• TABLE OF CONTENTS
HIDE
 Historic note
 Introduction
 Two-breed rotational crossbree...
 Experimental procedure
 Result and discussion
 Upgrading versus two-breed rotational...
 Cow-related traits
 Comparison of grade angus with...
 Comparison among the two-breed...
 Summary
 Literature Cited
 Tables
 Back Cover
 Front Cover
 Table of Contents
 Foreword






Title: Comparison of upgrading and rotational crossbreeding for genetic improvement of Brahman-native population of beef cattle
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027188/00001
 Material Information
Title: Comparison of upgrading and rotational crossbreeding for genetic improvement of Brahman-native population of beef cattle
Series Title: Bulletin Agricultural Experiment Stations, University of Florida, 0096-607X
Physical Description: 40 p. : ill. ; 23 cm.
Language: English
Creator: Restle, João, 1947-
Hargrove, Don Darrell, 1937-
Koger, Marvin, 1915-
Publisher: Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1986
 Subjects
Subject: Beef cattle -- Breeding -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 27-29.
Statement of Responsibility: João Restle, Don D. Hargrove, Marvin Koger.
General Note: "November 1986."
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00027188
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000880009
oclc - 15678572
notis - AEH7807

Table of Contents
    Historic note
        Historic note
    Introduction
        Page 1
    Two-breed rotational crossbreeding
        Page 2
    Experimental procedure
        Page 3
        Page 4
    Result and discussion
        Page 5
    Upgrading versus two-breed rotational crossbreeding
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
    Cow-related traits
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
    Comparison of grade angus with grade hereford
        Page 17
        Page 18
        Page 19
    Comparison among the two-breed rotational crosses
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
    Summary
        Page 25
        Page 26
    Literature Cited
        Page 27
        Page 28
        Page 29
    Tables
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
    Back Cover
        Page 42
    Front Cover
        Cover
    Table of Contents
        Contents
    Foreword
        Title page
Full Text





HISTORIC NOTE



The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida






INTRODUCTION

Most beef herds in Florida during the early 1950s were
composed of a mixture of Brahman and "Florida Native" cattle.
Females from those herds usually calved for the first time at 3
years of age or older and tended to calve in alternate years
thereafter. The combined effects of low calving percentage and a
slow growth rate of calves resulted in overall low productivity
(Koger, 1973a). More rapid improvement of a population such as
this normally would be achieved through the introduction of
improved genetic material than through the application of
conventional selection procedures within the population.
Improved genetic material can be introduced through upgrading
to a specific breed. Although upgrading has been used extensively
in the past, in both the United States and other countries,
limited experimental data are available on the results obtained.
Systematic crossbreeding is an alternative to upgrading as a means
for genetically improving performance in beef cattle and offers
the potential for combining desired characteristics from different
breeds while maintaining some degree of breed heterozygosity and
resulting heterosis. Information on the long-term results from
systematic crossbreeding of beef cattle, however, was unavailable
when these trials were initiated.
The objective of this study was to compare, generation by
generation, the long-term responses obtained from two upgrading
and three two-breed rotational crossbreeding programs for the
genetic improvement of Brahman-Native cattle prevalent in Florida
during the early 1950s.

LITERATURE REVIEW

Upgrading

Upgrading is defined as the continued mating, generation
after generation, of males of one breed to females descending from
stocks unrelated to the sire breed. Upgrading is the most
economical way of moving the performance of commercial stock
toward the level of purebreds (Lush, 1945). Although upgrading
has been used extensively in the past to gradually absorb and
replace cattle of native or nondescriptive breeding, few
experimental results from upgrading are available in the
literature.
One of the early studies on upgrading in beef cattle was that
of Semple and Dvorachek (1930), who reported results from crossing
Angus bulls with Native females. Birth weights for straightbred
Angus, Native, 1/2 Angus and 3/4 Angus calves were, respectively,
30.3, 29.1, 27.9, and 29.8 kg. Respective preweaning average
daily gains were 721, 767, 776, and 762 g.
Results of upgrading to Charolais from a Brahman base were
reported by Peacock et al. (1973). Weaning weights were 232, 269,
240, and 247 kg, respectively, for 1/2, 3/4, 7/8, and 15/16



1






Charolais. Weaning rates for 3/4 and 7/8 Charolais females were,
respectively, 88 and 82%.
Koger et al. (1975) reported the results from a crossbreeding
program involving the Brahman and Shorthorn breeds. Weaning
weights for straightbred Brahmans and Shorthorns were, respect-
ively, 173 and 146 kg. For the crosses derived from the Brahman
base, the weaning weights were 202, 205, and 173 kg, respectively,
for 1/2, 3/4, and 7/8 Shorthorn calves. Weaning rates were 72 and
71%, respectively, for 1/2 and 3/4 Shorthorn females. For the
crosses derived from the Shorthorn base, weaning weights were 184,
215, and 190 kg, respectively, for 1/2, 3/4, and 7/8 Brahman
calves. Weaning rates were 76 and 70%, respectively, for 1/2 and
3/4 Brahman females.
Chapman et al. (1970) reported mean birth weights of 28.2 and
26.8 kg, respectively, for 7/8 and 15/16 Angus calves. Respective
preweaning daily gains were .69 and .66 kg. In the same study,
mean birth weights of 15/16 and 31/32 Polled Hereford calves were
31.6 and 29.7 kg, and preweaning daily gains .66 and .62 kg,
respectively.

Two-breed Rotational Crossbreeding

In the two-breed rotational crossbreeding or crisscrossing
system, two sirebreeds are rotated systematically in successive
generations. In this system, crossbreds move toward a breed
composition that stabilizes at 2/3 of the sire breed and 1/3 of
the other breed used in the rotation.
Results from three generations of crossbreeding Brahman and
Devon cattle were reported by Kidder et al. (1964). Weaning
weights for Brahman, Devon, reciprocal F, backcross (3/4-1/4
calves produced by F dams), and 378-5/8 calves were,
respectively, 150, 159, 10, 181 and 178 kg.
Peacock and Koger (1980) cited calving rates of 75, 90, 85,
and 93%, respectively, for straightbred Angus and Brahman matings,
reciprocal matings of Angus-Brahman, and reciprocal Angus-Brahman
F females backcrossed to Angus and Brahman bulls. Respective
calf survival rates were 89, 91, 90, and 96%. Calf performance
data from the same study were reported by Peacock et al. (1981).
Weaning weights were 183, 181, 200, and 223 kg, respectively, for
Angus, Brahman, reciprocal F1, and reciprocal backcross calves.
Crockett et al. (1978a, 1978b) compared straightbred Angus,
Brahman and Hereford cattle with all possible two-breed rotational
crosses among these breeds. Relatively high levels of heterosis
were maintained for preweaning traits across the three generations
studied. Mean heterosis levels for pregnancy rate were 6.0, 3.7,
and 5.9%, respectively, for F, 3/4-1/4, and 3/8-5/8 dams.
Respective heterosis levels for calf survival were 7.5, 2.4, and
-0.5%. The decline in heterosis levels for calf survival observed
in the successive generations was a consequence of the marked
increase of calf survival in the straightbreds. Survival rate of
the crossbred calves also increased over the generations, but not
as much as that of the straightbreds. Cundiff et al. (1982)
reported that high levels of heterosis were maintained in two


2






generations of two-breed rotational crossbreeding among the Angus,
Hereford, and Shorthorn breeds.

EXPERIMENTAL PROCEDURE

Data for this study were collected at the Beef Research Unit,
Gainesville, starting with the 1957 breeding season and ending
with the 1972 calf cr8p. The unit is located in north central
Florida (Latitude 29 40' N) and the climate is considered
subtropical. Maximum and minimum average temperature for the last
10 years of the experiment was 26.6 C and the minimum average was
12.8 C. Average annual rainfall during the experimental period
was 1,322 mm. Soils in the experimental area vary from moderately
well drained to very poorly drained. The major soil type is Leon
fine sand.
The foundation females used to initiate this study were
approximately 3/4 to 7/8 Brahman and 1/8 to 1/4 "Native"
(descendants of Spanish cattle), and were classified as grade
Brahman. Most of these females were obtained as 2-year-old
heifers from a south Florida ranch in 1952, with smaller groups
added in 1953 and 1957.
During the five years preceding this project (1952 to 1956),
the foundation females were mated to Angus, Brahman, Hereford, and
Shorthorn bulls. Most of the heifers produced from these matings
were retained for breeding. In 1957, the foundation females that
remained in the herd and the females produced from 1953 to 1957
were assigned to one of the following mating groups: upgrading to
Angus and to Hereford and three two-breed-of-sire rotational
crossbreeding programs including Angus-Hereford, Angus-Brahman,
and Hereford-Santa Gertrudis. Most of the female progeny of
Shorthorn bulls and foundation cows were allotted to the
Hereford-Santa Gertrudis rotational crossbreeding group and the
remainder to the Angus and Hereford upgrading groups. A group of
3/4 Angus-1/4 Brahman females was added to the Angus-Hereford
rotation group in generation two.
Generation was defined on the basis of breed composition.
Table 1 shows the breed composition of dams and progeny by
generation. The progeny of foundation females were classified as
generation one. Table 2 shows the number of matings by year and
generation.
Pasture establishment, feeding, and herd management practices
were described previously (Koger et al., 1961; Koger et al., 1970;
Koger, 1973b; Koger et al., 1977). During the early years of the
experiment, the females were exposed to bulls during a 90-day
breeding season extending from March 1 to June 4. The breeding
season was reduced gradually to a 70-day period, beginning March
10. Most of the sires were used for one year in single-sire
breeding herds. Most sires used in the project were produced at
the Brooksville Beef Cattle Research Station, Brooksville,
Florida. Bull selection was based on the bulls' growth rates and
their dams' maternal ability.
Approximately 85% of all females born in the experimental
herds were brought into production. The percentage of young cows


3






in the herd increased with successive generations (Table 3).
Heifers were exposed the first time at 2 years of age during the
first 5 years preceding this project (1952 to 1956). From 1957
through 1967, half of the heifers were exposed as yearlings, while
the other half was exposed at 2 years of age. For a period of 6
years (1957 to 1962), yearling heifers were not culled for failing
to become pregnant, and calves from the 2-year-old heifers were
weaned at the beginning of the breeding season. Starting in 1963,
calves from 2-year-old heifers were weaned at the standard weaning
time near the end of August. After 1967, all heifers were exposed
as yearlings and the majority of those that failed to become
pregnant were eliminated.
Intensive culling was practiced in the cow herd. To the
extent that pregnant heifers were available as replacements, all
cows that were nonpregnant at weaning time were culled. By 1960,
the reproductive rate had increased markedly, making it possible
to cull all open cows, and in addition all cows that had lost
their calves and approximately 15% of the cows with the poorest
production records.
All calves were identified and weighed and the males
castrated within 48 hours after birth. At weaning time cows and
calves were weighed and scored for condition, and all females that
had been exposed to bulls were palpated for pregnancy.
Animals were maintained on pastures containing Pensacola
bahiagrass (Paspalum notatum Flugge) in combination with white
clover (Trifolium repens .. During winter months cows were
supplemented with grass ay, corn silage, or molasses to maintain
the cattle in a healthy state. Supplementation normally began in
December, after calving had started, and continued until
clover-grass pastures were in condition to be grazed, usually in
early March.
From weaning until spring forage became adequate, heifer
calves were supplemented on pasture to gain approximately 0.23 kg
per day. Yearling heifers were kept on pasture during winter and
received a protein supplement. Heifers calving at 2 years of age
were put on a full feed of corn silage plus 2.3 to 2.6 kg daily of
a protein-energy supplement from calving until the beginning of
the breeding season in early March. Thereafter, they were put on
clover-grass pasture and managed in the same manner as older cows.
A mineral mixture (50% trace mineralized salt and 50% steamed
bone meal) was always available to all animals.
Calf traits studied were birth weight, weaning weight, age at
weaning, average daily gain from birth to weaning, and condition
score at weaning. Statistical analyses of the calf traits, except
birth weight, did not include the first record of the heifers that
calved at 2 years of age and whose calves were weaned at the
beginning of the breeding season.
Cow-related traits studied were pregnancy rate, calf survival
rate, weaning rate, cow weight and condition score at weaning, and
cow productivity. Each female in the breeding herd was given a
code of one or zero each year for pregnancy, calf survival from
pregnancy to weaning, and weaning status. For the statistical
analyses of weaning rate, an estimated calf survival code of one
or zero was assigned at random for each cow that was culled


4






pregnant, based on the survival rate observed for the subclass to
which the cow belonged. This was done assuming that the culled
pregnant females would have had a similar calf survival rate as
the others in their subclass, had they stayed in the herd. Cow
productivity was calculated from individual records by using the
following formula: (cow pregnancy x calf survival x calf weaning
weight)/(cow weight.75 ). Cow weight was taken at the time the
calves were weaned. Cows that were culled were not included in
the statistical analyses for cow productivity.
Because of empty subclasses and confounding, it was not
possible to account for reciprocal crosses in the mathematical
model; thus, the reciprocal crosses were combined for statistical
analyses.
The model used in the statistical analyses of calf traits
included the fixed effects of mating system, mating group nested
within mating system, generation, year, and sex of calf and the
interactions of mating system x generation, and mating group
nested within mating system x generation. Age of dam was included
as a covariate (linear and quadratic). The mathematical model
used to analyze cow-related traits included the same effects as
that used for the calf traits, with the exception of sex of calf.
The effect of sex of calf was deleted from the model because it
did not affect significantly cow weight or cow condition score,
and it was not applicable for pregnancy and survival from
pregnancy to weaning.
Since there were five mating groups, four independent
orthogonal contrasts were possible. The following comparisons
were made: upgrading system vs rotational crossbreeding system;
grade Angus vs grade Hereford; Angus- Hereford cross vs Angus and
Hereford grades; Angus-Hereford cross vs Angus-Brahman and
Hereford-Santa Gertrudis crosses.
The data were analyzed by conventional least-squares
procedures for unequal subclass numbers (SAS, 1979).


RESULTS AND DISCUSSION

The effects of major interest in this study were mating
system, mating group within mating system, and the interactions of
mating system x generation and mating group within mating system x
generation. The two mating systems compared in this study were
upgrading and two-breed rotational crossbreeding. The upgrading
system was composed of two mating groups, upgrading to Angus and
to Hereford. These two mating groups will be referred to as grade
Angus and grade Hereford. The two-breed rotational crossbreeding
system included three mating groups: Angus-Hereford,
Angus-Brahman, and Hereford-Santa Gertrudis rotations. They will
be referred to as crosses.
The effects of year, sex of calf, and age of dam were
significant sources of variation for all calf traits studied,
whereas generation was a significant source of variation affecting
calf birth weight, weaning weight, and condition score. All
cow-related traits were affected significantly by year and age of
cow, while pregnancy rate and cow weight at weaning were affected


5






significantly by generation. Year effects in this study were
confounded partially with effects of individual sires, since most
of the bulls were used for only one year. The significant effects
of age of dam and sex of calf on the traits studied are in
agreement with those generally reported in the literature.
Although the effects of year, age of dam, and sex of calf will not
be discussed in detail, the least-squares means shown in tables
4-13 are adjusted for these effects.


Upgrading Versus Two-breed Rotational Crossbreeding

Upgrading was used extensively in the past by the commercial
beef producer to genetically improve beef cattle and has been used
more recently by purebred breeders as a means for increasing
numbers of some of the more recently imported European breeds.
This mating system results in a gradual replacement of the genetic
material of the original population by that of the introduced
breed or breeds. The highest levels of animal performance might
be obtained in the early generations of an upgrading program as a
result of (1) the combined effects of breed heterozygosity and the
associated phenotypic heterosis and (2) additive genetic effects
due to the incorporation of desirable genetic material from the
introduced breed. The theoretical breed heterozygosity of the
first generation animals produced in an upgrading program would be
100%, which, combined with the additive genetic effect, should
result in an increase in the animal performance over that of the
original foundation animals. The preweaning performance of second
generation calves might be expected to surpass that of the calves
produced in the first generation of upgrading, as shown by Peacock
et al. (1973) and Koger et al. (1975). The theoretical breed
heterozygosity of the calves in the second generation would be
50%; however, they would be nursing first generation dams for
which theoretical breed heterozygosity would be 100%. The average
of the theoretical breed heterozygosity of dam and progeny in the
first generation would be 50% (0% for the dam and 100% for the
calf), while in the second generation it would be 75%( (100% for
the dam and 50% for the calf).
An alternative to upgrading is systematic crossbreeding.
This mating system has become more popular in recent years. When
starting from the same foundation population, the first and second
generations of a two-breed rotational crossbreeding program would
be very similar to those produced through upgrading. Theoretical
breed heterozygosity would be equal for the two systems in the
first two generations. Thereafter, theoretical breed
heterozygosity would continue to decrease by half in each
successive generation of upgrading, while in the two-breed
rotation it would be moved toward an equilibrium of approximately
67%. If animal performance is affected by breed heterozygosity
and resulting heterosis, then a two-breed rotational crossbreeding
program would be expected to maintain animal performance at a
higher level than would an upgrading program.



6







Calf Traits

The calf traits commonly included in performance records are
birth weight, birth date, weaning weight, and condition score.
Birth weight. Birth weight is important since it is
positively correlated with weights taken at subsequent ages.
Heavy birth weights, however, are undesirable in the cow-calf
operation, because they are associated with calving difficulty
(Smith et al., 1976). Least-squares means for birth weight, age
at weaning, condition score and weaning weight are shown in Tables
4, 5, 6, and 7.
Average birth weight of the crosses (29.6 kg) was heavier
(P<.0001) than that of the grades (27.8 kg). The birth weights
found in this study were slightly above those reported from two
studies conducted in Florida in which the breeds used were similar
to those involved in this project (Cobb et al., 1964; Crockett et
al., 1978b). However, the birth weights were generally lower than
those reported from other areas. Birth weight was affected
(P<.02) by the mating system x generation interaction. Mean birth
weights for the grades were 27.2, 29.3, 28.6, 27.7, and 26.4 kg,
respectively, in generations 1 through 5. Respective birth
weights for the crosses were 27.6, 29.9, 30.1, 29.9, and 30.6 kg.
Birth weights of the grades and crosses were very similar in
generations 1 and 2 (Figure 1); thereafter, birth weight gradually
declined in each successive generation in the grades but remained
relatively constant in the crosses. Since the first two
generations in an upgrading program and a two-breed rotation are
essentially the same when starting from the same foundation
cattle, the similarities of birth weight in the two mating systems
in generations 1 and 2 were to be expected. The decline in birth
weight for the grades after generation 2 followed the decline in
theoretical breed heterozygosity.
A more direct comparison between upgrading and rotational
crossbreeding is that of the Angus and Hereford grades versus the
Angus-Hereford crossbreds. The Angus-Hereford crossbred calves
were sired by the same bulls that sired the Angus and Hereford
grades; thus, selection was relatively equal in the
Angus-Hereford crosses and grades. Mean birth weight of the
Angus-Hereford cross calves (28.6 kg) was heavier (P<.07) than for
the average of the Angus and Hereford grades (27.8 kg). Birth
weight of the grade calves gradually declined after generation 2
(Figure 2), while that of the Angus-Hereford cross calves
increased in generation 3 and remained relatively high through
generation 5. The absence of a gradual decline in birth weights
over generations in the Angus-Hereford crosses probably was due to
the higher levels of breed heterozygosity and the resulting
heterosis maintained in the rotational crossbreeding system.
However, Crockett et al. (1978b) found slight negative heterosis
for birth weight in three generations of rotational crossbreeding
of the Angus and Hereford breeds in the Florida Everglades.
Age at weaning. When all calves are weaned on the same day,
those born early in the calving season are older at weaning, and
other things being equal, are heavier at weaning. Early calving
has a double advantage to the cattleman. It results in heavier

7






---- ROTATIONAL CROSSBREEDING
-- UPGRADING


32 900

31

30 -- -' 850- -------------









240 230


g 235 220

230 2 10

225200
S220' 190







GENERATION GENERATION


Figure 1. Calf traits by generation for the upgrading and two-breed rota-

tional crossbreeding systems.



--- A-H ROTATIONAL CROSSBREEDING
UPGRADING TO A AND H


30 900

240 2 30
U -














F 27- 19750


240 2 230 4




Figure Calf traits by generation for the 22d rota
z 2309 2 -

S22 200
u/ -5 (























1 2 3 4 5 1 2 3 4 5
GENERATION GENERATION

Figure 2. Calf traits by generation for the Angus-Hereford rotational cross-

bred group and the average of the Angus and Hereford upgraded

groups.
As /8 /
20 / 21
11. /
/ (2 /
/ As










Fiur 2.Cl risb eeainfrteAgsHrfr oainlcos
bre gou ad heavrae f heAnusan Hreor ugrde
groups
~ us I ,8







calves at weaning and increases the chances for the cows to
rebreed. Breed differences for earliness of calving are due
mainly to differences in gestation length and date of conception.
Since age of calf directly affects weaning weight and consequently
the value of the calf, it was analyzed as a production trait by
using weaning weight standardized to a constant age. Mean age at
weaning in the upgrading system was 230.8 days which tended
(P<.15) to be higher than the average age observed for the calves
in the rotational crossbreeding system (228.7 days). The mating
system x generation interaction affected (P<.10) calf age at
weaning. Age of the grades at weaning declined from generations 1
to 2, increased in generations 3 and 4, and declined slightly in
generation 5. Ages of calves were 229.4, 227.0, 232.1, 233.5, and
232.3 days, respectively, for generations 1 through 5. For the
crossbreds, age increased from generation 1 to 2, declined in
generation 3 and increased slightly thereafter (228.4, 229.7,
227.5, 228.7, and 229.0 days). Grades were older than crosses in
generations 1, 3, 4 and 5, but younger in generation 2. The
tendency for the crosses to be younger at weaning was probably
due, in part, to a longer gestation period. Two of the mating
groups in the crosses, Angus-Brahman and Hereford-Santa Gertrudis,
included the Brahman and the Santa Gertrudis breeds in the
rotations. The Brahman breed and the Brahman x British crosses
have longer gestation periods than the British breeds and British
x British crosses (Gregory et al., 1979; Reynolds et al., 1980).
Mean age at weaning for the Angus-Hereford cross calves
(231.8 days) did not differ (P>.59) from the grade Angus and
Hereford groups (230.8 days). The nonsignificant difference in
age at weaning between the grades and Angus-Hereford cross calves
and the fact that age did not decline over generations of
upgrading are indications that heterosis had little effect on this
trait. Age of calf at weaning in the grades did not follow the
decline in theoretical breed heterozygosity over generations.
Koger et al. (1975) reported that heterosis for calf age at
weaning was not significant, while Reynolds et al. (1980) did not
find significant heterosis levels for gestation length or
earliness of calving.
Condition score. Condition score of the calf reflects, to
some extent, the dam's milking ability. Calves in the upgrading
system had an average condition score similar (P>.70) to that of
the calves in the rotational crossbreeding system (10.6 vs 10.7).
This trait was not affected (P>.47) by the interactions of mating
system x generation. In both grades and crosses the generation 1
calves (those nursing foundation cows) had the lowest average
condition score. This response suggests that the foundation cows
had poor milking ability.
The mean condition score of the Angus-Hereford cross calves
(10.9) was higher (P<.04) than that of the grades (10.6).
Condition scores of the Angus-Hereford cross calves and grades
were similar in generations 1 through 4; however, in generation 5
the crossbred calves had significantly higher condition scores
(11.3 vs 10.4). Crockett et al. (1978b) found higher condition
scores for Angus-Hereford rotational crossbreds than for the
straightbreds.

9







Weaning weight. Weaning weight is an important trait in the
cow-calf operation because it is related directly to the value of
the calf at weaning. This trait is determined by the calf's birth
weight, preweaning growth rate, and age at weaning. Average
weaning weight was heavier (P<.0001) for calves from the
rotational crossbreeding system (222.1 kg) than for the calves
from the upgrading system (213.7 kg), although the crossbred
calves tended to be younger at weaning than the grades (228.7 vs
230.8 days). The superior weaning weight of the crossbreds was a
result of a heavier birth weight (29.6 vs 27.8 kg) and a higher
preweaning daily weight gain (0.84 vs 0.80 kg). Weaning weight was
affected (P<.0001) by the mating system x generation interactions.
Mean weaning weights in generations 1 through 5 of the grades were
212.2, 225.7, 221.5, 211.4, and 197.8 kg, respectively.
Respective weaning weights for the crosses were 213.3, 225.6,
224.3, 223.2, and 224.1 kg. Weaning weights for grades and
crosses were almost identical in generations 1 and 2 (Figure 1).
Thereafter, weaning weight of the grades declined gradually in
each successive generation of upgrading, while there was almost no
variation in weaning weight in the successive generations of
rotational crossbreeding. Although age at weaning for the grades
increased from generation 2 to 4, weaning weight declined.
Weaning weight of the grade calves declined after generation 2 as
a result of a decrease in birth weight and average daily gain from
birth to weaning. Preweaning average daily gains for the grades
were 0.81, 0.86, 0.83, 0.79, and 0.74 kg, respectively, while for
the crosses the respective gains were 0.81, 0.85, 0.85, 0.84, and
0.84 kg. Changes in preweaning average daily gain over
generations for the upgrading and two-breed rotational
crossbreeding systems are shown in Figure 1.
The decrease in weaning weight of the grade calves after
generation 2 was consistent with results from a crossbreeding
study involving the Shorthorn and Brahman breeds reported by Koger
et al. (1975). In their study, weaning weight increased from
generation 1 (F 's) to generation 2 (breed composition of 3/4:1/4)
and declined in generation 3 (breed composition of 7/8:1/8).
Peacock et al. (1973) reported the results from a study of
upgrading to the Charolais breed from a Brahman base. They showed
that weaning weight increased from generation 1 to 2, decreased in
generation 3, and increased in generation 4.
Average weaning weight was similar (P>.22) for the grades and
Angus-Hereford rotational crossbred calves (213.7 vs 216.5 kg).
Weaning weight of the Angus-Hereford cross calves, however, did
not show a continuous decline from generations 2 through 5, as did
that of the grades (Figure 2). The Angus-Hereford cross calves
showed a marked decrease in weaning weight from generation 3
(222.3 kg) to 4 (211.0 kg), followed by an increase in generation
5 (223.6 kg). The decline in weaning weight in generation 4 was
due to a significant decline in the preweaning average daily gain
(Figure 2). Weaning weight of the Angus-Hereford crossbred calves
never declined below that recorded for generation 1 (202.3 kg),
whereas weaning weights of the grade Angus and Hereford calves in
generations 4 (211.4 kg) and 5 (197.8 kg) had decreased below that
recorded in generation 1 (212.2 kg). The absence of a gradual

10






decline in weaning weight of the Angus-Hereford cross calves
probably was due to the higher level of breed heterozygosity
maintained by the crisscross system. Crockett et al. (1978b)
reported a 5% heterosis level for weaning weight over three
generations of rotational crossbreeding of the Angus and Hereford
breeds.
Birth weight and weaning weight showed very similar response
patterns. Birth and weaning weights of the grades and crosses
were similar in generations 1 and 2; thereafter, the value for
both traits declined in the grades but remained relatively
constant in the crosses. Although age at weaning for the grades
increased from generation 2 to 4, weaning weight declined.
The similarity in both birth and weaning weights of the
grades and crosses in generations 1 and 2 can be explained by the
fact that the foundation females in all mating groups were grade
Brahmans. All first generation calves were basically first
crosses (1/2 grade Brahman and 1/2 of either Angus, Hereford or
Santa Gertrudis). The generation 2 calves were from first-cross
dams and were either backcrosses or crosses to a third breed.
Average birth and weaning weights of the grades and rotational
crossbreds began to differentiate in generation 3 and continued to
separate thereafter. The grade females were backcrossed in the
successive generations only to bulls from the same breed, which
resulted in a reduction of breed heterozygosity in each generation
and a consequent loss of heterosis.
A greater level of breed heterozygosity was maintained in the
rotational crossbreeding system. In an upgrading program the
breed heterozygosity theoretically would be 100, 50, 25, 12.5, and
6.25%, respectively, for generations 1 through 5. In a two-breed
rotational crossbreeding program, the respective theoretical breed
heterozygosity would be 100, 50, 75, 62.5, and 68.75%. Koger et
al. (1975) reported that heterosis observed was approximately
linear with breed heterozygosity in a crossbreeding program
involving the Brahman and Shorthorn breeds. After generation 2
the theoretical breed heterozygosity in the grades decreased by
half in each successive generation of upgrading, while in the
rotational crossbreeding system, breed heterozygosity was
maintained at a higher level. Theoretical breed heterozygosity in
both the grade Angus and Hereford declined from 100% in generation
1 to 6.25% in generation 5 (31/32 purebred breed: 1/32 grade
Brahman). The grades in generation 5 were carrying 31/32 (96.9%)
of the genetic material from the purebreds and, from a genetic
standpoint, they were very similar to purebreds. The rotational
crosses, on the other hand, moved toward an equilibrium of breed
heterozygosity of approximately 67% and a breed composition of
1/3:2/3 of the two breeds involved in the cross. In this study,
the theoretical breed heterozygosity for the Angus-Brahman which
best fit a typical two-breed rotation scheme was 68.75% in
generation 5 with a breed composition of 21/32 Angus-11/32 Brahman
and 21/32 Brahman-11/32 Angus. The results of this study showed
that birth and weaning weights of the rotational crossbred calves
did not decline over generations and that the rotational
crossbreeding system of mating was effective in maintaining
preweaning growth at a high level. These results, although


11






covering more generations, are consistent with those reported by
Crockett et al. (1978b).
The increases in birth weight, weaning weight and condition
score that occurred from generation 1 to 2 in both mating systems
probably were due to a combination of additive breed and heterosis
effects in both dam and progeny. The first generation calves were
all first crosses and were from foundation females. The
generation 2 calves were all nursing first cross dams, while the
calves themselves were 3/4 of either Angus or Hereford in the two
upgrading groups, or 3/4 Angus-1/4 Brahman or 3/4 Brahman-1/4
Angus in the Angus-Brahman crosses. In the Angus-Hereford and
Hereford-Santa Gertrudis rotation groups, calves were three-breed
crosses (Table 1). In generation 1, theoretical breed
heterozygosity for the calves was 100%, but they were nursing
foundation cows that evidently were of poor maternal ability, and
the low milk production limited to some extent expression of
growth potential in the calves. Theoretical breed heterozygosity
for the calves in generation 2 was 50% (grade Angus and Hereford,
and Angus-Brahman cross) or 100% (Angus-Hereford and
Hereford-Santa Gertrudis crosses), and 100% for their F, dams.
The dams of the generation 2 calves evidently had better mothering
ability, resulting in more rapid growth rate and higher condition
score of the calves. These results are consistent with those
reported by other workers (Peacock et al., 1973; Koger et al.,
1975; Peacock et al., 1981), who found higher preweaning growth
rate for backcross calves nursing F1 dams than for F1 calves
nursing straightbred dams.

Cow-Related Traits

The cow-related traits studied were pregnancy rate, calf
survival, weaning rate, cow weight, cow condition score, and cow
productivity. The respective least-squares means for these traits
are presented in Tables 8, 9, 10, 11, 12 and 13.
Pregnancy rate. Pregnancy rate is a measure of herd
fertility and is calculated as
Number of pregnant females 100
Number of females in the breeding herd
Mean pregnancy rate was higher (P<.07) for the grades than
for the crosses (90.6 vs 86.8%). Pregnancy rates of the grades
were 91.3, 86.9, 85.3, and 98.7%, in generations 1 through 4,
respectively. Respective pregnancy rates of the crosses were
89.8, 85.7, 86.1, and 85.6%. The interaction of mating system x
generation was not significant (P>.25). Pregnancy rates of the
grades and crosses were similar in generations 1, 2, and 3 (Figure
3); however, in generation 4 the grades had a 15% (13.1 percentage
points) higher pregnancy rate. The similarity in pregnancy rate
for the grades and crosses in generation 1 was to be expected,
since all females in this generation were basically Fl's, and were
produced from the same Brahman-Native foundation. The largest
drop in pregnancy rate in both mating systems occurred from
generation 1 to 2. This drop was larger than the difference
between F1 and backcross (3/4-1/4) females reported by Crockett
et al. (1978a).

12






Pregnancy rates in the rotational crosses remained fairly
consistent after generation 2, but declined through generation 3
in the grades. The very sharp increase in pregnancy rate for the
Angus and Hereford grades in generation 4 remains unexplained.
However, small numbers of observations were available for the
grades in generation 4; thus, the increase may have occurred as a
result of sampling.
There was no difference (P>.56) in the average pregnancy rate
of the grades and that of the Angus-Hereford rotational crossbreds
(90.6 vs 89.1%). Pregnancy rates of the Angus-Hereford crosses
were 89.4, 91.4, 87.9, and 87.7%, for generations 1 through 4,
respectively. The Angus-Hereford cross females showed a slight
increase in pregnancy rate from generation 1 to 2, while the
grades showed a decline (Figure 4). On the other hand, the grades
showed a sharp increase in pregnancy rate from generation 3 to 4
while there was almost no change for the Angus-Hereford crosses.
Calf survival rate. Calf survival, as used in this study,
was calculated by the following formula:
Number of cows weaning calves 1
Number of cows diagnosed pregnant
Mean calf survival rates were similar (P>.49) for the grade
and crossbred groups (91.6% and 92.8%), and were comparable to
those reported by Crockett et al. (1978a) and Peacock and Koger
(1980). Calf survival rate in the grades increased slightly from
generation 1 to 2 and decreased for generations 3 and 5 (92.7,
94.2, 93.2, and 86.3%). Among the crosses, calf survival rate
decreased slightly from generations 1 through 4 (94.8, 92.8, 92.6,
and 90.9%). The interactions of mating system with generation was
non-significant. The decline in calf survival that occurred over
generations in this study differed from the results reported by
Crockett et al. (1978a), who found a marked increase in survival
rate for both rotational crosses and straightbred controls in
three successive generations. The author suggested that the
increase in survival rate was influenced by the practice of
culling all cows which lost calves during the last five years of
the experiment. Although intensive culling was practiced during
this study, calf survival rate declined.
Mean calf survival rate in the Angus-Hereford cross tended to
be higher (P<. 18) than in the Angus and Hereford grades (94.3 vs
91.6%). Although survival rate in the Angus-Hereford crosses
dropped slightly from generation 1 to 2, it remained fairly
constant in generations 3 and 4 (96.0, 93.4, 94.9, and 93.0%),
while for the grades, calf survival rate increased slightly from
generations 1 to 2 and decreased thereafter. The tendency for
survival rate to be higher in the Angus-Hereford cross than in the
grades and the lack of a decline over generations probably were
due to a higher level of heterosis maintained by crisscrossing.
Crockett et al. (1978a) reported a slight positive heterosis for
calf survival rate in rotational crossbreeding of the Angus and
Hereford breeds.
Weaning rate. Weaning rate is the trait that has the
greatest impact on the economy of a commercial cow-calf operation.
Weaning rate is calculated as the product of pregnancy rate x calf
survival rate. Pregnancy rate of the grades was higher than that


13






ROTATIONAL CROSSBREEDING
-- UPGRADING


100 10 OO



90 > 90-
z u



L 80 -80-
LL0





90r 2.00-
Lg
90 90





f 80 10-- --
Z Q 160-
z
SI 50-


7 0 140-

2 3 4 2 3 4

GENERATION GENERATION


Figure 3. Cow-related traits by generation for the upgrading and two-breed
rotational crossbreeding systems.


.--- A-H ROTATIONAL CROSSBREEDING
----- UPGRADING TO A AND H


100- 100-
LU















80 80-
o


z rg I 60Ceo-


90-go-
z a
< 50

SW 8





60



70 0

3 70- C 1.40

2 3 4 I 2 3 4
GENERATION GENERATION

Figure 4. Cow-related traits by generation for the Angus-Hereford rotation-
al crossbred group and the average of the Angus and Hereford
upgraded groups.

14







of the crosses (90.6 vs 86.8%), but the grades tended to have a
slightly lower calf survival rate (91.6 vs 92.8%). As a result of
this, the mean weaning rate for the upgrading system (82.9%) was
similar (P>.33) to that of the rotational crossbreeding system
(80.5%). Interactions of mating system x generation were not
significant.
Weaning rates for the grades were 84.6, 82.0, 79.7, and 85.1%
in generations 1 through 4, respectively, while for the rotational
crosses they were 85.0, 79.5, 79.6, and 77.9%. Weaning rate in
the grades declined from generations 1 through 3 and increased in
generation 4. Although the grades had the lowest calf survival
rate in generation 4, they had the highest weaning rate, which
resulted from the very high pregnancy rate. Mean weaning rate in
the rotational crosses decreased from generation 1 to 2 and
remained fairly constant thereafter.
The drop in weaning rate from generation 1 to 2 was higher
for the crosses than for the grades. Both the grades and crosses
showed a similar drop in pregnancy rate from generation 1 to 2.
However, calf survival in the grades increased slightly in
generation 2, while it declined in the crosses.
Mean average weaning rate of the Angus and Hereford grades
(82.9%) was similar (P>.68) to that of the Angus-Hereford
rotational crossbreds (84.0%). The Angus-Hereford rotational
crossbreds tended to have a slightly lower pregnancy rate, but a
higher rate of calf survival.
Cow weight. Weight of cows was taken at the time their
calves were weaned. Mean weight of the cows in the upgrading
system (469.4 kg) was heavier (P<.04) than that of the cows in the
rotational crossbreeding system (462.0 kg). Cow weight was
affected (P<.02) by the interactions of mating system x
generation. Weights of the cows in the upgrading system were
similar in generations 1 and 2; however, they dropped sharply in
generations 3 and 4 (490.9, 489.8, 466.3, and 430.6 kg). Weight
of the cows in the rotational crossbreeding system decreased 6.8
kg from generations 1 to 2, 8.4 kg from generations 2 to 3, and
16.7 kg from generations 3 to 4. Grade cows were heavier in
generations 1, 2, and 3, whereas the crossbred cows were heavier
in generation 4. There was a much more rapid decline of weight in
the grade cows in generations 3 and 4 than in the crossbred cows.
Weight of cow did not follow the same response patterns as
birth and weaning weights over generations. Birth and weaning
weights increased from generations 1 to 2 in both mating systems,
while cow weight remained similar from generations 1 to 2 in the
upgrading system and declined in the rotational crossbreeding
system. The drop in birth and weaning weights that occurred in
the upgrading system after generation 2 was less than the drop
that occurred in the cow weight. Average birth weight in
generation 4 was slightly below that of generation 1 and weaning
weight in generation 4 was very similar to that in generation 1,
whereas the cow weight decreased by 60.3 kg from generations 1
through 4. Birth and weaning weights increased from generations 1
to 2 in the rotational crossbreeding system and remained fairly
constant thereafter, while cow weight declined from generations 1
through 4. The drop in cow weight from generations 1 to 4 in the


15






crosses was 31.9 kg. There was no downward trend in the condition
score of the cows over generations (Table 12), indicating that the
decline in weight of the cows probably was associated with a
decrease in body size.
The mean weight of the grade Angus and Hereford cows combined
was heavier than that of the Angus-Hereford crossbred cows in all
four generations. The average difference across the four
generations was 15 kg (P<.0002). Birth weight of the
Angus-Hereford crossbreds was heavier and weaning weight tended be
heavier than the means of the Angus and Hereford grades, whereas
cow weight was lighter. Although the Angus-Hereford crossbred
cows were sired by the same bulls that sired the Angus and
Hereford grade cows, their weight was-close to that of the grade
Angus cows, and below that of the grade Herefords.
Cow condition score. Condition scores of the cows were taken
at the time their calves were weaned. Cows in the upgrading
system tended (P<.20) to have higher condition scores than the
cows in the rotational crossbreeding system (7.3 vs 7.1). In
addition, cows in the upgrading system were heavier and had higher
pregnancy rates. On the other hand, cows in the rotational
crossbreeding system had lighter average weights and tended to
have lower condition scores than the grade cows, but gave birth
to heavier calves and weaned calves with heavier weights.
Although average condition score of the cows in the upgrading
system increased slightly from generations I to 2 and remained
constant in generation 3, pregnancy rate declined from generations
1 through 3. On the other hand, cow condition score decreased
slightly from generations 3 to 4, while pregnancy rate showed a
very high increase. Pregnancy rate in the rotational
crossbreeding system showed the largest drop from generations 1 to
2 even though cow condition score showed only a slight decrease.
Condition score in the crosses declined slightly from generations
2 to 3 and increased from generations 3 (6.8) to 4 (7.6), while
pregnancy rate remained fairly constant after generation 2. The
increase in cow condition score that occurred from generations 3
to 4 in the rotational crossbreeding system was due to a large
increase in condition score of the Angus-Brahman crossbred cows
(6.9 to 9.1).
The mean condition score of the grade Angus and Hereford cows
combined did not differ (P>.33) from that of the Angus-Hereford
rotational crossbred cows.
Cow productivity. Cow productivity reflects the combined
effects of cow reproduction, calf survival, and calf growth from
birth to weaning. Individual cow productivity in this study was
expressed as the ratio of calf weaning weight to metabolic weight
of the cow. Metabolic weight was used because it reflects more
closely the maintenance requirements of the cow than does live
weight. Individual cow productivity will be zero when the cow
does not wean a calf. Least-squares means for cow productivity
are shown in Table 13.
Cow productivity in the upgrading system (1.69) did not
differ (P>.34) from that in the rotational crossbreeding system
(1.75). The grades had a higher pregnancy rate, whereas the
rotational crossbred cows were lighter weight, tended to have a


16







higher calf survival rate, and weaned heavier calves. The
interactions of mating system x generation did not affect (P>.96)
cow productivity. In both mating systems generation 1 females (F
females nursing backcross and three-breed cross calves) had the
highest cow productivity. Cow productivity changes over
generations were similar for the grades and rotational crossbreds
(Figure 3). Cow productivity of both groups decreased from
generations 1 to 2, remained constant or declined slightly from
generations 2 to 3, and increased from generations 3 to 4.
Mean cow productivity of the Angus and Hereford grades was
lower (P<.08) than that of the Angus-Hereford rotational
crossbreds (1.69 vs 1.82). The Angus-Hereford crossbred cows were
smaller, tended to have higher weaning rates, and their calves
tended to be heavier at weaning. This is consistent with the
findings of Crockett et al. (1978b), who reported a tendency for
cow productivity to be higher in Angus-Hereford rotational
crossbreds than in straightbred Angus and Hereford.


Comparison of Grade Angus with Grade Hereford

Calf Traits

All calf traits studied were affected significantly by mating
group within mating system and by the interactions of generation x
mating group within mating system.
Birth weight. Grade Hereford calves were heavier at birth
than the grade Angus throughout the five generations of upgrading.
The average difference in birth weight across the five generations
was 4.6 kg (P<.0001). The heavier birth weights found for the
grade Hereford calves were consistent with comparisons of these
two breeds as straightbreds (Gregory et al., 1965; Gaines et al.,
1966; Sagebiel et al., 1973). Calf birth weight in the grade
Angus declined in generations 3, 4, and 5 (Figure 5), while in the
grade Hereford it declined in generations 4 and 5. Birth weight
in generation 5 in both grades had declined below that of the
generation 1 calves.
Age at weaning. Grade Angus calves averaged 5.6 days older
at weaning (P<.04) than the grade Herefords. The generation 1
Hereford calves (those produced by foundation females) were 11.1
days older than the Angus grades, whereas in generations 2 through
5 the Angus grades were older by 8.0, 8.7, 11.5, and 11.1 days,
respectively. Since all calves born in the same year were weaned
the same day, the oldest calves at weaning were those born
earliest in the calving season. The results for the grades found
in this study are in agreement with those reported for these two
breeds by Cobb et al. (1964) and Crockett and Kidder (1967).
The difference in age at weaning between the Angus and
Hereford grades in the later generations probably was influenced
more by differences in the average date of conception than by the
differences in gestation length. Smith et al. (1976) reported
only a four-day longer gestation for straightbred Hereford than
for straightbred Angus calves.
In the grade Herefords age at weaning decreased from


17







generations 1 to 2, increased in generation 3, remained the same
in generation 4, and declined slightly in generation 5. Age at
weaning in the grade Angus increased gradually from generations 1
through 4 and decreased slightly in generation 5. The increase
from generations 1 to 4 was 15.4 days, probably due to a gradual
reduction in gestation length. Reynolds et al. (1980) reported a
longer gestation for Brahman breed than for Angus breed (291.1 vs
280.0 days). Since the percentage of Brahman-Native breeding was
decreasing over generations and the percentage of Angus breeding
increasing, a gradual reduction in gestation length would have
been expected and, other things being equal, earlier calving would
have occurred. However, age at which heifers reach puberty and
the interval to first postpartum estrus also affect earliness of
calving and consequently, age of calf at weaning. Reynolds et al.
(1979) reported that Brahman cows had a longer interval from
calving to pregnancy than Angus cows (93.9 vs 81.6 days). Since
gestation length could not be determined in this study, it is
difficult to determine the exact causes that resulted in
differences in calf age at weaning.
Weaning weight. Grade Hereford calves were heavier (P<.0001)
at weaning than the grade Angus calves (220.5 vs 206.9 kg).
Weaning weights for the grade Hereford calves were 232.1, 230.1,
227.6, 214.1, and 198.8 kg, for generations 1 through 5.
Respective weaning weights for the grade Angus calves were 192.2,
221.2, 215.4, 208.7, and 196.8 kg. Grade Hereford calves were
heavier than grade Angus calves in all generations; however, the
difference in weaning weight between the two was much less in the
last two generations (Figure 5). Differences in weaning weight
between calves of the two mating groups varied from a high of 39.9
kg in generation 1 to a low of 2.0 kg in generation 5. Although
the grade Angus calves were older, they were lighter at weaning.
The heavier weaning weight of the grade Hereford calves was the
result of a heavier birth weight combined with a faster preweaning
growth rate. Average daily gains for the grade Hereford calves
were 0.87, 0.88, 0.86, 0.81, and 0.74 kg, for generations 1
through 5. The respective average daily gains for the grade Angus
calves were 746, 835, 799, 766, and 727 g. Although average daily
gains of the grade Hereford calves increased from generations 1 to
2 (867 vs 882 g), weaning weight declined slightly (232.1 vs 230.1
kg). This was the consequence of a marked decline in the age at
weaning from generations 1 to 2 (234.9 vs 223.0 days). In terms
of preweaning growth rate, grade Hereford and grade Angus calves
showed the same response patterns over generations of upgrading.
Changes in preweaning average daily gain over generations for the
Hereford and Angus upgraded groups are shown in Figure 5. In both
mating groups average daily gain increased from generations 1 to 2
and declined thereafter.
Condition score. Mean condition score was the same in both
groups of grades (-0.6). Condition scores of the grade Angus
calves were 9.7, 10.8, 10.8, 11.2, and 10.7 for generations 1
through 5. Respective condition scores of the grade Hereford
calves were 10.6, 10.8, 10.9, 10.7, and 10.1. Condition score of
the grade Angus calves increased from generations 1 through 4 and
declined in generation 5, while in the grade Hereford calves

18







condition scores increased from generations 1 through 3 and
declined thereafter.

Cow-Related Traits

Mating group within mating system affected significantly all
cow-related traits, while the interaction of generation x mating
group within mating system significantly affected cow weight and
condition score.
Pregnancy rate. Pregnancy rate of the grade Angus (91.7%)
did not differ significantly from that of the grade Hereford
(89.4%). Pregnancy rates in the grade Angus group were 92.3,
88.6, 86.1, and 99.6% for generations 1 through 4. Respective
pregnancy rates in the grade Hereford were 90.2, 85.1, 84.4, and
97.7%. In both mating groups pregnancy rate declined from
generations 1 through 3 and increased sharply in generation 4
(figure 6).
Calf survival rate. Grade Angus had a higher calf survival
rate (P<.02) than the grade Hereford (95.2 vs 88.0%). Survival
rate in the grade Angus decreased from generations 1 to 2,
increased from generations 2 to 3 and decreased again from
generations 3 to 4 (96.0, 92.6, 99.5, and 92.7%), while calf
survival rate in the grade Hereford increased from generations 1
to 2 and decreased thereafter (89.4, 95.7, 86.9, and 79.8%).
Weaning rate. Grade Angus had a higher (P<.05) weaning rate
than the grade Hereford (87.2 vs 78.5%), mostly because of the
higher calf survival rate. There was a drop in weaning rate from
generations 1 to 2 in the grade Angus; however, after generation 2
weaning rate showed an upward trend (88.6, 82.4, 85.7, and 91.9%).
Weaning rate in the grade Hereford was very similar in generations
1 and 2, while it declined from generations 2 to 3 and increased
from generations 3 to 4 (80.6, 81.5, 73.6, and 78.2%).
Cow weight. Grade Hereford cows were heavier than the grade
Angus in all four generations of upgrading. The average weight
superiority of the Herefords was 28.6 kg (P<.0001). Weight of the
grade Angus cows remained similar from generations 1 to 2 and
decreased sharply thereafter (474.9, 477.0, 443.4, and 424.9 kg).
Grade Hereford cows showed a slight decline in weight from
generations 1 to 2 and a large decline thereafter (506.8, 502.5,
489.2, and 436.4 kg). Grade Herefords were heavier than the grade
Angus at birth, weaning, and maturity.
Although birth and weaning weights in the grade Angus
increased by 10 and 15%, respectively, from generations 1 to 2,
cow weight remained similar. After generation 2 the value of all
three traits decreased. Birth and weaning weights declined by 8
and 6%, respectively, from generations 2 to 4, while cow weight
declined by 11%. Birth weight in the grade Herefords increased by
5% from generations 1 to 2, while weaning weight and cow weight
showed a very slight decline. Birth and weaning weights in the
grade Herefords decreased by 3 and 7%, respectively, from
generations 2 to 4, while cow weight declined by 13%. Cow weight
in both mating groups decreased at a more rapid rate than birth
and weaning weigths.


19






Cow condition score. Mean condition score of the grade Angus
cows (7.2) did not differ significantly from that of the grade
Hereford cows (7.4). Condition score of the grade Angus cows was
very similar throughout the four generations (7.1, 7.2, 7.2, and
7.1). Condition score of the grade Hereford cOWS increased from
generations 1 through 3 and declined from generations 3 to 4 (7.3,
7.5, 7.6, and 7.1). Although cow condition score did not show a
downward trend from generations 1 through 3 in the grade Angus and
actually increased in the grade Hereford, pregnancy rate in both
mating groups decreased from generations 1 through 3.
Cow productivity. Grade Angus had a higher (P<.05) average
cow productivity than the grade Herefords (1.80 vs 1.58). The
grade Hereford cows produced calves with a heavier weaning weight
(220.5 vs 206.9 kg), whereas the grade Angus cows were smaller
(455.1 vs 483.7 kg) and had a higher net calf crop weaned (87.2 vs
78.5%). Cow productivity is influenced to a greater extent by
differences in percentage of calves weaned than by differences in
weaning weight.
Cow productivity in the grade Angus declined from generations
1 to 2 and increased thereafter, while in the grade Herefords it
declined from generations 1 through 3 and increased in generation
4 (Figure 6). The highest cow productivity for both mating groups
was observed in generation 1, the F1 cows nursing backcross
calves.

Comparison Among the Two-breed Rotational Crosses

The three mating groups compared in the two-breed rotational
crossbreeding system were Angus-Hereford, Angus-Brahman, and
Hereford-Santa Gertrudis. The Angus-Brahman rotation was the
mating group that best fit a typical two-breed rotation scheme.
In the Angus-Hereford cross, generation 1 animals were 1/2
Angus-1/2 Brahman and 1/2 Hereford-1/2 Brahman; generation 2
animals were 2/4 Hereford-1/4 Angus-1/4 Brahman, and 2/4 Angus-1/4
Hereford-1/4 Brahman (Table 1). A typical scheme would start from
straightbred foundation with the generation 1 animals being 1/2
Angus-1/2 Hereford and 1/2 Hereford-1/2 Angus. In this study,
both grades and crosses started from the same Brahman-Native
foundation, while a typical two-breed rotation would start with
specific straightbreds for each cross. Crossbreeding programs in
commercial cattle operations normally must start with the stock in
hand, which usually is not purebred or straightbred.

Calf Traits

Birth weight. Mean birth weights for Angus-Hereford,
Angus-Brahman, and Hereford-Santa Gertrudis crosses were 28.6,
29.6, and 30.6 kg. Average birth weight of the Angus-Hereford
cross calves was lighter (P<.0001) than that of the Angus-Brahman
and Hereford-Santa Gertrudis crosses. The difference of 1.0 kg
in birth weight between the Angus-Hereford and Angus-Brahman
crosses was smaller than the 5.1 kg difference reported by

20






---- UPGRADING TO H
UPGRADING TO A

32 900,
31 -- ----- --
30 850



277-
I \


26 7850O
s25 x



240 235


235 225

230 25-

225- 205-

< 220 195


GENERATION GENERATION

Figure 5. Calf traits by generation for the Hereford and Angus upgraded

groups.



-- UPGRADING TO H
UPGRADING TO A







0 / ..
90 g







80L LL
s _j so-







225 -- 150-




70 1 40
1 I I I I) / IL
S 2 3 4 2 3 4

GENERATION GENERATION


Figure Cow-related traits by generation for the Hereford and Angus
upgraded groups.


21







Crockett et al. (1978b) between the same crosses over three
generations of rotational crossbreeding. The generation 1 calves
in their study were backcrosses produced by Fi females obtained by
crossing the specific breeds, while in this study the generation 1
calves in all mating groups were produced by females of the same
Brahman-Native breeding.
Birth weights of Angus-Hereford crossbreds declined slightly
from generations 1 to 2 (Figure 7), increased in generation 3,
declined in generation 4, and increased again in generation 5
(28.5, 27.7, 29.4, 28.4, and 28.9 kg, respectively). In the
Angus-Brahman cross, birth weight increased from generations 1 to
2, decreased in generation 3, and increased thereafter (26.2,
30.9, 29.1, 30.3, and 31.7 kg, respectively). In the
Hereford-Santa Gertrudis cross birth weight increased from
generations 1 to 2 and remained fairly constant thereafter (28.1,
31.2, 31.7, 31.0, and 31.1 kg, respectively).
Age at weaning. Age at weaning for the Angus-Hereford,
Angus-Brahman, and Hereford-Santa Gertrudis crosses were 231.8,
225.8, and 228.4 days, respectively. The Angus-Hereford crossbred
calves were older (P<.0007) than the Angus-Brahman and
Hereford-Santa Gertrudis crosses. Part of this difference in age
at weaning probably was due to differences in date of conception
and part due to differences in gestation length. Gregory et al.
(1979) reported that the gestation period of Brahman x British
crosses was longer than that of British x British crosses.
Age at weaning of the Angus-Hereford crossbred calves
increased from generations 1 to 2, decreased in generation 3, and
increased thereafter. In the Hereford-Santa Gertrudis cross age
fluctuated among generations without any definite trend. The
smallest variation in age at weaning among generations was
observed within the Angus-Brahman cross.
Weaning weight. Mean weaning weights of the Angus-Hereford,
Angus-Brahman, and Hereford-Santa Gertrudis crosses were 216.5,
221.0, and 228.8 kg, respectively. Mean weaning weight of
Angus-Hereford cross calves was lower (P<.0001) than that of
Angus-Brahman and Hereford-Santa Gertrudis crosses, although
Angus-Hereford cross calves were older at weaning. The
Angus-Hereford cross calves were lighter at birth and had a slower
preweaning growth rate (Figure 7) than calves from the other
crosses. Mean average daily gains of the Angus-Hereford,
Angus-Brahman, and Hereford-Santa Gertrudis crosses were 0.81,
0.85, and 0.87 kg, respectively. The difference in growth rate
presumably was due to additive breed and heterosis effects. Koger
(1980) stated that heterosis values reported for Brahman-European
crosses generally have averaged more than three times those for
crosses among European breeds. In this study the Hereford and
Santa Gertrudis were the breeds with the largest mature size.
Large mature size combined with heterosis for growth explains the
superior preweaning growth rates and weaning weights observed for
the Hereford-Santa Gertrudis rotation.
Weaning weight fluctuated among generations within each
program (Figure 7); however, no downward trend like that observed
in the grades was found.
Condition score. Mean condition scores for the

22






Angus-Hereford, Angus-Brahman, and Hereford-Santa Gertrudis
crosses were 10.9, 10.6, and 10.5, respectively. Mean condition
score of the Angus-Hereford cross calves was higher (P<.0005) than
that of the Angus-Brahman and Hereford-Santa Gertrudis crosses.

Cow-Related Traits

Pregnancy rate. Mean pregnancy rates for the Angus-Hereford,
Angus-Brahman, and Hereford-Santa Gertrudis crosses were 89.1,
85.9, and 85.4%, respectively. Mean pregnancy rate of the
Angus-Hereford cross was higher (P<.07) than that of the
Angus-Brahman and Hereford-Santa Gertrudis crosses. Pregnancy
rate in the Angus-Hereford cross increased slightly from
generations 1 to 2 and decreased from generation 2 to generations
3 and 4 (Figure 8). Pregnancy rate in the Angus-Brahman cross
decreased from generations 1 to 2, increased from generations 2 to
3 and decreased slightly during generation 4. Pregnancy rate for
the Hereford-Santa Gertrudis cross decreased from generations 1
through 3. The pregnancy rates reported in this study for the
Angus-Hereford and Angus-Brahman crosses are similar to those
reported by Crockett et al. (1978a) for similar rotations across
three generations of crossbreeding.
Calf survival rate. The Angus-Hereford cross tended to have
a higher (P<.15) calf survival than the Angus-Brahman and
Hereford-Santa Gertrudis crosses. The respective survival rates
were 94.3, 91.2, and 92.8%. Calf survival rate fluctuated among
generations without a definite trend in the Angus-Hereford and
Hereford-Santa Gertrudis crosses, while in the Angus-Brahman cross
it declined from generations 1 through 3.
Weaning rate. The Angus-Hereford crosses had a higher
pregnancy rate and tended to have a higher calf survival rate,
which resulted in a higher (P<.03) weaning rate for this cross
than that observed for the Angus-Brahman and Hereford-Santa
Gertrudis crosses. The respective weaning rates were 84.0, 78.2,
and 79.4%. Weaning rate showed a downward trend over generations
in the Angus-Hereford and Hereford-Santa Gertrudis crosses, while
it fluctuated among generations in the Angus-Brahman cross (Figure
8).
Cow weight. Mean weights of the Angus-Hereford,
Angus-Brahman, and Hereford-Santa Gertrudis crossbred cows were
454.5, 452.8, and 478.7 kg, respectively. Although birth and
weaning weights did not show a downward trend over generations in
any of the crosses, cow weight gradually decreased in each
successive generation of rotational crossbreeding. Weight of the
cows decreased over generations even though cow condition score
did not show a downward trend. The largest drop in cow weight
from generations 1 through 4 was observed for the Angus-Hereford
cross (47.8 kg), followed by that of the Hereford-Santa Gertrudis
cross (31.5 kg), while the smallest drop was recorded for the
Angus-Brahman cross (16.5 kg).
Cow condition score. Mean condition scores of the
Angus-Hereford, Angus-Brahman, and Hereford-Santa Gertrudis
crossbred cows were 7.1, 7.4, and 6.8, respectively. Condition


23






-- A-H ROTATIONAL CROSSBREEDING
-- A-B ROTATIONAL CROSSBREEDING
SH-SG ROTATIONAL CROSSBREEDING


34 950
33 o
32 z 900





240 240
31-- ---~ 00



2 2 I 500

261








220 200
AH ROTATIONAL CROSSBREEDING
26 <> 750


840- 240 r




.Z 230 22T ROSB
..-----.-- 0z/ v-.>

0 225- 20
> 210
S220 200-

2 3 4 5 I E 4 5
GENERATION GENERATION



Figure 7. Calf traits by generation for the two-breed rotational crossbred
groups.



A-IH ROTATIONAL CROSSBREEDING
-----A-B ROTATIONAL CROSSBREEDING
_.--- H-SG ROTATIONAL CROSSBREEDING



Uj -





-u --I U

90 2 z00





S190

808-

8 ?0 -
90> 0 -- --------- - -










70 I 40

1 2 3 4 1 2 3 4

GENERATION GENERATION


Figure 8. Cow-related traits by generation for the two-breed rotational

crossbred groups.
24






score of the Angus-Hereford crossbred cows varied less than for
the other two crossbred groups and showed a slight upward trend
from generations 1 through 3 and a decline from generations 3 to 4
(7.0, 7.2, 7.3, and 6.9). Condition score of the Angus-Brahman
crossbred cows decreased from generations 1 to 2 and increased
thereafter, with a high increase from generations 3 to 4 (6.9,
6.5, 6.9, and 9.1). The Hereford-Santa Gertrudis crossbred cows
showed a decrease in condition score from generations 2 to 3 and
an increase in generation 4.
Cow productivity. Mean cow productivity of the
Angus-Hereford cross was higher (P<.07) than that of the
Angus-Brahman and Hereford-Santa Gertrudis crosses. The respective
cow productivities were 1.82, 1.69, and 1.74. The Angus-Brahman
and Hereford-Santa Gertrudis crosses weaned calves with heavier
weights; however, they had lower average weaning rates.


SUMMARY

Upgrading and two-breed rotational crossbreeding
systems were compared. Brahman-Native foundation cows were
upgraded to Angus and Hereford and were used to initiate two-breed
rotational crossbreeding which included the Angus-Hereford,
Angus-Brahman ,and Hereford-Santa Gertrudis rotations.
Calves produced in the two-breed rotational crossbreeding
system had significantly heavier birth and weaning weights, and
higher average daily gains from birth to weaning than those from
the upgrading system. Calves of the upgrading system tended to be
older at weaning than the rotational crossbred calves. Mean calf
condition score at weaning was similar for both mating systems.
Birth and weaning weights increased from generations 1 to 2 in
both mating systems. Thereafter, both traits decreased in each
successive generation of upgrading, while they remained fairly
constant in the successive generations of rotational
crossbreeding.
Cows in the upgrading system were heavier at the time their
calves were weaned, tended to have higher condition scores and had
higher pregnancy rates. Cow weight declined over generations in
both mating systems; however, the rate of decline was greater in
the upgrading system.
No significant differences were observed between the two
mating systems for calf survival rate, weaning rate, and cow
productivity. Pregnancy rate decreased from generations 1 to 2 in
both mating systems. Pregnancy rate of the rotational crosses
remained fairly constant after generation 2, while for the grades
it declined through generation 3 and increased in generation 4.
Calf survival in the grades increased slightly from generations 1
to 2 and decreased thereafter. Among the rotational crossbreds
calf survival decreased slightly from generations 1 through 4.
Weaning rate in the grades declined from generations 1 through 3
and increased in generation 4. Mean weaning rate in the
rotational crosses decreased from generations 1 to 2 and remained
fairly constant thereafter. Cow productivity changes over
generations were similar for the grades and rotational crosses.


25






Cow productivity of both groups decreased from generations 1 to 2,
remained constant or declined slightly from generations 2 to 3 and
increased from generations 3 to 4.
Calves from the Hereford upgraded group had higher preweaning
average daily gains and were heavier at birth and weaning than
those of the Angus upgraded group, while those of the Angus
upgraded group were older at weaning. Average calf condition score
was the same in both groups. Preweaning average daily gains
increased in both groups from generations 1 to 2 and decreased
thereafter.
Grade Hereford cows were heavier than grade Angus cows, but
no significant difference was observed between the two for mean
cow condition score. The difference in the mean pregnancy rate
between the two groups was not significant. Grade Angus had
significantly higher calf survival rates, weaning rates, and cow
productivity values.
Angus-Brahman and Hereford-Santa Gertrudis rotational
crossbred calves had higher preweaning average daily gains and
were heavier at birth and weaning than the Angus-Hereford
crossbreds. The Angus-Hereford crossbreds were older and had
higher condition scores at weaning. Preweaning average daily gain
and weaning weight fluctuated among generations within the
Angus-Hereford and Hereford-Santa Gertrudis rotational crosses;
however, no downward trend was observed. Less variation was
observed among generations within the Angus-Brahman rotational
cross.
The Angus-Hereford crossbred cows had higher pregnancy rates,
tended to have higher calf survival rates, and had higher weaning
rates than the Angus-Brahman and Hereford-Santa Gertrudis
crossbred cows. Weaning rate tended to decrease over generations
in the Angus-Hereford and Hereford-Santa Gertrudis rotational
crosses. Mean condition scores were slightly higher for
Angus-Brahman crossbred cows than for the Angus-Hereford
crossbreds, while mean weights were similar. The Hereford-Santa
Gertrudis crossbred cows had the heaviest weights and the lowest
condition scores. Although the Angus-Hereford crossbreds weaned
the lighest calves, they had the highest net calf crop weaned, and
thus had the highest cow productivity.
















26







LITERATURE CITED
Chapman, H. D., T. M. Clyburn, and W. C. McCormick. 1970.
Grading, two- and three-breed rotational crossing as systems
for production of calves to weaning. J. Anim. Sci. 31:642.

Cobb, E. H., W. C. Burns, and M. Koger. 1964. Comparative
performance of British, Brahman and crossbred foundation
cattle. J. Anim. Sci. 23:848 (Abstr.).

Crockett, J. R., and R. W. Kidder. 1967. Effect of breed of sire
on calving date. J. Anim. Sci. 26:202 (Abstr.).

Crockett, J. R., M. Koger, and D. E. Franke. 1978a. Rotational
crossbreeding of beef cattle: Reproduction by generation.
J. Anim. Sci. 46:1163.

Crockett, J. R., M. Koger, and D. E. Franke. 1978b. Rotational
crossbreeding of beef cattle: Preweaning traits by
generation. J. Anim. Sci. 46:1170.

Cundiff, L. V., K. E. Gregory, and R. M. Koch. 1982. Effects of
heterosis in Hereford, Angus and Shorthorn rotational
crosses. U.S.D.A. Beef Res. Prog. No. 1, ARM-NC-21.

Gaines, J. A., W. H. McClure, 0. W. Vogt, R. C. Carter, and C. M.
Kincaid. 1966. Heterosis from crosses among British breeds
of beef cattle: Fertility and calf performance to weaning.
J. Anim. Sci. 25:5.

Gregory, K. E., G. M. Smith, L. V. Cundiff, R. M. Koch, and 0. B.
Laster. 1979. Characterization of biological types of
cattle-Cycle III: I. Birth and weaning traits. J. Anim.
Sci. 48:271.

Gregory, K. E., L. A. Swiger, R. M. Koch, L. J. Sumption, W. W.
Rowden, and J. E. Ingalls. 1965. Heterosis in preweaning
traits of beef cattle. J. Anim. Sci. 24:21.

Kidder, R. W., M. Koger, J. H. Meade, and J. R. Crockett. 1964.
Systems of crossbreeding for beef production in Florida.
Florida Agr. Exp. Sta. Bull. 673.

Koger, M. 1973a. Beef cattle performance during four generations
of selection in different breeding systems, starting with
Brahman-Native cattle at the Beef Research Unit. Proc. 1973
Beef Cattle Short Course. pp. 33-43. Univ. of Florida,
Gainesville.

Koger, M. 1973b. Upgrading and crisscrossing at the Beef
Research Unit, Gainesville, Florida, 1957-1970. In: M.
Koger, T. J. Cunha, and A. C. Warnick (Ed.) Crossbreeding
Beef Cattle Series 2. pp 64-70. Univ. of Florida Press,
Gainesville.

27







Koger, M. 1980. Effective crossbreeding systems utilizing Zebu
cattle. J. Anim. Sci. 50:1215.

Koger, M., W. G. Blue, G. B. Killinger, R. E. L. Greene, H. C.
Harris, J. M. Myers, A. C. Warnick, and N. Gammon, Jr. 1961.
Beef production, soil and forage analyses, and economic
returns from eight pasture programs in north central Florida.
Florida Agr. Exp. Sta. Bull. 631.

Koger, M., W. G. Blue, G. B. Killinger, R. E. L. Green, J. M.
Myers, N. Gammon, Jr., A. C. Warnick, and J. R. Crockett.
1970. Production responses and economic returns from five
pasture programs in north central Florida. Florida Agr. Exp.
Sta. Bull. 740.

Koger, M., R. E. L. Greene, G. B. Killinger, W. G. Blue, J. M.
Myers, N. Gammon, A. C. Warnick, and J. E. Moore. 1977.
Pasture programs and beef cattle breeding systems for beef
production in north central Florida. Florida Agr. Exp. Sta.
Bull. 789.

Koger, M., F. M. Peacock, W. G. Kirk, and J. R. Crockett. 1975.
Heterosis effects on weaning performance of
Brahman-Shorthorn calves. J. Anim. Sci. 40:826.

Lush, J. L. 1945. Animal Breeding Plans (3rd Ed.). Iowa State
Univ. Press, Ames.

Peacock, F. M., and M. Koger. 1980. Reproductive performance of
Angus, Brahman, Charolais and crossbred dams. J. Anim. Sci.
50:689.

Peacock, F. M., M. Koger, W. G. Kirk, E. M. Hodges, and A. C.
Warnick. 1973. Comparative performances of various beef
breeds and crosses in Florida. In: M. Koger, T. J. Cunha,
and A. C. Warnick (Ed.) Crossbreeding Beef Cattle Series 2.
pp 43-48. Univ. of Florida Press, Gainesville.

Peacock, F. M., M. Koger, T. A. Olson, and J. R. Crockett. 1981.
Additive genetic and heterosis effects in crosses among
cattle breeds of British, European and Zebu origin. J. Anim.
Sci. 52:1007.

Reynolds, W. L., T. M. DeRouen, S. Moin, and K. L. Koonce. 1979.
Factors affecting pregnancy rate of Angus, Zebu and
Zebu-cross cattle. J. Anim. Sci. 48:1312.

Reynolds, W. L., T. M. DeRouen, S. Moin, and K. L. Koonce. 1980.
Factors influencing gestation length, birth weight and calf
survival of Angus, Zebu and Zebu cross beef cattle. J. Anim.
Sci. 51:860.




28







Sagebiel, J. A., G. F. Krause, B. Sibbit, L. Langford, A. J. Dyer,
and J. F. Lasley. 1973. Effect of heterosis and maternal
influence on gestation length and birth weight in reciprocal
crosses among Angus, Charolais and Hereford cattle. J. Anim.
Sci. 37:1273.

SAS. 1979. SAS User's Guide. Statistical Analyses System
Institute Inc., Cary, NC.

Semple, A. T., and H. E. Dvorachek. 1930. Beef production from
purebred, grade, and native catle. U.S.D.A. Tech. Bull. 203.

Smith, G. M., D. B. Laster, and K. E. Gregory. 1976.
Characterization of biological types of cattle. I. Dystocia
and preweaning growth. J.Anim. Sci. 43:27.






































29








TABLE 1. BREED COMPOSITION FOR DAMS AND PROGENY

Angus-Hereford Angus-Brahman Hereford-Santa Gertrudis
Generation Angus upgrading Hereford upgrading rotation rotation rotation

Dams

Foundation Bb (14)c B (32) B (50) B (109) B (48)
11/2A 1/28 (102) 1/2H 1/2B (67) 1/2H 1/2B (46) 1/2A 1/2B (221) 1/2SG 1/2B (22)
1/2A 1/2B (43) 1/2H 1/2B (124)
1/2S 1/2B (157)

2 3/4A 1/4B (34) 3/4H 1/4B (47) 2/4H 1/4A 1/48 (79) 3/4A 1/4B (52) 2/4SG 1/4H 1/4B (132)
2/4A 1/4S 1/4B (19) 2/4H 1/4S 1/4B (100) 2/4A 1/4H 1/4B (80) 3/4B 1/4A (166) 2/4H 1/4SG 1/4B (34)
3/4A 1/4B (103) 2/4H 1/4S 1/4B (102)

3 7/8A 1/88 (44) 7/8H 1/8B (20) 5/8H 2/8A 1/8B (66) 5/8A 3/8B (84) 5/8SG 2/8H 1/88 (21)
6/8A 1/8S 1/88 (11) 6/8H 1/8S 1/8B (62) 4/8H 3/8A 1/8B (58) 5/8B 3/8A (46) 4/8SG 2/8H 1/8S 1/88 (82)
5/8A 2/8H 1/88 (53) 5/8H 2/8SG 1/8B (69)

4 15/16A 1/168 (18) 15/16H 1/16B (3) 10/16H 5/16A 1/16B (11) 11/16A 5/16B (34) 10/16SG 5/16H 1/16B (26)
14/16H 1/16S 1/16B (11) 10/16A 5/16H 1/16B (24) 11/16 5/16A (16) 10/16H 5/16SG 1/16B (8)
0 11/16A 4/16H 1/168 (16) 10/16H 4/16S8 1/16S 1/16B (33)
Progeny
1 1/2A 1/2B (9)c 1/2H 1/28 (16) 1/2A 1/2B (14) 1/2A 1/2B (71) 1/2H 1/2B (23)
1/2H 1/2B (16) 1/2SG 1/2B (4)

2 3/4A 1/4B (79) 3/4H 1/4B (43) 2/4A 1/4H 1/4B (32) 3/4A 1/4B (34) 2/4H 1/4SG 1/4B (15)
2/4H 1/4A 1/48 (32) 3/48 1/4A (136) 2/4H 1/45 1/4B (130)
2/4SG 1/4H 1/4B (84)
3 7/8A 1/88 (24) 7/8H 1/8B (31) 5/8A 2/8H 1/8B (56) 5/8A 3/8B (109) 5/8H 2/8SG 1/88 (86)
6/8A 1/8S 1/8B (15) 6/8H 1/8S 1/8B (63) 5/8H 2/8A 1/8B (65) 5/8B 3/8A (29) 5/8SG 2/8H 1/8B (24)
4/8H 3/8A 1/88 (66) 4/8SG 2/8H 1/8S 1/8B (71)
4 15/16A 1/16B (34) 15/16H 1/16B (13) 10/16A 5/16H 1/168 (46) 11/16A 5/16B (37) 10/16H 5/16SG 1/16B (12)
14/16A 1/16S 1/16B (6) 14/16H 1/16S 1/16B (42) 11/16A 4/16H 1/16B (44) 11/16B 5/16A (51) 10/16H 4/16SG 1/16S 1/16B (64)
10/16H 5/16A 1/168 (34) 10/16SG 5/16H 1/168 (48)
5 31/32A 1/32B (12) 31/32H 1/32B (2) 21/32A 10/32H 1/32B (8) 21/32A 11/32B (10) 21/32H 10/32SG 1/328 (14)
30/32H 1/32S 1/32B (6) 21/32H 10/32A 1/32B (17) 21/328 11/32A (23) 21/32SG 10/32H 1/32B (5)
20/32H 11/32A 1/328 (12) 20/32SG 10/32H 1/32S 1/32B (25)

aFoundation females were mostly of 3/4 Brahman-1/4 Native breeding and were classified as Grade Brahman (B).
A = Angus, H = Hereford; B = Brahman; S = Shorthorn; SG = Santa Gertrudis.
CNumbers in parentheses for dams indicate number of matings and for progeny indicate number of calves weaned.






TABLE 2. NUMBER OF MATINGS BY YEAR AND GENERATION

Year
Generation 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 Total

Foundation 70 61 53 21 15 13 8 5 4 3 253

1 47 75 97 101 92 77 69 57 47 41 31 20 15 8 5 782

2 1 4 16 33 56 72 89 96 99 93 95 86 82 69 57 948

3 3 6 14 22 37 53 64 80 111 109 117 616

4 1 2 3 8 17 35 56 78 200

Total 118 140 166 155 166 168 180 181 189 193 198 203 243 242 257 2,799




TABLE 3. PERCENT OF MATINGS BY AGE OF DAM AND GENERATION

Generation
Age of dam Foundation 1 2 3 4

Yearling 0 4.1 13.5 24.8 45.5

2-year-old 2.8 13.9 24.3 28.4 30.0

3-year-old 3.6 14.6 19.2 19.7 15.5

4-year-old 93.6 67.4 43.0 27.1 9.0
and older












TABLE 4. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR BIRTH WEIGHT (KG)

Generation
Mating system 1 2 3 4 5 Mean

Upgrading

Angus (A) 24.8 + 1.6 27.4 + .6 26.0+ .7 25.2 + .7 24.0 1.3 25.5 + .5

Hereford (H) 29.5 + 1.3 31.1 + .6 31.1 + .5 30.1 + .6 28.7 + 1.4 30.1 + .4


Mean 27.2 + 1.1 29.3 + .4 28.6 + .4 27.7 + .5 26.4 + 1.0 27.8 + .3


Rotational Crossbreeding

A-H 28.5 + 1.0 27.7 + .6 29.4 + .3 28.4 + .5 28.9 + .8 28.6 + .3

A-Brahman 26.2 .6 30.9 + .4 29.1 + .4 30.3 1 .5 31.7 + .8 29.6 + .2

H-Santa Gertrudis 28.1 + 1.0 31.8 + .4 31.7 + .4 31.0 + .5 31.1 + .7 30.6 + .3


Mean 27.6 .6 29.9+ .3 30.1 + .2 29.9 + .3 30.6 + .5 29.6 + .2










TABLE 5. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR AGE AT WEANING (DAYS)

Generation
Mating svsteml 1 2 3 4 5 Mean

Upgrading

Angus (A) 223.8 + 6.9 231.0 + 2.4 236.4 + 3.1 239.2 + 3.2 237.8 + 5.8 233.6 2.0

Hereford (H) 234.9 + 5.3 223.0 + 3.0 227.7 + 2.1 227.7 + 2.9 226.7 7.0 228.0 + 1.9


w Mean 229.4 + 4.6 227.0 + 1.9 232.1 + 1.9 233.5 2.3 232.3 + 4.7 230.8 1.4


Rotational Crossbreeding

A-H 223.2 + 4.2 237.2 + 2.5 230.6 + 1.5 233.6 + 2.1 234.4 + 3.5 231.8 + 1.2

A-Brahman 226.2 + 2.7 224.5 + 1.5 227.2 + 1.8 225.3 + 2.3 225.7 + 3.6 225.8 + 1.1

H-Santa Gertrudis 235.9 + 4.3 227.3 + 1.5 224.7 1.6 227.1 + 2.0 226.8 + 3.3 228.4 + 1.1


Mean 228.4 + 2.7 229.7 + 1.2 227.5 + 1.0 228.7 + 1.5 229.0 + 2.3 228.7 + .7












TABLE 6. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR CALF CONDITION SCORE
Generation
Mating system 1 2 3 4 5 Mean

Upgrading

Angus (A) 9.7 .43 10.8 + .15 10.8 .20 11.2 .20 10.7 + .37 10.6 + .13

Hereford (H) 10.6 + .34 10.8 + .19 10.9 + .13 10.7 1 .18 10.1 + .44 10.6 + .13


Mean 10.1 .29 10.8 .12 10.8 + .12 10.9 .14 10.4 + .30 10.6 1 .09


Rotational Crossbreeding

A-H 10.1 .26 11.1 + .16 10.9 + .09 10.9 + .13 11.3 + .22 10.9 .08

A-Brahman 10.3 .17 10.4 + .10 10.8 .11 10.8 + .14 10.8 + .23 10.6 1 .07

H-Santa Gertrudls 9.6 .27 10.8 .10 10.4 + .10 11.0 + .12 10.6 + .21 10.5 + .07


Mean 10.0 + .17 10.8 .07 10.7 + .07 10.9 + .09 10.9 + .15 10.7 1 .04










TABLE 7. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR WEANING WEIGHT (KG)

Generation
Mating system 1 2 3 4 5 Mean

Upgrading

Angus (A) 192.2 + 8.8 221.2 3.1 215.4 + 4.1 208.7 + 4.1 196.8 + 7.5 206.9 2.6

Hereford (H) 232.1 + 6.9 230.1 + 3.9 227.6 + 2.7 214.1 + 3.7 198.8 + 9.1 220.5 + 2.5


S Mean 212.2 + 5.9 225.7 2.5 221.5 + 2.4 211.4 2.9 197.8 + 6.1 213.7 + 1.8


Rotational Crossbreeding

A-H 202.3 + 5.4 223.4 + 3.2 222.3 + 1.9 211.0 + 2.7 223.6 + 4.5 216.5 1.5

A-Brahman 217.6 3.5 217.7 + 2.0 224.1 + 2.3 222.1 2.9 223.3 4.7 221.0 + 1.4

H-Santa Gertrudis 220.0 5.6 235.6 + 2.0 226.4 + 2.0 236.6 + 2.6 225.4 + 4.3 228.8 1.4


Mean 213.3 + 3.5 225.6 + 1.5 224.3 + 1.3 223.2 1.9 224.1 + 3.0 222.1 .9













TABLE 8. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR PREGNANCY RATE (%)
Generation
Mating system 1 2 3 4 Mean

Upgrading

Angus (A) 92.3 + 3.4 88.6 + 4.4 86.1 4.4 99.6 7.7, 91.7 + 2.6

Hereford (H) 90.2 + 3.9 85.1 + 2.7 84.4 + 3.8 97.7 + 8.7 89.4 + 2.7


Mean 91.3 + 2.7 86.9 + 2.6 85.3 3.1 98.7 + 6.0 90.6 + 1.9


Rotational Crossbreeding

A-H 89.4 + 3.5 91.4 + 2.0 87.9 + 2.8 87.7 + 4.8 89.1 1 1.7

A-Brahman 90.3 2.3 80.6 + 2.3 87.3 + 3.1 85.3 4.8 85.9 + 1.7

H-Santa Gertrudis 89.6 2.2 85.1 + 2.1 83.2 + 2.8 83.8 4.4 85.4 + 1.5


Mean 89.8 + 1.7 85.7 + 1.3 86.1 + 2.0 85.6 + 3.1 86.8 1.1










TABLE 9. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR SURVIVAL RATE (%)

Generation
Mating system 1 2 3 4 Mean

Upgrading

Angus (A) 96.0 + 2.9 92.6 + 3.7 99.5 3.8 92.7 6.5 95.2 2.2

Hereford (H) 89.4 3.3 95.7 + 2.4 86.9 3.4 79.8 + 7.3 88.0 + 2.3


SMean 92.7 + 2.2 94.2 + 2.2 93.2 + 2.7 86.3 + 5.0 91.6 + 1.6


Rotational Crossbreeding

A-H 96.0 + 3.0 93.4 + 1.7 94.9 + 2.4 93.0 + 4.2 94.3 + 1.5

A-Brahman 94.4 + 1.9 92.4 + 2.1 88.7 + 2.6 89.2 4.2 91.2 + 1.5

H-Santa Gertrudis 93.9 + 1.8 92.7 + 1.8 94.1 + 2.5 90.4 + 3.9 92.8 + 1.3


Mean 94.8 + 1.4 92.8 + 1.2 92.6 + 1.7 90.9 2.7 92.8 1.0












TABLE 10. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR WEANING RATE (%)
Generation
Mating system 1 2 3 4 Mean

Upgrading

Angus (A) 88.6 + 4.1 82.4 + 5.2 85.7 + 5.3 91.9 + 9.2 87.2 + 3.0

Hereford (H) 80.6 + 4.5 81.5 + 3.2 73.6 + 4.5 78.2 10.2 78.5 3.2


Mean 84.6 + 3.2 82.0 3.0 79.7 + 3.6 85.1 + 7.1 82.9 + 2.3


Rotational Crossbreeding

A-H 85.8 + 4.8 85.2 + 2.4 83.4 + 3.3 81.5 + 5.7 84.0 + 2.1

A-Brahman 85.1 + 2.7 74.7 + 2.7 77.1 + 3.6 75.9 + 5.7 78.2 + 2.0

H-Santa Gertrudis 84.2 2.6 78.7 + 2.5 78.2 + 3.3 76.4 + 5.2 79.4 1.8


Mean 85.0 + 2.0 79.5 1.6 79.6 + 2.4 77.9 + 3.7 80.5 + 1.3










TABLE 11. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR COW WEIGHT (KG)

Generation
Mating system 1 2 3 4 Mean

Upgrading

Angus (A) 474.9 + 5.5 477.0 7.1 443.4 + 7.2 424.9 + 13.1 455.1 4.2

Hereford (H) 506.8 6.7 502.5 4.7 489.2 + 6.4 436.4 + 15.8 483.7 4.8


SMean 490.9 4.4 489.8 + 4.2 466.3 + 5.1 430.6 + 10.6 469.4 + 3.3


Rotational Crossbreeding

A-H 472.0 5.8 464.4 3.4 457.0 + 4.7 424.2+ 7.9 454.4 + 2.9

A-Brahman 457.8 3.5 457.0 4.0 455.2 + 5.1 441.3 + 8.1 452.8 + 2.9

H-Santa Gertrudls 496.8 3.5 484.6 + 3.5 468.6 + 4.6 465.3 t 7.5 478.8 + 2.5


Mean 475.5 2.7 468.3 3.3 460.3 + 3.3 443.6 + 5.2 462.0 + 1.9












TABLE 12. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR COW CONDITION SCORE
Generation
Mating system 1 2 3 4 Mean

Upgrading

Angus (A) 7.1 + .24 7.2 + .32 7.2 + .33 7.1 + .56 7.2 + .19

Hereford (H) 7.3 + .31 7.5 + .22 7.6 + .29 7.1+ .72 7.4 + .22


SMean 7.2 + .20 7.4 + .19 7.4 + .23 7.1 + 47 7.3 + .15


Rotational Crossbreeding

A-H 7.0 + .26 7.2 + .16 7.3 + .22 6.9 + .34 7.1 + .13

A-Brahman 6.9 + .16 6.5 + .19 6.9 + .24 9.1 + .37 7.4 + .14

H-Santa Gertrudis 7.0 + .16 7.0 + .17 6.2 + .21 6.9 .32 6.8 + .11


Mean 7.0 + .12 6.9 + .11 6.8 + .16 7.6 + .24 7.1 + .09









TABLE 13. LEAST-SQUARES MEANS AND STANDARD ERRORS FOR COW PRODUCTIVITY

Generation
Mating system 1 2 3 4 Mean

Upgrading

Angus (A) 1.92 .10 1.67 + .13 1.76 + .13 1.86 + .24 1.80 + .08

Hereford (H) 1.67 + .12 1.64 + .08 1.46 + .11 1.54 + .26 1.58 + .08


Mean 1.80 + .08 1.66 + .08 1.61 + .09 1.70 + .18 1.69 + .06


Rotational Crossbreeding

A-H 1.85 + .11 1.81 + .06 1.71 + .08 1.90 + .14 1.82 + .05

A-Brahman 1.84 .07 1.61 + .07 1.62 + .09 1.67 + .14 1.69 + .05

H-Santa Gertrudis 1.90 + .07 1.65 + .06 1.75 + .08 1.67 + .13 1.74 + .04


Mean 1.86 + .05 1.69 + .04 1.69 + .06 1.75 + .09 1.75 + .03
















































UNIVERSITY OF FLORIDA


This publication was produced at a cost of $1641.00, or 54.7 cents per
copy, to provide information on comparison of upgrading and rotation-
al crossbreeding for genetic improvement of a brahman-native popula-
tion of beef cattle.

All programs and related activities sponsored or assisted by the Florida
Agricultural Experiment Stations are open to all persons regardless of race,
color, national origin, age, sex, or handicap.

ISSN 0096-607X






November 1986 Bulletin 851










Comparison of
Upgrading and Rotational Crossbreeding
for Genetic Improvement
of a Brahman-Native Population
of Beef Cattle





Joao Restle, Don D. Hargrove, and Marvin Koger













Agricultural Experiment Station
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
J. M. Davidson. Dean for Research







CONTENTS

Introduction . . . . . 1



Literature Review . . . . .. 1



Experimental Procedure . . . . .. 3



Results and Discussion . . . . .. 5



Upgrading Versus Two-breed Rotational Crossbreeding 6



Comparison of Grade Angus with Grade Hereford .... .17



Comparison Among the Two-breed Rotational Crosses 20



Summary . . . . . .... 25



Literature Cited . . . . .. 27










V






COMPARISON OF UPGRADING AND ROTATIONAL
CROSSBREEDING FOR GENETIC IMPROVEMENT
OF A BRAHMAN-NATIVE POPULATION


Joao Restle
Don D. Hargrove
Marvin Koger

Dr. Restle is an Associate Professor in the Animal Science
S Department, Federal University of Santa Maria, R.S., Brazil; Dr.
Hargrove is an Associate Professor, and Dr. Koger is a Professor,
respectively, in the Department of Animal Science, University of
Florida, Gainesville, Florida, 32611.




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