00
BEEF PRODUCTION IN RELATION TO CREEP FEEDING, ZERANOL
IMPLANTS AND BREED TYPE: II. WEANLING HEIFER DEVELOPMENT
AND COMPOSITION
D. L. Prichard*, T. T. Marshall, D. D. Hargrove,
and T. A. Olson
University of Florida,
Gainesville 32611
D. L. Prichard* T. T. Marshall, D. D. Hargrove, and T. A. Olson, 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 88-11.
*Corresponding author.
Abstract
Effects of preweaning creep feeding and zeranol implants on repro-
ductive tract development, udder and subcutaneous fat deposition, and
carcass composition were studied in 24 weanling heifers sired by Brahman
and Romana Red bulls and out of Angus and Angus x Brown Swiss F1
reciprocal crossbred cows. Creep treatment did not affect (P>.19)
ovarian weight, ovarian size, uterine horn diameter nor follicle number.
Heifers from the three creep treatments did not differ (P>.25) in udder
weight, total lipid or percent lipid in the udder. The noncreep-fed
(NC) heifers had a greater (P<.02) number of adipocytes per g of udder
tissue than did the long-term creep fed (LC) and short-term creep-fed
(SC) heifers. The LC heifers had significantly larger udder (166.0 vs
152.7 m) and subcutaneous adipocytes (166.7 vs 148.8 m) than NC
heifers. LC heifers had heavier (P<.10) empty body and hot carcass
weights than SC and NC heifers. Carcasses from LC heifers had more
(P<.04) separable fat, less (P<.11) separable lean and less (P<.05)
edible protein than carcasses from SC and NC heifers. Heifers implanted
with zeranol had a greater (P<.03) uterine horn diameter and heavier
(P<.02) uterine weight than non-implanted heifers. Percent lipid in the
udder was lower (P<.02) in heifers implanted with zeranol. Total udder
adipocytes did not differ (P>.22) between implanted and non-implanted
heifers; however, implanted heifers had smaller (P<.10) subcutaneous
adipocytes than non-implanted heifers. Implanted heifers had higher
(P<.02) cutability carcasses (lower yield grade number) than non-
implanted heifers. Zeranol implants increased carcass lean color
(P<.05) and maturity (P<.006). Zeranol decreased (P<.09) percent
separable fat and increased (P<.008) separable lean in the carcass.
Breed of dam did not affect (P>.17) development of the reproductive
tract of weanling heifers. Heifers from Angus dams had smaller (P<.08)
udders and less (P<.10) total fat in the udder than those from Fl dams,
and the heifers from Fl dams tended (P<.12) to have larger udder
adipocytes. Estimated separable and edible carcass components were not
affected (P>.19) by breed of dam. Brahman-sired heifers had a greater
ovarian weight (P<.04) and size (P<.02) than Romana Red-sired heifers.
Brahman-sired heifers had more (P<.004) total udder adipocytes;whereas,
Romana Red-sired heifers tended (P<.14) to have larger udder adipocytes.
Breed of sire did not affect (P>.18) estimated carcass composition or
USDA quality and yield grade traits.
(Key Words: Creep, Zeranol, Brahman, Romana Red, Reproductive tract,
Adipocytes, Carcass composition)
Introduction
The effects of creep feeding and preweaning growth stimulants on
future reproductive performance and maternal ability of replacement
heifers are of concern to many cattlemen. Most commercial cattlemen
sell some of their weaned heifers as feeder-stocker calves. By using
creep feed and growth stimulants, cattlemen can sell these heifers at
heavier weights and for more total dollars.
Excessive conditioning or fattening of suckling heifers may
influence subsequent development of desired maternal traits (Holloway
and Totusek, 1973). A detrimental effect of above average maternal
environment during the early life of heifer calves on their subsequent
producing ability has been shown by Mangus and Brinks (1971), Kress and
Burfening (1972) and Beltran (1978). Swanson (1960) and Holtz et al.
(1961) suggested that over-conditioned dairy heifers deposited excess
fat in their mammary system, and that this decreased future milk pro-
duction potential.
The effects of growth stimulants on future reproductive performance
of heifers are not well known. An important issue, from the producer's
point of view, is not whether creep feeding and growth stimulants
improve weaning weight, but how these practices affect future productive
potential of replacement heifers.
The purpose of this portion of the study was to evaluate the effects
of creep feeding, preweaning zeranol implants and breed type on repro-
ductive tract development, fat deposition in the udder, and body compo-
sition of weanling heifers.
Experimental Procedure
The preweaning creep feeding, zeranol treatments and breed types
compared in this study were described previously (Prichard et al.,
1988). Twenty-four weanling heifers used in this study were slaughtered
one day following weaning at about 7 mo of age. The gastrointestinal
tract from each heifer was cleaned of digesta for determination of empty
body weight. Carcasses were USDA quality and yield graded after a 24-h
chill at 1 to 2 C. The 9-10-11 rib section from the right side of each
carcass was removed and physically separated into fat, lean and bone to
estimate separable carcass components, as outlined by the procedure of
Hankins and Howe (1946). The soft tissue components (lean .plus fat) of
the 9-10-11 rib section were thoroughly mixed, ground and analyzed for
chemical composition by AOAC (1980) procedures. Chemical determinations
of the soft tissue components were used to estimate edible fat, protein
and moisture, according to the prediction equations developed by Hankins
and Howe (1946).
Reproductive tracts were removed from each heifer at time of
slaughter. Ovaries were weighed, measured and follicles larger than 3
mm in diameter were counted. Uterine weight (horns and body of uterus)
was recorded, and the outside diameter of the right uterine horn was
measured at the bifurcation. The udder was removed and weighed. One-
half of each udder was ground and sampled for percent lipid. Percent
lipid was determined using the Soxhlet Ether Extraction procedure
according to AOAC (1980).
Adipose tissue samples were taken from the udder and tail-head
region of each heifer. The subcutaneous sample from the tail-head
region was taken 5 cm to the right of the tail-head. Three thin slices
(approximately 200 mg) were obtained from each tissue sample using a
Stadie-Riggs microtome. Slices were fixed with 5 ml of 3% osmium
tetroxide and 3 ml of 50 mM collidine-HCL buffer solution (pH 7.4), as
described by Hirsch and Gallian (1968). The connective tissue matrix
surrounding the adipocytes was solubilized with 8 M urea as described by
Etherton et al. (1977). Adipocytes were rinsed through a 250- m nylon
screen with distilled water containing .01% triton X-100 (pH 10) into
200 ml volumetric flasks. A NaC1 solution (.154 M) was added to
increase volume to 200 ml. Duplicate 10 ml aliquots were removed from
each flask, added to 190 ml of a 45% sucrose solution, counted and sized
using a Coulter Counter Model TA II. A 560- m aperture was used. A
77.8- m standard of corn pollen was used to determine the volume of each
of the instrument's 16 channels. Standard particles and fixed
adipocytes were assumed to be spherical.
Data were analyzed by least-squares, fixed model procedures using
the Statistical Analysis System (SAS, 1979). The model used to analyze
all response variables included the fixed main effects of year, creep
treatment, zeranol treatment, breed of sire and breed of dam. Age at
the time of slaughter was included as a covariate. All interactions
were pooled and remained in the error term. Linear contrasts of the
least-squares means for creep treatments were computed for all response
variables affected (P<.10) by creep treatment.
Results and Discussion
Reproductive Tract Development. Least-squares means and probability
values for reproductive tract characteristics are shown in table 1.
Creep treatment did not affect (P>.19) ovarian weight, ovarian size,
uterine horn diameter nor follicle number of weanling heifers. Long-
term (LC) and short-term (SC) creep-fed heifers tended (P<.11) to have
heavier uterine weights than noncreep-fed (NC) heifers. No comparable
data were found in the literature. Cornwell (1981) fed long-yearling
heifers on three levels of nutrition and reported no significant effect
of nutritional level on ovarian size or weight or on uterine horn
diameter. Research by Hill et al. (1970) and Spitzer et al. (1978),
using long-yearling and yearling heifers, respectively, indicated that
ovarian size was reduced when heifers were on a restricted plane of
nutrition.
Heifers implanted with 36 mg of zeranol at 56 and 146 d of age had a
greater (P<.03) uterine horn diameter and heavier (P<.02) uterine weight
than non-implanted heifers. There was no effect (P>.20) of zeranol
implant on ovarian weight, size or number of follicles.
Breed of dam did not affect (P>.17) the development of the repro-
ductive tract of the weanling heifers. Brahman-sired heifers had a
greater ovarian weight (P<.04) and size (P<.02) than Romana Red-sired
heifers. Uterine horn diameter, uterine weight and follicle number were
not affected (P>.14) by breed of sire. The differences in ovarian
weight and size due to breed of sire may have been due to differences in
size of the heifers. Brahman-sired heifers weighed more (P<.02) at
slaughter than Romana Red-sired heifers (233 vs 211 kg). Foley et al.
(1964), using dairy cattle of all ages, reported a significant
correlation (.65) between weight of both ovaries and live weight. They
stated that age and live weight appeared to have more effect on ovarian
weight than did breed. However, the LC heifers in this study were
heavier (P<.02) at slaughter than NC heifers, yet there were no differ-
ences in ovarian size and weight due to creep treatment. Therefore, the
differences found in ovarian size and weight between the Brahman and
Romana Red-sired heifers may have been due to genetic differences,
independent of body size.
Udder and Subcutaneous Fat. Creep feeding did not increase (P>.25)
udder weight, percent lipid nor total lipid in the udder (table 2).
Though not significant, the least-squares means would indicate a
tendency for heifers to deposit more fat in the udder as length of creep
feeding increases. The NC heifers had a greater (P<.02) number of
adipocytes per g of udder tissue than did the LC and SC heifers;
however, the total number of adipocytes in the udder was not affected
(P>.58) by creep treatment. The LC heifers had larger (P<.04) udder and
subcutaneous adipocytes than NC heifers (166.0 and 166.7 m vs 152.7 and
148.8 m, respectively). The SC heifers tended (P<.15) to have larger
udder and subcutaneous adipocytes than NC heifers. Subcutaneous
adipocyte number per g of tissue was not affected (P>.49) by creep
treatment. Figure 1 illustrates the size distribution of adipocytes by
creep treatment. The LC and SC heifers had higher (P<.10) percentages
of total adipocyte volume composed of adipocytes greater than 160 m in
diameter than did NC heifers, whereas NC heifers had the highest (P<.05)
percentage of total adipocyte volume made up of adipocytes less than 129
m in diameter.
Data reported by Hood and Allen (1973), Allen (1976) and Garbutt et
al. (1979) indicate that adiposity in cattle may be influenced by
nutritional treatment during periods of growth and development. Allen
(1976) stated that changes in bovine cellular hypertrophy and hyper-
plasia are dependent on the location of the fat depot. He indicated
that intramuscular lipid accumulation is more dependent on cellular
hyperplasia than are subcutaneous depots. Results of this study would
indicate that cellular hypertrophy had occurred in the udder and sub-
cutaneous fat depots of creep-fed heifers. Therefore, any increase in
lipid accumulation in these fat depot areas would be due primarily to
adipocyte hypertrophy rather than hyperplasia.
Zeranol implants did not affect (P>.98) udder weight. Percent udder
lipid was lower (P<.02) in heifers implanted with zeranol; however,
total udder lipid was not affected (P>.68). Implanted heifers had more
(P<.07) adipocytes per g of udder tissue and tended (P<.14) to have
smaller udder adipocytes than non-implanted heifers. Total udder
adipocytes did not differ (P>.22) between implanted and non-implanted
heifers (8.55 and 7.06 x 109, respectively). Zeranol treatment did not
affect (P>.65) number of subcutaneous adipocytes per g of tissue;
however, implanted heifers had smaller (P<.10) subcutaneous adipocytes
than non-implanted heifers. Size distribution of udder and subcutaneous
adipocytes by zeranol treatment is shown in figure 2.
Heifers out of Angus dams had smaller (P<.08) udders and less
(P<.10) total fat in the udder than those from F1 dams (2.91 vs 3.49 kg
and 2.37 vs 2.86 kg). Breed of dam did not affect (P>.44) percent lipid
in the udder. Total udder adipocytes and udder adipocytes per g of
tissue were not affected (P>.35) by breed of dam. Heifers out of Fl
dams tended (P<.12) to have larger udder adipocytes than those produced
by Angus dams. Subcutaneous adipocyte size and number were not affected
(P>.61) by breed of dam.
Brahman-sired heifers had larger (P<.001) udders (3.85 vs 2.55 kg)
and more total fat in their udders (3.15 vs 2.08 kg) than Romana
Red-sired heifers. Percent lipid in the udder, however, was unaffected
(P>.78) by breed of sire. Number of udder adipocytes per g of tissue
was not affected (P>.31) by breed of sire. But as a result of more
total fat in the udder, Brahman-sired heifers had more (P<.004) total
adipocytes than those sired by Romana Red bulls. Romana Red-sired
heifers, however, tended (P<.14) to have larger udder adipocytes than
Brahman-sired heifers. In addition, Romana Red-sired heifers had fewer
(P<.08) adipocytes per g of subcutaneous adipose tissue but larger
(P<.09) subcutaneous adipocytes than those sired by Brahman bulls.
Breed type has been used to provide an explanation for differences
in adiposity in several studies; however, there have been few studies
specifically designed to investigate variations in adipocyte size and
number among breeds. Hood and Allen (1973, 1975) reported that
perirenal and subcutaneous adipose tissue in 14-mo-old Hereford x Angus
steers contained larger cells than the respective tissues from Holstein
steers of similar age and live weight. In addition, they observed that
a higher percentage of the total adipocyte volume for Hereford x Angus
steers was in the larger cell diameter ranges than for the same tissues
from Holstein steers. Figures 3 and 4 illustrate the distribution of
udder and subcutaneous adipocytes for breed of sire and breed of dam.
Carcass Characteristics and Composition. Least-squares means for
carcass characteristics and composition are shown in tables 3, 4 and 5.
The LC heifers had heavier (P<.005) empty body weights and less (P<.02)
gastrointestinal tract (GIT) fill than NC heifers. The LC heifers also
had heavier (P<.002) hot carcass weights and higher (P<.02) dressing
percentages than NC heifers. The LC heifers had heavier (P<.10) empty
body and hot carcass weights than SC heifers, but there was no dif-
ference (P>.21) in GIT fill or dressing percentage between heifers of
the two creep treatments. The SC heifers did not differ (P>.10) from NC
heifers for empty body weight, GIT fill, hot carcass weight or dressing
percentage.
Yield grade was not affected by creep treatment; however, carcasses
from LC heifers had more (P<.06) KPH fat, greater (P<.003) fat thick-
nesses and larger (P<.007) ribeyes than NC and SC heifers. Carcasses
from SC and NC heifers did not differ (P>.17) for KPH fat, fat thickness
or ribeye area. Ribeye area expressed as cm2 per 100 kg hot carcass
weight was not influenced (P>.84) by creep treatment. Creep treatment
did not affect (P>.47) marbling score, carcass maturity, lean color nor
fat color. Similar effects of long-term creep feeding on carcass
characteristics of weanling calves were reported by Scarth et al.
(1968), Corah and Bishop (1975) and Martin et al. (1980). Rouquette et
al. (1983), on the other hand, found no differences in carcass
characteristics between long-term and noncreep-fed calves.
Carcasses from LC heifers had a lower percent edible protein (P<.06)
than carcasses from NC and SC heifers (table 5). Creep treatment did
not affect (P>.26) percent edible fat or moisture in the carcass. The
LC heifers had a higher (P<.04) percent separable fat and tended (P<.11)
to have a lower percent separable lean content of the carcass than SC
and NC heifers. Carcasses from SC heifers had a higher (P<.07) percent
bone than carcasses from LC heifers, but did not differ (P>.17) from
those of NC heifers. Contrary to the above, Corah and Bishop (1975)
reported no difference in percent protein of carcasses between
noncreep-fed and creep-fed heifers slaughtered at weaning. Furthermore,
they observed that carcasses from noncreep-fed heifers had a higher
percent bone than those from creep-fed heifers.
The SC and NC heifers did not differ (P>.11) with respect to any
carcass trait including slaughter weight and hot carcass weight.
However, in the population from which these heifers were chosen, SC
calves were heavier (P<.001) at 210-d of age than NC calves.
Zeranol implants did not affect (P>.20) empty body weight, GIT fill,
hot carcass weight or dressing percent. Implanted heifers had higher
(P<.02) cutability carcasses (lower yield grade number) than non-
implanted heifers. Percent KPH and fat thickness were not affected
(P>.20) by zeranol treatment, but ribeye areas were larger (P<.06) in
the implanted heifers. The larger ribeye accounted for the lower yield
grade number of the carcasses from implanted heifers. Marbling score
and fat color were not affected (P>.41) by zeranol treatment; however,
zeranol implants increased lean color (P<.006) and maturity (P<.05), and
overall maturity (P<.07). Bone maturity was not affected (P>.17) by
zeranol. These results indicate that zeranol affects carcass traits
associated with body weight, and may increase maturity rate, as measured
by characteristics of the muscle. Gregory and Ford (1983), using late-
maturing bull calves, concluded that zeranol treatment effects on
carcass characteristics were of little consequence other than through
increases in body weight.
Estimated edible fat, protein and moisture in the carcass were not
affected (P>.30) by zeranol implants. Zeranol, however, did cause a
decrease in the percent separable fat (P<.09) and an increase (P<.008)
in the percent separable lean in the carcass. Percent separable bone
was not affected (P>.23) by zeranol treatment. Similar results for
estimated carcass components, using yearling steers, were reported by
Sharp and Dyer (1971).
Breed of dam did not affect (P>.23) empty body weight, GIT fill, hot
carcass weight nor dressing percent. Carcasses from heifers out of
Angus dams had more (P<.08) ribeye area per 100 kg of hot carcass weight
and tended (P<.11) to have less KPH fat than those out of F1 dams. This
resulted in a tendency for carcasses from heifers out of Angus dams to
be higher (P<.12) yielding than those out of F1 dams. Carcass fat
thickness, maturity, lean color and fat color were unaffected (P>.48) by
breed of dam. Estimated edible and separable carcass components were
not affected (P>.19) by breed of dam.
Brahman-sired heifers had heavier empty body (P<.009) and hot
carcass (P<.02) weights than Romana Red-sired heifers. Breed of sire
did not affect (P>.18) GIT fill, dressing percent, quality and yield
grade components, nor estimated carcass composition. These results are
in agreement with Koch et al. (1982) who mated Angus and Hereford cows
to various breeds of bulls and reported no differences in carcass
characteristics between Brahman and Sahiwal-sired steers, other than
Brahman-sired steers had heavier carcass weights.
These data indicate that an increase of subcutaneous fat in
long-term creep-fed heifers is due primarily to adipocyte hypertrophy.
Creep feeding also increases adipocyte size in the udder. Heifers
implanted preweaning with zeranol have a lower percent lipid in the
udder and smaller udder and subcutaneous adipocytes than non-implanted
heifers. Zeranol implants increase ribeye area and percent separable
lean and decrease percent separable fat in the carcasses of weanling
heifers.
LITERATURE CITED
Allen, C. E. 1976. Cellularity of adipose tissue in meat animals.
Fed. Proc. 35:2302.
AOAC. 1980. Official Methods of Analysis (13th Ed.) Association of
Official Analytical Chemists, Washington, DC.
Beltran, J. J. 1978. Evaluation of direct and maternal effects on
weaning traits in Brahman cattle. Ph.D. Dissertation. Univ. of
Florida, Gainesville.
Corah, L. R. and A. H. Bishop. 1975. Effect of creep feeding oat grain
to beef calves on their growth rate, carcass composition and
postweaning performance in a feedlot. Australian J. Exp. Agr. Anim.
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Cornwell, D. G. 1981. A comparison of the reproductive performance of
Brahman and Angus heifers on three levels of nutrition. M.S.
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Etherton, T. D., E. H. Thompson and C. E. Allen. 1977. Improved
techniques for studies of adipocyte cellularity and metabolism. J.
Lipid Res. 18:552.
Foley, R. C., D. L. Black, W. G. Black, R. A. Damon and G. R. Howe.
1964. Ovarian and luteal tissue weights in relation to age, breed
and live weight in nonpregnant and pregnant heifers and cows with
normal reproductive histories. J. Anim. Sci. 23:752.
Garbutt, G. J., W. B. Anthony, D. F. Walker and J. A. McGuire. 1979.
Perirectal adipose tissue development of postweaned rapidly growing
bull calves. J. Anim. Sci. 48:525.
Gregory, K. E. and J. J. Ford. 1983. Effects of late castration,
zeranol and breed group on growth, feed efficiency and carcass
characteristics of late maturing bovine males. J. Anim. Sci. 56:771.
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beef carcasses and cuts. USDA Tech. Bull. No. 926.
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Niswender. 1970. The effects of undernutrition on ovarian function
and fertility of beef heifers. Biol. Reprod. 2:78.
Hirsch, J. and E. Gallian. 1968. Methods for the determination of
adipose cell size in man and animals. J. Lipid Res. 9:110.
Holloway, J. W. and R. Totusek. 1973. Relationship between preweaning
nutritional management and subsequent performance of Angus and
Hereford females through three calf crops. J. Anim. Sci. 37:807.
Holtz, E. W., R. E. Erb and A. S. Hodgson. 1961. Relationship between
rate of gain from birth to six months of age and subsequent yields
of dairy cattle. J. Dairy Sci. 44:672.
Hood, R. L. and C. E. Allen. 1973. Cellularity of bovine adipose
tissue. J. Lipid Res. 14:605.
Hood, R. L. and C. E. Allen. 1975. Bovine lipogenesis: Effects of
anatomical location, breed and adipose cell size. Int. J. Biochem.
6:121.
Koch, R. M., M. E. Dikeman and J. D. Crouse. 1982. Characterization of
biological types of cattle (Cycle III). III. Carcass composition,
quality and palatability. J. Anim. Sci. 54:35.
Kress, D. D. and P. J. Burfening. 1972. Weaning weight related to
subsequent most probable producing ability in Hereford cows. J.
Anim. Sci. 35:327.
Mangus, W. L. and J. S. Brinks. 1971. Relationship between direct and
maternal effects on growth in Herefords. I. Environmental factors
during preweaning growth. J. Anim. Sci. 32:17.
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traits of and preweaning creep feeding effects on steers sired by
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Prichard, D. L., D. D. Hargrove, T. A. Olson and T. T. Marshall. 1988.
Effects of creep feeding, zeranol implants and breed type on beef
production: I. Calf and Cow Performance. J. Anim. Sci.(submitted).
Rouquette, F. M., Jr., R. R. Riley and J. W. Savell. 1983. Electrical
stimulation, stocking rate and creep feed effects on carcass traits
of calves slaughtered at weaning. J. Anim. Sci. 56:1012.
SAS. 1979. Statistical Analysis System User's Guide. SAS Institute
Inc., Cary, NC.
Scarth, R. D., R. C. Miller, P. J. Phillips, G. W. Sheritt 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.
Sharp, G. D. and I. A. Dyer. 1971. Effect of zearalanol on the
performance and carcass composition of growing-finishing ruminants.
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Spitzer,.J. C., G. P. Niswender, G. E. Seidel, Jr., and J. N. Wiltbank.
1978. Fertilization and blood levels of progesterone and LH in beef
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SUDDER
] SUBCUTANEOUS
ri
CREEP NC ISC LC NC SC LC NC SC LC NC LC NCC SC LC NC S LC
TREATMENT I I
DIAMETER, .m
8-25
26-80
81-128
129-160
161-202
203-320
Figure 1. Udder and subcutaneous adipocyte size distribution for noncreep (NC), short-term (SC) and
long-term (LC) creep-fed weanling heifers.
40.0 r
35.0
30.0
25.0
20.0
15.0 -
10.0
5.0 -
::: :::
:::::::
40.0
30 UDDER
n 35.0 -
S30.0 SUBCUTANEOUS
_ 25.0 .
I-
O 20.0
O 15.0
W 10.0
a. 5.0
ZERANOL NZ Z NZ Z NZ Z NZ Z NZ Z NZ Z
TREATMENT I I| I a _
DIAMETER, pmm 8-25 26-.7,0 81-128 129-160 161-202 203-320
Figure 2. Udder and subcutaneous adipocyte size distribution for weanling heifers not implanted (NZ) and
implanted (Z) with zeranol.
Ij: UDDER
I SUBCUTANEOUS
DIAMETER, .Lm
Figure 3.
heifers.
8-25
26-80
81-128
129-160 161-202 203-320
Udder and subcutaneous adipocyte size distribution for Brahman and Romana Red-sired weanling
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0
I
li.
0
I-
U
0:
(L
UDDER
H SUBCUTANEOUS
DIAMETER, p.m 8-25 26-80 81-128 129-160 161-202 203-320
Figure 4. Udder and subcutaneous adipocyte size distribution for weanling heifers from Angus and F1 Angus
x Brown Siwss dams.
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
TABLE 1. LEAST-SQUARES MEANS FOR REPRODUCTIVE TRACT CHARACTERISTICS
Uterine Number
Source of Ovarian Ovarian3 horn Uterine of
variation n weight, g size, cm diameter, mm weight, g follicles
Creep treatment
Probability level
No creep
Short-term
Long-term
Zeranol treatment
Probability level
No zeranol
Zeranol
Breed of sire
Probability level
Brahman
Romana Red
Breed of dam
Probability level
Angus
F1
Mean
RSDC
.37
2.06
2.50
2.71
.24
2.66
2.18
.04
2.87
1.97
.17
2.69
2.15
2.42
.91
.19
2.87
4.08
4.50
.20
4.31
3.32
.02
4.81
2.82
.18
4.32
3.31
3.82
1.73
.45
13.94
15.04
15.27
.03
13.61
15.89
.32
15.22
14.28
.59
14.50
15.00
14.75
2.17
.11
22.86
33.76
29.51
.02
23.44
33.97
.14
31.88
25.54
.49
27.32
30.10
28.71
9.55
aYear influenced ovarian size
bTotal of both ovaries.
CResidual standard deviation.
(P<.10) and number of follicles (P<.04).
.21
10.20
15.30
21.00
.90
15.20
15.80
.67
16.60
14.40
.27
18.20
12.80
15.50
11.40
TABLE 2. LEAST-SQUARES MEANS FOR UDDER AND SUBCUTANEOUS FAT PARAMETERS
Total Udder Total Udder Subcutaneous Subcutaneous
Udder Udder udder adipocyte Udder adipocyte adipocyte adipocyte
Source ofa weight, lipid, lipid, number/g6 adipocyte diameter, number/g diameter,
variation n kg % kg tissue (10 ) number (10 ) m tissue (10 ) m
Creep treatment
Probability level .25 .43 .28 .02 .58 .09 .49 0.08
No creep 8 2.89 79.82 2.35 3.05 8.60 152.70 3.36 148.80
Short-term 8 3.18 80.82 2.58 2.12 7.19 162.80 2.94 160.20
Long-term 8 3.54 82.56 2.91 2.13 7.63 166.00 2.93 166.70
Zeranol treatment
Probability level .98 .02 .68 .07 .22 .14 .65 .10
No zeranol 12 3.20 83.53 2.67 2.16 7.06 164.30 3.00 164.10
Zeranol 12 3.21 78.61 2.55 2.71 8.55 156.70 3.15 153.00
Breed of sire
Probability level .001 .78 .002 .31 .004 .14 .08 .09
Brahman 12 3.85 80.82 3.15 2.58 9.77 156.70 3.39 152.80
Romana Red 12 2.55 81.32 2.08 2.29 5.84 164.30 2.76 164.30
Breed of dam
Probability level .08 .44 .10 .35 .52 .12 .69 .61
Angus 12 2.91 80.39 2.37 2.56 7.44 156.50 3.15 156.90
F1 12 3.49 81.76 2.86 2.30 8.17 164.40 3.01 160.20
Mean 24 3.20 81.07 2.61 2.43 7.81 160.50 3.08 158.50
RSD .75 4.16 .68 .66 2.72 11.70 .79 14.90
year influenced (P<.04) all traits except % lipid in the udder.
Residual standard deviation.
TABLE 3. LEAST-SQUARE MEANS FOR EMPTY BODY WEIGHT, GASTROINTESTINAL TRACT FILL,
HOT CARCASS WEIGHT AND DRESSING PERCENT
Empty Gastrointestinal Hot
Source ofa body tract fill, carcass Dressing,
variation n weight, kg kg weight, kg %
Creep treatment
Probability level
No creep
Short-term
Long-term
Zeranol treatment
Probability level
No zeranol
Zeranol
Breed of sire
Probability level
Brahman
Romana Red
Breed of dam
Probability level
Angus
F.
Mean
RSDc
.02
195.30
209.50
226.20
.26
205.80
214.90
.009
222.10
198.70
.23
205.50
215.20
24 210.40
18.70
.06
13.80
11.60
9.30
.66
11.20
11.90
.40
11.00
12.20
.41
12.10
11.00
11.60
3.30
.007
122.90
133.40
145.70
.20
130.60
137.40
.02
140.80
127.20
.25
131.00
137.00
134.00
12.10
.06
62.85
63.74
64.37
.47
63.47
63.84
.22
63.34
63.97
.78
63.72
63.58
63.65
1.17
aYear influenced hot carcass weight (P<.04) and dressing % (P<.004).
Dressing % = (hot carcass weight/empty body weight) x 100.
cResidual standard deviation.
TABLE 4. LEAST-SQUARES MEANS FOR CARCASS CHARACTERISTICS
Ribeye
USDA Fat Ribeye area/100 kg d
Source of yield KPH, thickness, area, hot carcass, Marbling Maturity Lean Fat
variation n grade % cm cm cm score lean bone overall colore color
Creep treatment
Probability
level
No creep
Short-term
Long-term
Zeranol treatment
Probability
level
No zeranol
Zeranol
Breed of sire
Probability
level
Brahman
Romana Red
.22
2.30
2.20
2.50
.02
2.50
2.10
.66
2.40
2.30
.06
2.42
2.49
3.28
.20
2.93
2.52
.99
2.73
2.73
.003
.40
.41
.75
.007
43.70
46.60
51.40
.004
44.30
50.10
.18
48.40
46.00
.84
36.00
35.00
35.40
.06
34.00
36.90
.25
34.60
34.30
.71
3.50
2.70
3.80
.41
3.80
2.90
.94
3.30
3.40
.52
C 85
C 71
C 83
.05 .17
69 C 72
94 C 88
.52
C 81
C 73
C 87
.07
C 70
C 91
.81 .87 .83
83 C 81 C 82
80 C 79 C 79
.52
4.70
4.80
5.20
.006
4.40
5.50
.57
4.80
5.00
.94
2.20
2.20
2.20
.55
2.30
2.10
.55
2.10
2.30
Table 4. Continued.
Ribeye
USDA b Fat Ribeye area/100 kg d
Source of yield KPH, thickness, area, hot carcass, Marbling Maturity Lean Fat
variation n grade % cm cm cm score lean bone overall color color
Breed of dam
Probability
level .12 .11 .99 .63 .08 .69 .60 .69 .59 .48 .65
Angus 12 2.20 2.48 .52 47.60 36.70 3.10 C 78 C 78 C 78 4.80 2.20
F1 12 2.50 2.98 .52 46.80 34.20 3.60 C 84 C 82 C 83 5.00 2.30
Mean 24 2.30 2.73 .52 47.20 35.50 3.30 C 81 C 80 C 80 4.90 2.20
RSD9 .3 .72 .19 4.10 3.20 2.60 C 27 C 26 C 24 .80 .60
year influenced (P<.02) lean color.
Kidney, pelvic and heart fat.
c2 = practically devoid average; 3 = practically devoid +; and 4 = traces -.
dEvaluated by percentages (0-100%) within a maturity score, C = calf.
eLean color scores were as follows: 4 = cherry red and 5 = moderately dark red.
Fat color scores were as follows: 1 = white; 2 = cream; and 3 = slightly yellow.
gResidual standard deviation.
TABLE 5. LEAST-SQUARES MEANS FOR ESTIMATED CARCASS COMPOSITION
Estimated carcass compositionb
Source of Edible Edible Edible Separable Separable Separable
variations n fat, % protein, % moisture, % fat, % lean, % bone, %
Creep treatment
Probability level
No creep
Short-term
Long-term
Zeranol treatment
Probability level
No zeranol
Zeranol
Breed of sire
Probability level
Brahman
Romana Red
Breed of dam
Probability level
Angus
F
Mean
RSDC
.26
22.66
21.55
23.63
.62
22.87
22.36
.65
22.84
22.38
.80
22.49
22.74
24 22.61
2.37
.06
17.42
17.38
16.50
.30
16.92
17.28
.73
17.04
17.16
.25
17.29
16.90
17.10
.79
.68
59.70
60.52
59.64
.84
59.86
60.05
.54
59.67
60.24
.81
60.06
59.84
59.95
2.14
.04
22.80
22.19
26.61
.09
25.15
22.59
.33
23.15
24.58
.91
23.95
23.78
23.87
3.32
.11
60.80
60.16
57.91
.008
57.90
61.35
.26
60.29
58.96
.48
60.02
59.22
59.62
2.68
.07
16.94
17.82
16.27
.23
17.33
16.69
.89
17.05
16.97
.19
16.67
17.36
17.01
1.22
bYear influenced (P<.02) percent edible fat and moisture and separable fat and leans.
Predicted using equations developed by Hankins and Howe (1946).
cResidual standard deviation.
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