BEEF PRODUCTION IN RELATION TO CREEP FEEDING,
ZERANOL IMPLANTS AND BREED TYPE: I. CALF AND COW PERFORMANCE
D. L. Prichard*, D. D. Hargrove, T. A. Olson and
T. T. Marshall
University of Florida,
D. L. Prichard*, D. D. Hargrove, T. A. 01son and T. T. Marshall, North
Florida Research and Education Center, Route 3 Box 4370, Quincy, FL
32351. Contribution from the Animal Science Department, Inst. of Food
and Agric. Sci., Florida Stn., Univ. of Florida. Research Report 88-10.
A 2-yr study was conducted to evaluate the effects of creep feeding,
preweaning zeranol implants and breed type on calf and cow performance.
Two hundred calves sired by Brahman and Romana Red bulls and out of
Angus and Angus x Brown Swiss reciprocal crossbred (FI) dams were
stratified by breed type and sex to three creep treatments: no creep
feed (NC); long-term creep (LC), creep-fed from 56 to 210 d of age
(weaning); and short-term creep (SC), creep-fed from 146 to 210 d of
age. Alternate calves within sex, breed type and creep treatment were
implanted with 36 mg of zeranol at an average of 56 d and reimplanted 90
d later. The LC and SC calves had heavier (P<.001) 210-d weights than
NC calves (264 and 257 vs 231 kg, respectively) and the LC calves were
heavier (P<.001) at 146 d than NC calves. Frame score was not affected
(P>.20) by creep treatment. The LC calves had higher (P<.001) average
daily gains from 118 to 210 d of age and higher 146 and 210-d condition
scores than did NC calves. Cows with creep-fed calves gained more
weight during the breeding season than those with noncreep-fed calves.
Pregnancy rate was not affected (P>.46) by creep treatment of calf.
Zeranol implants increased (P<.01) 146 and 210-d weights (184 vs 175 kg
and 259 vs 243 kg) and average daily gains during all periods to
weaning. Cow weight gain, condition score, and pregnancy rate were not
affected (P>.14) by zeranol treatment of calf. Brahman-sired calves had
higher (P<.005) 146 and 210-d weights and frame scores than Romana
Red-sired calves. Calves out of Angus dams had lower (P<.001) 146 and
210-d weights, frame scores, and average daily gains from 56 to 146 and
to 210 days of age, but higher (P<.03) 210-d condition scores than
calves out of- F dams. The F cows gained more weight (P<.007) during
the breeding season, had a lower (P<.001) condition score and a higher
pregnancy rate (96.5 vs 86.8%) than the Angus cows. Cows with heifer
calves had a higher (P<.10) pregnancy rate than those with steer calves.
Spearman (rank-order) correlation coefficients between 146 and 210-d
weights of NC, SC and LC calves were .92, .92 and .94, respectively.
Rank-order correlation coefficients between 146 and 210-d weights of NC,
SC and LC calves out of Angus cows were .94, .90 and .88 respectively
and for Fl cows were .92, .91 and .93.
(Key Words: Creep, Zeranol, Brahman, Romana Red, Calf and Cow Perfor-
Gross income in the cow-calf facet of the beef industry is highly
dependent on the production of heavyweight calves at weaning. Creep
feeding and implanting with growth stimulants are methods of increasing
preweaning gains (Cundiff et al., 1966; Scarth et al., 1968; Utley and
McCormick, 1976; Stricker et al., 1979; Corah, 1980; Lowman, 1980; Ochoa
et al., 1981). Advantages other than weight gain of calves have been
reported for creep feeding. These include increased weight, condition
and pregnancy rate of the dam (Jones and Jones, 1932; Stricker et al.,
1979). Creep feeding, however, has been implicated in the possible al-
tering of the maternal rank (weaning weight of calf) of cows within a
herd (Burns et al., 1966; Ochoa et al., 1981). Furthermore, it has been
suggested that creep feed is utilized best by calves suckling dams with
limited milk production (Christian et al., 1965). Little is known about
the combined effects of growth stimulants with creep feeding and varia-
tions in the dam's milk production on the preweaning performance of
The objective of this study was to evaluate the effects of and
interactions among creep feeding, zeranol implants and breed type on
calf and cow performance.
Materials and Methods
This project was conducted at the Beef Research Unit, Gainesville,
from April 1 through September 1, 1981 and 1982. The research unit is
located in north central Florida (latitude 290 40'N). Average maximum
and minimum temperatures for the 1981 and 1982 experimental periods
respectively were 32.8 and 19.3 C and 31.3 and 19.1 C. Monthly rainfall
averages during the experimental periods were 80.9 mm in 1981 and 170.3
mm in 1982. The major soil type is Leon fine sand, and varies from
moderately well drained to very poorly drained.
Two hundred calves, sired by Brahman and Romana Red bulls and out of
Angus and Angus x Brown Swiss F1 reciprocal crossbred dams were used in
this study. The Romana Red breed was developed in the Dominican
Republic from a base of native red criollo cows topcrossed to Mysore and
Nelore bulls and is about seven-eights Bos indicus breeding. Calves
were stratified by breed type and sex to the following creep treatments:
no creep feed (NC); long-term creep (LC), creep-fed from 56 to 210 d
(weaning); and short-term creep (SC), creep-fed from 146 to 210 d of
age. The creep feed contained 14% crude protein, not more than 8% crude
fiber, not less than 2.5% crude fat and 9000 U.S.P. units of vitamin A
per .45 kg. Creep feeders were located near shade and water. Alternate
calves within sex, breed type and creep treatment subgroups were
implanted with 36 mg of zeranol at an average age of 56 d and reim-
planted 90 d later.
A 60-d breeding season, from about April 1 to June 1, was used.
Calves were identified, weighed and bull calves castrated within 24 h of
birth. Calves were weaned at an average age of 210 d, and weaning
weights of all calves were adjusted to this age. Cows were palpated for
pregnancy at weaning time.
Cows and calves were maintained in pastures consisting primarily of
Pensacola bahiagrass (Paspalum notatum Flugge) and white clover
(Trifolium repens L.). Brood cows were wintered on corn silage plus
molasses and cottonseed meal to meet NRC requirements, from early
December until about March 15, when an adequate quantity of clover was
available in the pastures.
Cow-calf pairs within the LC and SC creep treatment groups were
stratified by breed, sex of calf and zeranol treatment to one of two
replicates (pastures). Cow-calf pairs in the NC groups were considered
one replicate and placed in a single pasture each year. The same four
pastures were used both years for the LC and SC creep groups; however,
the two pastures used for the LC creep treatment in 1981 were used for
the SC creep treatment in 1982. A different pasture was used for the NC
group each year. Stocking rates varied from 1.17 to 1.69 cow-calf pairs
Data were analyzed by least squares, fixed model procedures using
the Statistical Analysis System (SAS, 1979). The model used for
analyses of calf traits included the fixed main effects of creep,
zeranol, breed of sire, breed of dam, sex, year and pasture nested
within creep treatment and year. Fixed main effects used in the model
for cow traits included creep, zeranol, breed of cow, breed of sire of
calf, .sex of calf, year and pasture nested within creep treatment and
year. Age of calf at the beginning of the trial was used as a covariate
(linear, quadratic) in final calf and cow models, except in the analyses
of 146 and 210 d weights. All cows in this study were 4 yr of age and
older, with the exception of six, which were 3 yr of age. Dam age
(linear, quadratic) was included in preliminary analyses; however, it
was removed from the calf model due to lack of significance. All two
and three-factor interactions were included in preliminary analyses.
Only significant interactions remained in the final models. Linear
contrasts of least-squares means for creep treatments were computed for
those calf and cow traits affected (P<.10) by creep treatment.
Response traits for the calf model were 146 and 210-d weights and
condition scores, preweaning average daily gain and frame score.
Spearman (rank-order) correlation coefficients were computed between 146
and 210-d weights of calves within creep treatment and within breed of
dam by creep treatment. Cow response traits included cow weight change
from the beginning (which was also the start of long-term creep feeding)
to the end of the breeding season, from the end of the breeding season
to July 1 (start of short-term creep feeding), and from July 1 to wean-
ing. Pregnancy rate and condition scores at the beginning and end of
the breeding season and at weaning were also analyzed. A scale of 1 to
17 was used for condition scoring of cows and calves (Andrade, 1980) and
frame scores were from 1 to 5 (Wakeman, 1978).
Results and Discussion
Weights and Weight Gains. Least-squares means for calf preweaning
performance traits are shown in table 1. Mean 210-d weight was 252 kg.
Long-term (LC) and short-term (SC) creep-fed calves were 33 and 26 kg
heavier (P<.001), respectively, at 210 d than noncreep-fed calves (NC).
The LC calves were heavier (P<.001) at 146 d and had a higher (P<.001)
average daily gain from 56 to 146 d than SC and NC calves. The LC
calves were consuming an average of .7 kg of creep feed'd-1 at 118 d of
age and 1.15 kg'd-1 by 146 d of age (figure 1). There was no difference
(P>.50) among creep treatments for average daily gain from 56 to 118 d
of age, suggesting that producers who creep feed calves prior to 4 mo of
age are receiving little benefit in terms of increased weight gains.
The LC and SC calves had higher (P<.01) average daily gains from 146 to
210 d of age than NC calves. The SC calves gained faster (P<.08) from
146 to 210 d of age than LC calves. This may have been a compensatory
response, since the LC calves had higher average daily gains from 118 to
146 d of age. Similar advantages for creep feeding of calves from about
60 d of age to weaning were reported by Kuhlman et al. (1961), Stricker
et al. (1979) and Martin et al. (1981). Burns et al. (1966) reported a
14 kg advantage due to creep feeding calves 60 d prior to weaning at 215
d of age. The 14 kg advantage is about half as much as was obtained in
this study for an equivalent time period.
The LC calves gained 28 kg more weight from 56 to 210 d of age than
did the NC calves. The LC calves consumed an average of 187 kg of creep
feed during this time and required 6.7 kg of creep feed per kilogram of
gain above the NC calves. The SC calves gained 22 kg more.than the NC
calves and had a creep efficiency of 5.3 kg of feed per additional
kilogram of gain. Creep feed efficiency did not differ (P>.15) between
LC and SC calves.
Spearman correlation coefficients between 146 and 210-d weights of
calves by creep treatments are presented in table 2. The rank-order
correlation coefficient for LC calves was .94, compared to .92 for both
NC and SC calves. The mean change in rank between 146 and 210-d weights
of NC and LC calves was 5 vs 6 positions for SC calves. Maximum change
in rank varied from 37 for NC calves to 16 for LC calves. These data
indicate that creep feeding may not necessarily mask the milk producing
differences among cows, as theorized by previous researchers (Christian
et al., 1965; Burns et al., 1966; Ochoa et al., 1981).
Calves implanted with zeranol were 9 kg heavier (P<.001) at 146 d of
age and 16 kg heavier (P<.001) at 210 d than non-implanted calves (table
1). These findings are in agreement with Corah (1980), who reported an
increase in weight gain of about 10 and 24 kg, respectively, for one and
two implants preweaning. Zeranol implanted LC and SC calves gained .18
and .14 kg/d more (P<.001), respectively, from 146 to 210 d of age than
did the non-implanted calves on the same creep treatments, whereas im-
planted NC calves gained .06 kg more (P<.10) than non-implanted NC
calves. These data suggest an additional growth response from zeranol
with increased nutrition, a finding similar to that reported by Davis
Calves produced by F1 dams were heavier (P<.001) than calves from
Angus dams at 146 and 210 d of age and had higher average daily gains
(P<.01) during all periods except from 146 to 210 d of age (table 1).
Breed of dam was confounded in this study with breed composition of
calf. All calves nursing F1 dams were 1/4 Brown Swiss, 1/4 Angus and
1/2 either Brahman or Romana Red breeding. Calves nursing Angus dams
were 1/2 Angus and 1/2 Brahman or Romana Red. Calves nursing reciprocal
crossbred Angus x Brown Swiss dams have been shown to grow more rapidly
than those nursing Angus dams (Gregory et al., 1978; Andrade, 1980;
Euclides et al., 1983). The additive response for growth rate obtained
from creep feed and milk consumption was partially confounded in this
study by the fact that calves with greater growth potential were nursing
dams with higher milk production. Euclides et al. (1983) showed that F1
dams produced about 1.5 kg/d more milk than Angus dams. These data do
not concur with the findings of Christian et al. (1965), Burns et al.
(1966) and Ochoa et al. (1981), who suggested that creep feeding tends
to mask the milk production differences among cows, and that calves
nursing poorer milking dams may compensate by eating more creep feed.
Wyatt et al. (1977) also stated that as milk intake of the calf
increases the non-milk inputs, forage and creep feed, are reduced.
There was no significant creep treatment by breed of dam interaction for
any calf trait. Rank-order correlations coefficients between 146 and
210-d weights were similar across both breeds of dam and creep
treatments (table 3).
The interaction of creep, zeranol and breed of dam affected (P<.03)
average daily gain from 146 to 210 d of age. The greatest response to
zeranol for average daily gain from 146 to 210 d of age was shown by SC
calves nursing Angus dams and by LC calves nursing Angus and F1 dams
(table 4). Zeranol implants increased (P<.03) the rate of gain from 146
to 210 d of age more in calves nursing Angus dams than in those nursing
F1 dams. Brahman-sired calves were heavier (P<.001) at 146 and 210 d of
age and had higher (P<.02) average daily gains from 56 to 210 d of age
than calves sired by Romana Red bulls.
Steer calves were heavier (P<.001) at 146 and 210 d of age and
gained faster in all periods (P<.001) than heifer calves (table 1). The
zeranol effect on 210-d weight was greater (P<.09) in steers than
in heifers. Implanted steers were 22 kg heavier at 210-d of age than
non-implanted steers, whereas the 210-d weight of implanted heifers was
11 kg heavier than that of non-implanted heifers. Davis (1980), on the
other hand, reported no significant zeranol treatment by sex of calf
interaction effect on calf weaning weight. Breed of dam by sex of calf
interaction affected 146-d (P<.05) and 210-d (P<.06) weights. Steer
calves nursing F1 dams were 25 and 33 kg heavier at 146 and 210 d of
age, respectively, than heifers nursing F1 dams. Comparable advantages
for steers nursing Angus dams over heifers nursing Angus dams were 14
and 20 kg.
Pasture, nested within creep treatment and year, affected (P<.003)
average daily gains from 56 to 118, 118 to 146, and 146 to 210 d of age.
Pastures were monitored each month for quality and quantity of available
forage. Available dry matter (kg) per cow-calf pair, mean pasture crude
protein percentage and mean pasture IVOMD percentage were used in depen-
dent analyses in an attempt to account for variability due to effect of
pasture. However, due to reduced R2 values and lack of agreement be-
tween actual means and least-square means, these covariables were
dropped from the final analyses in favor of the total effect of pasture.
Frame and Condition Scores. Least-squares means for frame and
condition scores are presented in table 1. Creep feeding did not affect
(P>.20) frame score at weaning. Stricker et al. (1979), on the other
hand, reported that creep feeding resulted in an increased frame size.
The LC calves were fatter (P<.001) at 146 d of age than calves not
receiving creep feed, and LC and SC calves were fatter (P<.001) than NC
calves at 210 d. There was no difference (P>.16) in condition score
between LC and SC calves at 210 d of age.
Zeranol implants did not affect (P>.23) frame score at weaning nor
condition score at 146 and 210 d of age. These results are in agreement
with those of Davis (1980) and Gerken et al. (1978). Corah (1980),
however, reported that calves implanted at birth with 36 mg of zeranol
and again at 4 mo of age had less condition at weaning than non-
Calves produced by F1 dams were larger framed (P<.001) than those
out of Angus dams, but had lower condition scores at 210 d (P<.03). The
F1 dams had been shown to produce more milk (Euclides et al., 1983) and
were nursing calves with one-fourth Brown Swiss breeding. These calves
were larger framed and later maturing, thus, did not fatten as early as
the one-half Angus calves nursing Angus dams. Brahman-sired calves had
larger frames (P<.001) than those sired by Romana Red bulls.
Steer calves were larger framed (P<.001) and thinner at 146 (P<.08)
and 210 d (P<.001) than heifer calves. Breed of dam by sex of calf
interaction affected (P<.06) frame score. Steers and heifers nursing Fl
dams had larger frames (3.5 and 3.0, respectively) than those nursing
Angus dams (2.8 and 2.6).
Least-squares means for cow weight change, condition score and
pregnancy rate are presented in table 5. Cow condition score at the
beginning of the breeding season did not differ (P>.57) among the three
calf creep-treatment groups. Cows with LC calves, however, gained more
(P<.09) weight during the 60-d breeding season and had a higher (P<.02)
average condition score at the end of the breeding season than those
nursing calves not receiving creep feed. Other authors have suggested
that increases in cow weight gain and condition due to creep feeding of
calves might result in a subsequent increase in pregnancy rate (Jones
and Jones, 1932; Stricker et al., 1979). In this study, however,
pregnancy rate was not affected (P>.46) by creep treatment of calf
(89.5% for the non-creep group vs 92.7% for the creep-fed group) even
though a difference did exist in cow weight change and condition score.
Creep treatment of the calf did not affect (P>.11) cow weight gain from
the end of the breeding season to July 1 but cows nursing SC and LC
calves gained more (P<.001) weight from July 1 until the calves were
weaned on September 1. Creep treatment of calf had no effect (P>.28) on
condition score of dam at weaning.
Weight gain, condition score and pregnancy rate of dam were not
affected by zeranol treatment of calves. In this study, zeranol
implanted calves gained more rapidly throughout the nursing period than
did non-implanted calves. Since zeranol implants in calves had no
affect on cow weight gain, condition score or pregnancy rate, the
increased weight gain of the calf apparently did not place an added
stress on the cow.
Angus cows gained less (P<.02) weight from the beginning of the
breeding season to July 1 but had higher (P<.001) condition scores than
did F1 cows. The Fl cows had a higher (P<.07) pregnancy rate than Angus
cows (96.6 vs 86.8%).
Cows nursing Brahman-sired calves gained more (P<.09) weight during
the breeding season than those nusring Romana Red-sired calves. There
was no difference, however, in weight gain of calves during the breeding
season due to breed of sire (table 1). Breed of sire of calf did not
affect (P>.19) cow condition score or pregnancy rate. Sex of calf did
not affect (P>.55) cow weight gain or condition score; however, cows
nursing heifer calves had a higher (P<.10) pregnancy rate than those
nursing steer calves.
It can be concluded that calves receive very little benefit from
creep feed prior to 120 d of age. Creep feeding calves from about 5 mo
of age until weaning at 7 mo results in more efficient utilization of
creep feed and almost as much increase in weight gain as creep feeding
from 2 mo of age. The effects of creep feed intake and milk intake on
preweaning weight gain were shown to be additive in calves with above
average growth potential. Increased levels of nutrition, from creep feed
and milk, should result in increased growth response to zeranol.
Pregnancy rate was not increased by creep feeding of calves when the
cows had adequate nutrition during the breeding season.
Andrade, V. J. 1980. Effect of nutritional level during late gestation
on the performance of two-year-old heifers. Ph.D. Dissertation Univ.
of Florida, Gainesville.
Burns, W. C., R. E. Deese and M. Koger. 1966. Creep feeding beef
calves in Florida: Effects on weight and market grade. USDA Prod.
Res. Rep. No. 88.
Christian, L. L., E. R. Hauser and A. B. Chapman. 1965. Association of
preweaning and postweaning traits with weaning weight in cattle. J.
Anim. Sci. 24:652.
Corah, L. R. 1980. The 1980's/ A new era in cattle management. Kansas
State Univ. Coop. Ext. Bull. L-557.
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certain factors and their two-way interactions on weaning weight in
beef cattle. J. Anim. Sci. 25:972.
Davis, D. I. 1980. Growth response of nursing calves to zeranol
implants. Texas Agr. Ext. Svc. Pub. 394-3644. p. 65.
Euclides, K., Filho, J. Restle, T. A. Olson, M. Koger and D. D.
Hargrove. 1983. Measures of efficiency of calf production from cows
of different size and milking ability. Florida Beef Cattle Res.
Rep. Univ. of Florida, Gainesville. p. 13.
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1978. Growth promoting implants A tool for profit in beef
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Agr. Exp. Sta. Bull. No. 470.
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creep-feeding fall calves until spring vs. weaning. J. Anim. Sci.
Lowman, B. 1980. The sequential implanting of beef cattle with Ralgro.
Ralgro Seminar, Ponteland, Newcastle upon Tyne. p. 1.
Martin, T. G., R. P. Lemenager, G. Srinivasan and R. Alenda. 1981.
Creep feed as a factor influencing performance of cows and calves.
J. Anim. Sci. 53:33.
Ochoa, P. G., W. L. Mangus, J. S. Brinks and A. H. Denham. 1981.
Effect of creep feeding bull calves on dam most probable producing
ability values. J. Anim. Sci. 53:567.
SAS. 1979. Statistical Analysis System User's Guide. SAS Institute
Inc., Cary, NC.
Scarth, R. D., R. C. Miller, P. J. Phillips, G. W. Sherritt and J. H.
Ziegler. 1968. Effects of creep feeding and sex on the rate and
composition of growth of crossbred calves. J. Anim. Sci. 27:596.
Stricker, J. A., A. G. Matches, G. B. Thompson, V. E. Jacobs, F. A.
Martz, H. N. Wheaton, H. D. Currence and G. F. Krause. 1979.
Cow-calf production on tall fescue-ladino clover pastures with and
without nitrogen fertilization or creep feeding: Spring calves. J.
Anim. Sci.. 48:13.
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acteristics of steers, steers implanted with zearalanol and bull
calves. Georgia Agr. Exp. Sta. Res. Rep. Univ of Georgia, Athens.
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cattle. Proc. 27th Annu. Beef Cattle Short Course. Univ. of
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J. Anim. Sci. 45:1138.
Short-Term Creep- -
168 182 196 210
Average daily creep
TABLE 1. LEAST SQUARES MEANS FOR CALF TRAITS.
Weight, kg Average daily gain, kg Frame score
Source of 146 210 56-146 56-118 118-146 146-210 56-210 score 146 210
variations n d d d d d d d 210 d d d
Breed of sire
Breed of dam
Table 1. Continued.
Weight, kg Average daily gain, kg Frame score
Source of 146 210 56-146 56-118 118-146 146-210 56-210 score 146 210
variation n d d d d d d d 210 d d d
Sex of calf
Probability level .001 .001 .001 .001 .001 .001 .001 .001 .08 .001
Steer 82 189 264 1.10 1.15 .99 1.17 1.13 3.1 9.4 10.4
Heifer 118 170 238 .98 1.06 .82 1.07 1.02 2.8 9.6 11.1
Mean 200 180 252 1.04 1.11 .91 1.12 1.08 3.0 9.5 10.8
RSD 16 21 .12 .16 .28 .14 .11 .5 .9 1.0
ayear influenced (P<.05) 146 and 210-d weights, daily gains in all periods except 118-146 d of age and
146-d condition score. Pasture nested within creep and year affected (P<.004) average daily gains from
56-118 d, 118-146 d and 146-210 d of age. Creep x year interaction affected (P<.05) 146-d weight. The
creep x zeranol interaction affected (P<.08) average daily gains from 56-118 d and 146-210 d. The creep
x breed of dam x zeranol interaction affected (P<.08) average daily gain from 146-210 d of age and 146-d
condition score. The breed of dam x zeranol interaction affected (P<.03) average daily gain from 146-210
d of age. The breed of dam x sex of calf interaction affected (P<.06) 146 and 210-d weights and frame
score. The zeranol x sex of calf interaction affected (P<.09) 210-d weight and condition score and
average daily gains from 56-146 d and 146-210 d of age.
Residual standard deviation.
TABLE 2. SPEARMAN CORRELATION COEFFICIENTS BETWEEN 146 AND
210-DAY WEIGHTS OF CALVES BY CREEP TREATMENT
Creep Meana Maximuma
Treatment Rs Change Change
NC .92 5 37
SC .92 6 27
LC .94 5 16
aExpressed as absolute values for changes in rank
TABLE 3. SPEARMAN CORRELATION COEFFICIENTS BETWEEN 146 AND
210-DAY WEIGHTS OF CALVES BY CREEP TREATMENT AND BREED OF
Breed of Creep Treatment
dam NC SC LC
R .94 .90 .88
Angus Mean change 2 3 3
Maximum change 6 7 8
R a .92 .91 .93
Fl Mean change a 3 4 4
Maximum change 18 12 12
aExpressed as absolute values for changes in rank.
TABLE 4. LEAST SQUARES MEANS FOR AVERAGE DAILY GAIN
FROM 146 TO 210 DAYS OF AGE BY CREEP TREATMENT, ZERANOL
TREATMENT AND BREED OF DAM
Creep treatment No No
zeranol Zeranol zeranol Zeranol
NC 0.83 0.91 0.90 0.94
SC 1.12 1.38 1.24 1.25
LC 1.07 1.26 1.15 1.33
Mean 1.02 1.19 1.10 1.17
TABLE 5. LEAST SQUARES MEANS FOR COW TRAITS
Weight change, kg Condition score
Source ofa Entire End of July 1 Beginning of End of breeding
variation breeding Breeding to to breeding season, Weaning, Pregnancyb
n season July 1 Weaning season, April 1 June 1 Sept. 1 %
Probability level .26
No zeranol 101 51.8
Zeranol 99 55.5
Breed of sire of calf
Probability level .09
Brahman 111 57.0
Romana Red 89 50.3
Breed of cow
Probability level .007
Angus 77 49.2
F1 123 58.2
Table 5. Continued.
Weight change, kg Condition score
Source ofa Entire End of July 1 Beginning of End of breeding b
variation breeding Breeding to to breeding season, Weaning, Pregnancy
n season July 1 Weaning season, April 1 June 1 September 1 %
Sex of calf
Probability level .75 .59 .61 .59 .55 .56 .10
Steer 82 53.8 5.8 18.1 5.7 7.0 7.7 88.6
Heifer 118 53.5 3.7 17.0 5.7 7.1 7.6 94.8
Mean 200 54.6 5.3 17.3 5.7 7.1 7.6 93.0
RSDc 19.6 14.9 13.9 .9 .9 1.1 24.7
year influenced (P<.002) all cow traits except pregnancy rate.
Pasture nested within creep and year affected (P<.002) weight change in all periods and condition scores
at the end of the breeding season (P<.10) and at weaning (P<.03), and also affected pregnancy rate
The creep x year interaction affected (P<.001) weight change in all periods and condition score at weaning
Breed of sire of calf x breed of cow interaction influenced (P<.04) condition score at weaning.
In the analysis of variance for pregnancy rate there were only two creep treatments.
Short-term creep-fed calves were considered as non-creep.
Residual standard deviation.