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
Technical Bulletin 663 December 1963
AFFECTING WEANING WEIGHTS
OF BEEF CATTLE IN THE EVERGLADES
J. H. Meade, Jr.
R. W. Kidder
J. R. Crockett
'r .", \
AGRICULTURAL EXPERIMENT STATIONS
University of Florida, Gainesville
J. R. Beckenbach, Director
IN TRODU CTION ............---- --..................................................-......... ... 3
EXPERIMENTAL METHODS ......-..--...... ......-......--..------ ......-..........-- ................ 4
EXPERIMENTAL RESULTS ........................... ... ...... ...- 4
D ISCUSSION ...... ... -----........ ... ... ...... ................. ................ 7
ADJUSTMENT OF RECORDS .............. ........... --- ---- ------....--.- .....
SUMMARY AND CONCLUSIONS ....--...........................-........ .....- 10
ACKNOWLEDGMENTS .-.....---...-.... .........-.. ....... ....--- ....-....-.........----- 10
LITERATURE CITED .....-.. -.....--. ................--- -- ............. 10
ENVIRONMENTAL FACTORS AFFECTING
WEANING WEIGHTS OF BEEF CATTLE
IN THE EVERGLADES1
J. H. MEADE, JR., R. W. KIDDER, M. KOGER AND J. R. CROCKETT 2
Much variability is encountered in measurements which are
used to evaluate beef cattle performance. This variability is
due to both genetic and environmental influences. The genetic
effect may be concealed by induced and natural environmental
factors which could confuse the breeder and hinder selecting
those animals having the greatest breeding value. The variance
due to environment may constitute a large portion of the total
variability and may be due to prenatal effects, sex, season of
birth, year of birth, climate, nutrition, and other less recognizable
influences. To properly evaluate beef cattle performance, the
breeder or producer must be aware of the factors affecting beef
production. A knowledge of how these factors influence per-
formance, together with proper estimates of their magnitudes,
will help the producer to evaluate more accurately the merit of
This study presents the analysis of records from the breed-
ing herd at the Everglades Experiment Station, Belle Glade,
Florida, and shows the significance of various environmental fac-
tors which affect weaning weights. Although genetic variation
is mentioned, and was included in the analysis, it is not con-
sidered in detail in this bulletin.
1This bulletin represents part of a dissertation presented by the senior
author to the Graduate Council of the University of Florida in partial ful-
fillment of the requirements for the degree Doctor of Philosophy.
2 Meade: Former Graduate Research Assistant, Animal Science Depart-
ment, University of Florida; presently, Assistant Professor, Department of
Experimental Statistics, North Carolina State College.
Kidder: Animal Husbandman, Everglades Experiment Station.
Koger: Animal Geneticist, Animal Science Department, University of
Crockett: Assistant Animal Geneticist, Animal Science Department, Uni-
versity of Florida.
4 Florida Agricultural Experiment Stations
Records were available on calves of Angus, Brahman, Devon,
Brahman-Angus, and Brahman-Devon breeding. The study cov-
ered the 10-year period from 1950 through 1959. The cattle
were maintained on Roselawn St. Augustinegrass pastures with
some supplemental feed during the winter months. Little selec-
tion was practiced except for the choice of sires used, and very
little culling was done except for age and successive reproductive
failures. Practically all heifers were kept in the herd for replace-
ments. Complete records were kept on this herd and included
breeding, reproduction, monthly weight changes, birth dates,
and birth and weaning weights of offspring.
Records of 933 calves were involved in the analysis. The
weaning weights were adjusted to 205 days of age for all calves.
The data were classified by sex, age of dam, month of birth, year
of birth, breed group, and lactation status of dam. Lactation
status of dam refers to the lactation record of the dam the pre-
vious year. For example, if a damn weaned a calf the previous
year, she was classified as lactating, while if she did not, she was
classified as non-lactating.
The significance of main effects and estimates of the magni-
tudes of the various factors were determined by the method of
least squares. All first-order interactions were tested for signi-
ficance with an approximate method given by Hazel (5)3.
The analysis of variance, summarized in Table 1, indicated
that variation in weaning weight is influenced by several factors.
The environmental factors of year, age of dam, sex, and month
of birth exert a highly significant influence, as does the genetic
effect contributed by the different breed groups. Four of the
15 possible first-order interactions were significant. All of these
significant interactions were involved with year.
Estimates of the magnitudes of these factors which influenced
production in the Everglades Experiment Station beef cattle
herd are given in Table 2. The deviations, from, the mean are
deviations from the over-all mean of 372.3 pounds at 205 days
8Figures in parentheses refer to Literature Cited.
Factors Affecting Weaning Weights of Beef Cattle 5
TABLE 1.-VARIANCE ANALYSIS FOR FACTORS INFLUENCING
Source df ms
Year 9 198,304**
Age of dam 5 20,556**
Sex 2 89,790**
Month of birth 2 22,187**
Breed group 8 97,660**
Lactation status 1 3,581
Residual 905 3,695
Significant first-order interactions
Year x sex 16 8,635**
Year x month of birth 18 8,949**
Year x breed group 58 6,440**
Year x lactation status 9 8,361*
t Tested by the method of Hazel (5).
"* (P < .05)
** (P < .01)
Year.-Year calved exhibited a highly significant influence
on the 205-day weights. The range was from 416.5 pounds in
1956 to 271.7 pounds in 1958.
Sex.-Differences between sexes had a highly significant ef-
fect on adjusted weaning weights. Bull calves were 11.3 pounds
heavier than steer calves and steer calves 20.3 pounds heavier
than heifer calves.
Age of Dam.-Age of dam at time of calving also showed a
highly significant effect, as shown by the range from 342.2 pounds
for 2-year-old to 388.1 pounds for 6- to 11-year-old cows.
Lactation Status.-The lactation status of the dam did not
significantly affect the 205-day weights. Calves from non-lac-
tating cows were 4.8 pounds heavier, however, than calves from
Month of Birth.-Season or month of birth had a highly signi-
ficant influence on weaning weights. Calves born in December
through June were 18.4 pounds heavier than those born in July
through October. November calves were 11.9 pounds heavier
than July-October calves.
6 Florida Agricultural Experiment Stations
TABLE 2.-ESTIMATES OF INFLUENCES ON 205-DAY WEIGHTS.
Classification Number Adjusted Deviation from
of Calves Mean (lbs.) Mean (lbs.)t
1950 49 410.6 38.3
1951 67 351.1 21.2
1952 79 370.4 1.9
1953 115 356.7 15.6
1954 80 399.7 27.4
1955 107 411.4 39.1
1956 99 416.5 44.2
1957 141 392.6 20.3
1958 140 271.7 -100.6
1959 56 342.3 30.0
Bulls 281 386.6 14.3
Steers 173 375.3 3.0
Heifers 479 355.0 17.3
Age of Dam
2 years 61 342.2 30.1
3 years 200 361.9 10.4
4 years 155 381.7 9.4
5 years 151 376.6 4.3
6-11 years 333 388.1 15.8
12-17 years 33 383.3 11.0
Lactating 497 369.9 2.4
Non4lactating 436 374.7 2.4
Month .,f Biilli
December-June 368 380.6 8.3
July-October 249 362.2 10.1
November 316 374.1 1.8
Bi eed Gr L,:lp
Alogu, 143 322.9 49.4
Brahman 67 330.2 42.1
Devon 171 349.8 22.5
F1's 34 359.6 12.7
Backcrosses 51 422.2 49.9
F1's 82 397.6 25.3
Backcrosses 106 399.7 27.4
Rotation crosses 102 393.3 21.0
Inter-se 177 375.4 3.1
t The over-all mean was 372.3 pounds.
Factors Affecting Weaning Weights of Beef Cattle 7
The results indicate that environmental factors have a sig-
nificant effect on weaning weights. These factors may conceal
genetic effects, and, therefore, affect the selection of breeding
animals. By accounting for a portion of this environmental
variability, the breeder can obtain a more valid estimate of the
true production potential of his herd.
The variation in weaning weights may fluctuate widely over
a period of several years. Years reflect differences due to man-
agement, climatic conditions, and other variables. In this study,
variability of year effects covered a range of 145 pounds and
was a highly significant factor. These results agree with those
reported by Godbey et al. (3), Brown (1), Godley et al. (4), and
Reynolds (13). Also, the significant interactions of year with
sex, month of birth, breed group, and lactation status indicate
that the effect of these factors may not be constant from year
to year. The interactions of year with breed group and month
of birth should not have much practical significance, since each
breeder is usually selecting within a breed group and using a
relatively short breeding season. Reynolds (13) did not find
interactions of year with sex and lactation status at the Range
Cattle Station. Thus, it seems plausible to state that these two
interactions may either be "location specific" or vagrancies of
sampling. It should be realized that interactions can be very
important; however, in these data the magnitudes of the year
effects overshadow the interactions.
Koger and Knox (9) presented data indicating steer calves
were 32 pounds heavier at weaning than heifer calves. In the
present study, bull calves were 11 pounds heavier than steer
calves and steer calves 20 pounds heavier than heifer calves at
205 days of age. Smith and Warwick (14) in a review of sex
influence on weaning weight reported male calves were 23 to
49 pounds heavier than females at weaning. Several other work-
ers have reported similar estimates.
These data indicate that weaning weights were heaviest from
cows 6 to 11 years of age. This agrees with Knapp et al. (6) who
reported that maximum weaning weights of calves may be ex-
pected from 6-year-old cows. Knox and Koger (7) presented
evidence that maximum production of range cows was reached
at 6 to 8 years of age with a decrease in later years. Reynolds
(13) and Meade et al. (11) indicated similar results.
8 Florida Agricultural Experiment Stations
Lactation status of the dam is the only variable included in
this study which had no statistically significant influence on 205-
day weights. This agrees with Meade et al. (11), who found that
lactation status had no effect on the weaning weights in a pure-
bred Brahman herd. Conversely, Reynolds (13) reported that
weaning weights at the Range Cattle Station were affected by
lactation status of the dam.
The season or month of birth has been reported to influence
the weaning weights of calves. The analysis in the present study
indicates that the range over different months is 18 pounds.
Calves born during the months of December through June showed
a 205-day weight of 381 compared to 362 pounds for calves born
July through October. November calves weighed 374 pounds.
These results are similar to those reported by Clum (2) in which
calves born in December through May were heavier than calves
born from July through November. At the Range Cattle Station,
Peacock et al. (12) observed that calves born December through
February were heavier than calves born during March through
April. Similar results were reported by Koger (8), Marlowe
et al. (10), Brown (1), and Reynolds (13).
Thus, published reports from various parts of the country,
as well as the results of this study, clearly indicate that there
are several non-genetic factors which cause variability in wean-
ing weights of beef calves. Therefore, it is to the breeders' ad-
vantage to account for as much of this variability as possible.
If appropriate adjustments for the effects of these factors are
made before breeding animals are selected, a more accurate eval-
uation of true genetic merit can be accomplished.
ADJUSTMENT OF RECORDS
The first adjustment or correction of records is to adjust them
to a constant age. There are several methods of doing this. One
of the most common is to multiply the average daily gain from
birth to weaning by the constant age desired (say 205, for an
adjustment to 205 days of age) and then add the birth weight.
There are other methods available which do not require a knowl-
edge of the birth weight of the calf. Usually the producer (if
a member of a performance testing association) has his calf
weights already adjusted to a constant age. Thus, he is ready
to look at some of the other factors which affect weaning weight
and to adjust for them, thereby obtaining adjusted weights which
Factors Affecting Weaning Weights of Beef Cattle 9
are estimates of what the calves would have weighed if they had
been raised under the same environmental conditions (i. e., if they
were all born the same year, and were of the same sex, and their
dams were the same age, etc.). The adjustment of records for
environmental factors requires a knowledge of exactly which ones
affect weaning weights in that particular herd and also reliable
estimates of their magnitudes. Due to the disproportionate na-
ture of beef cattle data, accurate estimates of the magnitudes
of these effects are not always easy to obtain. However, if ac-
curate and complete records are available, any beef cattle breed-
ing specialist can calculate them as they are needed.
If appropriate estimates of these factors are available, it is
relatively simple to adjust the weaning weight of each calf. Some
adjustment factors are multiplicative in nature and some of them
are simply additive constants. The following example is an il-
lustration of correcting the weaning weights of two calves to a
common basis by using the additive constants shown in Table 2.
Calf 1 had a 205-day weight of 401 pounds and was a steer
born in December 1959 to a lactating 7-year-old dam; and calf
2 had a 205-day weight of 313 pounds and was, a heifer born in
August 1959 to a non-lactating 2-year-old dam. In order to ad-
just these weights, we add the negative of the appropriate ef-
fects to the 205-day weights.
Calf 1 Calf 2
205-day weight ------...........-.............. 401.0 313.0
Year adjustment .........---..............-- 30.0 30.0
Sex adjustment ....------...............--..... 3.0 17.3
Age of dam adjustment ...-..........-..... 15.8 30.1
Lactation status adjustment .......... 2.4 2.4
Season of birth adjustment --....--.... 8.3 10.1
Adjusted weight -----...............--......... 406.3 398.1
If these correction factors are accurate, we have obtained a
more valid estimate of the true production of the dams of the
two claves. However, correction factors should not be used in-
discriminately. One should always be sure that he has accurate
factors for his particular herd.
10 Florida Agricultural Experiment Stations
SUMMARY AND CONCLUSIONS
A study was conducted at the Everglades Experiment Station,
Belle Glade, Florida, to determine the effect of certain environ-
mental factors on weaning weights of calves. Weaning data were
available on 933 calves covering the period from 1950 through
1959. Environmental factors studied were year of birth, age of
dam, sex, month or season of birth, and lactation status. Esti-
mates of these factors which might influence 205-day weights
were obtained by least squares procedures. The study included
calves of Angus, Brahman, Devon, Brahman-Angus, and Brah-
The variability of year effect covered a range of 145 pounds
and was a highly significant factor. Bull calves were 11 pounds
heavier than steer calves and steer calves 20 pounds heavier than
heifers at 205 days of age. Weaning weights were heaviest from
cows 6 to 11 years of age. Calves produced from cows younger
than 6 and older than 11 years were lighter at weaning.
Month or season of birth showed a significant influence on
weaning weight. Calves born in December through June were 7
pounds heavier than November calves and 18 pounds heavier than
calves born in July through October. Lactation status of dam
had no significant effect on 205-day weaning weight.
The results of this study indicate that factors other than
breeding have a significant influence on weaning weights. Beef
cattle producers should become aware of these environmental
factors and their effect on the production of their cattle.
The authors appreciate and acknowledge the service of many
others in accumulating the weight records, maintaining the rec-
ord books, and analyzing the data basic to this publication. Drs.
H. L. Chapman, Jr., D. W. Beardsley, and others made many of
the weight records. Applications of I.B.M. methods in analysis
of breeding herd data were developed and used by H. V. Clum and
J. M. Liddon. Also, the services of personnel in the Statistical
Laboratory of the University of Florida are appreciated.
1. Brown, C. J. Influence of year and season of birth, sex, sire and age
of dam on weights of beef calves at 60, 180 and 240 days of age. J.
Animal Sci. 19:1062. 1960.
Factors Affecting Weaning Weights of Beef Cattle 11
2. Clum, H. V. Genetic and phenotypic performance of Angus, Brahman,
Devon and crossbred cattle at the Everglades Station. Master's Thesis,
U. of Fla., Gainesville. 1956.
3. Godbey, E. G., W. C. Godley, L. V. Starkey, and E. K. Kyzer. Brahman
x British and British x Brahman matings for the production of fat
calves. So. Car. Agr. Exp. Sta. Bul. 468. 1959.
4. Godley, W. C., E. G. Godbey, E. D. Kyzer, and R. F. Wheeler. Crossbred
and purebred dams for the production of slaughter calves. J. Animal
Sci. 19:203. 1960.
5. Hazel, L. N. The covariance analysis of multiple classification tables
with unequal subclass numbers. Biometrics 2.21. 1946.
6. Knapp, B., Jr., A. L. Baker, J. R. Quesenberry, and R. T. Clark. Growth
and production factors in range cattle. Montana Agr. Exp. Sta. Bul.
7. Knox, J. H., and M. Koger. Effect of age on weight and production of
range cows. New Mexico Agr. Exp. Sta. Press Bul. 1004. 1945.
8. Koger, M. Improvement of beef cattle for the Southern Region through
breeding methods. A report to the Annual Meeting of the S-10 Tech-
nical Committee at Fayetteville, Arkansas. 1958.
9 Koger, M., and J. H. Knox. The effect of sex on weaning weight of
range calves. J. Animal Sci. 4:15. 1945.
10. Marlowe, T. J., and J. A Gaines. The influence of age, sex, and seasons
of birth of calf, and age of dam on preweaning growth rate and type
score of beef calves. J. Animal Sci. 17:706. 1958.
11. Meade, J. H., Jr., M. E. Hammon, and M. Koger. Factors influencing
performance in a Brahman herd. J. Animal Sci. 20:392. 1961.
12. Peacock, F. M., W. G. Kirk and M. Koger. Factors affecting the wean-
ing weight of range calves. Fla. Agr. Exp. Sta. Bul. 578. 1956.
13. Reynolds, W. L. Genetic and environmental influences affecting birth
weights, weaning data and reproductive performance in beef cattle.
Ph.D. Dissertation, U. of Fla., Gainesville. 1960.
14. Smith, H. J., and E. J. Warwick. Influence of sex of calf and age of
dam on calf weights and scores in beef cattle. A report to the Annual
Meeting of the S-10 Technical Committee at Knoxville, Tennessee. 1953.