Table of Contents
 Materials and methods
 Results and discussion
 Summary and conclusion
 Literature cited

Group Title: Bulletin - Agricultural Experiment Stations, University of Florida ; 780 (technical)
Title: Beef production of Brahman, Shorthorn, and their crosses on different pasture programs
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00026772/00001
 Material Information
Title: Beef production of Brahman, Shorthorn, and their crosses on different pasture programs
Series Title: Bulletin Agricultural Experiment Stations, University of Florida 780 (technical)
Physical Description: 19 p. : ill. ; 23 cm.
Language: English
Creator: Peacock, F. M ( Fentress McCoughan ), 1922-
Publisher: Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1976
Subject: Beef cattle -- Breeding   ( lcsh )
Beef cattle -- Feeding and feeds   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Bibliography: p. 18-19.
Statement of Responsibility: F. M. Peacock ... et al..
General Note: Cover title.
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Bibliographic ID: UF00026772
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000408102
oclc - 02112216
notis - ACF4513


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Table of Contents
    Table of Contents
        Page 1
        Table of Contents 2
        Page 2
    Materials and methods
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
    Results and discussion
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
    Summary and conclusion
        Page 14
    Literature cited
        Page 15
        Page 16
        Unnumbered ( 18 )
        Unnumbered ( 19 )
        Unnumbered ( 20 )
        Unnumbered ( 21 )
        Unnumbered ( 22 )
        Unnumbered ( 23 )
Full Text
bulletin 780 (technical) February 197I

Seef Production of Brahman, Shorthorn

And Their Crosses on Different

Pasture Programs

F. M. Peacock, M. Koger, W. G. Kirk, E. M. Hodges, and J. R. Crockett

h-- ---------_-----^? -----

Agricultural Experiment Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
J. W Sites. Dean for Research


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

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida


F. M. Peacock, M. Koger, W. G. Kirk, E. M. Hodges,
and J. R. Crockett

Mr. Peacock is Associate Animal Husbandman, ARC, Ona;
Dr. Koger is Animal Geneticist, University of Florida, Gainesville;
Dr. Kirk is Animal Scientist, Emeritus, and Dr. Hodges is Agrono-
mist, ARC, Ona; and Dr. Crockett is Associate Animal Geneticist,
AREC, Belle Glade.

This public document was promulgated at an annual
cost of $1,444.14 or a cost of 240 per copy to report results
of a study of cattle performance in south central Florida.


F. M. Peacock, M. Koger, W. G. Kirk, E. M. Hodges,
and J. R. Crockett

Mr. Peacock is Associate Animal Husbandman, ARC, Ona;
Dr. Koger is Animal Geneticist, University of Florida, Gainesville;
Dr. Kirk is Animal Scientist, Emeritus, and Dr. Hodges is Agrono-
mist, ARC, Ona; and Dr. Crockett is Associate Animal Geneticist,
AREC, Belle Glade.

This public document was promulgated at an annual
cost of $1,444.14 or a cost of 240 per copy to report results
of a study of cattle performance in south central Florida.


INTRODUCTION -..---_..--.--------.......--..--..----------- 1
MATERIALS AND METHODS .--...--...-----------.----...- 1
Breed Groups ..-...........---------.----------.. 1
Pasture-Management Programs --....-......-.....---------- 3
Program 1 .........----.... ------------------ 3
Program 2 ......------...-----------....----- 3
Program 3 .----................-------------- 4
General Management -...-....--...... 4----- ----------4
Data Analyses ------........---.. .------------------------- 4
Pregnancy Rate ....---........---------- ..------- 8
Calf Survival -..-...........--- ----------.------ 8
Weaning Rate .........------ ------------------.. 14
Age of Calf at Weaning ----. ..--.......----- .-------. 14
Condition Score .... ..........------------------..--- 15
Wean Weight and 205-day Weight --......-.....----------- 15
Annual Production Per Cow -----........--------------... 16
SUMMARY AND CONCLUSION ...------------. ... ---.-... 17
LITERATURE CITED ...-..-... ------------..-...-.--- 18

F. M. Peacock, M. Koger, W. G. Kirk, E. M. Hodges,
and J. R. Crockett

Beef production is the result of a combination of both genetic
and environmental factors. Genetic factors may be masked by
induced or natural environmental influences which hinder expres-
sion of hereditary traits. Environmental influences either com-
plement or limit the genetic potential of the animal. Thus, it is
important to assess the productivity of various breed groups in
alternative production systems in order to develop the most effi-
cient production programs. Limited information is available on
the comparative productive behavior of Brahman, European-
origin, and crossbred cattle under variable environmental
The purpose of this study was to evaluate the performance of
Brahman, Shorthorn and crossbred cattle involving those two
breeds on three pasture-management programs in the semi-tropi-
cal environment of south central Florida.

Materials and Methods
The study was designed to evaluate the comparative produc-
tion of Brahman, Shorthorn, and various crosses of these two
breeds when maintained on native, or a combination of native,
and all-improved pasture. The design-of the trial is shown in
Table 1.
Breed Groups
The herds on each of the forage programs included approxi-
mately 60 cows. Each herd included five breed groups as follows:
ten Brahman (B), ten 3/4 Brahman-1/4 Shorthorn (B3Si), twenty
Brahman-Shorthorn firstcrosses (Fi), ten 3/ Shorthorn-14 Brah-
man (S3B,) and ten Shorthorn (S). The trial was conducted in
two 5-year phases. During the first phase the B, the BS1, and
one-half of the F, cows were mated to Brahman bulls while the
remaining groups were mated to Shorthorn bulls. This proce-
dure resulted in a balanced design considering breed of calf but
resulted in confounding of breed of bull with breed of cow since
only one-half of the possible breed combinations were included
during one phase. The procedure was dictated, however, by the
availability of replacement females for the study and the decision


Table 1. Design of Trial.

Phase 1, 1957 to 1961 Phase 2, 1962 to 1966

Breed Pasture program Bred Pasture program
Breed of cow of sire 1 2 3 ofsire 1 2 3

Matings per year Matings per year
Brahman (B) B 10 10 10 S 10 10 10
% B / S (Ba) B 10 10 10 S 10 10 10
% B S (Fi) B 10 10 10 S 10 10 10
/2 B S (Fi) S 10 10 10 B 10 10 10
SB 3/4 S (B ) S 10 10 10 B 10 10 10
Shorthorn (S) S 10 10 10 B 10 10 10

to maintain 10 animals per breed group x year sub-cell rather
than five, which would have resulted had breed of cow and breed
of sire been used annually in all possible combinations. During the
second phase, breed of sire for the different cow groups was
reversed from that of the first phase. Thus, including both
phases each breed of cow was mated to bulls of both breeds. By
including two mating groups (30 F, cows mated each to B and S
bulls) across all years it was possible to remove year effects and
obtain a satisfactory comparison of all breed combinations.

Pasture-Management Programs

Program 1 This program involved native grasses, mainly
Aristida and Andropogon spp. (wiregrass and broomsedge).
During the first 5-year period, the 60 cows and their calves
grazed 812 acres of native range divided into five fields. Eighty
acres of each of these five fields were burned on alternate years.
A reduction to 772 acres in the program was made during the
second phase.
Supplemental feed was provided on native range only to the
extent necessary to prevent extreme weight loss in the cows.
Cows were supplemented during the winter months with 41%
cottonseed pellets and a limited amount of hay in the first phase.
In phase 2 an average of 555 pounds of hay, 52 pounds cotton-
seed meal (41%), and 52 pounds of citrus meal were fed over a
period averaging 109 days annually beginning in December.
Program 2 This program included a combination of 73 acres
of improved pasture plus 315 acres of native grasses for the 60-
cow herd. The improved pasture included 40 acres of Pensacola
bahiagrass (Paspalum notatum Flugge.), 15 acres of Coastal
bermudagrass (Cynodon dactylon (L.) Pers.) and 18 acres of
Pangola digitgrass (Digitaria decumbens Stent.) during the first
phase. For the second phase the bermudagrass was replaced by
digitgrass. Approximately 20 acres of the bahiagrass was grown
in conjunction with Hairy Indigo (Indigofera hirsuta Linn.)
with the remaining 20 acres being in combination with non-irri-
gated white clover (Trifolium repens L.) and Hubam sweetclover
(Melilotus alba Desv.). The cattle had access to the native
grasses continuously and generally to one field of improved
The annual fertilizer program per acre for improved grass
pastures was approximately 400 pounds of 8-8-8 (N-P.Os-KO)
plus 150 pounds of ammonium nitrate (33.3% N) for pangola-
grass, or a like amount of complete fertilizer plus 100 pounds of


ammonium nitrate for bahiagrass pastures. The legume pastures
received 250 pounds per acre of 0-8-24 fertilizer annually with an
extra application of muriate of potash averaging 32 pounds KO
per acre on the white clover.
Cattle were given supplemental feed only in the winter of 1957-
58 during phase 1. During the last 5-year period the cattle on
Program 2 received supplemental feed (43 pounds hay, 65 pounds
cottonseed meal and 31 pounds citrus meal per cow) for an aver-
age of 72 days annually from January to April.
Program 3 This program included only improved pastures.
During the first phase it included 76 acres of pangolagrass, 20
acres of which were irrigated and over-planted with white clover.
Due to pasture becoming less productive the area was increased
to 107 acres for the second phase. This change resulted in 70
acres of all pangola digitgrass, 27 acres of digitgrass overplanted
with white clover, and 10 acres of bahiagrass. Pasture fertiliza-
tion in Program 3 followed the same pattern as described for
Program 2.
Cattle in Program 3 were maintained in a high nutritional
status at all times. For the most part, the cattle maintained good
weights from pasture, as only an average of 280 pounds of hay
per cow was fed for each of the five winters.

General Management

The cattle on all programs were bred in a restricted season of
105 days extending from March 15 to July 1. All the calves were
weaned at one time in early September.
Replacement heifers were grown together from weaning until
being placed in their respective herds just prior to the breeding
season at two years of age.
Cows were culled on the basis of repeated reproductive failure
or failure to raise a calf.

Data Analyses

Individual performance data were recorded annually for preg-
nancy status, calf survival, weaning rate, age of calf at weaning,
weaning weight, 205-day weight, and market grade of calf. The
research was conducted in two phases, five years each. The sep-
arate analyses for both reproduction and production traits are
The observed data for pregnancy status, calf survival, and
weaning rate were recorded as 1 or 0 (zero). These individual


data were processed initially in separate analyses for each phase.
Least squares techniques as outlined by Harvey (4) were fol-
lowed, employing the same model for all analyses. All effects
were assumed to be fixed. Since subclass numbers were approxi-
mately proportional the above analyses yielded efficient esti-
mates of effects.
A third analysis was performed by pooling data for the two
phases. The least squares means for the breed x pasture program
subclasses from the above analyses were adjusted for differences
between phase and combined in a singled analysis. The adjust-
ments required were small for pregnancy and weaning rates and
nil for calf survival. The adjustment for combining the two
phases into a single analysis was made on the basis of differences
between phases for the two breed groups of F, cows which were
included during both periods of the study. These breed groups
represented a total of approximately 300 matings per phase.
There were no indications of interactions between the two phases.
Thus, it was concluded that the combined analyses yielded un-
biased estimates of effects. The error mean square used in testing
significance was the pooled error term for the two phases coded
by the harmonic mean of subclass numbers. The model for the
combined analyses for reproduction traits included breed of dam
(D), breed of sire (S), pasture program (P) and their inter-
actions (Table 2).
The individuals records for age of calf, condition score, 205-
day weight, and weaning weight were first analysed separately
for the two phases, employing a model including year, mating
groups (sire x dam), pasture program, sex, age of dam, and first
order interactions. Secondly, the data from the two groups of F,
cows which were included across both phases of the trial were
analyzed employing a similar model. On the basis of these pre-
liminary analyses records were adjusted for year, age of dam,
and sex on a within-program basis. The adjusted data then were
analyzed by least squares methods outlined by Harvey (4). The
models utilized are indicated in Table 3.
Individual records of calves weaned were analyzed for all
traits other than annual production per cow. In order to obtain
observations that approached normal distribution more closely
than a combination of individual zero and weight records, annual
production per cow was computed for 150 year x program x
breed-of-calf subgroups. This yielded five observations in each
of the 30 breed of calf x program groups. Analyses of these
observations yielded lower standard errors of estimates than
analysis of combined individual zero and weight records.


Table 2. Means Squares from Analysis of Breed x Pasture Program Subclass Means of Adjusted Record.

Source d.f. Pregnancy Rate Weaning Rate Survival Rate

Breed of dam (D) 4 226.97** 247.16"* 17.70
Breed of sire (S) 1 144.00" 1.78 128.50**
Pasture program (P) 2 896.70** 751.03** 12.15
Dx S 4 42.00 69.58 9.57
" DxP 8 97.26* 93.51* 4.26
SxP 2 33.59 17.86 5.40
DxSxP 8 45.67 56.18 8.63
Pregnancy and wean 1632 40.02 43.07
Survival 1188 10.32

"Significantly different at P (.05).
"* Significantly different at P (.01).

Table 3. Mean Squares from Analyses of Adjusted Records.
Weaning Condition 205-day Weaning Annual
Source d.f. Age Score Weight Weight Prod/Cow

Pasture program (P) 2 6,277** 588.1** 930,084** 1,398,182"* 45,610**
Breed of dam (D) 4 6,101** 44.8** 377,104** 402,613** 15,100"*
Breed of sire (S) 1 274 42.1 ** 88,665** 81,920** 1,015
"P x D 8 897 35.9** 14,987** 15,902** 2,165
PxS 2 2,514"* 3.4 4,496 5,060 1,200
Dx S 4 1,651 1.7 158,247*" 263,831** 5,500
PxDxS 8 3,430** 17.4** 3,306 11,324"* 890
Remainder 1209a 804 1.5 2,202 4,096 1,513

a Error df for production per cow was 120.

Results and Discussion
The results from the combined analyses for both reproduction
and productive traits are given in Tables 2 and 3. Least squares
means for reproduction are presented in Table 4 and for produc-
tion traits in Tables 5 and 6. Observed heterosis levels (percent
advantage of crossbreeds over the mean of the two purebred
breeds) are shown by pasture program in Tables 5 and 6.

Pregnancy Rate

Pregnancy rate was significantly influenced by both pasture
program and breed of cow as well as their interaction. The aver-
age pregnancy rates were 64%, 76%, and 81%o for the native,
combination, and improved programs, respectively. The rates
of improvement ranked in the anticipated order. The performance
on the improved area was somewhat lower than that reported by
Gonzalez-Padilla et al. (3) and Crockett et al. (2) for south
Florida. It is explained for the most part by the relatively low
response of the purebred cows (Brahman or Shorthorn) to the
improved pasture programs (Table 4). The overall averages for
the five breed groups of cows were: Brahman, 71%; 3/4 Brahman,
80%; F,, 76%; 1/4 Brahman, 75%; and Shorthorn, 64%. The ob-
servation that F, and backcross cows did not differ significantly
was noted also by Koger et al. (7) in a previous publication from
the same station.
The significant (P < .05) breed of cow x pasture interaction
provides an example of one form of genotype-environment inter-
action. This arose principally due to differential response to im-
proved pasture programs. The Brahman and Shorthorn cows had
an average pregnancy rate of 61% on native range versus 72%
on the highly improved program for a difference of 11%. For
crossbred cows the averages were 67% and 86% for the same
two programs for an increase of 19%.
The effect of breed of sire on pregnancy rate was significant
(P < .05), 76% for the Brahman and 72% for the Shorthorn
with no significant breed of sire x pasture-program interaction.

Calf Survival

Calf survival from birth to weaning is an important factor
affecting net productivity. The combined analysis for reproduc-
tion shows survival rate to be affected by breed of sire. Calves
sired by Brahman bulls had an average survival rate of 94%
while the survival rate of Shorthorn sired calves was 98%.


Table 4. Average Rates for Pregnancy, Calf Survival, and Weaning Classified by Breed of Cow X Pasture Program and
Breed of Sire X Program.

Pregnancy Rate % Survival Rate % Weaning Rate %

Program Program Program
1 2 3 Av. 1 2 3 Av. 1 2 3 Av.

Breed of dam
B 61 77 75 71 96 97 96 97 59 75 72 69
Bs 69 85 83 80 96 97 96 95 66 84 77 76
F1 61 83 85 76 96 97 96 96 59 81 82 74
Bi 71 68 87 75 99 100 97 98 71 68 84 75
S 61 62 69 64 95 94 93 94 58 58 64 60

Breed of sire
B 67 77 85 76 94 96 93 94 63 73 79 72
S 62 77 78 72 99 98 97 98 62 76 76 71

Table 5. Breed X Program Least Squares Means for Age at Weaning, Condition Score, and 205-day Weight for Breed of
Calf, Breed of Sire, Breed of Dam, and Crossbred Advantage for Different Traits.

Weaning Age Condition Score 205-day Weight

Program Program Program
1 2 3 Av. 1 2 3 Av. 1 2 3 Av.

days- - score I-bs
Breed of Calf
B x B 215 222 206 214 7.9 9.3 8.6 8.6 342 381 394 372
Bx B 219 223 219 220 7.9 9.2 10.0 9.1 356 409 430 398
B x F 221 225 225 224 8.3 9.8 10.8 9.7 387 453 488 442
B x Bi 219 214 222 218 8.2 8.8 10.3 9.1 359 418 465 414
B xS 223 227 238 229 7.2 9.2 10.7 9.0 307 381 411 366
SxB 204 219 234 219 9.0 9.8 10.4 9.8 382 444 441 422
S x B 220 225 233 226 8.8 9.3 10.8 9.6 379 418 433 410
SxF1 215 227 235 226 8.8 10.2 11.2 10.1 372 435 447 417
SxB1 217 218 212 216 7.8 9.2 10.3 9.1 318 380 404 367
SxS 224 225 223 224 6.2 9.0 10.9 8.7 230 320 356 302

Breed of Sire
B 219 222 222 221 7.9 9.3 10.1 9.1 350 408 438 398
S 216 223 227 222 8.1 9.5 10.7 9.5 336 399 416 384

Breed of Dam
B 209 220 220 217 8.5 9.6 9.7 9.2 362 413 417 397
B3 219 224 226 223 8.4 9.3 10.4 9.3 367 413 431 404
F1 218 226 230 225 8.6 10.0 11.0 9.9 380 443 467 430
B1 218 216 217 217 8.0 9.0 10.3 9.1 338 399 434 391
S 223 226 230 227 6.9 9.1 10.8 8.9 269 350 383 334

All groups 218 223 225 222 8.0 9.4 10.4 9.3 343 404 426 391

Advantage of crossbreds over purebreds %
Calf Dam
Fi PB -3 0 10 2 15 4 8 9 20 18 14 17
34 Fi -1 1 7 3 21 9 13 14 33 26 25 27
/ 3/4 0 -2 6 +1 21 -1 8 8 29 20 20 22
7/ 3/4 -1 -1 1 0 11 1 4 5 18 13 11 13

Table 6. Breed x Program Least Squares Means for Weaning Weight, Weaning Rate, and Production Per Cow for Breed of
Calf, Breed of Sire, Breed of Dam, and Crossbred Advantage for Different Traits.

Weaning Weight Weaning Rate Production Per Cow

Program Program Program
1 2 3 Av. 1 2 3 Av. 1 2 3 Av.

bs % Ibs
Breed of Calf
BxB 350 404 392 382 56 76 79 70 196 307 310 271
BxB3 372 435 453 420 65 75 70 70 242 326 317 295
B x F1 408 489 527 475 63 83 81 76 257 406 427 363
Bx B1 379 432 497 436 71 71 93 78 269 307 462 346
BxS 332 416 467 405 57 52 71 60 189 216 332 245
S x B 377 466 493 445 63 74 65 68 238 345 320 301
Sx B3 400 451 482 444 68 92 85 82 272 415 410 366
S x F 383 473 501 452 54 79 84 72 207 374 421 334
SxB1 328 400 416 381 71 65 75 71 233 260 312 268
SxS 244 338 380 321 59 65 69 61 144 220 224 196

Breed of Sire
B 368 435 467 424 62 71 79 71 231 312 370 304
S 346 426 454 409 63 75 74 71 219 323 337 293

Breed of Dam
B 363 435 442 414 59 75 72 69 214 326 318 286
Ba 386 443 467 432 66 84 77 76 255 372 360 329
FI 396 481 514 463 59 81 82 74 234 390 421 348
BI 354 416 457 409 71 68 84 75 252 283 384 306
S 288 377 423 363 58 58 64 60 167 219 271 219

All groups 357 430 461 416 63 73 76 71 224 318 351 298

Advantage of crossbreds over purebreds %
Calf Dam
Fi PB 19 19 25 21 4 -11 -1 -2 26 6 22 17
3/4 F1 33 30 33 32 2 15 20 13 37 48 58 50
3 3% 31 19 27 25 21 16 29 22 59 37 63 52
7 3/4 18 13 13 14 18 -1 5 8 40 11 18 21

The average death loss of 4% observed in this study is lower
than that reported from other studies in Florida (2,6).

Weaning Rate

Weaning rate is the product of pregnancy rate and survival
rate. Since death losses were small in this trial, the data on wean-
ing rate (Table 4) closely paralleled those of pregnancy. The one
exception of this trend pertained to breed of sire effects, which
were highly significant for pregnancy but approximately nil for
wean rate. This resulted from breed of sire effects being reversed
for pregnancy and survival rates.
The average weaning rate for the trial was 71%. The average
for the three pasture programs was 63%, 73%, and 76%, re-
spectively. The average weaning rates by breed of cow were: 69%
for the B; 76% for the BS,; 74% for the F,; 75% for the SB,;
and 60% for the S.
As was the cause for pregnancy rate, the cow groups re-
sponded differently to the pasture programs for weaning rates.
A good portion of the interaction effects resulted from the cross-
bred cows responding more to improved conditions than did the
purebreds. The average weaning rates for the three groups of
crossbred cows were similar, varying from 74% for the F, to 76%
for the BS, cows.

Age of Calf at Weaning

Where mating occurs in a restricted season and calves are
weaned all at one time, age at weaning is an important production
trait, influencing the weight and value of calf produced. It was
analyzed as a production trait in this study in addition to using
it for estimating weights at a constant age of 205 days.
Pasture program and breed composition of dam significantly
(P<.01) influenced age of calf. Age of calf varied from 218 days
for Program 1 to 226 days for Program 3 (Table 5). This trend
reflected the possibility of a shorter calving interval from calving
to estrus in the improved program (8,9). Age of calf varied from
214 days for the pure Brahman to 229 days for the F, calves out
of Shorthorn cows (P < .01). A long gestation period for Brah-
man cows along with a difference in interval to first postpartum
estrus likely entered into this difference (2,9,11,12). These re-
sults also suggest that the Shorthorn cows which did conceive,
did so early in the breeding season.


Condition Score
This trait was included because it reflects thrift and vitality
and generally is positively associated with prices received for
calves. The calves were scored to the nearest one-third of a Fed-
eral market grade for slaughtered calves. Scores of 6, 7, and 8
were used to designate low, medium, and high commercial, 9 to
11 for good, 12 to 14 choice, etc.
As seen in Table 5, condition score was significantly influ-
enced by pasture program (P), breed of dam (D), breed of sire
(S), and P x D interaction effects. Progeny of Brahman dams
improved by one-third of a grade in condition from Program 1 to
SProgram 3, progeny of crossbred dams improved two-thirds of a
grade, and the progeny of Shorthorn females increased by four-
thirds of a grade in the improved program.
Significant heterosis in the crossbreds was obvious for condi-
tion score with estimates of 9% for F1 calves in purebred dams,
14% for backcross calves on F, dams, 8% for B,S, or S1B, calves
on backcross cows, and 5% for SB1 and BS, calves on backcross
dams. Heterosis levels tended to be higher in the native pasture
program than on improved pastures for condition score.

Wean Weight and 205-day Weight
Estimated 205-day weight is a measure of growth rate, while
weaning weight reflects differences in both rate of growth and
age at weaning. In this study, the trends shown for pasture pro-
gram and breed group differences were similar for the two traits
(Table 5). Due to this similarity, the two traits will be discussed
in conjunction.
Significant main effects (P < .01) were found for pasture
program, breed of dam, and breed of sire. Interaction effects for
pasture program x breed classifications likewise were significant.
Average weaning weight was 416 pounds, varying from
357 pounds on the native to 461 pounds on improved pasture
(Table 6). Brahman-sired calves exceeded those sired by Short-
horn bulls by an average of 15 pounds. Weaning weights by breed
of dam across all pasture programs by ascending order were 363,
409, 414, 432, and 463 pounds for the S, B,S,, B, B S,, and F,
cows, respectively. Weaning weight of calves from the F, cows
averaged 100 pounds greater than that of the Shorthorn and 49
pounds more than that of the Brahman, indicating a high degree
of heterosis. Average weaning weights across all pasture pro-
grams, relative to breed of calf, were highest for the product of
the F, cow when sired by Brahman bulls, at 475 pounds, and


lowest for purebred Shorthorn calves, at 321 pounds. Weaning
weights dropped when either Shorthorn or Brahman breeding
in the calf exceeded three-fourths. The backcross calves, B,,S:
and B:,S,, out of BS:: and BS, dams, were second only to the
products of the-F, cows.
Breeding Brahman instead of Shorthorn bulls to Shorthorn
cows increased weaning weights 84 pounds, and breeding Short-
horn instead of Brahman bulls to Brahman cows increased wean-
ing weights 63 pounds. Improvements in weaning weights were
also obtained when Brahman bulls instead of Shorthorn were bred
to B,S,, cows (55 pounds) and Shorthorn instead of Brahman
bulls to B.,S, cows (24 pounds).
Highly significant interaction of breed of calf with pasture
program was observed (Table 6). This was due to a differential
response of calves; the Brahman increased only 32 pounds with
improvement in pastures, whereas the Shorthorn calves increased
136 pounds. Backcross calves, BSland S:,B,, responded similarly
with increases of 119 and 118 pounds for the two breed groups,
respectively. Interaction of breed of dam with pasture program
was highly significant, with the response to improved pastures
increasing as the proportion of Shorthorn breeding in the cow
increased. An interesting feature was that the Brahman female
produced as well on the intermediate program as she did on
highly improved pastures.
Heterosis levels for calf weights were high. The advantage
for crossbreds in weaning weights varied from 14% for BS, and
SB, calves nursing %/-14 cows to 32% for the reciprocal back-
cross calves on F1 dams (Table 6). Average heterosis levels for
205-day weight were slightly lower on the highly improved native
(20%) than on native range (25%) but approximately equal
(24% vs 25%) for the two programs for weaning weight.

Annual Production Per Cow
This trait is a measure of total herd performance to weaning.
It includes weaning rate times weaning weight. The average pro-
duction per cow was 298 pounds, with values for pasture pro-
grams varying from a low of 224 pounds for the native range
to 351 pounds for the highly improved pastures (Table 6). Breed
groups ranged from 196 pounds for the pure Shorthorn to a high
of 366 pounds for S.Bacalves on B3S, cows. Utilizing both breeds
of sires, the F, cow produced 348 pounds compared to 329 pounds
for the BS1 cows and 306 pounds for the SB, cows. Total pro-
duction for Brahman and B3S, cows on the intermediate pasture
program exceeded that on highly improved pasture.


The differential response of breed groups to the three pasture
programs followed the same pattern as that for calf weights. The
response to improved pasture was greater for cows with a pre-
dominance of Shorthorn breeding than for dams predominately
of Brahman breeding.
Heterosis levels observed for annual production per cow were
High. The level of heterosis for the reciprocal 3/8-5/ calves nursing
3/% blood cows on improved pasture was 63%. The advantage of
the F, cows over the average of the purebred increased linearly
with improvements in pasture program, 37% for the native
range, 48% for the intermediate program, and 58% for the im-
proved program. Responses of this magnitude emphasize the
utility of the Brahman and European crosses for improvement
of production performance in environments where the improved
temperate-zone breeds are not well adapted. They suggested also
that Zebu-European crosses may have utility under other condi-
In these data, calf growth was positively associated with Brah-
man breeding, suggesting that the additive effects of the Brah-
man for adaptability to this area contributed to growth of calf.
The data for breed groups probably can best be interpreted in
terms of: (1) additive genetic merit of the parent breeds in-
volved, (2) climatic adaptability of the various breed groups, and
(3) level of hybrid vigor influencing performance.

Summary and Conclusion

Five breed groups of dams including Brahman (B), Short-
horn (S), 3/4 B-1/4 S (B3S,), 1/2 B-1/2 S (F,), and %4 S-1/ B (SB,),
each mated to both Brahman and Shorthorn sires, grazed con-
tinuously on three different pasture programs. The pastures were
native (Pi), a combination of native and improved pasture (P,),
and all improved pastures including irrigated clover-grass area
Highly significant differences (P < .01) occurred in preg-
nancy rate and weaning rate for both breed of cow and pasture
program. Pregnancy rates for Brahman sires were higher
(P < .05) than for Shorthorn sires, but a higher survival rate
(P < .01) of Shorthorn sired calves made weaning rate for sires
non-significant. Average weaning rates by breed of dam were
69%, 76%, 74%, 75%, and 60% for B, B3, F,, B,, and S cows,
respectively. Weaning rates for pasture programs were 63%,
73%, and 76% for P,, P., and P3 programs, respectively.


Weaning age, condition score, 205-day weight, weaning
weight, and production per cow variations were highly signifi-
cant (P < .01) for pasture program, breed of dam, and breed of
calf. Breed of sire effects resulted in higher condition scores for
Shorthorn sired calves and heavier 205-day and weaning weights
for Brahman sired calves. Breed of sire effects were non-signifi-
cant for age at weaning and production per cow. However, mating
system was highly significant (P < .01) for production per cow.
Breed classifications for both calf and dam showed significant
(P < .01) first order interactions for all traits except for breed
of dam x pasture programs for weaning age.
Crossing the purebred Shorthorn and Brahman resulted in
increased weaning weights of 26% for calves of the Shorthorn
dams and 16% for the Brahman dams. Weaning weight of calves
from F, cows exceeded the average of the purebred progeny by
35% when sired by Brahman bulls and 29% when sired by
Shorthorn bulls. The advantage of all crossbreds over the av-
erage of the purebreds was 1.5%, 9.1%, 19.8%, 22.9%, 10.1%,
and 34.8%, respectively, for age at weaning, condition score,
205-day weight, weaning weight, weaning rate, and annual pro-
duction per cow.
Significant interactions for breed of cow x pasture program
was the result of F, cows responding more to improvements in
nutrition than the purebred groups. These F, cows responded
linearly in all traits with each increment of improvement in pas-
ture programs. Brahman breeding appeared to be associated with
growth, while Shorthorn breeding appeared to be related to de-
gree of condition relative to pasture program.

Literature Cited

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