BULLETIN 673
SYSTEMS OF CROSSBREEDING
FOR BEEF PRODUCTION IN FLORIDA
W. KIDDER
KOGER
H. MEADE
R. CROCKETT
AGRICULTURAL EXPERIMENT STATIONS
UNIVERSITY OF FLORIDA, GAINESVILLE
J. R. BECKENBACH, Director
MAY 1964
BRAHMAN
BRANGUS
X
-AW
x r
ETC.
E TC.
ANGUS
*V '
Opposite: Diagram of crisscrossing, using Brahman and Angus breeds.
After % blood cow is produced (second generation), purebred sires of the
two breeds are used alternately on crossbred cows produced in the system.
Blood composition stabilizes at % blood of the sire and Y3 blood of the
other breed used in the crisscross.
CONTENTS
Page
INTRODUCTION ...................... ..---- --.. ..---....----- 5
MATERIALS AND METHODS ........................ -----..- ---- -- 6
RESULTS ... -------------... ......... -. ........... ----....-- 9
DISCUSSION ................-......--- ........--...--------- --------------- 14
SUMMARY ....................... ............ ..... ---- ------- ----------- 18
LITERATURE CITED ............. ...-...-- ...-- -- .---- ......--.-.. --------- -- -- 18
SYSTEMS OF CROSSBREEDING FOR
BEEF PRODUCTION IN FLORIDA
R. W. KIDDER, M. KOCER, J. H. MEADE. AND J. R. CROCKETT 1
INTRODUCTION
The production of beef under south Florida conditions in-
volves some considerations which are peculiar to the area. Most
cattle-producing regions of the United States have straightbred
cattle which are reasonably well adapted for beef production.
However, this is not true in south Florida, where environmental
conditions are different from those prevailing throughout most
of the United States. Presently, there is no breed of cattle
which, in a straightbreeding system, has proved itself well-
adapted for commercial beef production under the conditions
currently prevailing in south Florida.
Many Florida cattlemen have tried crossbreeding in an effort
to increase production, because long periods of time are neces-
sary to develop breeds or strains adapted to special conditions.
They have found that crossbred calves have a greater growth
potential, especially before weaning, than straightened calves.
In addition, crossbred dams usually wean heavier calves than do
straightbred dams. Recommendations for sustained systematic
crossbreeding programs, however, have not been available to
ranchers, and many undesirable cattle of mixed breeding have
been produced. The inferior quality and lack of uniformity of
these cattle have frequently resulted in discouraging feedlot per-
formance and carcass quality along with a resultant lowered
market value. Ranchers have been searching for a means of
producing more acceptable as well as productive crossbreds.
Hence, experimental results from crossbreeding trials are of
primary importance to the beef cattle industry. Straightbred
cattle adapted to the area may be developed in the future, but
1Kidder: Animal Husbandman, Everglades Experiment Station, Belle
Glade.
Koger: Animal Geneticist, Animal Science Department, University of
Florida.
Meade: Former Research Assistant, Animal Science Department, Uni-
versity of Florida; now Assistant Statistician, Institute of Statistics, North
Carolina State College, Raleigh, North Carolina.
Crockett: Assistant Animal Geneticist. Animal Science Department,
University of Florida.
Florida Agricultural Experiment Stations
even then there is the probability that crossbreds will continue
to show superior performance.
This bulletin presents the results of an investigation to com-
pare the performance of various straightbred and crossbred
calves produced at the Everglades Experiment Station from
1950 through 1959.
MATERIALS AND METHODS
Beef cattle have been maintained at the Everglades Experi-
ment Station since 1931, when a Devon herd was established.
A herd of native Florida cattle was added in 1933, and graded
up to the Devon. Angus and Brahman herds were established
and a crossbreeding program was initiated in 1946.
The initial plan for the crossbreeding project was influenced
by the official recognition of Santa Gertrudis cattle as a breed
by the United States Department of Agriculture in 1940 (1)2
and by the crossbreeding work in Louisiana, reported by Rhoad
and Black (10). In both reports emphasis was placed on the
superior performance of crossbreds composed of 3/8 Brahman
and %8 British beef breeding. Consequently, one of the major
objectives during the first phase of the study was to produce
animals of 3/ Brahman 5 Devon breeding. The thought was
that adaptability to semitropical conditions would be derived
from the Brahman ancestory, while the Devon was used as the
European parent because the breed had demonstrated their abil-
ity to survive in the Everglades and were the only European
animals available to the station in numbers sufficient to initiate
a crossbreeding trial.
The mating systems used to produce the 38-% combination
are shown in Figure 1. The data from this phase of the study
have been summarized previously (Kidder and Chapman, 3;
Clum, 2; Kidder et al., 4; and Liddon, 7).
By 1952 animals of suitable blood composition were avail-
able to expand the study to include a comparison of different
systems of crossbreeding that could be used on a sustained basis
by commercial breeders. The Brahman and Devon breeds and
their crosses were used to initiate this study. The crossbreed-
ing systems compared with contemporary straightbreeding of
Brahman and Devon cattle include:
2 Numbers in parentheses refer to Literature Cited.
Crossbreeding for Beef Production in Florida
1. Production of firstcross (F1) calves from straightbred
dams. A majority of such calves were sired by Brahman
bulls and mothered by Devon cows because fewer number
of surplus Brahman cows for crossbreeding were avail-
able. The two reciprocal groups of F1 calves performed
similarly, so the data were pooled to simplify analysis and
presentation of the data.
2. Production of backcross calves from Fi dams. One-
half of the F, cows were bred to Brahman bulls and one-
half to Devon bulls. The two groups of backcross calves
were similar in performance. The data were pooled as
above to simplify presentation.
DEVON
3/8 BRAHMAN BRAHMAN
5/8 DEVON
3/4 BRAHMAN DEVON
1/4 DEVON (SIRE)
1/2 BRAHMAN
1/2 DEVON
BRAHMAN
AND (DAM)
1/2 BRAHMAN
1/2 DEVON
3/8 BRAHMAN DEVON
5/8 DEVON
1/4 BRAHMAN BRAHMAN
3/4 DEVON (SIRE)
1/2 BRAHMAN
1/2 DEVON
DEVON
(DAM)
Fig. 1.-Methods of mating Devon and Brahman cattle to produce recip-
rocal crossbreds and to obtain 3 Brahman and % Devon in the third
generation. Read charts from right to left.
Florida Agricultural Experiment Stations
3. Crisscrossing, with the two breeds of sire being alter-
nated generationwise on crossbred cows produced in the
system (Figure 2). The two reciprocal groups were
combined.
1/ --~-
1/3 D
2/3 D
1/3 D
5/8
1/4 D
6 5 // 2 I
GENERATION
Fig. 2.-Pedigree chart reading from right to left illustrating the criss-
cross method used in the Brahman (B)-Devon (D) crossbreeding experi-
ment. The % blood cows used to begin the program (at right) were
obtained as shown in Fig. 1. Blood composition would stabilize as shown
to left of chart at 2 blood of the breed of sire and 1V blood of the other
breed used in the cross.
Crossbreeding for Beef Production in Florida
4. Production of crossbred calves by mating crossbred
bulls to crossbred cows. This group is referred to here-
after as the inter-se group. Most of the bulls and fe-
males were of % Brahman-5' Devon breeding, although a
few calves resulting from mating F, bulls to 1,' Devon-
1/ Brahman and 3. Devon-1~ Brahman cows were included
in this group.
A limited number of Angus and Brahman-Angus crossbreds
were maintained also, and data from these groups are included
in Table 1 for reference.
All breed groups were maintained under comparable condi-
tions within years. They were maintained on pasture with
supplementary feeds such as fresh-cut sugarcane, grass silage,
or blackstrap molasses during the winter months.
Little culling was practiced except for age and successive
reproductive failure. Since nearly all heifers were kept in the
herd, little selection was practiced except for the choice of sires
used. Therefore, the records used were from a relatively unse-
lected population as compared with most beef herds.
Detailed individual weight records were obtained during the
pre- and post-weaning periods and on reproductive performance.
Weight data at 205 days, 12 months, and 18 months of age
were analyzed by the method of least squares to remove environ-
mental effects as reported by Meade (8, 9). Only the number of
animals and adjusted group means are presented herein, omit-
ting the remaining statistical tables for clarity of presentation.
RESULTS
The results are summarized in Table 1 and shown graphi-
cally in Figures 3 and 4. A total of 933 calves were weaned
between 1950 and 1959 including Brahman, Devon, Angus, and
crossbred calves. There were 415 replacement heifers from
which 12-month and 18-month weights were obtained.
Weaning Weight.-The average 205-day weight of all calves
was 372 pounds. The 205-day weight of all purebred groups was
less than that for any of the crossbreds. The Fi Brahman-Angus
calves, all mothered by Angus cows, were lighter than the other
crossbred groups, but their weight (360 pounds) was above that
of the parent breeds (323 and 330 pounds, respectively, for the
Angus and Brahman). The backcross calves mothered by first-
Florida Agricultural Experiment Stations
TABLE 1.-WEIGHTS OF PUREBRED AND CROSSBRED GROUP OF CATTLE AT
VARIOUS STAGES OF DEVELOPMENT.*
Breed Group
Purebred:
Brahman
Devon
Angus
Weaning Weight Post-weaning Weights
Number 205-day Number of 12-month 18-month
of calves weight heifers weight weight
Devon-Brahman crosses:
Firstcross 82 398 45 544 696
Backcrosses 106 400 48 515 651
Crisscross 102 393 48 512 654
Inter-se 177 375 83 468 610
Angus-Brahman crosses:
Firstcross 34 360 17 516 691
Backcross 51 422 22 491 627
Average for all
calves:
933 372
Weaning data include all calves of both sexes.
replacement heifers only.
cross Brahman-Angus cows were the
an average weight of 422 pounds.
415 486 632
Post-weaning data include data from
heaviest breed group with
A comparison of the different crossbreeding systems repre-
sented in the Brahman-Devon crossbred groups shows that the
firstcross, backcross, and crisscross calves were very similar in
weight. Calves resulting from the inter-se matings were inter-
mediate between the above crossbreds and the purebreds. This
loss in hybrid vigor, as compared with the remaining crossbreds,
was to be expected.
Twelve-Month Weight.-The average 12-month weight was
486 pounds. By this time some of the differences due to mother-
ing ability of the cows had disappeared, and the lifetime growth
potential of the calves was becoming more apparent. The Angus
calves were lightest in weight with an average weight of 397
pounds. The inter-se heifers were intermediate in weight be-
tween the Brahman and Devon, with weights of 468, 455, and
473 pounds, respectively. These weights along with those at
18 months indicate that the calves from inter-se mating showed
no hybrid vigor after weaning.
Crossbreeding for Beef Production in Florida 11
700
/
/
/
650 /
/ .
600/
z
550 /
-/
n 500 / /
400 Straightbreds
---- Firstcross
Backcross
350 -
C... risscross
--* Inter-se
205 DAYS 12 MO. 18 MO.
AGE
Fig. 3.-Showing comparative weights of animals from different systems
of crossing Brahman and Devon cattle.
Another interesting change occurred in the Angus-Brahman
crosses. From weaning to 12 months of age, the lir-I. -...
calves gained 156 pounds as compared to only 69 pounds for
the backcrosses. The superior growth potential of the first-
cross was evident by this time. The backcross calves which
were fat and heavy at weaning made low post-weaning gains
Florida Agricultural Experiment Stations
2() 550 /
o //
o 40
0 500
^ 450 /'/
400- /
350 -
205 DAYS 12 MO. 18 MO.
AGE
Fig. 4.-Showing weights of F, and backcross groups compared with
mean of straightbred Angus and Brahman progeny.
and were lighter in weight at 12 months of age than were the
F1 calves.
Eighteen-Month Weight.-The average 18-month weight was
632 pounds, with the breed groups showing only minor changes
in rank from the 12-month weight. The purebreds and the
inter-se animals remained among the lighter group. The
Crossbreeding for Beef Production in Florida
Angus backcross heifers mothered by firstcross Brahman-Angus
cows were lighter in weight than expected. Most of these
backcross heifers were sired by Angus bulls, and growth poten-
tial of the sires probably influenced the results.
The results above indicate that for certain breed combina-
tions, at least, growth rate is similar in firsteross calves moth-
ered by straightbred dams, backcrosses mothered by F, dams,
and crisscrosses sired by purebred bulls out of crossbred cows.
Offspring resulting from mating crossbred bulls to crossbred
cows showed some advantage over straightbreds at weaning,
but by 12 months of age weights were comparable to those of
the pure parent breeds.
Reproductive Efficiency.-Matings were made during a re-
stricted breeding season of 90 days, and reproductive efficiency
was determined for nine years. Weaning rates for this period
are shown for reference only in Table 2. Due to two outbreaks
of brucellosis during this time the data possibly were confounded
and thus were not analyzed.
TABLE 2.-WEANING PERCENT FROM THE VAP.RIO'S MATINGS OVER A
9-YEAR PERIOD (1951-1959).
Number Weaning
Breed of Cow Breed of Bull of Matings Percent
Brahman Brahman 126 50
Devon Devon 280 .58
Angus Angus 182 76
Brahman Devon
Devon Brahman 109 57
'2 B- 12 D Brahman & Devon 118 84
B-D Crisscross Brahman & Devon 166 61
B-D Crossbred B-D Crossbred 296 60
Angus Brahman 41 71
Biahman
/2 A- /2 B Angus 70 73
14 Florida Agricultural Experiment Stations
DISCUSSION
Some Essentials for Workable Crossbreeding Systems
Several important factors must be considered in planning a
practical crossbreeding system.
1. The system should be self-sustaining in that it produces
replacement heifers for the breeding herd. Progressive improve-
ment of a beef producing herd generally would be impractical if
it were necessary to purchase replacements or maintain auxiliary
herds for their production. Cattlemen have experienced greater
productive capacity in cattle raised at home than in similar
cattle moved onto the ranch. Purchase of replacement females
presents serious problems from the standpoint of herd health.
2. The program must be adapted to the individual ranch. A
small ranch cannot successfully operate a program which calls
for a large number of breeding groups and several breeds of
sires. The plan must be kept simple, and workable within the
limits of acreage, fencing, and personnel.
3. Most any cattleman will be more successful with the
breed of cattle he likes best; hence, the choice of breeds is
largely a matter of preference of the individual. In choosing
breeds, however, one should consider carefully the breeds and
breed combinations which have been tried and found profitable
in the area.
4. The manner in which steer calves are to be marketed may
have an influence on the choice of a breeding plan which will be
most useful on any particular ranch. Steer calves in which
the Brahman breed is predominant may be more profitably mar-
keted as fat calves or steers grown out on pasture. When
the steers are predominantly of British breeding, they do excep-
tionally well in the feedlot, and are in increasing demand as
feeders.
5. The breeds chosen for a crossbreeding program should
have good combining ability so that there will be hybrid vigor
in their crosses. Unless the crossbreds out-perform either of
the parent breeds, there is little to recommend crossbreeding.
The breeding plan chosen should result in enough hybrid vigor
to more than offset the extra costs involved over straight-
breeding.
C,-.. 1'. ,, .1,'. for Beef Production in Florida
6. The availability, cost, and quality of breeding stock, espe-
cially commercial bulls of the breeds selected, is an important
factor to be considered in establishing a commercial beef herd.
Breeders of purebred cattle in all of the beef breeds should
encourage crossbreeding programs for the production of com-
mercial meat animals. Experimental data presented in this
bulletin indicate that hybrid vigor can be obtained when cross-
bred cows are mated to purebred sires. Such programs would
produce a continuing market for quality breeding bulls of all
breeds. To provide the commercial cattleman with good quality
bulls for use in whatever system is most efficient in the produc-
tion of beef is the vitally essential, and only justifiable, role of
the purebred breeder.
Crossbreeding Systems
In this trial, calves resulting from inter-se crossbred matings
showed only slight hybrid vigor at weaning time and none in
the post-weaning period. This reduction in growth rate as com-
pared to other crossbreds occurred even though rigid selection
of sires was practiced, with only extremely growth sires being
used. Whether or not this loss would have occurred if female
selection had also been practiced is not known. Selection of
females on the basis of progeny records undoubtedly would have
been effective in improving weaning performance. In view of
the response to sire selection, however, the effectiveness of select-
ing crossbred females on the basis of their own growth rate
appears doubtful. Loss of hybrid vigor from inter-se mating
of crossbreds has been reported previously from Florida (5).
The remaining crossbreeding systems, in this trial, showed
striking superiority over straightbreds at all stages of devel-
opment. The FI animals showed slightly more hybrid vigor than
the backcrosses and crisscrosses as evidenced by more rapid
post-weaning growth and higher final weight. Due to the fact
that Fi calves nursed straightbred dams, however, their full
potential was not expressed at weaning because of mothering
ability of the dams. Thus, at weaning time, backcross and criss-
cross calves were comparable to or, in the case of Angus crosses,
exceeded the weight of F1 calves.
If a commercial cattleman is to capitalize on hybrid vigor,
it is important that crossbreeding be done systematically. Hy-
bridization in poultry has become a highly skilled science directed
Florida Agricultural Experiment Stations
by skilled professional personnel. Satisfactory schemes for prac-
tical crossbreeding of swine are well known among swine breed-
ers. Crossbreeding in cattle is more complicated than for other
species due to a long generation interval, low reproduction rate,
overlapping of generations, and expense of facilities for keeping
breeding groups separated. A few crossbreeding plans are pre-
sented which illustrate programs that may have merit, based on
experimental work to date. These are shown in pedigree form
in Fig. 5. A more detailed discussion of crossbreeding plans was
given by Koger (6).
Experimental data from this and other trials indicate that
an exact percentage of Brahman and British blood is not impor-
tant but rather that performance is similar for animals with
25 percent to 75 percent of Brahman breeding, with the former
producing higher grading animals.
A crisscross plan using two breeds is the most simple and
adaptable system for many ranch operations. It has been well
established that Brahman-European crosses possess a high level
of hybrid vigor and do well in warm climates. Thus, in south
Florida one of these breeds generally should be the Brahman
and the other the cattleman's choice from among the breeds of
European origin. This system is illustrated as Plan 1 in Fig. 5.
A crisscross plan using an American breed as the source of
Brahman breeding is illustrated in Fig. 5 as Plan 2. The
American breeds include the Brangus, Santa Gertrudis, Char-
bray, and Beefmaster.
A three-breed rotation may be considered by some of the
larger ranch operations. This is illustrated as Plan 3 in Fig. 5.
This plan is more complicated than a two-breed crisscross, and
it appears doubtful that hybrid vigor in a three-breed rotation
would be significantly greater than in a two-breed cross. There
is some loss in uniformity of cattle in this program, but hybrid
vigor is maintained at a high level.
The above systems have the advantages that replacement
heifers are produced in large numbers, which makes possible
rigid culling of cows on the basis of their production, and that
the breeding composition of both dams and calves is in the range
of high levels of hybrid vigor.
The use of firstcross (F1) dams to produce backcross progeny
gave results comparable to crisscrossing in this trial. The sys-
tem has the disadvantage, however, of difficulty in acquiring an
adequate number of replacements except in unusual circum-
Crossbreeding for Beef Production in Florida
GENERATION
Fig. 5.-Illustrating crossbreeding plans that might be applied in Florida.
To the right are shown possible foundation breeds, while stabilized blood
composition is shown in three generations to the left.
Plan 1. Brahman (B)-European (E) crisscross starting with European
females and Brahman bulls.
Plan 2. Angus (A)-Brangus (Bg) crisscross showing theoretical per-
cent of Angus and Brahman blood.
Plan 3. Three-breed rotation. A, B, and C may represent any three
breeds-for example, Angus, Brahman, and Charolais.
Florida Agricultural Experiment Stations
stances and for a limited number of producers. A shortage of
replacements precludes rigid selection or culling of females.
It must be remembered that herd management plays a very
important part in the success or failure of any breeding system.
Proper nutrition, health maintenance, selection and culling are
essential in sound breeding operations.
SUMMARY
Data from 1950 through 1959 are presented showing pre-
weaning and post-weaning performance of straightbreds and
the following Brahman-British breed combinations: firstcross,
backcross, two-breed rotation cross (crisscross), and crossbred
bulls mated to crossbred females (inter-se).
In the Brahman-Devon comparisons where all groups were
represented, weaning weights of firstcross, backcross, and criss-
cross calves exceeded those of straightbreds by 17 percent (397
vs. 340 pounds). Progeny from the inter-se matings were inter-
mediate (375 pounds, or 110 percent of straightbreds). At 18
months of age the average weights of firstcross, backcross, and
crisscross animals were 10 percent heavier (667 vs. 606 pounds)
than those of straightbreds, but the inter-se progeny were sim-
ilar in weight (604 pounds) to the straightbreds. Thus, cross-
breds with one straightbred parent showed dramatic hybrid
vigor for growth. The progeny of inter-se matings showed
some advantage over straightbreds at weaning, but by 12
months of age this advantage had disappeared. It was con-
cluded that crisscrossing is the most practical system of cross-
breeding for most ranch operations. The use of F1 females as
dams gives good results, but adequate numbers of replacement
females are difficult to acquire.
LITERATURE CITED
1. Clark, R. T., and A. L. Baker. Beef cattle breeds. USDA Tech. Bul.
1779. Rev. 1940.
2. Clum, H. V. Genetic and phenotypic performances of Angus, Brahman,
Devon and crossbred cattle at the Everglades Station. Master's
Thesis, Agriculture Library, University of Florida, Gainesville.
1956.
3. Kidder, R. W., and H. L. Chapman, Jr. A preliminary report of weight
performance of crossbred and purebred cattle at the Everglades
Experiment Station from 1943 to 1951. Proc. Assoc. of So. Agr.
Workers. 49:56. 1952.
Florida Agricultural Experiment Stations
stances and for a limited number of producers. A shortage of
replacements precludes rigid selection or culling of females.
It must be remembered that herd management plays a very
important part in the success or failure of any breeding system.
Proper nutrition, health maintenance, selection and culling are
essential in sound breeding operations.
SUMMARY
Data from 1950 through 1959 are presented showing pre-
weaning and post-weaning performance of straightbreds and
the following Brahman-British breed combinations: firstcross,
backcross, two-breed rotation cross (crisscross), and crossbred
bulls mated to crossbred females (inter-se).
In the Brahman-Devon comparisons where all groups were
represented, weaning weights of firstcross, backcross, and criss-
cross calves exceeded those of straightbreds by 17 percent (397
vs. 340 pounds). Progeny from the inter-se matings were inter-
mediate (375 pounds, or 110 percent of straightbreds). At 18
months of age the average weights of firstcross, backcross, and
crisscross animals were 10 percent heavier (667 vs. 606 pounds)
than those of straightbreds, but the inter-se progeny were sim-
ilar in weight (604 pounds) to the straightbreds. Thus, cross-
breds with one straightbred parent showed dramatic hybrid
vigor for growth. The progeny of inter-se matings showed
some advantage over straightbreds at weaning, but by 12
months of age this advantage had disappeared. It was con-
cluded that crisscrossing is the most practical system of cross-
breeding for most ranch operations. The use of F1 females as
dams gives good results, but adequate numbers of replacement
females are difficult to acquire.
LITERATURE CITED
1. Clark, R. T., and A. L. Baker. Beef cattle breeds. USDA Tech. Bul.
1779. Rev. 1940.
2. Clum, H. V. Genetic and phenotypic performances of Angus, Brahman,
Devon and crossbred cattle at the Everglades Station. Master's
Thesis, Agriculture Library, University of Florida, Gainesville.
1956.
3. Kidder, R. W., and H. L. Chapman, Jr. A preliminary report of weight
performance of crossbred and purebred cattle at the Everglades
Experiment Station from 1943 to 1951. Proc. Assoc. of So. Agr.
Workers. 49:56. 1952.
Crossbreeding for Beef Production in Florida 19
4. Kidder, R. W., J. Liddon, H. V. Clum, and M. Koger. Growth response
of Angus, Brahman and Devon cattle and various crosses of these
breeds in subtropical climate of the Florida Everglades. J. Ani.
Sci. 15:1209. (abstract). 1956.
5. Koger, M. Practical crossbreeding plans. pp. 204-211. Crossbreeding
beef cattle, Edited by Cunha, Koger, and Warnick. University of
Florida press. 1963.
6. Koger, M., R. W. Kidder, F. M. Peacock, W. G. Kirk, and M. W.
Hammond. Crossbreeding systems in beef cattle. J. Ani. Sci. 20:908.
(abstract). 1961.
7. Liddon, J. M. Environmental and genetic factors affecting growth
patterns of Brahman, Angus, Devon and crossbred cattle. Masters'
Thesis, Agriculture Library. University of Florida, Gainesvillk. 1957.
8. Meade, J. H., Jr. Influence of heredity and environment on weaning and
post-weaning weights in beef cattle. Ph.D. Dissertation, Agriculture
Library, University of Florida, Gainesville. 1961.
9. Meade, J. H., Jr., R. W. Kidder, M. Koger, and J. R. Crockett. Environ-
mental Factors Affecting Weaning Weights of Beef Cattle in the
Everglades. Fla. Agr. Exp. Sta. Tech. Bul. 663. 1963.
10. Rhoad, A. 0., and W. H. Black. Hybrid beef cattle for subtropical cli-
mates. USDA Cir. No. 673. 1943.
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