and marketing

situations for traits such as growth rate and size,

milk production, carcass composition, age at puberty, and climatic and nutritive adaptability. Large

breed differences exist for these traits and breed

differences may be used to achieve and maintain

optimum additive genetic (breed) composition

through the formation of composite breeds.

The focus of this bulletin is to present a summary of

results from a major experiment that was conducted

to accomplish the following objectives: (1) to estimate the retention of combined individual and

maternal heterosis (H' + H"") for major bioeconomic

traits in advanced generations of inter se mated

composite populations established with contributions by either four or five purebreeds and (2) to

evaluate the potential of composite breeds as a

procedure to use breed differences, or breed

complementarity, to achieve and maintain optimum

performance levels for major bioeconomic traits on a

continuing basis in harmony with the production

environment and market requirements.
Experimental Procedure

Populations

Matings were made to establish three composite

populations (MARC I, MARC II, and MARC III) as

indicated in table 1. In this experiment the F^ generation is defined as the first generation that reflects the

final breed composition of a composite population.

As indicated in table 1, the Fj, F^, and F^ generations

were mated inter se to produce, respectively, F^-,

F3-, and F^-generation progeny. Five breeds contributed to the MARC I population (1/4 Charoláis, 1/4

Limousin, 1/4 Braunvieh, 1/8 Hereford, and 1/8

Angus—a 75:25 ratio of continental breeds to

British breeds). Four breeds contributed to the

MARC II population (1/4 Gelbvieh, 1/4 Simmental,

1/4 Hereford, and 1/4 Angus—a 50:50 ratio of

continental breeds to British breeds). Four breeds

contributed to the MARC III population (1/4

Pinzgauer, 1/4 Red Poll, 1/4 Hereford, and 1/4

Angus—a 25:75 ratio of continental breeds to

British breeds).

Composite populations were formed from the same

sires and dams that were represented in the nine

contributing parental breeds shown in table 1.

Genetic expectations for individual (H') heterosis

and maternal (H"") heterosis for each generation are

provided in table 1. The numbers of sires used and

individuals born each year for each contributing

Table 1. Matings to establish composites, retention of heterozygosity, and expected retention of heterosis

Composite populations

MARCI MARC II MARC III Mean

Parents of F^ generations^ (C X LH) X (B X

or

(C X LA) X (B X

Reciprocals

LA) (GH) X (SA)

or

LH) (GA) X (SH)

(PA) X (RH)

or

(PA) X (HR)

Reciprocals

Breed composition of F,

and subsequent generations

0.25B, 0.25C, 0.25L

0.125H,0.125A

0.25G, 0.25S

0.25H, 0.25A

0.25P, 0.25R

0.25H, 0.25A

Fj Heterozygosity* 0.94« 1 1 0.98

F^ Heterozygosity 0.78 0.75 0.75 0.76

F3 Heterozygosity 0.78 0.75 0.75 0.76

Dam Progeny

Heterosis" F, F, 0.78 H'+0.94 H"> 0.75 H' + 1 H 0.75 H' + 1 H'" 0.76H' + 0.98 H"'

Heterosis F^ F3 0.78 H'+0.78 H-" 0.75 H' + 0.75 H"- 0.75 Hi + 0.75 H"- 0.76H' + 0.76 H-"

Heterosis F^ F4 0.78 H'+0.78 H-" 0.75 H¡ + 0.75 H'" 0.75 H' + 0.75 H"' 0.76H' + 0.76 H"-

^Composite populations were established from same animals used in purebred foundation, where C = Charoláis,

L = Limousin, H = Hereford, B = Braunvieh, A = Angus, G = Gelbvieh, S = Simmental, P = Pinzgauer, and R = Red Poll.

^Retention of initial F^ heterozygosity following crossing and subsequent random mating within the crosses (inter sé) is

proportional to 1 - 2P¡^ where P. is the fraction of each of n breeds contributing to the foundation of a composite

population. Loss of heterozygosity occurs between the F^ and F^ generations. If inbreeding is avoided, further loss of

heterozygosity does not occur.

^0.94 instead of 1 because both sires and dams of the F^ generation were one-fourth Limousin.

"hi' denotes individual heterosis expressed by progeny of a given generation and H"" denotes maternal heterosis expressed

by their dams assuming that retention of heterosis is proportional to retention of heterozygosity. F^ progeny express the

maternal heterosis (H"') of their F^ dam.
Table 2. Number of sires used and individuals bom by birth year and breed group

Total

No. no. of Individuals born

Breed

group

of

sires

indiv.

born 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991

Red Poll 51 1,322 47 129 109 114 110 109 109 88 80 84 84 87 87 85

Hereford 68 1,491 142 114 101 118 116 109 113 93 100 104 104 102 102 73

Angus 78 2,076 168 167 227 234 216 225 225 98 85 86 86 84 88 87

Limousin 56 1,478 86 127 117 115 117 121 107 99 106 98 105 96 104 80

Braunvieh 58 1,384 105 107 114 112 115 117 114 95 84 81 85 84 86 85

Pinzgauer 37 816 17 72 115 134 78 75 74 76 86 89

Gelbvieh 51 1,214 19 26 50 93 137 163 116 89 90 89 86 85 84 87

Simmental 67 1,410 145 117 111 110 116 113 111 90 88 80 82 82 84 81

Charoláis 57 1,421 90 101 118 104 116 108 117 97 99 96 100 90 94 91

MARC I-F, 20 583 33 87 141 112 107 103

MARC I-F^ 24 1,081 38 74 121 147 132 145 121 117 100 86

MARC I-F3 45 806 41 65 128 116 122 107 108 119

MARC I-F^ 24 401 37 62 84 105 113

MARC II-F, 17 730 143 198 183 132 74

MARC II-F2 28 1,328 48 100 181 223 199 117 110 105 98 82 65

MARC II-F3 42 974 42 99 174 115 116 107 105 103 113

MARC II-F4 25 533 47 74 77 99 112 124

MARC III-F, 15 556 115 108 118 113 102

MARC III-F2 24 925 42 70 129 174 144 112 100 85 69

MARC III-F3 31 694 38 73 119 132 118 97 117

MARC Ill-F^ 14 307 29 62 93 123

OJ
Table 3. Heterozygosity of different mating types and estimated increase in performance

as a result of heterosis

Mating type

Estimated

Retained

heterozygosity

relative to F,^ (%)

increase in

weight weaned

per cow

exposed* (%)

0 0

66.7 15.5

85.7 20.0

93.3 21.7

50.0 11.6

46.9 10.9

37.5 8.7

62.5 14.6

65.6 15.3

75.0 17.5

68.8 16.0

65.6 15.3

78.1 18.2

68.8 16.0

Pure breeds

Two-breed rotation

Three-breed rotation

Four-breed rotation

Two-breed composite

F3—1/2A, 1/2B

F3—5/8A, 3/8B

F3—3/4A, 1/4B

Three-breed composite

F3—1/2A, 1/4B, 1/4C

F3—3/8A, 3/8B, 1/4C

Four-breed composite

F3—1/4A, 1/4B, 1/4C, 1/4D

F3—3/8A, 3/8B, 1/8C, 1/8D

F3—1/2A, 1/4B, 1/8C, 1/8D

Five-breed composite

F3—1/4A, 1/4B, 1/4C, 1/8D, 1/8E

F3—1/2A, 1/8B, 1/8C, 1/8D, 1/8E

Six-breed composite

F3—1/4A, 1/4B, 1/8C, 1/8D, 1/8E, 1/8F

Seven-breed composite

F3—3/16A, 3/16B, 1/8C, 1/8D, 1/8E,

1/8F, 1/8G

Eight-breed composite

F3—1/8A, 1/8B, 1/8C, 1/8D, 1/8E,

1/8F, 1/8G, 1/8H

81.3

85.2

87.5

18.9

19.8

20.4

^Retention of initial F, heterozygosity after crossing and subsequent random (inter se) mating within the crosses is

proportional to {n-1 )/n when n breeds contribute equally to the foundation. When breeds used in the foundation of a

composite breed do not contribute equally, percentage of mean F, heterozygosity retained is proportional to 1 - XP,^

where P, is the fraction of each of n contributing breeds to the foundation of a composite breed. This loss of heterozygosity

occurs between the F, and F^ generations, and if inbreeding is avoided, further loss of heterozygosity in intense mated

populations does not occur.

*Based on heterosis effects of 8.5 percent for individual traits and 14.8 percent for maternal traits and the assumption that

retention of heterosis is proportional to retention of heterozygosity.
purebreed and for each generation of each composite

population are shown in table 2. Table 3 shows the

retained heterozygosity relative to the F^ generation

for different mating types and the estimated increase

in cow productivity assuming that retained heterosis

is proportional to retained heterozygosity.

Contributing purebred contemporaries have been

maintained for the Pinzgauer breed since 1982 and

for all other breeds since 1978. The first 3/4

Pinzgauer was produced in 1980, and the first 7/8

Pinzgauer (purebred for female animals in breed

registry) was produced in 1982. The 15/16

Pinzgauer (purebred for registry of male animals)

were produced after 1984. Pinzgauer females (7/8)

producing (15/16) Pinzgauer progeny were included

in the data analyses.

The Braunvieh population averaged between 3/4 and

7/8 Braunvieh and was established by using semen

from nine Braunvieh sires originating in Switzerland

and the Federal Republic of Germany (Bavaria) on a

foundation of purebred (registered and unregistered)

Brown Swiss females. The females were obtained as

calves from dairy herds in Wisconsin and Minnesota

in 1967 and 1968. The breed substitution from

Brown Swiss to Braunvieh started in 1969.

The Simmental, Limousin, Gelbvieh, and Pinzgauer

populations were established by mating 20 or more

sires of each breed to purebred dams from the same

Hereford and Angus populations used in the experiment (except as noted), followed by repeated backcrossing to the four breeds of sire. Grade-up

programs to these breeds started at the U.S. Meat

Animal Research Center in 1969 for Simmental, in

1970 for Limousin, in 1975 for Gelbvieh, and in

1977 for Pinzgauer. A sample of 3/4 Gelbvieh

females bred to produce 7/8 Gelbvieh progeny was

purchased in 1977 to augment the Gelbvieh population. The females had been graded up from a female

population of Charoláis X Angus, with the same

sample of Gelbvieh sires used in the Gelbvieh gradeup program at the research center.

The Charoláis population was established primarily

with the purchase of registered purebred Charoláis

females in 1977 and was augmented by Charoláis

graded up from an Angus X Hereford base started in

1967 at the research center. Charoláis sires were

sampled from a broad genetic base.

The Red Poll population was established from

registered females purchased from several sources in

1966, 1967, and 1968, with sires sampled from a

broad genetic base.

The Hereford and Angus breeds were maintained as

closed populations (except as noted) since about

1960. A sample of Hereford sires and dams was

added in 1966, but this sample did not produce any

male progeny that were used to maintain the population. A sample of Angus sires was introduced in

1967 and 1968, but no male progeny produced from

these matings were used to maintain the population.

Sires used to maintain the purebred populations were

descended from males and females used in the

foundation of the composite population to which a

purebreed contributed. The purebreds were maintained as registered populations recorded in the

appropriate herd book of a breed record society. The

data included in this study represent the progeny of

from 37 to 78 sires of each parental breed and 14 or

more sires in each generation of each composite

population (table 2)

Mating Procedure

All yearling heifers were exposed to natural service

by yearling bulls (except as noted) for a mating

season of 42 days. Since 1987 in Limousin and 1988

in Herefords, bulls 2 or more yr old were used on

yearling heifers because of late puberty in both sexes

of these breeds. Females 2 or more yr old were

mated by artificial insemination (AI) for 28 days,

followed by natural-service exposure for 28 days,

for a total mating season of 56 days. More than 80

percent of sires were used in 2 or more yr. From

1978 until 1984, the mating season for yearling

heifers was from mid-May until late June, and for

dams 2 or more yr old it was from the first of June

until late July. Since 1985 the mating season for

yearling heifers was from late May until near midJuly, and for dams 2 or more yr old it was from midJune until almost mid-August. This adjustment of

about 2 wk in mating and calving season was made

to allow greater synchrony of breeding and calving

with nutritive and climatic environment.
Nonpregnant animals were retained in all breed

groups until 1985, unless they were not pregnant for

2 successive yr. Since 1985, all nonpregnant animals

were removed each year from all breed groups.

Nonperformance criteria, such as age, color, and

extremes in skeletal size, were used to remove

excess cows to maintain population size for each

breed group. No females were removed from the

project before being exposed to breeding. An attempt was made to maintain a similar age distribution of dams in each breed group. The F^ generation

of each composite population was removed from the

experiment at an age of 1 yr because further loss of

heterosis is not expected beyond F^-generation

progeny (table 1). Genetic expectations for individual and maternal heterosis (H' + H"") for each

generation of each composite population are presented in table 1

Dams in each breed group were assigned to sires on

a stratified random basis within ages. Half-sib or

closer matings were avoided. The same basic criteria

were used to identify sires for breeding use in all

populations. The intent was to avoid extremes in

weight, condition, and muscular and skeletal

anatomy. Reducing dystocia was considered in

identifying sires for use in all breed groups. Larger

scrotal circumference also was favored, particularly

in breeds that are late to reach puberty (that is,

Hereford and Limousin). Polledness and color

patterns of red or red with white markings were

preferred for bulls used in all generations of each

composite population. An effort was made to maintain a broad pedigree base in all breed groups.

Genetic defects in some breed groups (that is,

"double muscling" in Gelbvieh, MARC I, and

MARC II; "parrot mouth" in Gelbvieh and

Braunvieh; malocclusion in Hereford, Angus, and

Simmental; hydrocephalus in Red Poll and MARC

III; and ataxia in Simmental), however, resulted in

some compromise of pedigree breadth by avoiding

carriers or close relatives of carriers.

Management of Heifers and Cows

Generally, female populations were fed and managed consistent with their requirements. The general

plan was to group females in three fully integrated

management units under the day-to-day supervision

of a coordinator who had operational responsibility

for this project. When a composite population and its

contributing parental breeds had similar feed and

management requirements, they were grouped and

managed together as follows:

• Group 1: All generations of the composite

MARC I population plus Braunvieh, Charoláis,

and Limousin.

• Group 2: All generations of the composite

MARC II population plus Simmental,

Gelbvieh, and Pinzgauer.

• Group 3: All generations of the composite

MARC III population plus Hereford, Angus,

and Red Poll.

The only deviation from this practice was during the

28-day natural service mating season when all dams

were in single-sire mating pastures. The Pinzgauer

females were managed with the composite MARC II

population for two reasons: (1) the three management groups had to contain similar numbers of

animals and (2) the feed and management requirements of Pinzgauer females are similar to those of

Simmental and Gelbvieh. Even though the populations were in three management groups, uniform

management protocols were followed for the three

units. Types of improved pastures (cool- and warmseason grasses), winter feeding programs, and all

basic management practices were the same and were

provided consistent with requirements. The sites

where the three management groups were maintained were contiguous; different management

groups used the same pastures at different times. All

groups received the same feed but the amounts

varied to be consistent with requirements.

Two-yr-old dams were fed a mixture of corn silage

and alfalfa haylage along with alfalfa and grass hay,

starting from 2 to 3 mo before calving and continuing until pastures were adequate to meet their requirements, which was usually in mid- to late April.

All older females were fed mixtures of alfalfa and

grass hay to meet nutritive requirements, usually

from November until mid- to late April. After 1986,

economic considerations favored feeding these

animals limited quantities of corn silage and alfalfa

haylage during the winter feeding period.
Feeding of Young Heifers and Young Bulls

The mean birth date was April 7, and calves were

weaned the first week of October in most years at an

average age of 180 days. After an adjustment feeding period (28 days), heifers were fed diets of corn

silage, alfalfa haylage, and a protein-mineral-vitamin

supplement for three consecutive time periods of

approximately equal length. Diets provided 2.34

megacalories of metabolizable energy per kilogram

of dry matter (Meal of ME/kg of DM) and 11.62

percent crude protein (CP) during period 1, 2.24

Meal of ME/kg of DM and 12.34 percent CP during

period 2, and 2.18 Meal of ME/kg of DM and 11.70

percent CP during period 3. Heifers received these

diets until they were placed on an improved coolseason grass pasture from mid- to late April, depending on adequacy of pasture to meet nutritive

requirements.

After an adjustment feeding period of 28 days after

weaning, intact males were fed a diet of corn silage,

rolled corn, and protein-mineral-vitamin supplement

(2.69 Meal ME/kg of DM, 12.88 percent CP) for

140 days.

Data Collection

Calves were weighed at birth, in the middle of the

breeding season (end of AI breeding period), at

weaning, and at 28, 84, 140, and 168 days after

weaning. Yearling heifers were weighed at the

beginning and end of the mating season and when

they were palpated for pregnancy. Thereafter,

females were weighed, measured for height, and

scored for condition three times a year at the following times: (1) before calving, (2) at the start of the

breeding season, and (3) when they were palpated

for pregnancy in late October and early November.

Observations of estrus were made in yearling heifers

starting about March 1 and continuing until the start

of the mating season. Yearling heifers were palpated

for pregnancy per rectum about 2 mo after the end of

the mating season, and animals 2 or more yr old

were palpated about 1 mo after calves were weaned.

Calving difficulty score was subjectively evaluated

using the following descriptive scores:

1 = no difficulty,

2 = little difficulty by hand,

3 = little difficulty with a calfjack,

4 = slight difficulty with a calfjack,

5 = moderate difficulty with a calfjack,

6 = major difficulty with a calfjack,

7 = caesarean birth, and

8 = abnormal presentation.

Percentage of calving difficulty was analyzed (scores

1 and 2 = 0; scores 3, 4, 5, 6, and 7=1; and scores

of 8 were excluded from the analyses). Scores of 8

also were excluded from the analysis of calving

difficulty score.

Growth, Feed Efficiency, and Carcass and Meat

Data of Castrate Males

The castrate males included in this study were the

unselected male progeny of 21 Red Poll, 22 Hereford, 23 Angus, 24 Limousin, 26 Braunvieh, 27

Pinzgauer, 27 Gelbvieh, 19 Simmental, 25 Charoláis, 39 MARC I, 30 MARC II, and 24 MARC III

sires. The steers were F3-generation progeny in the

three composite populations. Animals included in

this part of the study were born in 1988, 1989, 1990,

and 1991 from dams that were 2, 3, 4, and 5 or more

yr old.

Feeding and Management

The mean birth date of animals included in this part

of the experiment was April 13. In the last 3 yr,

animals were weaned at an average age of approximately 150 days on September 7 or 11. Because of

drought, animals were weaned on August 18 in 1988

at an average age of 127 days. Animals were initially placed on a weaning diet that provided 2.65

Meal of ME/kg of DM and 15.4 percent CP and that

was composed of ground alfalfa hay, rolled corn,

corn silage, and protein-mineral supplement. After

the animals adjusted to weaning over a period of

about 30 days, corn silage gradually replaced the

ground alfalfa hay and a portion of the rolled corn so

that the diet provided 2.69 Meal of ME/kg of DM

and 12.88 percent CP and consisted of corn silage
(66 percent), rolled corn (22 percent), and proteinmineral supplement (12 percent). At an average age

of 203 days (between October 30 and November 15)

over the 4 yr, animals of each breed group were

stratified by weight and randomly assigned to a

treatment. Before assigning animals to a treatment,

seven to nine males in each breed group were identified as candidate replacement sires. These sires

represented a broad pedigree base and were near the

mean weight of their respective breed group. Two

finishing diets varying in dietary energy content

were used for each year-breed-group subclass. Feed

level 1 (finishing diet) consisted of 2.82 Meal of

ME/kg of DM and 11.50 percent CP. Feed level 2

(finishing diet) consisted of 3.07 Meal of ME/kg of

DM and 11.50 CP. The diet (on a dry-matter basis)

for feed level 1 consisted of corn silage (59.77

percent), rolled corn (32.77 percent), and proteinmineral supplement (7.46 percent). The diet (on a

dry-matter basis) for feed level 2 consisted of corn

silage (18.00 percent), rolled corn (75.24 percent),

and protein-mineral supplement (6.76 percent).

Immediately after the animals were assigned to a

treatment, they were castrated.

The animals were kept on the backgrounding diet

(2.69 Meal of ME/kg of DM and 12.88 percent CP)

for different periods in different years before they

were put on the finishing diet. The average age at

which the animals were placed on a finishing diet in

each birth year was as follows: 1988, 319 days;

1989, 293 days; 1990, 264 days; and 1991, 212 days.

Feed-consumption data in each year were recorded

for each pen starting on the following dates: 1988,

November 9; 1989, 1990, and 1991, December 4.

Slaughter and Processing Procedures

Animals were serially slaughtered at four end points,

with 20, 21, or 22 days between slaughter dates and

63 days between the first and fourth slaughter. The

initial slaughter date was between May 21 and 26 in

each of the 4 yr. The number of days between initial

weight (203 days) to final weight averaged 204, 224,

245, and 267 days for the four slaughter groups.

Thus, the mean feeding period from initial to final

weight was 235 days and the mean slaughter age

was 438 days. Steers were assigned to slaughter

groups on a random basis stratified by weight, based

on the last weight taken before the start of the serial

slaughter schedule. The final weight of each animal

was recorded at 7 a.m. after the animals were given

access to feed and water the previous night. All

steers remaining were weighed at each slaughter

date. Weights of steers slaughtered at the first three

slaughter dates were approximately the same as

weights of steers remaining in a pen.

Steers were slaughtered in a commercial facility.

Following a chill period of 24 hr, data on fat thickness at the 12th rib, perirenal fat percentage, and

longissimus muscle area were obtained, and the right

side of each carcass was returned to the U.S. Meat

Animal Research Center to obtain carcass cut-out,

chemical composition, and sensory panel data. For

animals born in 1988,1989, and 1990, limitations on

carcass processing capability forced random sampling of sides for detailed cut-out and sensory data.

Cut-out data were obtained on all but 65 carcasses in

the 3 yr.

Carcasses were processed into wholesale cuts of

round, loin, rib, chuck, plate, flank, and brisket plus

shank. Each wholesale cut was processed further by

cutting it into boneless steaks, roasts, lean trim, and

fat trim to 0.3 inches, except that the dorsal and

lateral vertebral processes were left in the short loin

and dorsal vertebral processes and ribs were left in

standing rib roasts. Lean trim was targeted to contain

20 percent fat and was adjusted to this fat level

based on chemical analysis of the lean trim. Further

processing removed all subcutaneous and accessible

intermuscular fat (0 inches fat trim) from any surface, and the remaining bone was removed from the

short loin and from the standing rib roasts. The 9-

10-11th rib cut was removed and processed by the

procedures described for wholesale cuts and kept

separate from the remainder of the rib. Soft tissue

(lean and fat) from the 9-10-11th rib cut was ground

and sampled for determination of water and fat.

The retail product included trimmed (0.3 inches or 0

inches of fat trim) steaks and roasts plus lean trim

adjusted to 20 percent fat based on chemical analysis

of the lean trim. Lean trim was ground and sampled

for water and fat determinations to provide a basis

for adjusting individual animal yields more precisely

to 80 percent lean and 20 percent fat in the lean trim.
Carcass lean was calculated by adding the total of

boneless roasts and steaks trimmed to 0 inches of

subcutaneous and accessible intermuscular fat, and

lean trim with all fat subtracted based on chemical

analysis of the lean trim. Carcass fat was calculated

as the sum of the physically removed perirenal,

subcutaneous, and accessible intermuscular fat plus

fat mathematically removed from the lean trim based

on chemical analysis of the lean trim. Carcass bone

included all bone from the carcass.

Three measures of composition resulted from these

procedures: (1) retail product, fat trim, and bone; (2)

carcass lean, carcass fat, and carcass bone; or (3)

estimated lean, fat, and bone from the 9-10-11th rib

and the wholesale rib.

Three longissimus muscle steaks, cut 1-inch thick

from the 5th and 6th and from the 12th ribs, were

frozen on day 9 after slaughter and used for chemical determination of water and fat in the longissimus

muscle and for shear force and sensory panel evaluation of the longissimus muscle. Sample preparation

followed AMSA (1978) guidelines.

Analysis of Data

Data were analyzed by least squares mixed model

procedures (Harvey 1985). The models included the

fixed effects of breed group, year, age of dam, and

other fixed effects as appropriate. Sire within breed

group was included in all models as a random effect

for analysis of all traits. Linear functions of means

for parental breeds and for each generation of each

composite population were computed to estimate

retained heterosis. Retained heterosis was estimated

from the mean of a composite population minus the

mean of the contributing purebreeds weighted by

their contribution (1/4 or 1/8) to the composite

population. Sire within breed group mean square

was used as the error term for linear contrasts to

estimate retained heterosis effects. Studentized

Range as described by Snedecor and Cochran (1980)

was computed to obtain approximations of differences required for significance among breed group

means. For greater detail on data analyses, experimental procedures, and experimental results, see

Gregory et al. (1991a-<i; 1992a-c; 1994a-^; 1995a-c).

Results and Discussion

Heterosis and Heterosis Retention

Heterosisfor Growth Traits in Both Sexes

Heterosis effects on birth weight, 200-day weight,

368-day weight, 368-day height, 368-day condition

score, and 368-day muscling score (males only)

were evaluated separately for each sex in F^, F^, and

combined F3 and F^ generations of the three composite populations (tables 4 and 5). Combined individual and maternal heterosis (H' + H"") was

significant in the F^ F^, and combined F3 and F^

generations for each composite population and for

the mean of the three composite populations in both

sexes for most of the traits evaluated. There was

little reduction in heterosis between the F^ and F^

generations or between the F^ generation and the

combined F^ and F^ generations. In both sexes, mean

heterosis retained in combined F3 and F^ generations

was significantly greater than genetic expectation

based on retained heterozygosity for birth weight

and for 368-day weight, but did not differ (/7>0.05)

from genetic expectation for other traits. The effects

of heterosis on muscling score in males was not

important. These results support the hypothesis that

heterosis in cattle for traits related to growth and size

can be accounted for by dominance effects of genes

(tables 4 and 5).

Heterosisfor Puberty Traits in Females and

Scrotal Circumference in Males

Heterosis effects were evaluated in F^, F^, and F3

generations of females and in the F^, F^, and combined F3 and F^ generations of males in the three

composite populations. Traits included percentage of

females reaching puberty at 368, 410, and 452 days;

adjusted age and adjusted weight at puberty; and

scrotal circumference of males (table 6). Heterosis

was significant for most measures of puberty in each

generation of each composite population and for the

mean of the three composite populations. Although

results are not presented, heterosis for age at puberty

was largely independent of heterosis effects on 368-

day weight.
Table 4. Effects of heterosis on growth traits of females

Linear contrasts

Birth 200-day 368-day 368-day 368-day

weight weight weight height condition

(lb) (lb) (lb) (inches) score^

Heterosis

MARC I

Fj minus purebreds

F^ minus purebreds

F3^^ minus purebreds

Observed minus expected*

MARCH

F^ minus purebreds

F^ minus purebreds

F^^^ minus purebreds

Observed minus expected*

MARC HI

Fj minus purebreds

F^ minus purebreds

F3^^ minus purebreds

Observed minus expected*

Mean heterosis, all composites

F^ minus purebreds

F^ minus purebreds

F^^^ minus purebreds

Observed minus expected*

5.3** 40.1** 64.6** 0.8** 0.8**

5.7** 40.0** 57.3** 9** .5**

6.2** 40.0** 60.4** 1.1** _4**

2.0* 8.4* 9.9 4** -.2*

2.4** 49.0** 56.9** .8** .8**

5.3** 25.4** 44.1** .4** 5**

4.2** 31.5** 49.8** .6** .4**

2.4** -5.1 7.0 -.1 -.2*

3.7** 30.2** 50.3** .7** .4**

3.7** 33.3** 52.7** 4** .5**

4.6** 25.8** 46.1** .5** 4**

1.8 3.1 8.4 .0 .1

4.0** 39.7** 57.3** .8** .7**

4.8** 32.6** 51.4** .6** 5**

5.1** 32.4** 52.0** y** 4**

2.0** 2.2 8.4* .1 -.1

^Evaluated on a scale of 1-9, 9 = highest, 1 = lowest.

*L¡near contrasts of observed and expected heterosis to test hypothesis that retained heterosis is proportional to retained heterozygosity.

*p<0.05.

'*p<0.01.
Table 5. Effects of heterosis on growth traits of males

Birth 200-day 368-day 368-day 368-day 368-day

weight weight weight height condition muscling

Linear contrasts (lb) (lb) (lb) (inches) score^ score^

Heterosis

MARC I

Fj minus purebreds

F^ minus purebreds

F^^^ minus purebreds

Observed minus expected*

MARCH

Fj minus purebreds

F^ minus purebreds

F3^^ minus purebreds

Observed minus expected*

MARC III

Fj minus purebreds

F^ minus purebreds

F^^^ minus purebreds

Observed minus expected*

Mean heterosis, ail composites

Fj minus purebreds

F^ minus purebreds

F3^^ minus purebreds

Observed minus expected*

^Evaluated on a scale of 1 to 9, 9 = highest, 1 = lowest.

^Linear contrasts of observed and expected heterosis to test hypothesis that retained heterosis is proportional to retained heterozygosity.

*p<0.05.

^*p<0.01.

2.2* 32.8** 58.2** 0.7** 0.4** 0.10

4.2** 34.8** 51.8** j** 2** .02

4.4** 31.5** 34.4** .6** .1 -.08

2.6* 6.0* -11.0 .1 -.2* -.16

3.3** 65.3** 75.0** 1.3** _4** .00

6.2** 29.1** 54.7** 5** .5** .04

5.5** 37.7** 71.7** .8** .4** -.01

3.1** -11.2** 15.4* -.1 .1* -.02

4.0** 37.0** 57.6** g** 4**

4.6** 38.4** 69.2** .7** .4** .08

5.1** 32.2** 73.2** .7** 2** .14

2.2 4.2 30.0** .0 -.2 -.06

3.1** 45.0** 63.5** o** 4** .12

5.1** 34.2** 58.6** .6** .4** .04

5.1** 33.7** 59.8** y** 2** .02

2.6** -0.4 11.5* .0 -.1 -.07
to Table 6. Effects of heterosis on puberty traits of females and scrotal circumference of males

Percent reaching puberty in:

Linear contrasts

368

days

410

days

452

days

Adjusted

age at

puberty^

(days)

Adjusted

weight at

puberty^

(lb)

Scrotal

circumference

(cm)

Heterosis

MARC I

Fj minus purebreds

F2 minus purebreds

F3^^ minus purebreds*

Observed minus expected^

MARCH

Fj minus purebreds

F^ minus purebreds

F^^^ minus purebreds*

Observed minus expected^

MARC HI

F^ minus purebreds

F2 minus purebreds

F^^^ minus purebreds

Observed minus expected^

Mean heterosis, all composites

F^ minus purebreds

F2 minus purebreds

F3^^ minus purebreds*

Observed minus expected^

24.2** 23.6** 10.8** -22** 22** 0.9**

22.5** 23.9** 10.2** -22** 20** 1.1**

19.5** 21.3** 6.1** -21** 18** 1.4**

.6 2.7 -2.3 4 0 .7*

29.4** 26.0** 4.3* -20** 22** 1.6**

22.2** 20.0 4.1* _19** 15** 1.0**

19.9** 17.7** 2.0 -20** 15** 1.3**

-2.1 -1.8 -1.2 5 0 .1

24.3** 21.7** 7.6** -20** 15** 1.5**

15.7** 14.5** 2.6 -13** 29** .7**

10.0** 9.5** 1.9 _11** 29** .7**

-8.3 -6.8 -3.8 -4 18 -.4

26.0** 23.8** 7.5** -21** 20** 1.3**

20.2** 19.5** 5.6** -18** 22** Ç**

16.5** 16.1** 3.3* _17** 20** 1.1**

-3.3 -2.0 -2.4 1 4 .1

^Adjusted to 100 percent puberty basis.

^^4 generation for scrotal circumference only.

^Linear contrasts of observed and expected heterosis to test hypothesis that retained heterosis is proportional to retained heterozygosity.

*p<0.05.

**p<0.01.
Heterosis was significant for scrotal circumference

in each generation of each composite population and

for the mean of the three composite populations.

Results from a separate analysis showed that heterosis effects on scrotal circumference are mediated

through heterosis effects on growth rate and through

factors that are independent of growth rate. There

was close agreement in heterosis retained for puberty traits in females and for scrotal circumference

in males with genetic expectation based on retained

heterozygosity. These results support the hypothesis

that puberty traits in females and scrotal circumference in males can be accounted for by dominance

effects of genes (table 6).

Heterosisfor Birth Weight, Birth Date, Dystocia,

and Survival as Traits ofthe Dam

Heterosis effects were evaluated as traits of the dam

in F^-generation progeny of F^-generation dams and

combined F3- and F^-generation progeny of combined F^- and F3-generation dams in each of the

three composite populations and for the mean of the

three composite populations. Traits included birth

weight; birth date (Julian); percentage calving

difficulty; and percentage survival at birth, 72 hr

after birth, and at weaning (table 7). Effects of

heterosis were significant for birth weight for each

generation of each composite population and for the

mean of the three composite populations. Generally,

heterosis effects for percentage calving difficulty

(dystocia) were not significant. Effects of heterosis

were significant for date of birth (earlier) in each

generation of each composite population and for the

mean of the three composite populations. Heterosis

effects on percentage survival to weaning were

positive but generally were not significant. Heterosis

retained for birth weight, birth date, and percentage

survival in combined F3- and F^-generation progeny

of combined F^- and F3-generation dams did not

differ (p>0.05) from genetic expectation based on

retained heterozygosity. These results support the

hypothesis that heterosis in cattle for these traits can

be accounted for by the dominance effects of genes

(table 7).

Heterosisfor Reproductive and Maternal Traits

Heterosis effects in Fj-generation dams producing

F^-generation progeny and retained heterosis in

combined F^- and F3-generation dams producing F3-

and F^-generation progeny were evaluated. Traits

included percentage of dams pregnant, percentage

calf crop born, percentage calf crop weaned, 200-

day calf weight per female exposed to breeding, and

200-day calf weight (table 8). Also, breed group

means and estimates of the effects of heterosis on

the percentage of fetal death loss based on females

palpated while pregnant are presented (tables 9 and

10).

Heterosis effects were significant for all traits in F^-

generation females producing F^-generation progeny

for each composite population and for the mean of

the three composite populations (table 8). For 200-

day calf weight, heterosis effects were significant for

each generation of each composite population and

for the mean of the three composite populations. For

200-day calf weight, heterosis retained for the

composite MARC II population and for the mean of

the three composite populations was greater

(p<0.01) than genetic expectation based on retained

heterozygosity.

Heterosis effects for reproductive traits in F^-generation dams producing F^-generation progeny were

less in composite populations MARC II and MARC

III than in composite population MARC I. In the

MARC I and MARC II populations, heterosis

retained for reproductive traits in combined F^- and

F3-generation dams producing F3 and F^ progeny did

not differ (p>0.05) from genetic expectation based

on retained heterozygosity. In the MARC III population, loss of heterosis for reproductive traits (other

than for percentage pregnant) between F^-generation

dams producing F^-generation progeny and combined F^- and F3-generation dams producing F3- and

F^-generation progeny, was greater than genetic

expectation based on retained heterozygosity (table

8). This greater-than-expected heterosis loss was the

result of a higher rate of fetal death between the

diagnosis of pregnancy and parturition (tables 9 and

10).

In another major experiment involving Angus,

Hereford, and Shorthorn, there was no evidence that

heterosis (H') had an effect on either embryonic or

fetal survival. However, maternal heterosis (H"") was

important for early embryonic survival but not for

fetal survival between the diagnosis of pregnancy

and parturition (Wiltbank et al. 1967; Cundiff et al.

13
^ Table 7. Effects of heterosis on birth and survival traits for calves born from dams of all ages

Linear contrasts

Birth

weight

(lb)

Birth

date

(Julian)

Calving

difficulty

(%)

Survival

At birth

(%)

At 72 hr

(%)

At weaning

(%)

Heterosis

MARC I

F^ minus purebreds^

F^ & F3 minus purebreds^

Observed minus expected*

MARCH

F^ minus purebreds^

F^ & F3 minus purebreds^

Observed minus expected*

MARC III

Fj minus purebreds^

F^ & F3 minus purebreds*

Observed minus expected*

Mean heterosis, all composites

F^ minus purebreds^

F^ & F3 minus purebreds^

Observed minus expected*

6.0** -2.3** 0.4 -0.9 0.0 1.2

6.0** -2.4** 1.6 .3 .5 2.5

.4 .3 1.2 .5 1.4

5.7** -2.7** 1.4 .6 .6 1.8

5.7** -1.8** 3.3* .7 .9 2.6*

.9 -.5 2.1 .2 .4 1.0

4.2** -1.8** -3.2* 1.2 2.3* 3.3**

4.4** -2.7** -.4 .3 1.0 .1

.9 1.2 -2.4** -.7 -1.0 -2.7

5.3** -2.3** -.5 .3 1.0 2.1**

5.3** -2.3** 1.5 .4 .8 1.7

.7 .3 1.9 .1 -.1 -.1

T^-generation females producing F^-generation progeny and combined F^- & F3-generation females producing

F3- Si F^-generation progeny.

^Linear contrasts of observed and expected heterosis to test the hypothesis that retained heterosis is proportional to retained heterozygosity.

*p<0.05.

**p<0.01.
Table 8. Effects of heterosis on reproductive and maternal traits of dams of ali ages

Linear contrasts

Pregnant

(%)

Calves

born

(%)

Calves

weaned

(%)

200-day calf

weight per

female exposed

to breeding

(lb)

200-day

calf weight

(lb)

Heterosis

MARC

F| minus purebreds^ 7.5** 7.9** 7.8** 65** 36**

F^ & F3 minus purebreds^

Observed minus expected*

7.3**

.8

6.4**

-.5

6.6

-.2

60**

4

37**

5

MARCH

F, minus purebreds^ 3.6** 4.0** 5.0* 45** 28**

F^ & Fj minus purebreds^

Observed minus expected*

1.0

-1.9

1.2

-2.0

2.2

-1.8

40**

4

40**

16**

MARC HI

F, minus purebreds^ 5.5** 4.2** 6.2** 56** 36**

Fj & F3 minus purebreds^

Observed minus expected*

1.9

-2.6

-2.6

-6.0

-2.5

-7.5**

9

-36**

31**

1

Mean heterosis, all composites

F| minus purebreds^ 5.5** 5.4** 6.3** 55** 33**

F2 & F3 minus purebreds^

Observed minus expected*

3.4**

-1.2

1.7**

-2.8*

2.1

-3.1*

37**

-9

36**

'7**

^F^-generation females producing F^-generation progeny and combined F^- & F^-generation females producing F^- & F^-

generation progeny.

^Linear contrasts of observed and expected heterosis to test hypothesis that retained heterosis is proportional to retained

heterozygosity.

*p<0.05.

**p<0.01.

1974). Results from the current experiment do not

indicate a heterosis effect in either the Fj generation

or the combined F^ and F3 generations for fetal

survival between the diagnosis of pregnancy and

parturition in MARC I and MARC II populations

(table 10).

Subsequent to completion of this experiment and in

two other populations developed through the use of

composite MARC III bulls, fetal death loss between

pregnancy diagnosis and parturition has not differed

from other populations including composites MARC

I and MARC II. Thus the lower fetal survival observed in composite MARC III in this experiment

seems to have been a chance event or possibly

resulted from an epistatic combination that was

restored with relative ease.

For MARC I and MARC II populations, these

resuhs support the hypothesis that heterosis for

reproductive and maternal traits in cattle can be

accounted for by the dominance effects of genes.

The same conclusion can be made for maternal traits

in MARC III populations (for example, 200-day calf

weight).

15
Table 9. Breed group means for fetal death loss based on females palpated pregnant

Fetal death

Breed 2-yr-old dams 5-yr-old dams Dams of all ages

group Number % Number % Number %

Overall mean 4,744 3.8 5,153 3.6 16,820 3.7

Red Poll 305 4.9 338 3.9 1,127 6.1

Hereford 260 2.8 461 1.9 1,200 3.3

Angus 476 3.2 601 3.7 1,736 4.2

Limousin 254 2.9 422 .9 1,207 1.9

Braunvieh 316 3.2 338 2.4 1,130 3.1

Pinzgauer 285 2.8 94 3.4 759 3.0

Gelbvieh 344 2.8 185 3.3 941 2.4

Simmental 344 1.4 297 3.4 1,110 2.7

Charoláis 306 7.0 330 1.2 1,173 2.9

Parental breed mean 3.4 2.7 3.3

D.05^ for parental breeds 4.9 4.2 5.0

MARC I

F; 175 4.0 523 .9 1,070 2.2

^2 ^ ^3* 394 3.2 145 2.8 946 3.7

MARCH

F,* 242 3.5 640 2.7 1,369 2.5

^2 & F3* 461 4.0 273 3.2 1,282 3.0

MARC III

F,* 202 3.4 440 6.4 989 5.4

F2 & F3* 380 8.5 66 14.4 781 9.3

D.05^ for all breed groups 5.4 4.7 5.5

^D.05 = the approximate difference between means required for significance.

*F^-generation females producing F2-generation progeny or combined F^- & F3-generation females producing F3- & F^-

generation progeny.

HeterosisforActual Weighty Adjusted Weight, Hip

Height, and Condition Score in Females

Heterosis effects were evaluated in the three composite populations in the F^, F2, and F3 generations

separately and combined. Because heterosis did not

differ (p>0.05) between generations, only the results

16

from analysis of combined (Fj, F^, and F3) generations of females 2 yr old or older are presented in

table 11. Traits included actual weight, weight

adjusted to a common condition score, hip height,

and condition. The effects of heterosis were generally important (/?<0.05) for all traits in Fj, F^, and F3
Table 10. Effects of heterosis on fetal death based on females palpated pregnant

Linear contrasts

Fetal death loss (%) in dams that were:

2 yr 5 or more All

old yr old ages

Heterosis

MARC I

F, minus purebreds^

F2 & Fj minus purebreds^

Observed minus expected*

MARCH

F, minus purebreds^

F^ & F3 minus purebreds^

Observed minus expected*

MARC HI

F, minus purebreds^

Fj & F3 minus purebreds^

Observed minus expected*

Mean heterosis, all composites

F, minus purebreds^

Fj & F3 minus purebreds^

Observed minus expected*

0.0

.8

.8

-1.0

-1.4

-.6

0

-5.1**

-5.1**

-.3

-1.9*

-1.6«

1.0

-1.0

-1.9

.3

-.2

-.4

-3.2**

-11.2**

-8.6**

-.6

—4.1**

-3.6**

0.7

-.8

-1.4

.7

.1

-.5

-1.3

-5.1**

—4.0**

0

-2.0**

-2.0**

+F,-generation females producing F^-generation progeny and combined F_,- & Fj-generation females producing Fj- & F^-

generation progeny.

*Linear contrasts of observed and expected heterosis to test hypothesis that retained heterosis is proportional to retained

heterozygosity.

äp<0.10.

*p<0.05.

**p<0.01.

generations separately and combined in the three

composite populations. Although the estimates of

heterosis for these traits in 1-yr-old females are not

presented, generally the magnitude of heterosis

observed at 1 yr did not differ from that observed at

2-7 or more yr old. Thus, heterosis effects on

weight did not change after the females were 1 yr

old.

Adjusting weight to a common condition score

resulted in an average reduction by about one-fourth

of heterosis effects on actual weight. In other words,

about one-fourth of the effects of heterosis on weight

resulted from the effects of heterosis on condition

score. Although estimates of heterosis are not presented separately for each of the three generations of

1-yr-old females or females age 2 and greater and for

17
Actual Adjusted Hip

weight weight* height Condition

(lb) (lb) (inches) score^

Table 11. Effects of heterosis on actual weight, adjusted weight, hip height, and condition score in

females 2-7 or more yr old with composite generations combined

Linear contrasts

Heterosis^

MARC I

F|, Fj, & Fj minus purebreds

MARCH

F,, F^, & Fj minus purebreds

MARC III

F|, F^, & Fj minus purebreds

Mean heterosis, all composites

46**

20**

61**

42**

34**

12**

45**

30**

0.4"

2**

0.4"

2-iî*

a**

^Heterosis effects did not differ between generations.

^Adjusted to a common condition score.

^Evaluated on a scale of 1 to 9, 9 = highest, 1 = lowest.

*p<0.05.

**p<0.01.

the mean of the three populations, retained heterosis

in the F3 generation did not differ (p>0,05) from

genetic expectation based on retained heterozygosity. These results support the hypothesis that the

effects of heterosis on actual weight, adjusted

weight, hip height, and condition score of females

can be accounted for by the dominance effects of

genes.

Retained Heterosisfor Milk Yield and

200-Day Weight ofProgeny

Retained heterosis in F^-generation females nursing

F^-generation progeny was evaluated in females ages

3, 4, and 5 or more yr old. As indicated in table 1,

for F^-females nursing F3-generation progeny the

genetic expectation for retained heterosis averages

0.76 of the Fj level. Traits evaluated included 12-hr

milk yield, estimated 200-day milk yield, 200-day

weight of progeny, and 200-day weight of progeny

adjusted to a common estimated milk yield (table

12). Milk yield was estimated using the weigh/nurse/

weigh procedure at intervals of 5 wk when calf age

averaged 8, 13, and 18 wk. The effects of heterosis

on milk yield were significant for each of the three

composite populations. Average effects of retained

heterosis for the three populations on 12-hr milk

yield was 1.48 lb (14.5 percent), and on 200-day calf

weight it was 34 lb (6.9 percent). Adjusting 200-day

weight of progeny to a common estimated 200-day

milk yield resulted in mean retained heterosis in the

three populations of 14 lb, suggesting that about 59

percent of the retained heterosis effects observed for

200-day weight of progeny was accounted for

through retained heterosis effects on milk yield.

Retained Heterosisfor Growth, Carcass,

and Meat Traits

Retained heterosis for growth, carcass, and meat

traits was evaluated in castrate males from the F^

generation (tables 13-16). As indicated in table 1,

genetic expectation for retained heterosis in the F^

generation of the three composites averages 0.76 of

the Fj level. Retained heterosis was important in

each of the three composites and for the mean of the

three composites for initial weight, final weight,

average daily gain (ADG), carcass weight, rib-eye

18
Table 12. Effects of heterosis on milk yield and 200-day weight of progeny

(F^-generation females nursing F3-generation progeny)

Estimated 200-day Adjusted

12-hour 200-day weight 200-day

mille milk of weight

yield yield progeny of progeny^

Linear contrasts (lb) (lb) (lb) (lb)

Heterosis

MARC I minus purebreds 1.78** 719** 36** 14*

Percent heterosis 17.1 16.7 7.3 2.7

MARC II minus purebreds 1.25** 504** 41** 22**

Percent heterosis 12.1 11.9 8.2 4.7

MARC III minus purebreds 1.4Ü** 499** 26** 7

Percent heterosis 14.2 12.1 5.1 1.5

Mean heterosis, all composites

Composites minus purebreds 1.48** 574** 34** 14*

Percent heterosis 14.5 13.6 6.9 3.0

^Adjusted to a common estimated milk yield.

*p<0.05.

**p<0.01.

area, and estimated kidney, pelvic, and heart fat

(table 13). Retained heterosis was significant for

marbling score in the MARC II population but not in

either of the other two composites (table 13). There

was no retained heterosis for adjusted fat thickness

at the 12th rib or for dressing percentage.

Retained heterosis was significant for weight of

totally trimmed retail product, fat trim, and bone at

0.0 inches fat trim (table 14) and for weight of

carcass lean, carcass fat, and carcass bone in the

three composites (table 15). When evaluated on an

age constant basis, the MARC II and MARC III

populations had a significantly smaller percentage of

retail product and percentage of carcass lean and a

significantly greater percentage of fat trim and

carcass fat than the mean of parental purebreds. In

contrast, the MARC I population did not differ from

parental purebreds in carcass composition. When

carcass composition was adjusted for the effects of

carcass weight, MARC II and MARC III populations did not differ from the mean of contributing

purebreds in carcass composition. Thus, the effects

of retained heterosis on carcass composition in

MARC II and MARC III populations were through

heterosis effects on carcass weight. Generally, the

composites had a smaller percentage of bone and

greater bone weight than the mean of contributing

purebreds.

Effects of retained heterosis on traits relating to

carcass and meat quality are presented in table 16.

Table 13 shows that the MARC II population had a

significantly higher marbling score than contributing

purebreds, and table 16 shows significantly more fat

in the longissimus muscle, as determined by chemical analysis. Results reveal the higher percentage of

fat in MARC II and MARC III populations than in

contributing purebreds, whereas composite MARC I

populations did not differ (p>0.05) from contributing purebreds.

Generally, the effects of retained heterosis on carcass and meat quality traits were not important (table

16). For the MARC III population, however, the

19
o Table 13. Effects of retained heterosis on growth and carcass traits of F3-generation progeny

Average Kidney,

daily Dressing pelvic,

Initial Final weight Carcass percent- Adjusted Rib-eye and heart Marbweight weight gain weight age fat+ area* fat« ling

Linear contrasts (lb) (lb) (lb) (lb) (%) (inches) (inches^) (%) score

Heterosis

MARC I minus

purebreds 30.2** 45.9** 0.07* 29.5** 0.08 -0.05 0.54** 0.29** -^.03

MARC II minus

purebreds 51.2** 67.7** .06 42.3** .13 .08 .43** .33** .15**

MARC III minus

purebreds 22.9** 37.0** .06 26.2** .29 .08 .48** .28** .04

Mean heterosis 34.8** 50.3** .06** 32.6** .17 .02 .48** .30** .05

^Adjusted fat thickness at 12*^ rib.

*Area of the longissimus muscle.

^Estimate of kidney, pelvic, and heart fat.

Ilp<0.10.

*p<0.05.

**p<0.01.
Table 14, Effects of retained heterosis on carcass composition of F -generation progeny

Retail

%

product^

lb

Fat trim* Bone

Linear contrasts % lb % lb

Heterosis

MARC I minus purebreds -0.11 18.1** 0.49 9.3** -0.38** 1.5

MARC II minus purebreds -1.90** 12.6** 2.35** 26.7** -.44** 3.1**

MARC III minus purebreds -.89** 10.1* 1.00** 14.1** -.1 3.3**

Mean heterosis _ 07** 13.7** 1.28** 16.5** -.31** 2.6**

^Totally trimmed retail product (0.0 inches fat) includes steaks and roasts plus lean trim

adjusted to 20-percent fat based on chemical analysis of lean trim.

*AII subcutaneous (0.0 inch) and accessible intermuscular fat removed.

*p<0.05.

**p<0.01.

Table 15. Effects of retained heterosis on carcass lean, carcass fat, and carcass

bone of F3-generation progeny

Lean f Fat* Bone

Linear contrasts % lb % lb % lb

Heterosis

MARC I minus purebreds -0.12 16.0** 0.50 11.3** -0.38** 1.6

MARC II minus purebreds -1.68** 11.4** 2.12** 27.8** -.44** 3.0**

MARC III minus purebreds -.77** 94** .87* 14.9** -.10 3.3**

Mean heterosis -.86** 12.3** 1.16** 18.0** -.31** 2.6**

^Carcass lean includes steaks and roasts to 0 inches of fat cover plus fat-free lean trim based

on chemical analysis of lean trim.

*Carcass fat includes fat trim plus fat in lean trim (estimated by chemical analysis of lean trim).

*p<0.05.

**p<0.01.

21
bo Table 16. Effects of retained heterosîs on carcass and meat quality traits of

F^-generation progeny

Adjusted fat

(inches)

Marbling

score^

Long,

muscle fat

Fat in

9-11 rib cut

Shear

force

(lb)

Sensory panel scores

Linear contrasts Tenderness Juiciness Flavor

Heterosis

MARC I minus

purebreds -0.01 -0.03 -0.08 0.05 -0.33 0.16 0.00 0.01

MARC II minus

purebreds .01 .15** .29* 2.28** -.35 .02 -.02 .08*

MARC III minus

purebreds .01 .04 .04 1.37** çy** -.24** -.07 -.02

Mean heterosis .00 .05 .08 1.23** .09 -.02 -.03 .02

+A marbling score of 4.00-4.90 = slight, 5.00-5.90 = small.

*Chemical fat in longissimus muscle.

^Chemical fat in 9-11 rib cut.

'Force required to shear a 0.5-inch core.

*p<0.05.

^*p<0.01.
effects of retained heterosis were significant for

greater shear force and lower sensory panel score for

tenderness. Table 37 shows that two parental breeds

of the MARC III population (Red Poll and

Pinzgauer) may have been primarily responsible for

these significant differences since these breeds had

among the lowest values for shear force and the

highest values for tenderness. These differences are

unlikely to be the result of sampling error among

steaks because shear force and sensory panel tenderness scores were evaluated on different steaks from

the longissimus muscle.

Retained Heterosisfor Different

Measures ofGain Efficiency

The effects of retained heterosis on different measures of gain efficiency are presented in table 17 for

F3-generation castrate males. Serial slaughter of

castrate males at average ages of 407, 427, 448, and

470 days, with an overall average age of 438 days,

permitted adjustment by regression to evaluate

efficiency of gain to different end points. Retained

heterosis was not consistent among the composite

populations for the different measures of gain

efficiency. Because of their higher initial weight, the

MARC I and MARC III populations were less

efficient than the mean of parental purebreds in the

time constant period (0 to 207 days). To fat constant

end points of marbling score and percentage fat in

the longissimus muscle (table 17), the MARC II

population was more efficient and the MARC I and

MARC III populations less efficient than the mean

of parental purebreds in liveweight gain.

Generally, more favorable levels of retained heterosis were observed for the composite MARC II

population than for composite MARC I and MARC

III populations for different measures of gain efficiency. The generally lower gain per megacalories

of metabolizable energy in composites relative to the

mean of parental purebreds in some measures of

gain efficiency is due to higher initial weights and

thus to higher maintenance requirements during the

evaluation period. The higher initial weights resulted

from retained individual (H') and maternal (H"")

heterosis. Although retained individual heterosis

affected postweaning gain (table 13), it was not

sufficient to offset the higher maintenance requirement associated with higher initial weight for most

measures of gain efficiency.

Differences Among Parental Breeds

Differences in Growth Traits (Males and Females)

Differences among parental breeds include the sum

of the additive direct and additive maternal genetic

effects (G' + G""). The effects of breed group were

important (/?<0.01) for all growth traits evaluated in

females (table 18) and males (table 19). Weights

were adjusted to a mean age of dam of 3.5 yr.

The approximate differences between means, of

parental breeds and of all breed groups, required for

statistical significance (D.05) are presented in table

18 for females and table 19 for males. Means for

birth weight of females ranged from 71.9 lb in

Angus to 97.7 lb in Pinzgauer and of males from

77.0 lb in Angus to 108.0 lb in Pinzgauer. Means for

200-day weight of females ranged from 392 lb in

Hereford to 536 lb in Gelbvieh and of males from

419 lb in Hereford to 571 lb in Gelbvieh. Means for

368-day weight of females ranged from 631 lb in

Hereford to 787 lb in Simmental and Charoláis and

of males from 842 lb in Hereford to 1,052 lb in

Simmental. Means for hip height of females at 368

days ranged from 44.1 inches in Hereford to 48.8

inches in Braunvieh, Gelbvieh, Simmental, and

Charoláis and of males from 45.7 inches in Hereford

to 50.8 inches in Simmental. For condition score at

368 days, means for females ranged from 3.7 in

Limousin to 5.9 in Angus and for males from 3.3 in

Limousin to 5.6 in Hereford and Angus. Means for

muscle score of males at 368 days ranged from 4.0

in Red Poll to 6.9 in Limousin. Muscle score was

not recorded in females at 368 days.

Differences for each sex among parental breeds in

birth weight, 200-day weight, and 368-day weight

suggest great opportunity to select among breeds for

growth traits in combined additive direct (G') and

additive maternal (G"") genetic effects.

Differences in Female Puberty Traits and Male

Scrotal Circumference

Differences among parental breeds reported here

include the sum of additive direct and additive

maternal genetic effects (G' + G"").

23
Table 17. Retained heterosis for different measures of gain efficiency of F -generation castrate males

Live-•weight gain (LWG) and retail product gain (RPG) per Meal of ME

Gain To a retail To a Toa

constant Toa product wt. marb- longissimus

From carcass of 463 lb ling muscle fat

Time constant 684 to weight of (0 inches score content

Linear contrasts 0 to 207 days 1,191 lb 7341b fat trim) of 5.00 of 4%

LWG RPG LWG LWG RPG LWG LWG

Heterosis grams

MARC I minus

purebreds -2.37** -0.90* 0.14 -1.23* 1.13* -2.71** -3.12**

MARC II minus

purebreds .12 .29 2.57** 1.54* .35 .98+ 1.64*

MARC III minus

purebreds -1.00+ -.84* .34 -.10 .28 -.69 -.91

Mean heterosis -1.08** -.48+ 1.02* .07 .59+ -.81* -.80+

*p<0.05.

**p<0.01.

Puberty in females. Means for different measures

of puberty are presented by breed group in table 20.

The approximate difference required for statistical

significance (D.05) of parental breeds and of all

breed groups is also listed. The percentage of parental breeds reaching puberty by 368 days (the end of

the feeding period), 410 days (the start of the breeding season), and 452 days (the end of the breeding

season) was, respectively, 65.3 (range from 31.7 in

Hereford to 89.7 in Braunvieh), 72.9 (range from

39.9 in Hereford to 94.2 in Braunvieh), and 92.6

(range from 79.3 in Limousin to 100 in Braunvieh).

Parental breed differences in adjusted age at puberty

ranged from 350 days in Braunvieh to 411 days in

Hereford, with a mean of 376 days. This range of 61

days between breed group means is of major importance when females are exposed to mating as yearlings in a restricted 42-day mating season. Of equal

interest and significance is the difference observed

among breeds in the percentage that reached puberty

at the start of the breeding season (410 days). This

parental breed difference (39.9 percent vs. 94.2

percent) is more than twice as great as the heterosis

effect on percentage reaching puberty at the start of

the breeding season (410 days). These results suggest a high relationship among breeds between age

at puberty and breed history of selection for milk

production.

The parental breed differences in adjusted age and

weight at puberty reported here are likely underestimated because observations on date of first estrus

were not started until March 1. We can assume that a

higher percentage of breed groups that reach puberty

at younger ages had already reached puberty before

observations for estrus were started than for breed

groups that reached puberty later. Cumulative

percentages of groups that reached puberty by 368,

410, and 452 days are not as likely to be underestimated. Thus, greater attention should focus on

differences among cumulative percentages of groups

that reached puberty by 368, 410, and 452 days than

on differences in adjusted age at puberty.

24
Table 18. Breed group means for growth traits of females

Birth 200-day 368-day 368-day 368-day

Breed weight weight weight hip height condition

group Number (lb) (lb) (lb) (inches) scored

Overall mean 7,785 87.8 490 750 47.2 5.2

Red Poll 521 80.7 445 675 45.7 5.0

Hereford 537 76.5 392 631 44.1 5.6

Angus 780 71.9 423 681 44.5 5.9

Limousin 526 82.9 450 692 47.2 3.7

Braunvieh 490 94.8 525 776 48.8 4.6

Pinzgauer 282 97.7 520 776 48.4 4.6

Gelbvieh 439 92.2 536 785 48.8 4.8

Simmental 506 91.3 527 787 48.8 4.6

Charoláis 538 95.0 512 787 48.8 4.7

D.05* 2.6 11.5 17.4 .4 .2

MARC I

F, 239 92.2 514 794 48.0 5.5

F2 430 92.4 512 785 48.0 5.2

F3&F4 304 93.0 514 789 48.4 5.1

MARCH

F, 331 85.6 518 778 47.2 6.1

F, 536 88.4 494 765 46.8 5.8

F3&F, 436 87.3 500 770 47.2 5.7

MARC III

F, 243 85.6 476 741 46.4 5.7

F3 394 85.6 478 743 46.1 5.8

F3&F, 253 86.2 472 736 46.1 5.6

D.05S 3.3 14.1 21.4 .5 .3

^Evaluated on a scale of 1 to 9, 9 = highest, 1 = lowest.

*D.05 is the approximate difference between means of parental breeds required for significance.

^D.05 is the approximate difference between means of breed groups required for significance.

Results from a separate analysis indicate that breed

group differences in age at puberty are largely

independent of breed group differences in weight at

368 days.

Scrotal circumference in males. Means of scrotal

circumference are presented by breed group in table

20, along with the difference (D.05) required for

statistical significance between means of parental

breeds and of all breed groups. Mean scrotal circumference adjusted for age of dam by regression (linear, 0.434; quadratic, -0.084) (3.6 yr) and for date of

birth by regression (linear, -0.043) (354 days) was

32.4 cm for all parental breeds. Scrotal circumference at 368 days ranged from 29.0 cm in Limousin

to 34.1 cm in Gelbvieh.

25
Table 19. Breed group means for growth traits of males

Birth 200-day 368-day 368-day 368-day 368-day

Breed weight weight weight hip height condition muscling

group Number (lb) (lb) (lb) (inches) score^ score^

Overall mean 7,055 94.2 523 986 48.8 4.9 5.3

Red Poll 419 86.2 487 902 47.6 5.0 4.0

Hereford 489 81.8 419 842 45.7 5.6 4.6

Angus 754 77.0 450 882 46.1 5.6 5.1

Limousin 477 90.0 481 911 49.2 3.3 6.9

Braunvieh 454 102.1 556 1,019 50.4 4.2 5.0

Pinzgauer 222 108.0 560 1,039 49.6 4.8 4.8

Gelbvieh 377 98.1 571 1,036 50.4 4.3 5.6

Simmental 451 98.1 562 1,052 50.8 4.6 5.7

Charoláis 421 102.3 542 1,034 50.4 4.1 5.9

D.05t 3.1 12.8 22.0 .4 .2 .2

MARC I

F, 242 95.7 536 1,014 49.6 4.7 5.8

Fa 448 97.7 538 1,008 49.6 4.5 5.7

F3&F4 247 97.9 534 990 49.6 4.4 5.6

MARCH

F, 344 91.9 567 1,028 49.6 5.5 5.2

Fz 555 95.0 529 1,008 48.8 5.6 5.3

F3&F, 403 94.4 538 1,025 49.2 5.5 5.2

MARC III

F, 237 92.4 516 975 48.4 5.7 4.9

F, 381 92.8 518 986 48.0 5.6 4.7

F3&F, 134 93.5 512 988 48.0 5.4 4.8

D.05^ 3.7 15.4 26.5 .5 .3 .2

^Evaluated on a scale of 1 to 9, 9 = highest, 1 = lowest.

*D.05 is the approximate difference between means of parental breeds required for significance.

^D.05 is the approximate difference between means of breed groups required for significance.

Significant differences among breed groups re- Correlations. Correlation coefficients between

mained in scrotal circumference after adjusting by group means for puberty traits in females and scrotal

regression for differences in weight at 368 days. circumference in males were 0.88 (p<0,01) or higher

This result suggests that differences among breed (table 21). Correlation coefficients between breed

groups in scrotal circumference are influenced only group means for puberty traits in females and perin part by breed group differences in weight at 368 centage of yearlings pregnant were 0.87 (p<0.01) or

days. higher (table 22).

26
Table 20. Breed group means for puberty traits in females and scrotal circumference in males

Number of

females

Puberty traits in females

Number oi

males

Breed

group

Percent

368

days

reaching puberty by:

410 452

days^ days*

Adjusted

age«

(days)

Adjusted

weight«

(lb)

Scrotal

circum-

' ference"

(cm)

Overall mean 6,034 72.4 79.8 94.8 370 736 6,649 32.8

Red Poll 450 83.7 88.6 97.4 359 650 410 33.1

Hereford 427 31.7 39.9 82.8 411 695 472 30.3

Angus 670 46.1 57.4 93.3 393 697 738 32.1

Limousin 403 36.1 44.0 79.3 408 743 464 29.0

Braunvieh 359 89.7 94.2 100.0 350 732 444 33.7

Pinzgauer 246 85.8 92.1 96.6 360 739 215 33.0

Gelbvieh 330 86.3 92.9 99.1 353 745 366 34.1

Simmental 358 77.4 86.8 98.0 363 758 437 33.7

Charoláis 406 50.7 60.6 86.5 391 814 406 32.2

Parental breed 65.3 72.9 92.6 376 730 32.4

mean

D.05^ 11.0 10.0 6.2 8.1 20.7 .7

MARC I

F, 182 78.0 85.5 99.2 366 767 240 32.5

F2 332 76.3 85.8 98.7 366 765 405 32.7

F3&F4'' 190 73.4 83.0 94.6 367 763 201 33.0*+

MARCH

F, 274 89.8 95.2 97.6 360 745 340 34.1

F2 410 82.6 89.3 97.4 361 738 502 33.6

F3&F;+ 239 80.3 86.9 95.3 360 739 344 33.8**

MARC III

F. 243 86.2 91.2 100.0 361 710 233 33.6

F, 358 77.6 84.0 95.1 368 723 330 32.8

F3&F/+ 157 71.8 79.0 94.4 370 723 102 32.8**

D.05« 13.5 12.4 7.7 10.0 25.6 .9

MIO days = start of breeding season.

* 452 days = end of breeding season.

^ Adjusted to a 100-percent puberty basis.

II Adjusted to a common age.

Î D.05 is the approximate difference between means of parental breeds required for significance.

^^ F^-generation for scrotal circumference only.

** D.05 is the approximate difference between means of all breed groups required for significance.

27
General. These results reveal large differences

among breeds in percentage reaching puberty at 368,

410, and 452 days; in age of females at puberty; and

in scrotal circumference of males and show a high

correlation among breed group means for these

traits. Breed differences in these traits provide

considerable opportunity to use genetic differences

among breeds to optimize additive genetic value to

meet a wide range of production situations.

Adjusting female age at puberty for differences in

368-day weight by regression had little effect on

breed rank or variation among breeds for age at

puberty, suggesting that differences in age at puberty

among breeds is largely independent of breed differences in growth rate to 368 days. Adjusting scrotal

measurements by regression for differences in

weight at 368 days resulted in some reduction in

variation among breeds in scrotal circumference (the

range was reduced from 5.1 to 3.7 cm). However,

significant breed differences in scrotal circumference were still present. Although differences in

scrotal circumference among breeds are partially

attributable to breed differences in weight at 368

days, there are important differences (p<0,01)

among breeds in scrotal circumference that are

independent of weight.

Differences in Birth Weight, Birth Date,

Dystocia, and Survival

Differences among parental breeds include additive

direct genetic effects and additive maternal genetic

effects (G' + G"^).

Table 21. Correlation coefficients among parental breed means for puberty traits in

females and scrotal circumference in males

Female puberty traits Scrotal circumference (cm)

Percentage in puberty at 368 days

Percentage in puberty at 410 days

Percentage in puberty at 452 days

Age at puberty (in days)

Age at puberty (adjusted for 368-day weight)

0.88**

.95**

_ Q1 **

_ Ql **

*/7<0.01.

Table 22. Correlation coefficients among parental breed means for puberty traits and

percentage of females pregnant as yearlings

Female puberty traits

Percentage in puberty at 368 days

Percentage in puberty at 410 days

Percentage in puberty at 452 days

Age at puberty (in days)

Age at puberty (adjusted for 368-day weight)

Pregnancy (%)

0.87**

.89**

.97**

-.89**

-.88**

**jr7<0.01.

28
Calves with 2-yr-old dams. Table 23 gives birth

and survival data for calves from 2-yr-old dams. The

mean birth weight of parental breed calves was 83.1

lb. Birth weight ranged from 69.4 lb in Angus to

93.3 lb in Braunvieh. The mean Julian birth date for

parental breed calves was 79. The Julian birth date

ranged from 74 in Red Poll and Pinzgauer to 88 in

Limousin. Breed rank for birth date is highly associated with age at puberty or gestation length or both.

The mean for calving difficulty (percentage of dams

requiring assistance) in parental breeds was 52.6

percent. Calving difficulty ranged from 31.8 percent

in Angus to 73.8 percent in Braunvieh. Mean calf

survival at weaning for parental breeds was 80.4

percent. Survival at weaning ranged from 74.3

percent in Hereford to 85.4 percent in Red Poll.

Results from a separate analysis showed that the

effects of breed group were important (p<0.01) for

percentage calving difficulty and survival at birth, at

72 hr, and at weaning, independent of breed group

effects on birth weight. The sex of the calf had an

important effect (p<0.01) on percentage calving

difficulty, independent of the effects of sex on birth

weight. Sixty-two percent of the male calves and 46

percent of the female calves (adjusted to a common

birth weight) required assistance.

Calf weight at birth had an important effect on

birthing difficulty and calf survival. Each 1-lb

increase in birth weight resulted in a 1.9-percent

(linear) increase in the need for assistance at birth.

The negative linear and quadratic (curvilinear)

regressions (p<0.01) of survival percentage at birth,

at 72 hr, and at weaning on birth weight reflect the

importance of birth weight on calf survival percentage and the curvilinearity of the effect. The significant effect of breed group on percentage calving

difficulty and survival at birth, at 72 hr, and at

weaning (adjusted to a common birth weight) reflect

important differences among breed groups for these

traits, independent of the effects of breed group on

birth weight. Thus, there appears to be some opportunity to reduce dystocia and to increase calf survival rate by considering factors other than birth

weight, such as anatomical characteristics of the

dam and the calf. Similarly, the greater percentage

of calving difficulty in the birth of males at a common birth weight shows that sex of the calf has an

important effect, independent of the effects of sex on

birth weight.

Calves with dams 3 yr old or older. The mean

birth weight of parental breed calves born from

dams 3 or more yr old was 92.6 lb. Birth weight

ranged from 76.3 lb in Angus to 104.5 lb in

Pinzgauer (table 24). The mean birth date (Julian) of

parental breed calves was 105. Julian birth date

ranged from 99 in Angus to 109 in Limousin and

Braunvieh. The mean calving difficulty of parental

breed calves was 8.6 percent. Calving difficulty

ranged from 0.9 percent in Angus to 15.9 percent in

Pinzgauer. Mean calf survival at weaning of parental

breed calves was 92.6 percent. Survival at weaning

ranged from 88.1 percent in Simmental to 95.6

percent in Red Poll.

In a separate analysis, gestation length, birth date,

birth weight, calving difficulty, and survival at birth

and at 72 hr were analyzed for calves born to dams 3

or more yr old. Data on gestation length were not

available on calves born from 2-yr-old dams. Breed

group effects were significant for gestation length,

birth date, birth weight, and calving difficulty but

not for survival at birth and at 72 hr. A regression

analysis of these traits on gestation length, gestation

length within sex, and gestation length within breed

group was conducted. The analyses revealed that the

linear regressions of all traits on gestation length

(days) were significant; that is, birth date, 1 day;

birth weight, 0.9 lb; survival at birth, 0.1 percent;

and survival at 72 hr, 0.2 percent. Gestation length

accounted for 90 percent of the breed group variation in birth date, 14 percent of the breed group

variation in birth weight, and 31 percent of the breed

group variation in percentage calving difficulty.

Calves with dams of all ages. Mean birth weight of

parental breed calves from dams of all ages was 90.2

lb. Birth weight ranged from 74.7 lb in Angus to

101.9 lb in Pinzgauer (table 25). Mean birth date

(Julian) of parental breed calves from dams of all

ages was 99. Julian birth date ranged from 93 in

Angus to 104 in Limousin. Mean calving difficulty

of parental breed calves from dams of all ages was

19.7 percent. Calving difficulty ranged from 8.8

percent in Angus to 28.5 percent in Braunvieh.

Mean calf survival at weaning of parental breed

calves with dams of all ages was 89.7 percent.

29
Table 23. Breed group means for birth and survival of calves from 2-yr-old dams

Calf Calf Calving

Number

birth

weight

birth

date

difficulty^

Survival of calves (%)

Breed At At At

group of births (lb) (Julian) (%) birth 72 hr weaning

Overall mean 4,140 83.8 78 52.5 95.5 89.0 81.0

Red Poll 268 76.7 74 54.0 95.7 90.6 85.4

Hereford 242 74.5 84 49.1 93.2 86.2 74.3

Angus 433 69.4 75 31.8 93.0 86.2 81.4

Limousin 210 79.4 88 40.6 96.0 85.1 76.2

Braunvieh 287 93.3 80 73.8 98.2 90.8 81.0

Pinzgauer 250 92.4 74 62.1 95.2 88.9 82.3

Gelbvieh 321 88.4 79 60.5 93.6 88.1 79.2

Simmental 312 85.3 79 52.5 97.9 91.2 80.9

Charoláis 261 88.4 78 48.6 98.0 92.8 82.8

Parental breed mean 83.1 79 52.6 95.6 88.9 80.4

D.05* 3.3 3.3 13.2 5.1 8.0 9.9

MARC I

F,§ 167 88.4 77 55.5 95.4 89.8 82.1

^2 & F3* 308 90.0 79 56.6 96.8 90.7 82.9

MARCH

F,^ 232 83.8 76 50.6 94.6 86.8 78.4

F2 & ^3^ 393 85.8 75 57.1 95.1 87.8 83.1

MARC III

F,^ 192 80.9 72 46.2 95.1 89.5 84.4

F2 ^ ^3^ 264 81.4 76 48.4 95.2 90.1 81.2

D.05' 3.7 3.7 14.9 5.8 9.1 11.2

^ Percentage of dams requiring assistance.

* D.05 is the approximate difference between means of parental breeds required for significance.

^ F^-generation females producing F^-generation progeny and combined F^- & F3-generation females

producing F3- & F^-generation progeny.

*" D.05 is the approximate difference between means of all breed groups required for significance.

30
Table 24. Breed group means for birth and survival of calves from dams 3 or more years old

Calf Calf Calving

Number

birth

weight

Gestation

length

birth

date

difficulty^

Survival of calves (%)

Breed At At At

group of births (lb) (days) (Julian) (%) birth 72 hr weaning

Overall mean 10,710 93.3 287 104 8.1 98.2 96.3 93.3

Red Poll 706 86.2 288 103 3.0 98.7 97.4 95.6

Hereford 818 81.1 288 107 5.1 97.6 95.7 93.9

Angus 1,133 76.3 283 99 .9 98.5 94.9 91.7

Limousin 871 88.6 289 109 7.2 98.3 96.6 93.2

Braunvieh 714 100.1 290 109 13.2 98.2 96.9 91.9

Pinzgauer 391 104.5 287 103 15.9 96.1 94.4 91.6

Gelbvieh 611 97.7 287 107 8.3 99.2 97.6 93.7

Simmental 671 97.0 287 106 14.4 97.0 93.4 88.1

Charoláis 784 101.4 286 105 9.8 98.8 97.3 93.4

Parental breed mean 92.6 287 105 8.6 98.0 96.0 92.6

D.05* 2.4 1.6 2.8 5.1 2.0 2.8 4.0

MARC I

F,^ 828 98.1 287 106 8.2 97.2 96.2 93.3

F, & F/ 453 97.9 288 104 8.9 98.6 96.5 94.9

MARCH

F,^ 1,031 94.2 287 102 8.3 98.7 96.9 94.8

F, & F3S 662 93.3 287 104 9.3 98.8 96.5 93.8

MARC III

F,« 664 91.5 287 103 3.3 98.9 98.1 96.0

F2 ^ ^3 307 91.7 286 100 6.1 97.9 96.2 93.2

D.05' 2.9 1.9 3.3 5.8 2.3 3.2 4.7

^ Percentage of dams requiring assistance.

* D.05 is the approximate difference between means of parental breeds required for significance.

^ F^-generation females producing F^-generation progeny and combined F^- & F^-generation females

producing F^- & F^-generation progeny.

""D.OS is the approximate difference between means of all breed groups required for significance.

Survival at weaning ranged from 86.4 percent in

Simmental to 93.4 percent in Red Poll.

General. These results show large differences

among breeds in percentage calving difficulty,

particularly in calves from 2-yr-old dams. While the

means are not presented, calves with difficult births

from 2-yr-old dams were significantly heavier at

birth and had significantly lower survival rates at 72

hr and at weaning than calves from 2-yr-old dams

that did not have difficult births. Large differences

were observed among breed groups in calving

difficulty and calf survival, independent of the

effects of breed group on birth weight. This result

suggests some opportunity to reduce calving diffi31
Table 25. Breed group means for birth and survival of calves from dams of all ages

Calf Calf Calving

Number

birth

weight

birth

date

difficulty^

Survival of calves (%)

Breed At At At

group of births (lb) (Julian) (%) birth 72 hr weaning

Overall mean 14,850 91.1 98 19.2 97.6 94.5 90.4

Red Poll 974 83.8 96 15.9 98.0 95.9 93.4

Hereford 1,060 79.4 101 16.5 96.6 93.3 89.2

Angus 1,566 74.7 93 8.8 97.2 92.8 89.3

Limousin 1,081 86.4 104 15.7 97.8 93.8 89.2

Braunvieh 1,001 98.6 102 28.5 98.3 95.5 89.3

Pinzgauer 641 101.9 96 27.4 96.0 92.9 89.0

Gelbvieh 998 95.2 100 21.5 97.9 95.3 90.4

Simmental 983 94.2 99 23.9 97.3 92.9 86.4

Charoláis 1,045 98.1 98 19.5 98.7 96.3 90.9

Parental breed mean 90.2 99 19.7 97.5 94.3 89.7

D.05* 2.2 2.4 5.8 2.2 3.2 4.2

MARCI

V 995 95.9 98 19.5 97.0 94.7 90.8

F^&FjS 761 96.1 98 20.7 98.2 95.1 92.0

MARCH

F/ 1,263 91.7 96 19.1 97.8 94.1 90.6

F^ifeFj« 1,055 91.7 96 21.0 97.9 94.5 91.4

MARC III

F,^ 856 89.1 94 13.9 98.1 96.0 93.5

F2&F3S 571 89.3 94 16.7 97.3 94.7 90.3

D.05' 2.6 2.7 6.6 2.5 3.7 4.8

^ Percentage of dams requiring assistance.

* D.05 is the approximate difference between means of parental breeds required for significance.

^ F^-generation females producing F^-generation progeny and combined F^- & F^-generation females

producing F^- & F^-generation progeny.

^D.05 is the approximate difference between means of all breed groups required for significance.

32
culty and to increase calf survival by considering

factors other than birth weight such as anatomical

characteristics of the dam and calf. Similarly, greater

calving difficulty was observed in male calves than

in female calves, independent of sex effects on birth

weight, indicating that anatomical differences

between sexes likely contribute to dystocia. In a

separate analysis of births from 2-yr-old females,

calf survival at weaning was lowest (p<0.05) in the

smallest and largest birth weight classes and did not

differ (p>0.05) among intermediate birth weight

classes. These resuhs document that intermediate

birth weights are optimum for increased survival.

Differences in Reproductive and Maternal Traits

Differences among parental breeds include additive

direct genetic effects and additive maternal genetic

effects (G' + C").

Because age has an important effect on reproductive

and maternal traits of different breeds, results are

presented for females of three different ages—2 yr

old, 5 or more yr old, and all ages combined.

Females 2 yr old. Means of parental breeds and of

all breed groups are presented in table 26, along with

the approximate difference between means required

for significance.

Large differences (p<0.01) were observed among

parental breeds for the percentage of females pregnant when bred as yearlings in a 42-day mating

season. The means ranged from 54.7 percent in

Limousin to 85.6 percent in Gelbvieh. Breed group

means for percentage of female yearlings pregnant

were highly associated (p<0.01) with breed group

means in measures of puberty (table 22). Large

differences (p<0.01) in the percentage of calves born

were observed among parental breeds. The differences between the percentage of pregnancies and the

percentage of calves born (an average of 2.6 percent)

reflect errors in diagnosing pregnancy by rectal

palpation and fetal losses between pregnancy diagnosis and parturition. Rank of parental breeds for

percentage of calves born was similar to the rank of

breeds for percentage pregnant—Limousin had the

lowest birth rate (53.0 percent) and Gelbvieh the

highest (83.2 percent). Large differences (/?<0.01)

were observed among parental breeds in the percentage of calves surviving to weaning. Differences

between the percentage of calves born and the

percentage surviving to weaning reflect calf mortality. Calf mortality averaged 13.7 percent and included calves that were dead at birth. Rank of

parental breeds for percentage of calf crop weaned

was similar to the rank of breeds for calf crop

born—Limousin had the lowest percentage (4L8

percent), and Braunvieh the highest (66.4 percent).

Large differences (p<0.01) were observed in 200-

day calf weight per female exposed to breeding.

These values reflect differences among parental

breeds in the percentage of calves weaned and 200-

day calf weight; that is, reproduction rate, calf

survival, and preweaning growth for additive genetic

maternal effects (G"') and additive direct genetic

effects (G'). Because of the importance of fitness

traits (that is, reproduction rate and survival) in

contributing to this measure of output per female,

there was considerable similarity in breed rank for

200-day calf weight per female exposed and measures of fitness. Hereford ranked lowest (178 lb) and

Gelbvieh ranked highest (340 lb) in 200-day calf

weight per female exposed to breeding.

Large differences (p<0.01) were observed in 200-

day calf weight. Hereford ranked the lowest (378 lb)

and Gelbvieh highest (506 lb). These values include

breed differences in additive maternal genetic effects

(G"') and additive direct genetic effects (G') for

preweaning growth.

Females 5 or more yr old. Means are presented by

breed group in table 27, along with the approximate

difference required for significance (D.05). Comparisons of differences can be made between parental breeds and between means of all breed groups.

Because of the large differences among breeds in

reproductive traits of 2-yr-old females associated

with age differences at puberty (tables 21 and 22), it

was desirable to evaluate breed differences in reproductive and maternal traits after the animals were

mature (at an age of 5 to 10 yr old, at parturition).

Parental breed differences were large (/7<0.05) for

200-day calf weight per female exposed to breeding.

Hereford ranked lowest (348 lb) and Charoláis

highest (477 lb). However, Charoláis, Braunvieh,

Gelbvieh, Simmental, and Pinzgauer did not differ

(/7>0.05) from each other. The Hereford breed was

lighter (p<0.05) than all breed groups except Angus,

33
Table 26. Breed group means for reproductive and maternal traits of females 2 yrs old

Calf Calf 200-day calf

crop crop weight per 200-day

Number of Percentage born weaned female exposed calf weight

Breed group females pregnant^ (%)t (%)t to breeding (Ib)^ (lb)

Overall mean 6,535 77.3 74.4 60.6 284 463

Red Poll 436 81.0 77.0 66.2 286 432

Hereford 453 64.1 62.3 46.8 178 378

Angus 685 77.9 75.4 61.8 249 402

Limousin 474 54.7 53.0 41.8 179 427

Braunvieh 426 83.0 80.3 66.4 334 500

Pinzgauer 373 81.6 79.3 64.1 314 486

Gelbvieh 458 85.6 83.2 66.2 340 506

Simmental 477 82.4 81.2 66.0 331 498

Charoláis 476 72.3 67.2 56.2 269 478

Parental breed mean 75.8 73.2 59.5 276 456

D.05* 10.5 11.4 11.6 54.0 11.5

MARC I

F/ 230 78.2 75.1 62.1 305 487

F^&FjS 551 86.3 83.5 69.0 336 486

MARCH

F,^ 331 73.9 71.3 56.7 269 472

F2&F3S 714 74.8 71.8 59.1 288 484

MARC III

F,^ 250 82.2 79.4 66.9 308 460

F2&F35 501 81.6 74.7 60.5 275 451

D.05« 11.9 13.0 13.2 61.5 13.0

^Based on females exposed to breeding; pregnancy determined by rectal palpation.

*D.05 is the approximate difference between means of parental breeds required for significance.

^F^-generation females producing F^-generation progeny and combined F^- & F3-generation females

producing F3- & F^-generation progeny.

^D.05 is the approximate difference between means of all breed groups required for significance.

34
Table 27. Breed group means for reproductive and maternal traits of females 5 or more years old

Breed group

Number of

females

Percentage

pregnant^

Calf

crop

born

(%)t

Calf

crop

weaned

(%)t

200-day calf

weight per

female exposed

to breeding (Ib)^

200-day

calf weight

(lb)

Overall mean 7,920 90.8 87.4 83.0 438 528

Red Poll 607 89.6 86.1 84.2 411 489

Hereford 728 86.0 84.4 80.7 348 431

Angus 1,030 91.3 87.9 82.4 384 465

Limousin 736 87.8 87.0 82.6 406 491

Braunvieh 599 90.6 88.4 84.2 476 566

Pinzgauer 188 90.5 87.4 79.3 445 565

Gelbvieh 328 88.5 85.6 82.6 474 571

Simmental 516 87.8 84.8 78.8 453 575

Charoláis 569 90.8 89.7 85.2 477 560

Parental breed mean 89.2 86.8 82.2 430 523

D.05* 5.7 7.6 8.3 44.1 12.3

MARCI

624 92.9 92.1 86.6 473 546

^2 & F3* 202 95.2 92.5 88.6 484 546

MARCH

F,« 820 93.3 90.7 85.3 448 523

F, & F3^ 347 91.3 88.4 84.4 467 553

MARC III

F,' 522 92.4 86.5 83.0 427 516

F.&F« 104 94.4 80.8 77.4 406 525

D.05« 6.6 8.7 9.5 50.9 14.3

* Based on females exposed to breeding; pregnancy determined by rectal palpation.

* D.05 is the approximate difference between means of parental breeds required for significance.

* F,-generation females producing F^-generation progeny and combined F^- & Fj-generation females

producing F^- & F^-generation progeny.

II D.05 is the approximate difference between means of all breed groups required for significance.

35
and this difference approached significance

(p<0.10).

Large parental breed differences (p<0.01) were

observed for 200-day calf weight. Hereford (431 lb)

was significantly lighter than all other breed groups.

Simmental (575 lb) was significantly heavier

(p>0.05) than the other breeds except for Braunvieh,

Gelbvieh, and Pinzgauer.

Females of all ages. Means of reproductive and

maternal traits are presented by breed group in table

28, along with the approximate difference (D.05)

required for significance. Comparisons of differences can be made between parental breeds and

between means of all breed groups.

Large differences (p<0.01) in the percentage of

females pregnant were observed among parental

breeds. Limousin had the lowest percentage (74.8

percent) and Red Poll the highest (86.6 percent). The

Limousin and Hereford breeds did not differ

(p>0,05) from each other, nor did the Red Poll,

Braunvieh, Angus, Simmental, Charoláis, Gelbvieh,

and Pinzgauer. Large differences (p<0.01) were

observed among parental breeds for calf crop born

percentage. Limousin ranked lowest (73.4 percent)

and Pinzgauer highest (83.7 percent). Again, the

Limousin and Hereford breeds did not differ

(p>0.05) from each other. The Red Poll, Braunvieh,

Angus, Simmental, Charoláis, Gelbvieh, and

Pinzgauer did not differ (p>0.05) significantly.

Large differences (/7<0.01) were observed among

parental breeds for calf crop weaned percentage.

Limousin ranked lowest (66.0 percent) and Red Poll

highest (76.2 percent). The means for Limousin,

Hereford, and Simmental did not differ (p>0,05)

from each other. The means for Red Poll, Braunvieh,

Angus, Charoláis, Gelbvieh, and Pinzgauer also did

not differ (p>0.05) from each other. Differences

between the calf crop born percentage and the calf

crop weaned percentage reflect calf mortality and

include calves that were dead at birth. The mean

difference for all breeds was 8.0 percent. Simmental

had the highest calf mortality rate (10,8 percent) and

Red Poll the lowest (5.1 percent).

Large differences (p<0,01) were observed among

parental breeds in 200-day calf weight per female

exposed to breeding. Hereford ranked the lowest

(280 lb) and Gelbvieh the highest (413 lb). Hereford

ranked lower (p<0,05) than all other breed groups

except Limousin. The difference between Hereford

and Limousin, however, approached significance

(/?<0.10). Gelbvieh did not differ (/?>0.05) from

Pinzgauer, Braunvieh, and Charoláis.

Large differences (p<0.01) were observed among

parental breeds in 200-day calf weight. The Hereford breed was the lightest (407 lb) and was significantly lighter (p<0,05) than all other parental breeds.

The Simmental and Gelbvieh breeds were the

heaviest (544 lb) and were significantly heavier

(p<0.05) than all parental breeds except Braunvieh.

General. For most of the traits measured for the

three age groups, the differences among means for

the parental breeds were greater for the 2-yr-old

females than for the age groups "5 or more yr old"

and "of all ages." Such was the case for pregnancy

rate, percentage calf crop born, percentage calf crop

weaned, and 200-day calf weight per female exposed to breeding. The large differences in pregnancy rate among parental breed 2-yr-old females

can be largely accounted for by differences in

measures of puberty (tables 21 and 22). Even though

the differences for females of all ages were of lesser

magnitude, large differences (p<0.05) were observed

for pregnancy rate, percentage calf crop born,

percentage calf crop weaned, and 200-day calf

weight per female exposed to breeding. Pregnancy

rates of yearlings were lower and therefore reduced

the overall pregnancy rate when averaged over all

ages.

DifferencesforActual Weight, Adjusted Weight,

Hip Height, and Condition Score ofFemales

Data on 1-yr-old females were collected 168 days

after weaning, at the end of the breeding season (452

days) and when the females were palpated for

pregnancy (522 days). Data on females 2 yr old and

older were collected in February (about 2 mo before

calving), in June (before the start of the breeding

season), and in October (when the females were

palpated for pregnancy). The results presented in

tables 29-32 reflect the mean values of observations

made within a year. The approximate difference

required for significance between means of parental

breeds and between means of all breed groups are

presented in tables 29-32. Cows from which no calf

36
Table 28. Breed group means for reproductive and maternal traits of females of all ages

Breed group

Number of

females

Percentage

pregnant^

Calf

crop

born

(%)t

Calf

crop

weaned

(%)t

200-day calf

weight per

female exposed

to mating (Ib)^

200-day

calf weight

(lb)

Overall mean 24,342 84.7 81.6 73.8 372 502

Red Poll 1,710 86.6 81.3 76.2 356 467

Hereford 1,835 78.9 76.3 68.2 280 407

Angus 2,763 84.6 81.0 72.6 320 439

Limousin 1,958 74.8 73.4 66.0 306 461

Braunvieh 1,696 85.0 82.4 73.9 400 539

Pinzgauer 1,066 86.3 83.7 74.8 401 534

Gelbvieh 1,365 85.2 83.2 75.5 413 544

Simmental 1,718 83.1 80.8 70.0 382 544

Charoláis 1,804 83.2 80.8 73.7 387 522

Parental breed mean 83.1 80.3 72.3 361 495

D.OS* 4.6 5.5 5.0 28.2 8.4

MARC I

1,281

1,301

88.7

88.5

86.7

85.2

78.8

77.6

414

409

522

523

MARCH

F, & F/

1,739

1,825

86.5

84.0

84.3

81.5

76.6

73.8

394

389

512

523

MARC III

F,^

F2 & ^3^

1,202

1,079

89.6

86.0

84.8

78.0

79.2

70.5

395

349

497

492

D.05' 5.3 6.2 5.7 32.2 9.7

^Based on females exposed to breeding; pregnancy determined by rectal palpation.

*D.05 is the approximate difference between means of parental breeds required for significance.

^F^-generation females producing F^-generation progeny and combined F^- & F^-generation females

producing F3- & F^-generation progeny.

•D.05 is the approximate difference between means of all breed groups required for significance.

37
was weaned in a given year were excluded from the

data set for that year.

Differences among parental breeds include additive

direct genetic effects and additive maternal genetic

effects (G' + G'").

1-yr-old females. Breed group means for 1-yr-olds

are provided in table 29 for actual weight, weight

adjusted to a common condition score, hip height,

and condition score. Large differences were observed among breed groups for all traits evaluated.

2-yr-old females. Breed group means for 2-yr-olds

are provided in table 30 for actual weight, weight

adjusted to a common condition score, hip height,

and condition score. Large differences were observed among breed groups for all traits evaluated.

The magnitude of difference in weight between

specific breed groups was reduced considerably as a

result of adjusting weight to a common condition

score.

6-yr-old females. Breed group means for 6-yr-olds

are provided in table 31 for actual weight, weight

adjusted to a common condition score, hip height,

and overall condition score. Again, large differences

were observed among breed groups for all traits

evaluated. Similarly, the magnitude of difference in

weight was reduced considerably as a result of

adjusting to a common condition score.

Females 2-7 or more yr old. Breed group means

for females 2-7 or more yr old are provided in table

32 for actual weight, weight adjusted to a common

condition score, hip height, and condition score.

Large differences were observed among breed

groups for all traits evaluated.

Differencesfor Milk Yield and 200-Day

Weight ofProgeny

Milk yield data were recorded using the weigh/

nurse/weigh procedure for the 12 breed groups when

calf age averaged 8, 13, and 18 wk (table 33). Large

differences were observed among parental breeds in

12-hr milk yield. Herefords were lowest and

Braunvieh produced significantly more than all

breed groups except Simmental (though the difference between Braunvieh and Simmental approached

significance). The order in which parental breeds

ranked for 12-hr milk yield was similar to the order

in which they ranked for 200-day weight of progeny.

The correlation among breed group means for 12-hr

milk yield with 200-day weight of progeny was

0.91.

Differences among parental breeds in 200-day

weight adjusted by regression to a common estimated milk yield are expected primarily to reflect

differences in additive direct genetic effects (G') for

200-day weight. For 200-day weight adjusted to a

common milk yield. Red Poll, Hereford, Angus, and

Limousin did not differ (/?>0.05) from each other

and all were significantly lighter than Braunvieh,

Pinzgauer, Gelbvieh, Simmental, and Charoláis,

which did not differ (p>0.05) from each other (table

33).

Differences in Growth, Carcass, and Meat Traits

Differences among parental breeds reported here

include the sum of the additive direct and additive

maternal genetic effects (G' + G"").

Breed group means for growth and carcass traits.

Breed group means for contributing purebreds and

for composites are presented in table 34. Large

differences were observed among breed groups in

growth traits and carcass traits measured in the

cooler. Initial weight was taken at an average age of

203 days and final weight was taken at slaughter at

an average age of 438 days (the average length of

the feeding period was therefore 235 days). Steers

were serially slaughtered at four end points at average ages of 407, 427, 448, and 470 days.

For initial weight, Herefords were lightest (p<0.05)

and Gelbvieh, Pinzgauer, Simmental, and Braunvieh

were heaviest and did not differ (p>0.05) from each

other. The initial weight of Charoláis approached

that of the heaviest breed groups, and Angus, Red

Poll, and Limousin had intermediate initial weights.

For final weight, Herefords were lightest but did not

differ (p>0.05) from Angus, Red Poll, and

Limousin. Simmental, Charoláis, Gelbvieh, and

Braunvieh were heaviest but did not differ (/7>0.05)

from each other, whereas Pinzgauer differed

(/?<0.05) only from Simmental among the heavier

breed groups. For ADG, Red Poll was lowest but

was not significantly different (p>0.05) from Angus,

38
Table 29. Breed group means for actual weight, adjusted weight, hip height, and condition

score of 1-yr-old females

Breed group

Overall mean

Red Poll

Hereford

Angus

Limousin

Braunvieh

Pinzgauer

Gelbvieh

Simmental

Charoláis

D.05§

Number

of

females

Actual

weight

(lb)

Adjusted

weight^

(lb)

Hip

height

(inches)

Condition

score*

23,292 807 812 48.6 5.0

1,578 739 743 47.2 5.0

1,575 712 694 45.7 5.7

2,211 743 730 46.1 5.6

1,665 756 783 48.4 3.6

1,488 842 862 50.0 4.6

957 831 847 49.6 4.6

1,254 851 864 50.0 4.8

1,584 860 875 50.4 4.7

1,665 866 880 50.0 4.7

21.2 20.0

MARC I

F„F,,&F3

MARCH

MARC III

2,973

3,633

853

833

853

820

49.6

48.4

5.2

5.8

F,,F,,&F3 2,709 803 792 47.6 5.6

D.05« 26.0 23.2 .5 .3

^Weight adjusted to a common condition score.

^Evaluated on a scale of 1 to 9, 9 = highest, 1 = lowest.

^D.05 is the approximate difference between means of parental breeds required for significance.

1 D.05 is the approximate difference between means of all breed groups required for significance. Heterosis effects did not

differ between generations.

Limousin, and Pinzgauer; Simmental and Charoláis

were higher (p<0.05) than all breed groups.

For carcass weight, Herefords were lightest but did

not differ (/?>0.05) from Red Poll and Angus.

Simmental, Charoláis, Gelbvieh, and Braunvieh had

the heaviest carcass weights and did not differ

(/?>0.05) from each other. Pinzgauer and Limousin

had intermediate carcass weights. For dressing

percentage, Limousin was significantly higher than

all other breed groups; Angus and Charoláis were

intermediate. Differences in dressing percentage

among other breed groups were relatively small even

though some were significant. Adjusted fat thickness

at the 12th rib ranged from 0.14 inches for Gelbvieh

39
Table 30. Breed group means for actual weight, adjusted weight, hip height, and condition score of

2-yr-old females

Breed group

Number

of

females

Actual

weight

(lb)

Adjusted

weight^

(lb)

Hip

height

(inches)

Condition

score*

Overall mean 13,002 1,024 1,029 52.3 5.3

Red Poll 924 906 930 49.9 5.0

Hereford 714 944 910 49.0 6.0

Angus 1,320 933 924 48.5 5.6

Limousin 723 999 1,038 51.8 4.3

Braunvieh 903 1,052 1,080 52.6 4.8

Pinzgauer 753 1,025 1,047 52.0 5.0

Gelbvieh 879 1,069 1,078 53.2 5.3

Simmental 972 1,085 1,098 53.7 5.2

Charoláis 945 1,146 1,146 53.3 5.5

D.05S 30.6 26.9 .4 .2

MARC I

F F &F 1,518 1,069 1,071 52.1 5.4

MARCH

F,,F,,&F3 1,797 1,041 1,019 51.4 6.0

MARC III

F,, F,, & F3 1,554 1,019 1,005 50.5 5.8

D.05« 38.6 34.0 .6 .3

^Weight adjusted to a common condition score.

^Evaluated on a scale of 1 to 9, 9 = highest, 1 = lowest.

^D.05 is the approximate difference between means of parental breeds required for significance.

'D.OS is the approximate difference between means of all breed groups required for

significance. Heterosis effects did not differ between generations.

and Charoláis to 0.46 inches for Hereford and

Angus. For marbling score, Limousin was lowest but

not lower (p>0.05) than Gelbvieh. Angus was

highest but not higher (p>0.05) than Red Poll,

Hereford, and Pinzgauer in marbling score.

Braunvieh, Simmental, and Charoláis had intermediate marbling scores that were not different (p>0.05)

from each other. The order in which the breeds

ranked for REA and carcass weight was similar

except Limousin had the highest REA value, although not significantly higher than the REA of

Braunvieh and Gelbvieh. Differences among breed

groups in KPH generally were small; Red Poll had

significantly higher KPH than the other breed

groups.

40
Table 31. Breed group means for actual weight, adjusted weight, hip height, and condition

score of 6-yr-old females

Breed group

Overall mean

Red Poll

Hereford

Angus

Limousin

Braunvieh

Pinzgauer

Gelbvieh

Simmental

Charoláis

Number

of

females

Actual

weight

(lb)

Adjusted

weight^

(lb)

Hip

height

(inches)

Condition

score*

4,455 1,301 1,287 52.5 5.7

339 1,200 1,188 51.2 5.8

396 1,257 1,173 50.4 6.9

585 1,230 1,184 50.0 6.4

390 1,261 1,294 52.8 4.5

318 1,318 1,334 53.4 5.2

90 1,274 1,290 52.8 5.2

201 1,349 1,352 53.9 5.5

273 1,341 1,349 54.3 5.3

315 1,438 1,431 54.3 5.7

D.05ä 38.1 33.1 .5 .3

MARC I

MARCH

F„ F,, & F3

MARC III

F,, F,, & F3

492

672

384

1,358

1,290

1,296

1,341

1,263

1,248

52.8

52.4

51.6

5.9

6.1

6.4

D.05' 40.4 36.2 .6

^Weight adjusted to a common condition score.

*Evaluated on a scale of 1 to 9, 9 = highest, 1 = lowest.

^D.05 is the approximate difference between means of parental breeds required for significance.

IID.05 is the approximate difference between means of all breed groups required for

significance. Heterosis effects did not differ between generations.

Large differences were observed among breed

groups in percentage of carcasses that were equal to

or greater than USDA Choice quality grade. The

range was from a low of 14 percent in Limousin to a

high of 77 percent in Angus. Differences among the

Hereford, Angus, and Red Poll (British breeds)

were, not significant. Among continental breeds.

Pinzgauer had the highest percentage of USDA

Choice quality grade (55 percent), but this percentage, was not significantly higher than that of

Braunvieh (42 percent). Differences among the

continental breeds were significant, ranging from 14

percent to 55 percent.

41
Table 32. Breed group means for actual weight, adjusted weight, hip height,

condition score of females 2-7 or more yr old

and

Number Actual Adjusted Hip

of weight weight^ height Condition

Breed group females (lb) (lb) (inches) score*

Overall mean 49,251 1,210 1,208 52.4 5.5

Red Poll 3,447 1,098 1,105 50.8 5.4

Hereford 3,516 1,149 1,091 50.0 6.5

Angus 5,022 1,118 1,094 49.6 6.0

Limousin 3,822 1,175 1,213 52.4 4.4

Braunvieh 3,393 1,241 1,266 53.5 4.9

Pinzgauer 2,184 1,197 1,217 52.8 5.1

Gelbvieh 2,706 1,257 1,266 53.9 5.3

Simmental 3,258 1,261 1,272 54.3 5.3

Charoláis 3,618 1,352 1,349 53.9 5.5

D.OS« 27.8 24.5 .4 .18

MARC I

F F & F 5,820 1,270 1,263 52.8 5.7

MARCH

F F & F 7,389 1,217 1,193 52.0 6.0

MARC III

F,, F,, & F3 5,076 1,202 1,171 51.2 6.0

D.05« 26.7 23.6 .4 .17

^Weight adjusted to a common condition score.

*Evaluated on a scale of 1 to 9, 9 = highest, 1 = lowest.

^D.05 is the approximate difference between means of parental breeds required for significance.

lD.05 is the approximate difference between means of all breed groups required for

significance. Heterosis effects did not differ between generations.

Differences among composites were significant in

percentage of carcasses that were equal to or greater

than USDA Choice quality grade, ranging from 42

percent in MARC I to 65 percent in MARC III. The

breed composition of the MARC I population is

three-fourths continental, and breed composition of

the MARC III population is three-fourths British.

Breed composition of the MARC II population is

one-half continental and one-half British, and 57

percent of the population was graded USDA Choice

or higher—almost as high as the MARC III population.

As expected, differences were small among the

breed groups in the percentage of carcasses meeting

42
Table 33. Breed group means for 12-hr milk yield, estimated 200-day milk yield, and

200-day weight of progeny

Breed group

Number

of observations

12-hr

milk

yield

(lb)

No.

of

cows

Estimated

200-day

milk

yield

(lb)

200-day

weight of

progeny

(lb)

Adjusted

200-day

weight of

progeny^

(lb)

Overall mean 1,686 11.5 595 4,604 503 494

Red Poll 118 11.9 46 4,774 478 463

Hereford 122 6.7 45 2,774 408 459

Angus 125 9.3 48 3,735 454 472

Limousin 149 10.2 50 4,114 456 459

Braunvieh 147 14.2 52 5,680 558 520

Pinzgauer 156 12.9 52 5,173 531 505

Gelbvieh 150 12.7 51 5,120 545 520

Simmental 151 13.1 51 5,283 545 516

Charoláis 146 10.5 50 4,212 518 518

D.05* 1.3 531 28.4 24.2

MARCP 155 12.5 52 5,034 527 505

MARC IP 147 11.7 50 4,732 529 514

MARC III§ 120 11.6 48 4,613 494 481

D.05' 1.3 560 30.0 25.6

^Adjusted to a common estimated milk yield.

*D.05 is the approximate difference between means of parental breeds required for significance.

^F^-generation females nursing F3-generation progeny.

'D.OS is the approximate difference between means of all breed groups required for

significance.

or exceeding the USDA Select quality grade. However, these differences were significant, with

Limousin and Gelbvieh the lowest.

Breed group means for carcass composition.

Breed group means for carcass composition are

presented in table 35. Composition is listed as the

percentage and weight of retail product, fat trim, and

bone with all subcutaneous and accessible intermuscular fat removed (0 inches of fat trim). Breed group

means for carcass lean, carcass fat, and carcass bone

(by percentage and weight) are presented in table 36.

Percentage of retail product ranged from 60.1 in

Herefords to 72.3 in Limousin (table 35). Percentage

of carcass lean ranged from 53.8 in Hereford to 64.6

in Limousin (table 36).

The mean liveweight of Gelbvieh, Simmental, and

Charoláis was 121 lb heavier than that of Limousin

(table 34), yet Limousin was equal to Gelbvieh,

43
^ Table 34. Breed group means for growth and carcass traits measured in a cooler

No. Carcass Dressing Adj. Estim. Percentage Percentage

Breed of Weight (lb) ADG+ weight percentage fat* REA« KPH Marbling aUSDA aUSDA

group steers Initial Final (lb) (lb) (%) (inches) (inches^) (%) score' Choice Select

Overall mean 1,661 569 1,210 2.74 734 60.58 .26 12.10 2.77 4.97 46 95

Red Poll 114 551 1,158 2.58 694 59.98 .30 10.76 3.30 5.30 71 100

Hereford 146 478 1,118 2.72 675 60.33 .46 10.52 2.41 5.21 60 100

Angus 118 514 1,136 2.64 697 61.32 .46 10.56 2.64 5.41 77 100

Limousin 142 531 1,144 2.61 728 63.43 .17 13.41 2.47 4.43 14 84

Braunvieh 139 602 1,250 2.78 747 59.73 .18 13.21 2.79 4.84 42 94

Pinzgauer 118 608 1,228 2.65 730 59.45 .17 12.26 2.74 5.16 55 98

Gelbvieh 150 611 1,250 2.73 750 59.94 .14 12.97 2.68 4.53 15 85

Simmental 127 604 1,281 2.90 767 59.79 .16 12.56 2.50 4.80 34 92

Charoláis 126 586 1,263 2.90 767 60.66 .14 12.49 2.80 4.71 24 96

D.05+^ 23.6 42.3 .11 27.3 .81 .05 .54 .26 .28 19 8

MARC I-F3 178 584 1,241 2.81 761 61.24 .23 12.94 2.94 4.79 42 91

MARC II-F3 148 604 1,263 2.81 765 60.48 .32 12.09 2.88 5.13 57 100

MARC III-F3 155 560 1,197 2.70 725 60.56 .36 11.52 3.06 5.31 65 98

D.05« 24.2 43.4 .13 28.0 .83 .06 .56 .27 .28 20 9

^ADG = Average daily weight gain.

Adjusted fat thickness at the 12'^ rib.

^REA = Area of longissimus muscle.

'Estimated KPH = estimate of kidney, pelvic, and heart fat.

M score of 4.00-4.90 = slight; a score of 5.00-5.90 = small.

^^D.05 is the approximate difference between means of parental breeds required for significance.

**D.05 is the approximate difference between means of all breed groups required for significance.
Table 35. Breed group means for carcass composition after all subcutaneous and accessible

intermuscular fat was removed (0 inches of fat trim)

Number of

carcasses

Retail

%

product^

lb

Fat trim Bone

Breed group % lb % lb

Overall mean 1,596 65.8 459 18.9 133 15.2 106

Red Poll 114 62.6 412 22.4 150 14.9 98

Hereford 132 60.1 386 25.5 166 14.4 92

Angus 117 61.5 406 24.4 164 14.1 93

Limousin 138 72.3 499 13.4 94 14.3 98

Braunvieh 137 67.3 478 16.1 117 16.5 117

Pinzgauer 119 66.8 463 17.0 119 16.1 112

Gelbvieh 147 70.0 499 14.2 104 15.8 112

Simmental 126 68.4 495 15.5 116 16.1 117

Charoláis 124 68.7 499 15.0 111 16.2 118

D.05* 1.5 17.6 1.6 14.1 .4 4.4

MARC I, F3 157 67.2 486 17.9 131 14.9 108

MARC II, F3 146 63.1 459 22.3 164 14.7 107

MARC III, F3 139 61.9 427 23.3 164 14.8 102

D.05« 1.5 18.3 1.7 14.6 .4 4.6

^Retail product includes steaks and roasts plus lean trim adjusted to 20 percent

fat based on chemical analysis of lean trim.

*D.05 is the approximate difference between means of parental breeds required for significance.

^D.05 is the approximate difference between means of all breed groups required

for significance.

Simmental, and Charoláis in retail product weight

and weight of carcass lean (tables 35 and 36). This

occurred because Limousin had a higher dressing

percentage, higher retail product percentage, and

smaller bone percentage than the other three breeds.

Differences in carcass composition were small

among the British breeds (Red Poll, Hereford, and

Angus) (tables 35 and 36). Differences in carcass

composition among the continental breeds were

greater than among the British breeds, ranging from

66.8 percent retail product and 59.8 percent carcass

lean in Pinzgauer to 72.3 percent retail product and

64.6 percent carcass lean in Limousin.

Differences in carcass composition among composites were important (p<0.05) and were associated

with breed composition of British breeds relative to

continental breeds (tables 35 and 36). The MARC III

population had 6L9 percent retail product and 55.3

percent carcass lean, whereas the MARC I population had 67.2 percent retail product and 60.0 percent

45
Table 36. Breed group means for carcass lean, carcass fat, and carcass bone

Number

Lean^ Fat* Bone

Breed group % lb % lb % lb

Overall mean 1,596 58.8 410 26.0 182 15.2 106

Red Poll 114 56.0 369 29.1 194 14.9 98

Hereford 132 53.8 345 31.8 207 14.4 92

Angus 117 54.9 362 31.0 207 14.1 93

Limousin 138 64.6 446 21.1 147 14.3 98

Braunvieh 137 60.1 428 23.3 168 16.5 117

Pinzgauer 119 59.8 414 24.1 168 16.1 112

Gelbvieh 147 62.4 445 21.8 158 15.8 112

Simmental 126 61.1 442 22.8 168 16.1 117

Charoláis 124 61.2 444 22.5 165 16.2 118

D.05« 1.3 15.6 1.5 13.9 .4 4.4

MARC I, F3 157 60.0 434 25.1 183 14.9 108

MARC II, F3 146 56.4 410 29.0 213 14.7 107

MARC III, F3 139 55.3 382 29.9 209 14.8 102

D.05« 1.4 16.1 1.5 14.6 .4 4.6

^Carcass lean includes steaks and roasts with all subcutaneous and accessible

intermuscular fat removed, plus fat-free lean trim based on chemical analysis of lean trim.

*Carcass fat includes fat trim plus fat in lean trim based on chemical analysis of lean trim.

^D.05 is the approximate difference between means of parental breeds required for significance.

ID.05 is the approximate difference between means of all breed groups required for significance.

carcass lean. The MARC II population had 63.1

percent retail product and 56.4 percent carcass lean.

Breed group means for carcass and meat quality

traits. Breed group means for factors relating to

meat quality are presented in table 37. Differences in

marbling score ranged from 4.43 in Limousin to

5.41 in Angus. Differences among the British breeds

(that is, Angus, Hereford, and Red Poll) were not

significant for marbling score. Differences in marbling score among the continental breeds were

greater than differences among the British breeds,

ranging from 4.43 in Limousin to 5.16 in Pinzgauer.

Pinzgauer did not differ (p>0,05) from the British

breeds in marbling score. Differences in marbling

score among composites were closely associated

with their continental breed composition relative to

British breed composition; for example, MARC I

was 4.79, MARC II was 5.13, and MARC III was

5.31.

Fat in the longissimus muscle, determined by chemical analysis, was highly associated with marbling

score but was more variable. The range in longissimus muscle fat was from 2.82 percent in Limousin to

4.80 percent in Angus.

46
Table 37. Breed group means for carcass and meat quality traits

Long. Fat in Retail

Adj. Marb- muscle 9-11 Shear product

fat*

(inches)

ling

score*

fat«

(%)

rib cut

(%)

force'

(lb)

Sensory panel 0 inches trim

Bree^group Tender.' Juici.** Flavor** (%)

Overall mean 0.26 4.97 3.96 33.01 11.22 5.07 5.17 4.87 65.8

Red Poll .30 5.30 4.65 38.34 10.41 5.15 5.25 4.96 62.6

Hereford .46 5.21 4.53 40.09 11.16 5.10 5.25 4.80 60.1

Angus .46 5.41 4.80 40.01 9.92 5.55 5.38 4.92 61.5

Limousin .17 4.43 2.82 26.51 12.39 4.88 5.01 4.82 72.3

Braunvieh .18 4.84 3.67 29.83 11.22 5.06 5.12 4.90 67.3

Pinzgauer .17 5.16 4.22 30.82 9.86 5.43 5.20 4.96 66.8

Gelbvieh .14 4.53 3.22 27.60 12.74 4.63 5.04 4.75 70.0

Simmental .16 4.80 3.72 28.67 12.08 4.80 5.14 4.83 68.4

Charoláis .14 4.71 3.38 28.02 11.38 4.95 5.12 4.88 68.7

D.05SS .05 .28 .50 2.20 .99 .27 .19 .13 1.5

MARC I, F3 .23 4.79 3.56 31.15 11.05 5.22 5.14 4.87 67.2

MARC II, F3 .32 5.13 4.36 36.37 11.14 5.04 5.18 4.90 63.1

MARC III, F3 .36 5.31 4.59 38.69 11.29 5.06 5.20 4.88 61.9

D.05" .06 .28 .52 2.28 1.04 .28 .20 .14 1.5

^Adjusted fat = subcutaneous fat at the 12^^ rib.

*A score of 4.00-4.90 = slight, 5.00-5.90 = small.

^Chemical fat in cross section of longissimus muscle.

"Shear force required to cut a 0.5-inch core from the longissimus muscle.

*"A tenderness score of 4 = slightly tough, 5 = slightly tender, 8 = extremely tender.

^^A juiciness score of 4 = slightly dry, 5 = slightly juicy, 8 = extremely juicy.

**A flavor score of 4 = slightly bland, 5 = slightly intense, 8 = extremely intense.

^^D.05 is the approximate difference between means of parental breeds required for significance.

I ID.05 is the approximate difference between means of all breed groups required for significance.

Shear force (the force required to cut a 0.5-inch core

from the longissimus muscle) ranged from 9.86 lb in

Pinzgauer to 12.74 lb in Gelbvieh. With the exception of Pinzgauer, these values tended to be slightly

higher in continental breeds than in British breeds.

Sensory panel scores for tenderness, juiciness, and

flavor were less variable than shear force values.

The British breeds tended to have slightly higher

scores for tenderness than the continental breeds.

The Pinzgauer breed had the most favorable score

for tenderness among the continental breeds and

generally scored equal to the British breeds. Values

for the Braunvieh breed did not differ (p>0.05) from

47
those of the Hereford and Red Poll in either shear

force or tenderness score.

Differences Among Breed Groupsfor Different

Measures ofGain Efficiency

Breed group means for different measures of gain

efficiency are presented in table 38. Adjusting gain

efficiency to different end points and with different

measures of output was made possible as a result of

serial slaughter and collection of data on carcass cutout. Gain efficiency was evaluated for the following:

• from 0 to 207 days (time-constant period)

• from 684 to 1,191 lb (gain-constant period)

• to a weight of 734 lb (carcass weight constant)

• to a retail product weight of 463 lb

Table 38. Breed group means for different measures of gain efficiency

No. of

carcasses

Live-weight gain (LWG) and retail product gain (RPG) per Meal of ME

Time constant

0 to 207 days

LWG RPG

Gain

constant

From 684 to

L191 lb

LWG

Toa

carcass

weight of

7341b

LWG

To a retail

product

weight of

4631b

RPG

Toa

marbling

score

of 5.00+

LWG

To a longissimus muscle

fat content

of 4%

Breed group LWG

grams

Overall mean 1,599 51 38 50 51 40 50 50

Red Poll 114 49 35 48 48 28 51 52

Hereford 133 54 34 48 51 24 57 61

Angus 117 50 35 48 49 26 54 57

Limousin 138 54 47 51 54 57 47 41

Braunvieh 138 50 38 51 51 42 49 48

Pinzgauer 119 50 39 50 50 40 51 51

Gelbvieh 148 48 40 49 49 49 45 43

Simmental 126 51 38 52 52 46 49 48

Charoláis 125 52 40 52 53 50 49 46

D.05* 1.9 1.3 2.4 2.0 1.6 1.9 2.3

MARC I, F3 157 50 39 51 51 45 48 45

MARC II, F3 146 51 37 52 52 37 52 54

MARC III, F3 138 50 35 49 50 30 53 54

D.05« 2.0 1.3 2.5 2.1 1.7 2.0 2.4

^A score of 5.00-5.90 = small.

*D.05 is the approximate difference between means of parental breeds required for significance.

^D.05 is the approximate difference between means of all breed groups required for significance.

48
• to a marbling score of 5.00

• to a longissimus muscle fat content of 4 percent.

Gain efficiencies are expressed as liveweight gain

per megacalories of metabolizable energy (Meal/

ME) and retail product weight per Meal of ME

(table 38). Significant differences were observed

among breed groups for all measures of gain efficiency.

Breed groups that had the smallest weight to maintain (for example, Limousin and Hereford) tended to

be more efficient in liveweight gain in the timeconstant period (0 to 207 days). Even though Angus

and Limousin had similar initial weights, Limousin

produced 12 g more (p<0.05) retail product per Meal

of ME than Angus. With the exception of Limousin,

breeds that gained at a higher rate tended to be more

efficient in liveweight gain in the gain-constant

period (684 to 1,191 lb) because of a shorter period

of maintenance. Limousin gained at a slower-thanaverage rate (table 34) but efficiency of liveweight

gain (684 to 1,191 lb) was above average.

Because Limousin had a higher dressing percentage,

higher percentage of retail product, and lower

percentage of bone than the other breeds, it was the

most efficient in measures of efficiency where the

end point was retail product weight or where the

output was retail product gain.

To marbling score constant or longissimus muscle

fat percentage end points, breeds with the lowest

marbling scores and lowest percentage of fat in the

longissimus muscle (for example, Limousin and

Gelbvieh) tended to be less efficient, whereas breeds

with the highest marbling scores and the highest

percentage of fat in the longissimus muscle (for

example, Hereford and Angus) tended to be more

efficient. The Pinzgauer breed was most efficient to

longissimus muscle fat percentage and marbling

score constant end points among the continental

breeds.

Inbreeding Coefficients

Inbreeding coefficients are presented in table 39 by

year for each breed group.

Genetic and Phenotypic Variances

Genetic standard deviations (a ) and phenotypic

coefficients of variation (CV) for all breed groups,

contributing purebreds, and composites are presented in table 40 for growth and carcass traits of

castrate males; in table 41 for production traits of

intact males; and in table 42 for production traits of

females. Phenotypic coefficients of variation are not

presented for traits that do not have a normal distribution (for example, categorical traits) or for traits

with a finite score.

Genetic standard deviations and phenotypic coefficients of variation were similar for composites and

contributing purebreds. Thus, greater genetic variation and phenotypic coefficients of variation for

composite populations in comparison to contributing

purebreds were not observed. Our interpretation of

these results is that for bioeconomic traits that are

influenced by a large number of genes, genetic

standard deviations and phenotypic coefficients of

variation are similar for composites and for the

average of the contributing purebreds.

Heritabiiities

Estimates of heritability (h^) and their estimated

standard errors (SE) for all breed groups, contributing purebreds, and composites are presented in table

43 for growth and carcass traits of castrate males, in

table 44 for production traits of intact males, and in

table 45 for production traits of females. Generally,

there was close agreement in h^ for all breed groups,

contributing purebreds, and composites. There was

no tendency for h^ to be higher in composites than in

contributing purebreds. Because of similarity of

estimates among the three groupings and the smaller

standard errors as a result of greater numbers, only

estimates of h^ for all breed groups combined are

discussed.

Growth and Carcass Traits ofCastrate Males

Heritabiiities of traits reflecting carcass composition

were intermediate in size and were of a magnitude

similar to growth traits (table 43). Heritability of

marbling score and of longissimus muscle fat percentage were of the same magnitude (0.48 and 0.49,

respectively) and were higher than h^ for growth

traits. Heritability of traits relating to meat palatability generally were low. Muscling score in the live

animal, a subjective evaluation, had the highest h^

among the traits analyzed (0.64 ± 0.10).

49
CJi Table 39. Inbreeding coefficients by birth year and breed group

Inbreeding; coefficients (%)

Breed

group

Year of birth

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 Mean

Red Poll 3.48 3.84 3.18 3.66 4.01 5.02 5.36 5.66 6.34 6.49 7.08 7.79 8.70 5.32

Hereford 4.38 3.95 4.40 4.99 6.03 5.21 5.41 7.27 7.78 7.14 7.83 8.90 9.36 6.25

Angus 2.69 4.71 3.80 5.41 6.12 6.80 7.16 7.87 7.51 7.88 8.21 8.14 8.87 6.08

Limousin .84 1.01 1.32 2.01 2.32 2.50 2.96 2.98 4.11 3.99 3.95 5.08 5.29 2.90

Braunvieh .74 1.00 2.21 2.14 1.64 2.39 2.64 3.32 4.28 4.39 4.58 5.46 4.91 2.89

Pinzgauer — 2.07 1.98 2.18 2.30 5.52 3.23 4.46 3.97 4.51 3.34

Gelbvieh 4.03 1.06 .61 .69 1.22 2.44 1.78 3.52 4.33 3.74 3.80 3.30 4.07 2.62

Simmental .49 .27 .80 .68 1.00 .82 1.39 1.82 2.45 2.23 2.34 2.81 3.11 1.41

Charoláis .10 1.12 1.24 1.16 1.06 1.36 2.29 2.56 3.01 3.66 3.69 4.19 4.83 2.28

MARCI

F, .32 .40 .17 .16 .24 .30 .25

F, .90 .75 .49 .54 .76 .70 .77 .86 1.18 .79 .75

F3 2.31 1.97 2.58 2.31 1.95 2.67 2.87 2.41

F4 5.36 3.83 4.05 3.42 3.94

MARCH

F. .00 .00 .00 .00 .00 .00

F, .39 .47 .77 .37 .49 .74 .91 .90 .56 1.22 1.44 .69

F3 — — 1.91 1.42 1.25 1.62 1.99 1.72 2.18 2.53 1.78

F4 — 3.90 2.75 2.56 3.18 3.50 3.15

MARC III

F, .00 .00 .00 .00 .00 — .00

F, 1.01 .95 1.17 1.22 1.07 1.31 .87 1.43 1.76 1.19

F3 — 3.49 2.34 2.04 2.36 2.75 3.49 2.63

F4 7.75 5.74 4.04 5.20
Table 40. Genetic standard deviations (a ) and phenotypic coefficients of variation (CV) for growth and

carcass traits of castrate males

All breed groups

CV

Purebreds Composites

Trait (r

8

CV cr

g

CV

Birth weight (lb) 6.0 0.12 5.7 0.12 5.7 0.13

200-day weight (lb) 30.6 .10 29.3 .10 31.3 .11

Slaughter weight

at 438 days (lb) 51.2 .08 47.8 .08 63.3 .08

Carcass weight at

438 days (lb) 30.2 .08 27.3 .08 39.5 .09

Longissimus muscle

area (inches^) .6 .10 .5 .10 .8 .10

Retail product (%) 2.2 .05 2.2 .04 2.3 .06

Fat trim (%) 2.2 .20 2.3 .19 1.9 .20

Bone trim (%) .5 .07 .5 .07 .1 .07

Carcass lean weight (lb) 19.0 .09 17.9 .08 23.6 .09

Carcass fat weight (lb) 17.2 .18 19.0 .18 13.9 .19

Bone weight (lb) 6.0 .09 6.2 .08 4.6 .10

Longissimus muscle

fat (%) .8 .28 .6 .27 1.0 .29

Shear force (lb) .9 .22 .4 .22 1.3 .21

The low h^ of shear force (0.12 ± 0.08) suggests that

differences in shear force were likely associated with

high variance. This estimate of h^ for shear force is

lower than most estimates in the literature; for

example, Koch et al. (1982) reported an estimate of

0.31.

Production Traits ofIntact Males

Traits associated with size (that is, weight and

height) had intermediate heritability (0.35 to 0.48)

(table 44). Heritability of scrotal circumference was

of a magnitude similar to growth and size traits (0.43

± 0.04). Heritability of subjective scores (that is,

condition, muscling, trimness, and kind) were of

similar magnitude and were at the lower end of the

h^ range for size-related traits (0.30 to 0.35). The h^

for both expressions of calving difficulty (that is,

calving difficulty score and percentage requiring

assistance) were of sufficient magnitude (0.27 ± 0.08

and 0.31 ± 0.09, respectively) to suggest response to

selection among calves with 2-yr-old dams. The h^

of calving difficulty—either calving difficulty score

or percentage calving difficulty—^was greater in

calves with 2-yr-old dams than calves with dams 3

yr old or older. This was expected because of the

higher frequency of calving difficulty of calves from

2-yr-old dams. The h^ for gestation length of calves

born to females 3 yr old or older was 0.46 ± 0.06.

These estimates of h^ tend to be higher than those

typically reported for 200-day weight but lower than

those reported for 368-day weight.

51
Table 41. Genetic standard deviations (ar^ and phenotypic coefficients of variation (CV)

for production traits of intact males

All breed groups Purebreds Composites

Trait

'^g CV

^'g

CV ^'s CV

Birth weight (lb) 7.3 0.12 7.7 0.11 7.1 0.12

Preweaning ADG (lb) .13 .11 .11 .10 .13 .11

200-day weight (lb) 28.9 .09 24.2 .09 26.0 .09

Postweaning ADG (lb) .20 .11 .20 .11 .20 .11

368-day weight (lb) 46.5 .08 47.2 .08 44.1 .08

368-day height (inches) .9 .03 .8 .03 .9 .03

368-day condition score^ .47 .47 .46

368-day muscle score* .38 .40 .33

368-day trimness score^ .48 .50 .42

368-day kind score" .66 .48 .70

368-day scrotal circumference (cm) 1.60 .08 1.53 .07 1.61 .07

CD score, dams of all ages^ .43 .45 .41

CD score, dams 2 yr old^ .70 .78 .59

CD score, dams ^3 yr old^ .22 .29 .06

Gestation length, born from

dams ^3 yr old (days) 2.7 .01 2.7 .01 2.6 .01

^Evaluated on a scale of 1 to 9, 9 = very fat, 1 = emaciated.

^Evaluated on a scale of 1 to 9, 9 = very thickly muscled, 1 = very thinly muscled.

^Evaluated on a scale of 1 to 9, 9 = very lacking in trimness, 1 = very trim.

•Evaluated on a scale of 1 to 9; scored within breed group on overall anatomical desirability, 9 = very desirable, 1 = very

undesirable.

""CD = calving difficulty, scored on a scale of 1 to 7, 7 = caesarean birth, 1 = no difficulty.

Production Traits ofFemales

Estimates of heritability of weights, heights, and

condition scores for 2, 3, 4, and 5 yr olds are based

on means of observations made about 2 mo before

the start of calving, immediately before the start of

breeding, and when pregnancy status was determined about 1 mo after weaning. Estimates of

heritability of weight at 1 yr are based on the mean

of weights taken just before the start of breeding

(410 days), after breeding (452 days), and when

pregnancy was diagnosed (522 days). Estimates of

h^ of hip height and condition score at 1 yr are based

on the mean of observations made at 368 days and

522 days. Height and condition score were not

recorded at 410 days and 452 days. The h^ of

weights were remarkably similar at all ages (table

45). The h^ of height and condition score were

similar at all ages except 5 yr, when both were

lower. Because the number of observations decreased as age increased, standard errors of h^

tended to increase with age. Higher h^ were expected

52
Table 42. Genetic standard deviations (a ) and phenotypic coefficients of variation (CV) for production

traits of females

All breed groups

CV

Purebreds Comp

'^g

osites

Trait

g

CV CV

Birth weight (lb) 6.6 0.12 6.8 0.11 6.4 0.12

200-day weight (lb) 25.6 .09 27.1 .09 21.2 .09

368-day weight (lb) 39.9 .09 41.9 .09 36.8 .09

410-day weight (lb) 36.6 .09 39.9 .08 33.3 .09

452-day weight (lb) 42.6 .08 47.6 .08 35.7 .08

522-day weight (lb) 44.5 .08 49.6 .08 37.9 .08

Weight, 1 yr (lb) 42.1 .08 46.7 .08 37.3 .08

Weight, 2 yr (lb) 60.2 .08 61.5 .07 59.5 .08

Weight, 3 yr (lb) 65.3 .08 69.2 .08 63.1 .08

Weight, 4 yr (lb) 66.6 .08 55.3 .08 78.7 .08

Weight, 5 yr (lb) 69.7 .08 74.7 .07 71.2 .08

368-day height (inches) .9 .03 .8 .03 .9 .03

Height, 1 yr (inches) .9 .03 .9 .02 .9 .03

Height, 2 yr (inches) .9 .02 .9 .02 .9 .02

Height, 3 yr (inches) .9 .02 .9 .02 .8 .02

Height, 4 yr (inches) .8 .02 .9 .02 .8 .02

Height, 5 yr (inches) .7 .02 .7 .02 .8 .02

Gestation length,

>3 yr old (days) 2.5 .01 2.2 .01 2.8 .01

Puberty age (days) 15.2 .07 15.7 .08 13.6 .07

for weights, heights, and condition scores at 1, 2, 3,

4, and 5 yr old than at 368 days and earlier because

these estimates of h^ were based on means of three

observations made in different seasons at 1 yr

through 5 yr. The h^ for weights, heights, and condition scores through 368 days were similar to those

reported for males from the same population (table

44).

The h^ for calving difficulty score for calves born

from 2-yr-old dams, for calves born from dams 3 yr

old or older, and for calves born from dams of all

ages generally were higher than h^ for percentage

calving difficulty. This was expected because percentage calving difficulty is expressed as a binary

trait (that is, 0 or 1), whereas calving difficulty score

is classified into seven categories.

The h^ of calving difficulty score and percentage

calving difficulty were higher for calves from 2-yrold dams than for calves from dams 3 yr old or

older. This is likely associated with the higher

frequency of calving difficulty of calves from 2-yrold dams. However, the h^ of calving difficulty of

female calves is similar to that of male calves (table

44), and male calves experience a higher frequency

of calving difficulty than female calves.

53
Table 43. Herítabilíties (h^) and standard errors (SE) for all breed groups, purebreds, and composites

for growth and carcass traits of castrate males

All breed

h^

groups

SE

Purebreds Comp(

h^

Dsites

Trait h^ SE SE

Birth weight 0.25 0.08 0.24 0.10 0.26 0.17

Preweaning ADG .35 .09 .35 .10 .30 .17

200-day weight .34 .09 .33 .10 .31 .17

Postweaning ADG .36 .09 .33 .10 .48 .18

Slaughter weight, 438 days .28 .08 .26 .10 .37 .18

Carcass weight .23 .08 .20 .10 .34 .17

Dressing percentage .19 .08 .22 .10 .08 .15

Adjusted fat at 12'" rib .25 .08 .20 .10 .39 .18

Marbling score^ .48 .09 .45 .11 .55 .19

Longissimus muscle area .22 .08 .17 .09 .35 .18

Retail product, 0 inches

of fat trim* (%) .47 .09 .51 .11 .42 .18

Fat, 0 inches of

fat trim« (%) .35 .09 .43 .11 .21 .16

Bone 0 inches of

fat trim (%) .21 .08 .27 .10 .01 .15

Retail product weight,

0 inches of fat trim* .28 .08 .26 .10 .39 .18

Fat trim weight,

0 inches of fat trim^ .32 .09 .43 .11 .17 .16

Bone weight .39 .09 .46 .11 .19 .16

' A score of 4.00 to 4.90 = slight, 5.00 to 5.90 = small.

* Retail product includes steaks and roasts plus lean trim adjusted to 20-percent fat based on

chemical analysis of lean trim.

^ All subcutaneous and accessible intermuscular fat removed.

Continued

54
Table 43. Heritabílities (h^) and standard errors (SE) for all breed groups, purebreds, and composites

for growth and carcass traits of castrate males—Continued

All breed

h^

groups

SE

Purebreds Comp

h^

osites

Trait h^ SE SE

Carcass lean weight' .28 .08 .25 .10 .39 .18

Carcass fat weight' .29 .09 .40 .10 .15 .16

Longissimus muscle fat^+ (%) .49 .09 .36 .10 .75 .20

9-10-11 rib fat+t (%) .26 .08 .33 .10 .13 .16

Shear force** .12 .08 .05 .09 .31 .17

Tenderness score^^ .22 .08 .12 .09 .51 .18

Juiciness score" .25 .08 .06 .09 .70 .20

Flavor score" .07 .08 .08 .09 .04 .15

Muscling score*** .64 .10 .64 .12 .82 .20

Fat score*** .27 .08 .30 .10 .29 .17

' Carcass lean includes steaks and roasts trimmed to 0 inches of fat cover plus fat-free lean trim based on chemical

analysis of lean trim.

*" Carcass fat includes fat trim plus fat in lean trim based on chemical analysis of lean trim.

^^ Ether-extracted fat.

** Shear force required to cut through a 0.5-inch core of longissimus muscle.

^^ A tenderness score of 4 = slightly tough, 5 = slightly tender, 8 = extremely tender.

'I A juiciness score of 4 = slightly dry, 5 = slightly juicy, 8 = extremely juicy.

'"'" A flavor score of 4 = slightly bland, 5 = slightly intense, 8 = extremely intense.

^^^ Scores ranged from 3 to 27, with 6, 15, and 24 reflecting low, average, and high, respectively, for muscle or fat.

The h^ for gestation length for female calves from

dams 3 yr old or older was the same as it was for

male calves (0.45 ± 0.06 vs. 0.46 ± 0.06) (table 44).

The h^ for age at puberty was slightly lower (0.31 ±

0.04) than some estimates in the literature.

Genetic Correlations

Estimates of genetic correlations (r ) between

growth and carcass traits of castrate males are shown

below the diagonal in table 46. Estimates of production traits of intact males are shown below the

diagonal in table 47; production traits of females are

shown below the diagonal in table 48. The correlations were estimated from purebred and composite

breed groups combined with records adjusted for

differences in age and days on feed. It is assumed

that correlations do not differ among contributing

purebreds and composites.

Growth and Carcass Traits ofCastrate Males

Slaughter and carcass weight were highly correlated

with weight of all carcass components, that is, bone,

lean, and fat (table 46). Adjusted fat thickness at the

12th rib was positively correlated with marbling

score, fat trim percentage, fat weight, longissimus

fat percentage, tenderness, juiciness, flavor, and fat

score and was negatively correlated with retail

product and bone percentages, lean weight, shear

force, and muscling score. The positive correlations

of intramuscular fat, as measured by marbling score

or longissimus muscle fat, with fat trim percentage

and fat weight and the negative correlation with

retail product percentage illustrate the difficulty of

genetically increasing intramuscular fat in the

longissimus muscle while maintaining a favorable

lean-to-fat ratio in the carcass. The r of retail prod55
Table 44. Heritabilitíes (h^) and standard errors (SE) for all breed groups, purebreds, and composites of

intact males

All breed groups

(n=7,536)

h^ SE

Purebreds

(n=4,115)

h^ SE

Composites

(/i=3,421)

Trait h^ SE

Birth weight 0.44 0.04 0.54 0.06 0.37 0.05

Preweaning ADG .38 .04 .24 .04 .32 .05

200-day weight .35 .04 .27 .04 .27 .05

Postweaning ADG .43 .04 .44 .05 .37 .05

368-day weight .35 .04 .40 .05 .28 .05

368-day height .48 .04 .41 .05 .48 .06

368-day condition score^ .34 .04 .36 .05 .30 .05

368-day muscling score* .35 .04 .36 .05 .30 .05

368-day trimness score* .34 .04 .37 .05 .27 .05

368-day kind score' .30 .03 .17 .04 .32 .05

368-day scrotal circumference .43 .04 .40 .05 .43 .06

CD score, dams of all ages' .26 .03 .28 .04 .24 .05

CD, dams of all ages^^ (%) .21 .03 .19 .04 .24 .05

CD score, dams 2 yr old' .27 .08 .34 .12 .19 .12

CD, dams 2 yr old^^ (%) .31 .09 .30 .12 .33 .13

CD score, dams >3 yr old' .13 .05 .21 .07 .01 .07

CD, dams >3 yr old+^ (%) .07 .05 .12 .07 .00 .00

Gestation length, dams >3 yr old** .46 .06 .44 .09 .44 .10

^ Evaluated on a scale of 1 to 9, 9 = very fat, 1 = emaciated.

* Evaluated on a scale of 1 to 9, 9 = very thickly muscled, 1 = very thinly muscled.

^ Evaluated on a scale of 1 to 9, 9 = very lacking in trimness, 1 = very trim.

1 Evaluated on a scale of 1 to 9; scored within breed group on overall desirability, 9 = very desirable, 1 = very undesirable.

*" Calving difficulty score was rated as follows: 1 = no difficulty, 2 = little difficulty by hand, 3 = little difficulty with calf

jack, 4 = slight difficulty with calf jack, 5 = moderate difficulty with calf jack, 6 = major difficulty with calf jack, and 7 =

caesarean birth.

++ Calving difficulty (%) was scored as follows: scores 1 and 2 = 0; scores 3, 4, 5, 6, and 7 = 1.

** Calves conceived by artificial insemination.

uct percentage and marbling score was -0.60 ± 0.20.

Longissimus muscle area was positively correlated

with measures of carcass lean and with muscle score

and negatively correlated with shear force. Shear

force was highly correlated with tenderness score,

but the standard error was large. Muscle score,

which was subjectively evaluated in the live animal,

had favorable genetic correlations with carcass

composition, suggesting that visual evaluation of

differences in muscle thickness can have value in

selecting for changes in carcass composition.

56
Table 45. Heritabilities (h^) and standard errors (SE) for all breed groups, purebreds,

and composites of females

All breed

h^

groups

SE

Purebreds Comp

h^

losites

Trait h^ SE SE

Birth weight (lb) 0.42 0.04 0.48 0.05 0.36 0.06

Preweaning ADG .33 .03 .35 .04 .24 .05

200-day weight (lb) .32 .03 .38 .05 .21 .04

Postweaning ADG .37 .04 .36 .04 .39 .06

368-day weight (lb) .38 .04 .43 .05 .31 .05

410-day weight (lb) .32 .03 .40 .05 .24 .05

452-day weight (lb) .42 .04 .55 .05 .27 .05

522-day weight (lb) .45 .04 .59 .06 .30 .05

Weight, 1 yr (lb) .45 .04 .59 .06 .32 .06

Weight, 2 yr (lb) .52 .06 .58 .07 .47 .08

Weight, 3 yr (lb) .43 .06 .50 .09 .38 .09

Weight, 4 yr (lb) .41 .08 .31 .10 .52 .12

Weight, 5 yr (lb) .43 .10 .57 .15 .41 .14

368-day height (inches) .43 .04 .43 .05 .43 .06

Height, 1 yr (inches) .52 .04 .54 .06 .49 .07

Height, 2 yr (inches) .50 .05 .55 .07 .45 .08

Height, 3 yr (inches) .42 .06 .52 .09 .32 .09

Height, 4 yr (inches) .40 .08 .48 .11 .33 .11

Height, 5 yr (inches) .27 .10 .31 .15 .32 .13

368-day condition score^ .40 .04 .45 .05 .31 .05

Condition score, 1 yr^ .40 .04 .46 .06 .29 .05

Condition score, 2 yr^ .40 .05 .50 .07 .28 .07

Condition score, 3 yr^ .38 .06 .36 .08 .36 .09

Condition score, 4 yr^ .47 .08 .49 .11 .31 .10

Condition score, 5 yr^ .29 .10 .40 .15 .11 .11

CD score, dams 2 yr old* .33 .09 .42 .11 .24 .14

CD, dams 2 yr old« (%) .26 .09 .26 .11 .29 .14

CD score, dams >3 yr old* .20 .05 .20 .07 .18 .08

CD, dams >3 yr old« (%) .13 .05 .16 .07 .04 .07

CD score, dams of all ages* .31 .03 .37 .05 .18 .04

CD, dams of all ages«(%) .17 .03 .18 .04 .14 .04

Gestation length (days)' .45 .06 .34 .08 .58 .10

Age at puberty (days) .31 .04 .30 .05 .30 .06

^ Evaluated on a scale of 1 to 9, 9 = very fat, 1 = emaciated.

* Calving difficulty score was rated as follows: 1 = no difficulty, 2 = little difficulty by hand, 3 = little difficulty with calf

jack, 4 = slight difficulty with calf jack, 5 = moderate difficulty with calf jack, 6 = major difficulty with calf jack, and 7 =

caesarean birth.

^ Calving difficulty (%) was scored as follows: scores 1 and 2 = 0; scores 3, 4, 5, 6, and 7 = 1.

" Calves conceived by artificial insemination.

57
g Table 46. Genetic and phenotypic correlations among growth and carcass traits of castrate maies^ (/i=l,594)

Trait 1. 2. 3. 4. 5. 6. 7.

1. Birth weight 0.36 0.44 0.39 -0.04 -0.10 0.20

2. 200-day weight 0.29±.20 ^—^^ .59 .58 .16 .01 .24

3. Slaughter weight .27±.21 .40±.17 .92 .25 .12 .36

4. Carcass weight .18±.25 .42+. 18 .92±.04 ^^^^^^ .28 .13 .40

5. Adjusted fat IT*' rib -.06±.25 .15±.22 .23+.23 .13±.25 ^—^^^^.25 -.06

6. Marbling score* -.08±.20 .12±.17 .27±.18 .31±.20 .44±.18 ^^.^^-i)5

7. LMA* .17±.26 .49±.21 .45±.21 .66±.20 -.06±.27 -.02±.21 ^^

8. Retail product^ (%) -.16±.20 -.09+. 18 -.28±.21 -.12±.22 -.76±.32 -.60±.20 .32+. 19

9. Fat trim« (%) .04+.22 .03±.19 .19±.20 .08±.23 .82±.ll .66±.12 .26±.25

10. Bone trim (%) .54±.24 .26±.25 .37±.30 .18±.32 -.27±.34 -.28±.25 -.25±.31

11. Carcass bone weight .39±.17 .47±.14 .81±.08 .75±.ll -.05±.21 .08±.16 .31±.20

12. Carcass lean weight' .04±.25 .36±.18 .58±.14 .76±.10 -.48±.26 -.12±.19 .86±.14

13. Carcass fat weight"^ .05±.23 .18±.20 .57+. 14 .51±.17 .80±.12 .65±.14 .07±.25

14. Long, muscle fat« (%) .10±.20 .14±.17 .24±.18 .26±.19 .33±.18 .98±.06 .20±.21

15. Shear force^^ -.08±.35 -.34±.34 -.05±.34 -.10±.37 -.23±.37 -1.00±.48 -.48±.39

16. Tenderness score" .29±.28 .54±.24 .07±.25 .15±.28 .14±.27 .32±.20 .56±.31

17. Juiciness score*" .14±.25 .41±.22 .06±.24 .03±.26 .34±.24 .23±.18 .24±.27

18. Flavor score^^^ -.68±.58 .48±.46 -.34±.44 -.12±.47 .10±.46 .33±.37 .22±.50

19. Muscling score*** .30±.17 .31±.15 .14+. 16 .25±.18 -.38±.19 -.18±.14 .54±.17

20. Fat score*** .07±.24 -.10±.21 .20±.22 .15±.24 .38±.21 .39±.18 -.04±.26

^Genetic correlations and their standard errors are below the diagonal and phenotypic correlations above.

*LMA = Longissimus muscle area. A score of 4.00 to 4.90 = slight, 5.00 to 5.90 = small.

^Retail product includes steaks and roasts plus lean trim adjusted to 20-percent fat based on chemical analysis of lean trim.

1 All subcutaneous and accessible intermuscular fat removed.

''^Carcass lean includes steaks and roasts trimmed to 0 inches of fat cover plus fat-free lean trim

based on chemical analysis of lean trim.

^^Carcass fat includes fat trim plus fat in lean trim based on chemical analysis of lean trim.

** Ether-extracted fat from a cross section of the longissimus muscle.

^^Shear force required to cut through a 0.5-inch core.

""A score of 4 = slightly tough, 5 = slightly tender, 8 = extremely tender.

•fi'ö A score of 4 = slightly dry, 5= slightly juicy, 8 = extremely juicy.

^^^A score of 4 = slightly bland, 5 = slightly intense, 8 = extremely intense.

***Scores ranged from 3 to 27, with 6, 15, and 24 reflecting low, average, and high, respectively, for muscle or fat.

Continued
Table 46. Genetic and phenotypic correlations among growth and carcass traits of castrate males^ (/i=l,594)—Continued

Trait 8. 9. 10. 11. 12. 13. 14.

1. Birth weight 0.05 -0.10 0.21 0.54 0.42 0.11 -0.06

2. 200-day weight -.12 .13 -.08 .50 .52 .38 .02

3. Slaughter weight -.25 .28 -.23 .72 .79 .66 .12

4. Carcass weight -.24 .30 -.32 .66 .81 .67 .13

5. Adjusted fat 12'" rib -.56 .60 -.42 -.06 -.03 .60 .27

6. Marbling score* -.43 .46 -.31 -.09 -.07 .38 .63

7. LMA* .25 -.18 -.13 .30 .55 .06 -.11

8. Retail product« (%) ^^^^ -.96 .37 .04 .29 -.82 -.48

9. Fat trim' (%) -.98±.36 ^ ^^^ -.60 -.16 -.21 .88 .49

10. Bone trim (%) -.08±.21 -.14±.29 ^^^-^^^ .44 -.14 -.61 -.26

11. Carcass bone weight -.20±.16 .03±.19 .79±.16 .70 .20 -.08

12. Carcass lean weight' .56±.16 -.59±.26 .19±.28 .54±.13 .24 -.13

13. Carcass fat weight" -.88±.36 .90+.04 -.07±.30 .35±.18 -.16±.22 .41

14. Long, muscle fat« (%) -.55±.20 .64+. 11 -.43±.25 .03±.16 .06±.19 .65±.13 ^ -^^

15. Shear force«« .00±.28 -.04+.31 .18±.37 -.02±.29 -.14±.34 -.05±.34 -.77±.41

16. Tenderness score" .03±.21 -.07+.23 .18±.30 .27±.23 .24±.26 -.02±.25 .20±.20

17. Juiciness score'' -.20±.21 .15±.21 .22±.28 .18±.21 -.07+.24 .08±.23 .29±.18

18. Flavor score'^^ -.16±.39 -.11±.39 -.22±.54 -.16±.39 .09±.44 -.05±.43 .30+.36

19. Muscling score*** .32±.13 -.39±.17 .33±.20 .32±.14 .46±.15 -.32±.17 -.15±.14

20. Fat score«* -.54±.25 .61±.16 -.34±.33 -.04±.20 -.18±.23 .54±.17 .46±.18

^Genetic correlations and their standard errors are below the diagonal and phenotypic correlations above.

*LMA = Longissimus muscle area. A score of 4.00 to 4.90 = slight, 5.00 to 5.90 = small.

^Retail product includes steaks and roasts plus lean trim adjusted to 20-percent fat based on chemical analysis of lean trim.

'All subcutaneous and accessible intermuscular fat removed.

*"Carcass lean includes steaks and roasts trimmed to 0 inches of fat cover plus fat-free lean trim

based on chemical analysis of lean trim.

^^Carcass fat includes fat trim plus fat in lean trim based on chemical analysis of lean trim.

**Ether-extracted fat from a cross section of the longissimus muscle.

^^Shear force required to cut through a 0.5-inch core.

""A score of 4 = slightly tough, 5 = slightly tender, 8 = extremely tender.

•D'il A score of 4 = slightly dry, 5= slightly juicy, 8 = extremely juicy.

^^^A score of 4 = slightly bland, 5 = slightly intense, 8 = extremely intense.

***Scores ranged from 3 to 27, with 6, 15, and 24 reflecting low, average, and high, respectively, for muscle or fat.

Continued
ON Table 46. Genetic and phenotypic correlations among growth and carcass traits of castrate males^ (w=l,594)—Continued

Trait 15. 16. 17. 18. 19. 20.

1. Birth weight -0.02 -0.04 -0.05 0.00 0.11 0.08

2. 200-day weight -.06 .03 .02 .05 .10 .18

3. Slaughter weight -.08 .02 -.01 .11 .12 .40

4. Carcass weight -.07 .02 .01 .09 .15 .38

5. Adjusted fat 12"' rib -.06 .05 .09 .09 -.09 .33

6. Marbling score* -.24 .20 .21 .12 -.09 .21

7. LMA* .02 -.02 -.04 .03 .25 .16

8. Retail product^ (%) .16 -.11 -.14 -.14 .23 -.36

9. Fat trim' (%) -.17 .13 .15 .16 -.19 .41

10. Bone trim (%) .13 -.11 -.09 -.13 -.05 -.38

11. Carcass bone weight .02 -.04 -.04 .00 .11 .08

12. Carcass lean weight^' .00 -.01 -.06 .02 .28 .20

13. Carcass fat weight'^ -.16 .10 .11 .16 -.07 .51

14. Long, muscle fat** (%) -.23 .17 .20 .12 -.10 .13

15. Shear force» ^ ^^^ -.57 -.19 -.23 -.01 -.09

16. Tenderness score" -1.00±.77 ^^^ .60 .17 .02 .04

17. Juiciness score'' -.96±.54 .88+. 13 —^^^ -.06 -.02 -.04

18. Flavor score^"^ -1.00±1.00 .63±.52 .79±.66 ^ ~—^^^ -.02 .13

19. Muscling score*** .06±.24 .07±.19 .06±.18 -.25±.35 .01

20. Fat score*** -.26±.36 .02±.26 -.17±.24 .21+.44 -.03±.17 ^^

^Genetic correlations and their standard errors are below the diagonal and phenotypic correlations above.

*LMA = Longissimus muscle area. A score of 4.00 to 4.90 = slight, 5.00 to 5.90 = small.

^Retail product includes steaks and roasts plus lean trim adjusted to 20-percent fat based on chemical analysis of lean trim.

'AH subcutaneous and accessible intermuscular fat removed.

""Carcass lean includes steaks and roasts trimmed to 0 inches of fat cover plus fat-free lean trim

based on chemical analysis of lean trim.

^^Carcass fat includes fat trim plus fat in lean trim based on chemical analysis of lean trim.

**Ether-extracted fat from a cross section of the longissimus muscle.

^^Shear force required to cut through a 0.5-inch core.

""A score of 4 = slightly tough, 5 = slightly tender, 8 = extremely tender.

•Ji*" A score of 4 = slightly dry, 5= slightly juicy, 8 = extremely juicy.

^^^A score of 4 = slightly bland, 5 = slightly intense, 8 = extremely intense.

***Scores ranged from 3 to 27, v^ith 6, 15, and 24 reflecting low, average, and high, respectively, for muscle or fat.
Production Traits ofIntact Males

The r among size traits, calving difficulty scores

and calving difficulty percentage, and gestation

length are presented below the diagonal in table 47

for contributing purebreds and composites combined. Genetic correlations among size traits were

highly variable, ranging from —0.02 ± 0.07 between

birth weight and preweaning ADG and 0.97 ± 0.01

between preweaning ADG and 200-day weight. The

low r between preweaning and postweaning ADG

(0.04 ± 0.07) is not consistent with other reports

(Koch et al. 1982). The r of birth weight with

calving difficulty score and calving difficulty percentage were similar in calves from dams of all ages,

from 2-yr-old dams, and from dams 3 yr old or

older, ranging from 0.55 ± 0.13 to 0.82 ± 0.29.

The r of 0.62 ± 0.04 between 368-day weight and

368-day height (table 47) suggests that selection for

either trait would result in changes in the other. The

r^ of 0.65 ± 0.05 between 368-day height and 368-

day kind score suggests that selection for taller

animals will result in higher scores for kind as kind

score was applied in this study. The r between

muscling score and height was low (A). 10 ± 0.07).

The r between 368-day weight and 368-day condition score was relatively low (that is, 0.24 ± 0.07).

The higher r between birth weight and calving

difficulty score and percentage calving difficulty

(range of 0.55 ± 0.13 to 0.82 ± 0.29) than between

birth weight and 368-day weight (that is, 0.36 ±

0.06) suggests that calving difficulty could be

reduced by reducing birth weight while maintaining

368-day weight. A similar conclusion was reached

by Dickerson et al. (1974) in which a selection index

of I = [368-day weight - (3.2 x birth weight)] was

suggested. The relatively high r of gestation length

with calving difficulty score and with percentage

calving difficulty (that is, 0.57 ± 0.18 and 0.54 ±

0.26, respectively) suggests that some reduction in

gestation length would favor reduced calving difficulty. The relatively low r^ between gestation length

and birth weight (0.21 ±0.11) is noted. The r of

scrotal circumference with other traits evaluated was

generally low.

Production Traits ofFemales

Estimates of r and their standard errors for purebreds and composites combined are presented in

table 48 below the diagonal. Separate analyses were

run for six different age classes of individuals—ages

1, 2, 3, 3 or older, 4, and 5 yr. Data recorded through

522 days were included in all analyses. The reason

for this approach was to use all of the data available

in each age class. For example, gestation length was

available only for calves conceived by artificial

insemination in females 3 yr old or older. Further,

many of the females were removed from their

population based on nonperformance criteria by the

age of 5 yr. Differences in magnitude of standard

errors for h^ in table 45 reflect differences in the

number of observations for different traits. The r

g

were not estimated for all combinations of the 33

traits shown in table 45. Only the r among selected

weights, heights, condition scores, calving difficulty

scores, gestation length, and age at puberty are

presented in table 48. For example, percentage

calving difficulty is not included because calving

difficulty score is a more descriptive evaluation of

differences in the trait than the percentage calving

difficulty is.

The r between birth weight and subsequent weights

were similar for all ages to 2 yr but not at 5 yr (table

48). The high standard error reflects the relatively

small number of observations made at 5 yr. The r

between weight and height generally were high at

each age. The r for weight and height with condition score were variable at each age but tended to be

relatively low. The r^ for 200-day and 368-day

weight with subsequent weights were much higher

than the r^ for birth weight and subsequent weights.

The r^ between height at 368 days and height at

subsequent ages were only slightly higher than r

between weight at 368 days and weight at subsequent ages. The r between condition score at 368

days and condition score at subsequent ages were

relatively low (for example, 0.30 ± 0.09 and 0.36 ±

0.18). Calving difficulty score of calves from 2-yrold dams was not correlated with height at 368 days

(r^=0.20 ± 0.16) or at 2 yr {x=Qm ± 0.09). The r^

between calving difficuhy score at 2 yr and weight

at 2 yr was low (0.09 ± 0.09) and not important.

The r between birth weight and calving difficulty

score at 2 yr (0.59 ± 0.14) was higher than the r

between birth weight and calving difficulty score at

3 yr old or older (0.44 ± 0.14). The higher r between

61
as

^ Table 47. Genetic and phenotypic correlations^ among production traits of intact males

Trait 1. 2. 3. 4. 5. 6. 7.

1. Birth weight ^^^ 0.15 0.37 0.30 0.42 0.44 0.01

2. Preweaning ADG -0.02±.07 ^^-^^^ .97 .20 .73 .46 .17

3. 200-day weight .24±.07 .97±.01 ^^^^^ .25 .78 .54 .16

4. Postweaning ADG .30±.06 .04±.07 .11±.07 ^ .8 .48 .30

5. 368-day weight .36±.06 .63±.04 .70±.04 .79±.03 ^^^^64 .30

6. 368-day height .40±.06 .46±.06 .55±.05 .39±.06 .62±.04 ^^^^^^.^-£7

7. 368-day condition score -.07±.07 .01±.08 -.01±.08 .34±.07 .24+.07 -.23±.07

8. 368-day muscle score .31±.07 .05±.08 .13±.08 .24±.07 -.26±.07 -.10±.07 .12±.08

9. 368-day trimness score -.16±.07 .15±.08 .10±.08 -.08±.07 .01±.08 -.10±.07 .25±.07

10. 368-day kind score .20±.07 .33±.07 .37±.07 .18±.07 .36±.07 .65±.05 -.27±.08

11. Scrotal circumference .01±.07 .26±.07 .26±.06 .02±.07 .18±.07 .30±.06 .08±.07

12. CD score, dams of all ages* .60±.06 -.09±.08 .06±.08 .21±.08 .19±.08 .24±.07 .04±.08

13. CD, dams of all ages« (%) .59±.06 .05±.09 .20±.09 .27±.08 .32±.09 .31±.08 -.04±.09

14. CD score, dams 2 yr old* .62±.12 -.08±.13 .00±.14 .11±.14 .07±.15 .14±.13 -.20±.15

15. CD, dams 2 yr old« (%) .55±.13 .09±.12 .16±.13 .22±.13 .27±.13 .23±.12 -.08±.14

16. CD score, dams s3 yr old* .62±.17 -.06±.22 .12±.21 .11±.19 .14±.19 .38±.17 -.29±.21

17. CD, dams >3 yr old« (%) .82±.29 .15±.30 .17±.25 .30±.26 .54±.26 -.28±.30 -.12±.27

18. Gestation length. .21+. 11 -.15±.14 -.08±.13 .16±.12 .07±.12 .13±.10 -.08±.13

dams >3 yr old

^Genetic correlations and their standard errors are below the diagonal. Phenotypic correlations are above the diagonal.

*Calving difficulty score was rated as follows: 1 = no difficulty, 2 = little difficulty by hand, 3 = little difficulty with calf jack,

4 = slight difficulty with calf jack, 5 = moderate difficulty with calf jack, 6 = major difficulty with calf jack, and 7 = caesarean birth.

^Calving difficulty (%) was scored as follows: scores 1 and 2 = 0; scores 3, 4, 5, 6, and 7 = 1.

Continued
Table 47. Genetic and phenotypic correlations^ among production traits of intact males—Continued

Trait 8. 9. 10. 11. 12. 13. 14.

1. Birth weight 0.07 0.00 0.24 0.11 0.32 0.26 0.53

2. Preweaning ADG .11 .08 .31 .31 -.03 -.02 -.02

3. 200-day weight .12 .08 .34 .32 .04 .04 .09

4. Postweaning ADG .16 .08 .29 .23 .09 .07 .13

5. 368-day weight .18 .10 .40 .34 .08 .07 .14

6. 368-day height -.09 .00 .53 .25 .11 .10 .17

7. 368-day condition score .10 .26 -.10 .10 .00 -.02 .01

8. 368-day muscle score -.08 -.01 .00 .04 .05 .06

9. 368-day trimness score -.20±.08 "^""^-^ -.20 .06 -.02 -.04 -.03

10. 368-day kind score -.03±.08 -.22±.08 ^^^^-^^ .18 .05 .05 .07

11. Scrotal circumference -.17±.07 .13±.07 .22±.07 -.20 -.20 .01

12. CD score, dams of all ages* .12+.08 -.11±.08 .23±.09 -.06±.08 ^^^-^^^ .77

13. CD, dams of all ages« (%) .19±.09 -.09±.09 .19±.09 -.06±.09 .93±.02 ^^^^

14. CD score, dams 2 yr old* .33+. 16 -.29±.14 -.06±.16 -.17±.18 ^"^^

15. CD, dams 2 yr old« (%) .44±.15 -.23±.13 .00±.15 -.10±.17 1.00±.05

16. CD score, dams >3 yr old* -.21±.20 -.31+.20 .34±.19 -.25±.19

17. CD, dams >3 yr old« (%) -.23±.27 .21±.25 -.14±.25

18. Gestation length. .19±.12 -.11±.12 .09±.12 -.34±.ll

dams >3 yr old

^Genetic correlations and their standard errors are below the diagonal. Phenotypic correlations are above the diagonal.

*Calving difficulty score was rated as follows: 1 = no difficulty, 2 = little difficulty by hand, 3 = little difficulty with calf jack,

4 = slight difficulty with calf jack, 5 = moderate difficulty with calf jack, 6 = major difficulty with calf jack, and 7 = caesarean birth.

^Calving difficulty (%) was scored as follows: scores 1 and 2 = 0; scores 3, 4, 5, 6, and 7 = 1.

Continued

ON
^ Table 47. Genetic and phenotypic correlations^ among production traits ofintact males—Continued

Trait 15. 16. 17. 18.

1. Birth weight 0.42 0.26 0.24 0.27

2. Preweaning ADG .02 -.06 -.04 .01

3. 200-day weight .10 .00 .02 .07

4. Postweaning ADG .12 .06 .05 .04

5. 368-day weight .14 .04 .04 .07

6. 368-day height .16 .06 .06 .11

7. 368-day condition score .00 .00 -.03 .00

8. 368-day muscle score .06 .05 .04 -.02

9. 368-day trimness score -.04 -.01 -.02 .01

10. 368-day kind score .08 .03 .03 .07

11. Scrotal circumference .02 -.05 -.04 -.02

12. CD score, dams of all ages*

13. CD, dams of all ages« (%)

14. CD score, dams 2 yr old* .80

15. CD, dams 2 yr old« (%)

16. CD score, dams >3 yr old* ---..^^ .79 .11

17. CD, dams >3 yr old« (%) 1.00±.22 .11

18. Gestation length, dams >3 yr old .57±.18 .54±.26 """""~"""~-~~~

^Genetic correlations and their standard errors are below the diagonal. Phenotypic correlations are above the diagonal.

*Calving difficulty score was rated as follows: 1 = no difficulty, 2 = little difficulty by hand, 3 = little difficulty with calf jack,

4 = slight difficulty with calf jack, 5 = moderate difficulty with calf jack, 6 = major difficulty with calf jack, and 7 = caesarean birth.

^Calving difficulty (%) was scored as follows: scores 1 and 2 = 0; scores 3, 4, 5, 6, and 7 = 1.
Table 48. Genetic and phenotypic correlations^ among production traits of females

Trait 1. 2. 3. 4. 5. 6. 7.

1. Birth weight *>•..^^ 0.40 0.42 0.42 0.40 0.44 0.46

2. 200-day weight (kg) 0.34±.06 ^^^~^"~~~^~-^ .82 .61 .50 .56 .50

3. 368-day weight (kg) .33±.06 .84±.02 .76 .64 .63 .58

4. Weight, 2 yr .36±.07 .74±.05 .85±.03 ""^"^----^ .58 .69

5. Weight, 5 yr .08±.21 .66±.12 .83±.08 .48

6. 368-day height .35±.06 .66±.04 .70±.04 .68±.06 .51±.15 "^^'^^'---^ .77

7. Height, 2 yr .49±.07 .63±.06 .67±.05 .74±.04 .92±.02 ""^^"" ^--^

8. Height, 5 yr .25±.24 .44±.18 .48±.46 .47±.16 .88±.10

9. 368-day condition score* -.02±.07 .14±.07 .25±.07 .15±.08 .24±.16 -.15±.07 -.03±.09

10. Condition score.

dams 2 yr old* .03±.09 .32±.09 .36±.08 .48±.07 .01+. 10 .10±.09

11. Condition score,

dams 5 yr old* -.20±.25 -.02±.21 .34±.20 .56±.16 -.14±.24

12. CD score, dams 2 yr old« .59±.14 .06±.15 .09±.16 .09±.09 .20±.16 .00±.09

13. CD score, dams >3 yr old« .44±.14 .36±.17 .24+. 16 .12±.15

14. Gestation length (days) .30±.10 -.23±.12 -.14±.12 -.14±.ll

15. Puberty age (days) .03±.08 -.14±.09 -.05±.08 .11±.12 -.05+. 10 -.11±.08 .17±.12

^Genetic correlations and their standard errors are below the diagonal. Pheilotypic correlations are above the diaeonal. Continued

^Evaluated on a scale of 1 to 9, 9 = very fat, 1 = emaciated.

^Calving difficulty score was rated as follows: 1 = no difficulty, 2 = little difficulty by hand, 3 = little difficulty with calf jack,

4 = slight difficulty with calf jack, 5 = moderate difficulty with calf jack, 6 = major difficulty with calf jack, and 7 = caesarean birth.

ON
g^ Table 48. Genetic and phenotypic correlations^ among production traits of females—Continued

Trait 8. 9. 10. 11. 12. 13. 14. 15.

1. Birth weight 0.42 0.02 0.03 -0.03 0.43 0.12 0.29 0.05

2. 200-day weight .39 .19 .20 .08 .10 .04 .06 -.12

3. 368-day weight (kg) .49 .32 .27 .13 .14 .05 .07 -.11

4. Weight, 2 yr .11 .47 .09 .00

5. Weight, 5 yr .70 .10 .41 .01

6. 368-day height .71 -.05 -.04 -.12 .18 .03 .08 -.06

7. Height, 2 yr -.11 .02 .10 .02

8. Height, 5 yr -.17 -.02 .03

9. 368-day condition score* -.23±.21 ^^^^^ .26 .21 -.02 -.03 .04 -.09

10. Condition score,

dams 2 yr old* .30±.09 ""-^ .00 -.02

11. Condition score,

dams 5 yr old* -.14±.26 .36±.18 -.06

12. CD score, dams 2 yr old« .09±.13 -.14±.10 ^^^

13. CD score, dams >3 yr old* .09±.18 ^^^->-^ .05

14. Gestation length (days) .06±.13 -.07±.14 ^"^^-^^

15. Puberty age (days) .02±.ll -.02±.08 -.09±.14 -.17±.ll ^"^

^Genetic correlations and their standard errors are below the diagonal. Phenotypic correlations are above the diagonal.

^Evaluated on a scale of 1 to 9, 9 = very fat, 1 = emaciated.

^Calving difficulty score was rated as follows: 1 = no difficulty, 2 = little difficulty by hand, 3 = little difficulty with calf jack,

4 = slight difficulty with calf jack, 5 = moderate difficulty with calf jack, 6 = major difficulty with calf jack, and 7 = caesarean birth.
birth weight and calving difficuUy score at 2 yr (0.59

± 0.14) than between birth weight and 368-day

weight (0.33 ± 0.06) suggests some opportunity to

reduce calving difficulty score by reducing birth

weight while maintaining 368-day weight. A similar

conclusion was reached by Dickerson et al. (1974) in

which a selection index of I = [368-day weight —

(3.2 Xbirth weight)] was suggested. These estimates

of r

g

for females are similar to the r

g

for males from

the same population (table 47), with the exception of

r^ between gestation length and calving difficulty

score of calves from females 3 yr old or older, which

was considerably higher in males than females (0.57

± 0.18 vs. -0.07 ± 0.14) (table 48).

Phenotypic Correlations

Estimates of phenotypic correlations (r ) for all

breed groups are presented above the diagonal in

table 46 for growth and carcass traits of castrate

males, above the diagonal in table 47 for production

traits of intact males, and above the diagonal in table

48 for some production traits of females. These

phenotypic correlations are presented for purebred

and composite breed groups combined.

Growth and Carcass Traits ofCastrate Males

Phenotypic correlations of marbling score and

percentage longissimus muscle fat with palatability

attributes (tenderness, juiciness, and flavor) were

below 0.30 (table 46). Although marbling score is

the primary factor determining carcass quality grade

in cattle of the age in this study, it is not very useful

for predicting palatability. This is consistent with the

findings of other studies at the U.S. Meat Animal

Research Center with cattle of similar age and

nutritional background.

Production Traits ofIntact Males

Phenotypic correlations among size traits for intact

males were intermediate to high (table 47). The r

between 368-day height and 368-day kind score

(0.53) was higher than for any other combination.

The r of 368-day kind score and 368-day scrotal

circumference with different measures of growth

were low to intermediate. The r among different

anatomical scores generally were low. As expected,

a high r between calving difficulty score and percentage calving difficulty was observed in females of

different age classes (0.77, 0.80, and 0.79). The r^ of

calving difficulty score and percentage calving

difficulty with gestation length were low (0.11 and

0.11) and the r were 0.57 and 0.54.

Production Traits ofFemales

The r followed the pattern of the r^ but generally

were lower (table 48). The r between weights at

different ages and between heights at different ages

and between weights and heights at the same age

were relatively high. The r of calving difficulty

score at the ages presented, gestation length, and age

at puberty with weight, height, and condition score at

368 days generally were low and not important.

Adjustment Factors for Age of Dam

Adjustment factors for age of dam are provided in

table 49 for each sex of all breed groups.

Composite Breed Formation

The distribution of numbers by herd size in the U.S.

beef breeding herd is as follows: 35 percent represented by herds of 50 cows or fewer, 55 percent

represented by herds of 100 cows or fewer, and 87

percent represented by herds of 500 cows or fewer

(U.S. Department of Agriculture 1987). On farms

and ranches that have beef cows, 80 percent have 50

cows or fewer, 93 percent have 100 or fewer, and

more than 99 percent have 500 or fewer.

With 55 percent of the U.S. beef breeding herd and

93 percent of the farms and ranches that have beef

cows represented by units of 100 cows or fewer,

there are obvious limitations on feasible options for

optimum crossbreeding systems. The limitations are

most significant if female replacements are produced

within the herd and natural service breeding is used.

Further, fluctuation between generations in additive

genetic (breed) composition in breed-rotation crossbreeding systems restricts the extent to which breed

differences can be used to match climatic adaptability and performance characteristics to the climatic

and nutritive environment and other resources that

may be most economical to provide. Thus, the

67
^ Table 49. Adjustment factors for adjusting age of dam to a mature basis by sex and breed group

Age of dam

(yr)

Females Intact males

Breed group

Birth

weight

(lb)

Preweaning

ADG

(lb)

Postweaning

ADG

(lb)

Birth

weight

(lb)

Preweaning

ADG

(lb)

Postweaning

ADG

(lb)

Red Poll 2 8.1129 0.1742 -0.1014 10.7804 0.2050 -0.0397

3 3.8360 0.1257 -0.0460 5.6658 0.1213 0.0044

4 -2.8439 0.0132 -0.0088 1.1464 0.0243 0.0507

Hereford 2 8.4215 0.1962 -0.0728 10.0750 0.2712 -0.0220

3 3.9903 0.1168 -0.0463 7.0547 0.1830 0.0331

4 2.5794 0.0639 -0.0022 2.9541 0.0860 0.0353

Angus 2 5.8642 0.2116 -0.0705 8.2011 0.2778 -O.0198

3 2.4912 0.1411 -0.0220 3.3289 0.1653 0.0309

4 0.0000 0.0705 -0.0132 0.7275 0.0661 0.0000

Limousin 2 10.6261 0.2249 0.0309 12.3457 0.1962 -0.1345

3 5.4894 0.1675 0.0331 7.6279 0.1367 0.0110

4 0.5732 0.0926 0.0220 2.4691 0.0573 0.0044

Braunvieh 2 9.4136 0.2513 -0.0132 7.5617 0.2337 -0.0397

3 5.9965 0.1587 0.0265 5.2469 0.1279 -0.0044

4 0.7055 0.0353 0.0022 1.4330 0.0375 0.0353

Pinzgauer 2 15.9171 0.3571 -0.0044 22.5750 0.4563 0.0309

3 6.3933 0.1918 0.0309 9.3474 0.2910 0.0705

Gelbvieh

4

2

3.1746

13.3818

0.0397

0.2579

0.0507

-0.0265

4.7619

11.0009

0.1235

0.2998

0.0705

-0.0309

3 8.4215 0.1565 0.0220 4.2328 0.2160 -0.0088

4 3.3289 0.0816 0.0265 -1.2566 0.0772 0.0287

Continued
Table 49. Adjustment factors for adjusting age of dam to a mature basis by sex and breed group—Continued

Age of dam

(yr)

Females Intact males

Breed group

Birth

weight

(lb)

Preweaning

ADG

(lb)

Postweaning

ADG

(lb)

Birth

weight

(lb)

Preweaning

ADG

(lb)

Postweaning

ADG

(lb)

Simmental 2 12.5882 0.1918 -0.0772 13.3157 0.3175 -0.0309

3

4

7.5838

0.0441

0.1036

0.0044

-0.0066

-0.0044

6.5035

0.3968

0.2028

0.0904

-0.0022

0.0375

Charoláis 2 13.4700 0.2756 -0.0176 18.6728 0.3175 -0.0088

3

4

4.0564

1.1464

0.2160

0.0617

-0.0287

-0.0485

7.0547

2.0062

0.2513

0.0948

0.0000

0.0375

MARC I 2 12.4339 0.2116 -0.0265 12.0811 0.2535 -0.0287

3 6.7019 0.1455 -0.0132 6.6799 0.1477 0.0353

4 2.4030 0.0353 -0.0309 1.4550 0.0287 0.0309

MARCH 2 7.4515 0.2072 -0.0750 10.0529 0.2690 -0.0485

3 0.5071 0.1190 -0.0595 0.6393 0.1764 0.0176

4 -0.5291 -0.0132 -0.0551 -0.4850 0.0441 -0.0022

MARC III 2 13.3818 0.2006 -0.0617 12.0811 0.2734 -0.0353

3 3.5714 0.1279 -0.0683 1.2787 0.1455 -0.0287

4 1.8519 -0.0110 -0.0132 0.6614 0.0683 0.0220

ON
formation of composite breeds based on a

multibreed foundation is an attractive alternative, or

supplement, to continuous crossbreeding systems to

use high levels of heterosis on a continuing basis.

Once a new composite breed is formed, it can be

managed as a straightbred population. The management problems associated with small herd size and

wide fluctuations between generations in additive

genetic (breed) composition in rotational crossing

systems are avoided provided there is a source of

seedstock (bulls) of the composite breed desired.

Retention of initial heterozygosity after crossing and

subsequent random {inter se) mating within the

crosses is proportional to (n-l)/n, where n is the

number of breeds involved in the initial cross

(Wright 1922, Dickerson 1969, 1973). This loss in

heterozygosity occurs between the F^ and F^ generations. If inbreeding is avoided, further loss of heterozygosity in an inter se mated composite

population does not occur. This expression [that is,

(n-l)/n] assumes equal contribution of each breed

used in the foundation of a composite breed. Where

the breeds used in the foundation of a composite

breed do not contribute equally, percentage of mean

Fj heterozygosity retained is proportional to 1 -

SP.^, where P. is the fraction of each of n breed's

contributing to the foundation of a composite breed;

for example, heterozygosity retained in a three-breed

composite formed from 3/8 breed A, 3/8 breed B,

and 1/4 breed C can be computed as 1 - [(3/8)^ +

(3/8)2 + (1/4)2] ^ 55 5 percent. Obviously, the

maximum number of breeds that can be used to

contribute to achieving an optimum additive genetic

(breed) composition is preferred because retention of

heterozygosity is a function of the number of breeds

contributing to the foundation [that is, (n-l)/n].

However, use of a greater number of contributing

breeds should be balanced against the potential loss

in average genetic merit of including the additional

breeds.

Table 3 provides information on level of heterozygosity relative to the Fj that is retained after equilibrium is reached for two-, three- and four-breed

rotation crossbreeding systems and is presented for

two-, three-, four-, five-, six-, seven-, and eightbreed composites, with breeds contributing in

different proportions in several of the composites.

Estimates of increase in weight produced per cow

exposed to breeding, based on the assumption that

retention of heterosis is approximately proportional

to retention of heterozygosity, are presented in table

3 for each mating type.

Existing breeds of cattle are mildly inbred lines, and

because heterosis in cattle can be accounted for by

dominance effects of genes, heterosis involving Bos

taurus breeds can be accounted for as recovery of

accumulated inbreeding depression that has occurred

in breeds since their formation. Deviation of heterosis from linear association with heterozygosity

results from epistatic effects of genes. For loss of

favorable epistatic combinations that may have

become fixed or are maintained by either natural or

deliberate selection in parental breeds, the deviation

from linearity of loss in heterosis with loss in heterozygosity is negative (greater). However, for loss

of unfavorable epistatic combinations that may have

become fixed through chance, the deviation from

linearity of loss in heterosis with loss in heterozygosity is likely to be positive (less). Both genetic

situations may exist, but the likelihood would seem

to be greater for favorable than for unfavorable

epistatic combinations in parental breeds, particularly for fitness traits (for example, reproduction and

survival). Also, heterosis may deviate from heterozygosity in a positive direction if a threshold

effect (nonlinear) of heterozygosity relative to

heterosis should exist. Results from the comprehensive experiment reported in this bulletin show that

heterosis in composite populations, generally, is

retained in proportion to retained heterozygosity and

thus can be accounted for by dominance effects of

genes. Other than for characters affected by natural

or automatic selection (for example, fitness), the

likelihood is small that fixed favorable epistatic

combinations are important because of changing

selection goals that have characterized beef cattle

breeding.

Because retention of heterosis is, generally, linearly

associated with retention of heterozygosity, composite breed formation offers much the same opportunity as rotational crossbreeding for retaining high

levels of individual and maternal heterosis, in addition to heterosis for male reproductive performance

(table 3). Composite breeds offer the opportunity to

70
use genetic differences among breeds (that is, breed

complementarity) to achieve and maintain the

performance level for such traits as climatic adaptability, growth rate and size, carcass composition,

milk production, and age at puberty that is optimum

for each of a wide range of production environments

and to meet specific market requirements. Further,

composite breeds provide herds of any size with an

opportunity to use heterosis and breed complementarity simultaneously.

A specific composite breed does not permit the use

of different genotypes (complementarity) for male

and female parents (Cartwright 1970). However,

specialized paternal and maternal composite breeds

may be developed for use in production systems in

which the production resource base and market

requirements favor the exploitation of complementarity. This may be the case when the slaughter

animal is finished under more favorable environmental conditions than the environment where

breeding herds are maintained. Between-breed

selection is highly effective for achieving and

maintaining an optimum additive genetic composition (performance level) for such specialized breeds

by using several breeds to contribute to the foundation for each specialized composite breed. There is

opportunity to develop both general purpose and

specialized maternal and paternal composite breeds

through careful selection of fully characterized

candidate breeds to achieve an additive genetic

(breed) composition that is better adapted to the

production situation than is feasible through continuous crossbreeding or through intrabreed selection.

The maintenance of effective population size sufficiently large that the initial advantage of increased

heterozygosity is not dissipated by re-inbreeding is

essential for retention of heterozygosity (heterosis)

in composite breeds. Thus, the resource requirement

for development and use of composite breeds as

seedstock herds is high and, from an industry standpoint, requires a highly viable and creative seedstock

segment. Early re-inbreeding and a small number of

inadequately characterized parental breeds contributing to the foundation of composite breeds have

likely limited the success of some previous efforts in

composite breed development.

For the seedstock segment that develops composite

breeds, it is suggested that the number of females be

appropriate for the use of not less than 25 sires per

generation. Use of 25 sires per generation should

result in a rate of increase in inbreeding of about 0.5

percent per generation. With an average generation

interval of 5 yr, the accumulated inbreeding in a

composite breed after 50 yr (that is, 10 generations)

would be about 5 percent. Further, a large number of

sires (that is, 15-20) of each purebreed contributing

to the foundation of a composite breed should be

sampled in order to minimize the rate of inbreeding

in subsequent generations of inter se mating. Because some of the foundation sires used from each

contributing breed are not likely to leave sons, the

genetic base will likely be reduced in the first generation. Inbreeding may be viewed as the alternative

to heterosis and must be avoided in order to retain

high levels of heterozygosity and thus heterosis in

composite breeds.

An alternative procedure for keeping rate of inbreeding low in a composite population or breed is to

keep the composite open to the introduction of new

germplasm. This may be from new samples of the

same breeds contributing initially to the composite

or by including contributions from additional breeds.

In addition to providing an effective procedure for

keeping inbreeding at a low level, an "open concept"

in maintaining a composite breed allows for continuing use of breed differences to adjust bioeconomic

traits closer to the optimum level in harmony with

changes in production resource base and with market

requirements. Thus an "open concept" has greater

flexibility and is generally favored by the authors of

this bulletin. An "open concept" does not lessen the

need to sample a large number of sires and to use a

large number of sires per generation. Inbreeding

"bottle necks" can develop unless a large number of

sires are used in each generation.

The development of composite breeds may now be

viewed as a predictable procedure when contributions to a composite are limited to Bos taurus

breeds. However, because of the dynamic nature of

the beef cattle industry, characterization of candidate

breeds is needed on a continuing basis in a range of

production environments. This information is

needed to provide the basis for effective choices of

71
contributing breeds in order to approach the most

favorable additive genetic (breed) composition

consistent with the role perceived for each composite. Experimental comparisons involving adequate

samples of each breed of interest provide the most

reliable estimates of breed differences.

Heterosis from crosses of Bos indicas breeds with

Bos taurus breeds is considerably greater (perhaps

twofold) than crosses among Bos taurus breeds. We

do not believe that these experimental results on

heterosis retention in composite populations with

contributions limited to Bos taurus breeds should be

extrapolated to include composite breeds that have

contributions from both Bos taurus and Bos indicus

breeds. Rather, we believe that a large scale, comprehensive experiment is needed to estimate retention of heterosis in advanced generations of inter se

mated composite populations with contributions by

both Bos taurus and Bos indicus breeds. However,

from the limited information available, results

suggest that heterosis from breed crosses ofBos

taurus with Bos indicus breeds can be accounted for

by dominance effects of genes because heterosis in

advanced generations seems to be retained in proportion to retained heterozygosity.

In summary, the following factors favor the use of

composite breeds:

• It is simple and provides a high level of heterosis

or hybrid vigor.

• It is highly effective for using breed differences

or breed complementarity to achieve and maintain an optimum additive genetic (breed) composition for production and carcass traits.

• It provides a high degree of uniformity within

and between generations.

• It offers small herds an opportunity to use high

levels of heterosis and breed complementarity,

assuming seedstock herds exist to provide bulls

on a continuing basis.

References

American Meat Science Association. 1978. Guidelines for

cooking and sensory evaluation of meat. National Live Stock

and Meat Board, Chicago.

Cartwright, T.C. 1970. Selection criteria for beef cattle for the

future. Journal of Animal Science 30:706-711.

Cundiff, L.V., K.E. Gregory, and R.M. Koch. 1974. Effects of

heterosis on reproduction in Hereford, Angus and Shorthorn

cattle. Journal of Animal Science 38:711-727.

Cundiff, L.V., K.E. Gregory, R.M. Koch, and G.E. Dickerson.

1986. Genetic diversity among cattle breeds and its use to

increase production efficiency in a temperate environment. In

G.E. Dickerson and R. Johnson, eds., Proceedings of the Third

World Congress on Genetic Applications to Livestock Production, vol. 9, pp. 271-282. University of Nebraska, Lincoln

Dickerson, G.E. 1969. Experimental approaches in utilizing

breed resources. Animal Breeding Abstracts 37:191-202.

Dickerson, G.E. 1973. Inbreeding and heterosis in animals. In

Proceedings of the Animal Breeding and Genetics Symposium

in Honor of Dr. Jay L. Lush, pp. 54-77. American Society of

Animal Science, Champaign, IL

Dickerson, G.E., N. Kunzi, L.V. Cundiff, et al. 1974. Selection

criteria for efficient beef production. Journal of Animal

Science 39:659-673.

Gregory, K.E., and L.V. Cundiff. 1980. Crossbreeding in beef

cattle: Evaluation of systems. Journal of Animal Science

51:1224-1242.

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1982. Comparison of crossbreeding systems and breeding stocks used in

suckling herds of continental and temperate areas. Plenary

session. In Carlos Luis De Cuenca, ed.. Proceedings of the

World Congress on Genetic Applications to Livestock Production, vol. 5, pp. 482-503. University of Madrid, Madrid, Spain.

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1991a. Breed

effects and heterosis in advanced generations of composite

populations for preweaning traits of beef cattle. Journal of

Animal Science 69:947-960.

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1991b. Breed

effects and heterosis in advanced generations of composite

populations for growth traits of both sexes of beef cattle.

Journal of Animal Science 69:3202-3212.

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1991c. Breed

effects and heterosis in advanced generations of composite

populations for birth weight, birth date, dystocia and survival

as traits of dam in beef cattle. Journal of Animal Science

69:3574-3589.

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1992a. Breed

effects and heterosis in advanced generations of composite

populations on reproduction and maternal traits of beef cattle.

Journal of Animal Science 70:656-672.

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1992b. Breed

effects and heterosis in advanced generations of composite

populations on actual weight, adjusted weight, hip height, and

condition score of beef females. Journal of Animal Science

70:1742-1754.

72
Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1992c. Breed

effects and heterosis on milk yield and 200-day weight in

advanced generations of composite populations of beef cattle.

Journal of Animal Science 70:2366-2373.

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1994a. Breed

effects, dietary energy density effects, and retained heterosis on

different measures of gain efficiency in beef cattle. Journal of

Animal Science 72:1138-1154.

Gregory, K.E., L.V. Cundiff, R.M. Koch, et al. 1994b. Breed

effects and retained heterosis for growth, carcass, and meat

traits in advanced generations of composite populations of beef

cattle. Journal of Animal Science 72:833-850.

Gregory, K.E., L.V. Cundiff, R.M. Koch, et al. 1994c. Breed

effects, retained heterosis, and estimates of genetic and

phenotypic parameters for carcass and meat traits of beef cattle.

Journal of Animal Science 72:1174-1183.

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1995a. Genetic

and phenotypic (co) variances for growth and carcass traits of

purebred and composite populations of beef cattle. Journal of

Animal Science 73:1920-1926.

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1995b. Genetic

and phenotypic (co) variances for production traits of intact

male populations of purebred and composite beef cattle.

Journal of Animal Science 73:2227-2234.

Gregory, K.E., L.V. Cundiff, and R.M. Koch. 1995c. Genetic

and phenotypic (co) variances for production traits of female

populations of purebred and composite beef cattle. Journal of

Animal Science 73:2235-2242.

Gregory, K.E., D.D. Lunstra, L.V. Cundiff, et al. 1991d. Breed

effects and heterosis in advanced generations of composite

populations for puberty and scrotal traits of beef cattle. Journal

of Animal Science 69:2795-2807.

Harvey, W.R. 1985. User's guide for LSMLMW. Mixed

Model Least-Squares and Maximum Likelihood Computer

Program. The Ohio State University, Columbus.

Koch, R.M., L.V. Cundiff, and K.E. Gregory. 1982. Heritabilities and genetic environmental and phenotypic correlations of

carcass traits in a population of diverse biological types and

their implications in selection programs. Journal of Animal

Science 55:1319-1329.

Snedecor, G.W., and W.G. Cochran. 1980. Statistical methods,

7th ed. Iowa State University Press, Ames.

U.S. Department of Agriculture. 1987. Agricultural statistics.

Wiltbank, J.N., K.E. Gregory, J.A. Rothlisberger, et al. 1967.

Fertility in beef cows bred to produce straightbred and crossbred calves. Journal of Animal Science 26:1005-1010.

Wright, S. 1922. Effects of inbreeding and crossbreeding on

guinea pigs. IIL U.S. Department of Agriculture Technical

Bulletin No. 1121.

Glossary

Additive genetic value: The average performance

or average breeding value of individuals within a

breed for bioeconomic traits resulting from the

average effects of all alíeles (favorable and unfavorable) on a specific trait in the breed. Additive individual or additive direct genetic effects (G') are the

result of genotype of the individual, whereas additive maternal genetic effects (C") are the result of

genotype of the dam, that is, reproductive traits and

maternal ability. Thus, additive genetic value = G' +

G"". Differences among breeds are large for additive

genetic value for most bioeconomic traits.

Alíele: A different form of the same gene that

maintains identity, except for rare mutations, in

successive generations. Each alíele has a specific

unique sequence of nucleotides or base pairs.

Backcross: The progeny resulting from mating a

cross such as AB to either parent breed such as

AxABorBxAB.

Bioeconomic trait: Any biological trait of economic

importance.

Coefficient of variation (CV): An expression of

variation relative to the mean. The CVis usually

expressed as a percentage and is calculated as 100

a/X, where a is the standard deviation and X is the

mean.

Complementarity: The use of breed differences to

achieve a more optimum additive and nonadditive

breed composition for production and carcass traits

of economic value. Another use of the word in

specific crossbreeding systems (for example, terminal sire systems) is the organization of matings to

maximize the influence of desired characteristics

and minimize the influence of undesired characteristics of each breed used.

Composite: A new breed or population that is

established with contribututions from two or more

existing breeds and is generally mated inter se to

animals of the same breed composition. Composites

may be closed or open to the introduction of genes

from the same breeds or additional breeds. Such

introductions may be made to adjust additive genetic

value of the composite for specific traits or to reduce

73
the rate of inbreeding. The primary objectives of

composite breeds are (1) it is a simple procedure to

use high levels of heterosis, (2) it is a highly effective procedure to use breed differences or breed

complementarity, and (3) it results in a high level of

uniformity both within and between generations.

Dominance: The result of one gene "A" producing

the same phenotype whether paired with "A" or its

alíele "a." In such a situation, "a" is recessive to

"A." Dominance effects result from the interaction

of alíeles from the same locus. For example, for coat

color, black (B) is dominant to red (b), because

hétérozygotes (Bb) express black coat color the

same as homozygotes for the black alíele (BB). Red

coat color is expressed in animals that are homozygous for red coat color (bb). In a population sense,

dominance is the deviation from the average effects

of genes "A" and "a" in the population.

Epistasis or epistatic effects: The result of interaction of genes from different loci. The effects of

specific gene combinations (epistasis) may be

favorable or unfavorable.

Fj generation: The first generation resulting from

the crossing of two breeds such as AxB or BxA.

Generally, the sire breed is listed first. The Fj generation of a composite resulting from three or four or

more breeds is the first generation that reflects the

"final" breed composition such as results from

mating breeds AxBC or ABxCD.

F^, F3, and F^ generations: Generations resulting

from mating two individuals from the F, generation

to produce F^ progeny, two individuals from the F^

generation to produce F^ progeny, and two individuals from the F3 generation to produce F^ progeny,

respectively.

Gene: The basic unit of inheritance occupying a

specific location (locus) on a chromosome. Genes

are segments of deoxyribonucleic acid (DNA)

molecules connected in double-helix strands of

DNA that make up chromosomes.

Genetic correlation (r ): An estimate of the degree

to which genetic variation in one trait is associated

with genetic variation in another. Values can range

from-1 to +1.

Genotype: The expression of the genetic makeup of

an individual.

Heritability (h^): An estimate of the percentage of

the total variation observed that is due to additive

effects of genes, that is.

h' =

a2

n ^+iJ ^

or additive genetic variance

additive genetic variance + environmental variance

Heritability also is the proportion of differences

among individuals, measured or observed, that is

transmitted to their offspring. Heritability for a trait

can vary between 0 and 1 but is generally expressed

in percentage units.

Heterosis (also referred to as hybrid vigor): The

difference between the cross and the average of the

parental breeds, weighted by their contribution.

Observed heterosis is determined by summing

heterosis for individual traits (H') and heterosis for

maternal traits (H"").

Individual or direct heterosis (H'): Heterosis

expressed as a result of genotype of the individual.

This includes heterosis for growth traits. Heterosis

for reproductive traits, other than for age at puberty,

is generally classified as maternal heterosis because

it is evaluated in progeny of crossbred dams.

Maternal heterosis (H""): Heterosis expressed as a

result of genotype of the dam that is in addition to

individual or direct heterosis. Heterosis for reproductive and maternal traits expressed either in the

dam (that is, reproductive traits) or in progeny (that

is, maternal ability) is normally classified as maternal heterosis. Individual heterosis relative to maternal heterosis is individual expression relative to

expression as a result of maternal environment.

Paternal heterosis (RP): Heterosis expressed as a

result of genotype of the sire. Heterosis effects in the

percentage of calves born that may be attributable to

increased libido and/or fertility of F^ sires compared

with the average of parental purebred sires.

Heterozygosity: The result of having different

alíeles from the same allelic series at a given locus

or location on a chromosome pair, for example, Aa.

Homozygosity: The result of having two copies of

the same alíele at a given locus or location on a

chromosome pair, for example, AA or aa.

Inbreeding: The result of mating animals that are

more closely related than the average in the popula74
tion or breed. Inbreeding increases homozygosity

(for example, AAbb...x or aaBB...x), whereas

crossing increases heterozygosity (AaBb). Because

A may produce a more favorable effect and is

dominant to its alíele a, and B may produce a more

favorable effect and is dominant to its alíele b,

dominance effects of genes can account for heterosis

among crosses of Bos taurus breeds. In the example

given, only two loci are indicated. The number of

loci where dominance may be involved in the expression of a bioeconomic trait is believed to be

large. Because of chance segregation and recombination of genes from both parents, it is not feasible

to achieve homozygosity of all favorable alíeles with

dominance effects such as AABB....X. All breeds

that have been established for an extended period are

mildly inbred, and heterosis can likely be accounted

for as recovery of accumulated inbreeding depression that has occurred in breeds since their formation, that is, AaBb is superior to either AAbb or

aaBB. Inbreeding results in loss of vigor, particularly for fitness traits (that is, survival and reproduction) and crossing restores vigor.

Inter se mating: Mating of animals of the same

breed composition to each other.

Mean: The arithmetic average of all individuals in a

given group or population.

Nonadditive gene effects: Effects determined by

specific pairs of genes at the same location on a

chromosome (that is, dominance) or by specific

combinations of genes at different locations on

chromosomes (that is, epistasis). Nonadditive gene

effects cause heterosis or the opposite—inbreeding

depression.

Phenotype: The appearance or performance of an

animal. The expression of genotype plus environmental factors that affect appearance or performance

level for any trait. Phenotypic, adjective,

Phenotypic correlation (r ): An estimate of the

degree to which phenotypic variation in one trait is

associated with phenotypic variation in another.

Phenotypic correlation values can range frorii -1 to

+1.

Rotational cross or rotational crossing: The

continuous crossing of breeds in a given sequence

generation after generation, such as ABABA or

ABCABCA.

r : See phenotypic correlation.

Standard deviation: The square root of variance or

cr. Symbolized by cr (the Greek letter sigma). For

traits that have a normal distribution characterized

by a bell-shaped curve, 68 percent of the population

are bracketed by the mean ± 1 standard deviation, 95

percent of the population are bracketed by the mean

± 2 standard deviations, and 99.6 percent of the

population are bracketed by the mean ± 3 standard

deviations.

Variance: The measure of variation among individuals in a given group or population. Symbolized

by o"^ (the Greek letter sigma squared).

75