INFLUENCE
OF MELENGESTROL
ACETATE
AND ENERGY
INTAKE
UPON WEIGHT
AND MILK YIELD AND COMPOSITION OF ANGUS-HOLSTEIN
COWS AND
PROGENY
GROWTH
RATE 1
L. L.
M. C. RuGrI, J. M. STOUT, M. J. SIMPSON,
T. A. LONG AND H. R. PURDY 2
The Pennsylvania State University, University Park
WILSON,
E efficacy
T H(MGA)
a for
of melengestrol acetate
synchronization of estrus
has been established (Zimbelman and Smith,
1966; Schul et al., 1967; Wilson et al.,
1969b). Since MGA can be fed during gestation without a depression of calving percent
or ease of calving (Schul et al., 1967), perhaps MGA can be used to suppress estrus of
nonpregnant cows when maintained with pregnant cows. This is an important consideration
since open cows suckling calves are not usually
culled until the calves are weaned. Prior to
culling open cows at weaning, the milk production of the herd may be decreased due
to periodic occurrence of estrus.
Beef producers are becoming more interested in the production level of beef-dairy
crossbred cows because of the potential for
increased milk production. Wilson et al.
(1969a) in comparing 85 and 115% of
N.R.C. (1963) digestible energy (DE) recommendations for mature lactating beef cows,
reported that Angus-Holstein crossbred cows
receiving the higher level maintained their
initial weights while producing more than the
amounts of milk from beef cows (Montsma,
1960; Wistrand and Riggs, 1966; Melton et
al., 1967). However, weight changes and milk
production of Angus-Holstein cows receiving
moderate and high D E levels have not been
compared. Therefore, the objectives of this
study were to determine the effects of MGA
and energy intake on weight changes, milk
yield and composition and progeny growth
rate of group-fed pregnant and open AngusHolstein cows.
1 Department of Animal Science, published with the approval of the Director, The Pennsylvania Agricultural Experiment Station, No. 3702 of the Journal Series.
2 Appreciation is extended to the Pennsylvania Department
of 5ustice, A. T. Prassee, Commissioner, and the State Correctional Institution at Rockview, A. C. Cavell, Superintendent, for granting permission for use of cattle; to the Tuco
Products Co., The Upjohn Co. and the Leon Falk Family
Trust for grants-in-aid; and to W. H. Cloninger and A. E.
Branding. Dept. of Dairy Sci., for technical consultation.
8 6-dehydro-16-methylene-6-methyl-17a-acetoxyprogest er on e
(MGA), product of The Upjohn Co., Kalamazoo, Mich.
956
Materials and M e t h o d s
The 24 cows used in this trial were fallcalving Angus-Holstein F1 cows maintained
by the State Correctional Institution at Rockview, Bellefonte, Pennsylvania. The cows
ranged in age from 4 to 6 years. Initial calf
age averaged 19.3 days and ranged from 12
to 29 days. The 12 steer and 12 heifer calves
were half-sibs, sired by an Angus bull. Initial
cow weight was the average of two weights on
consecutive days following 8-hr. periods without access to feed or water. Initial calf weights
were obtained on the same two days following 4-hr. periods of cow-calf separation. Initial and final cow condition scores were the
averages of three experienced scorers. The
scores were coded with 1 and 17 as the least
and greatest degrees of fatness, respectively.
The cows were randomly allotted to four
lots with stratification on cow and calf weight
and calf age and sex. Two of the lots received
33,600 kcal per head per day (moderate D E
level, corresponding to 100% of N.R.C., 1963
recommendations) and the other two lots
received 38,640 kcal (high D E level, 115%
of N.R.C., 1963 recommendations) per head
per day. The D E values of the ration components were estimated from proximate analyses and digestion coefficients from N.R.C.
(1963). The forages were 70% orchardgrass30% alfalfa silage (50% dry matter harvested
in mid-bloom stage) and Reed canarygrass
hay (mid-bloom), with mean as-fed calculated values of 1,305 and 2,100 kcal DE/kg,
respectively. The as-fed proportions of silage:
hay (2 : 1 ) and forage:concentrate (9 : 1) were
the same for the two rations. The moderate
DE ration consisted of 12.0 kg silage, 6.0 kg
hay, 0.55 kg soybean meal and 1.45 kg ground
shelled corn per head daily. The high D E
ration consisted of 13.7 kg silage, 6.9 kg hay
and 2.31 kg ground shelled corn per head
daily. The rations contained equal amounts
of total protein, which exceeded N.R.C. rec-
M E L E N G E S T R O L ACETATE AND E N E R G Y I N T A K E
ommendations by approximately 42%. The
four lots were group-fed at 7:00 am and
4:30 pro. The calves were not creep-fed and
were allowed to remain with the cows at feeding time.
One each of the moderate and high energy
lots received 1.0 mg per head daily starting
28 days after initiation of the trial. MGA
was fed to the two lots for 14 days and then
withdrawn. On the third day after withdrawal
of MGA, the first post-treatment estrus was
observed in the MGA lots and all cows exhibiting estrus within the subsequent 53 days
were bred artificially. During the breeding
period all cows except one in the MGA-high
energy lot exhibited estrus.
Breeding was discontinued on the 56th day
after MGA withdrawal and MGA feeding was
resumed (1.0 mg/head) and continued until
the end of the trial, 84 days later. According
to rectal palpation on the 143rd day of the
trial, two cows in each lot were not pregnant.
None of the cows in the MGA lots exhibited
estrus after the resumption of MGA feeding
and open cows not receiving MGA continued
cycling.
Consumption and production of milk were
measured each 14 days throughout the trial.
The general procedure was to separate the
cows and calves at 5:00 pro. At 5:00 am the
next day, the calves were allowed to nurse
their dams for approximately 20 minutes.
The dams were then confined in individual
stalls, 40 U.S.P. units (2 cc) of oxytocic
principle were injected into the coccygeal vein
and the cows were handstripped. The cows
and calves remained separated until 5:30 pm
when the calves were weighed and immediately allowed a 20-rain. suckling period. After
suckling, the calves were reweighed and the
difference between the pre- and post-suckling
weights was considered to be the quantity of
milk consumed. Calf weights were obtained
to the nearest 45 g with a specially-built
scale. 4
After obtaining the post-suckling weights,
the calves were returned to a separate pen
and the cows confined in individual stalls,
injected with oxytocic principle and handstripped. The cows and calves remained separated overnight and at 6:00 am the cows were
injected with oxytocic principle and machinemilked. The cows were handstripped approximately 4 rain. after removal of the machines
and the amounts of milk obtained with the ma4 Available
Nebraska.
from
Olson
Bros.
Scale
Service,
Scottsbluff,
957
chines and by handstripping were combined
to represent the 12-hr. milk yield. Since only
one of the four lots could be milked at one
time, the order of milking was alternated,
and the milking times staggered so that the
periods between milkings were 12 hours.
Samples of the 12-hr. production were collected for determination of % butterfat, BF
(Barnard, Kroger and Watrous, 1967), protein (Ashworth, Seals and Erb, 1960) and
solids-not-fat, SNF (Haenlein, 1962). The
yield and composition traits were used to
calculate 12-hr. solids-corrected milk yield,
SCM (Tyrrell and Reid, 1965).
Period 1 (first 98 days of trial) and final
(182 days) weights were obtained on 2
consecutive days after 8- and 4-hr. shrink
periods for cows and calves, respectively. All
milk production and weight data were summarized separately for periods 1, 2 and over
the entire trial. Cow weight and condition
score changes were coded by the addition of
100 kg and 10 units for analysis. Decoded
means are presented in the subsequent tables.
The least-squares analysis (Harvey, 1960)
included the three main effects of MGA treatment, ration and calf sex and the three, twoway interactions. Initial calf age and cow and
calf weights were included as continuous, independent variables.
Results and Discussion
Mean weight change of cows in period 1
was not significantly affected by energy level
(table 1). However, weight changes during
period 2 and over the entire trial were significantly ( P < . 0 5 ) affected by energy level.
Average final weights of the moderate and
high energy levels were 430.1 and 457.9 kg,
respectively ( P < . 0 5 ) . In an earlier study
(Wilson et al., 1969a), Angus-Holstein cows
receiving 115% of N.R.C. (1963) DE recommendations maintained their initial weight in
a 123-day trial initiated at an average of 76.3
days postpartum. In the present study, cows
receiving an estimated allowance of 38,640
kcal had a mean weight change of 4.9 kilograms. This suggests that a D E level of
approximately 38,000 kcal should be fed to
Angus-Holstein cows to maintain their body
weights during lactation.
Neither MGA nor calf sex significantly affected cow weight change, although the lots
receiving MGA tended t o lose slightly less
weight during both periods. The average
change in condition score during the trim
958
WILSON E T AL.
averaged --.8 and 0.8 units for the moderate
and high energy levels, respectively ( P < . 0 5 ) .
Neither the energy level fed the cows nor
MGA treatment significantly affected calf
average daily gain during either of the two
periods. Calf gain during both periods and
final calf weight were significantly ( P < . 0 5
or P < . 0 1 ) affected by calf sex. Mean final
weights of steers and heifers were 225.8 and
193.0 kg, respectively ( P < . 0 5 ) . Overall
means of calf gain for periods 1 and 2 were
935 and 881 g/day, respectively. None of the
three, two-way interactions were significant
for any of the cow or calf weight traits.
Yield and Composition o] Milk. Retained
milk averaged 0.53 and 0.64 for the 100
and 115% energy levels, respectively, and
was not significantly affected by any of the
main effects (table 2 ).
The means of 12-hr. milk yield were 4.21
and 5.27 kg for the moderate and high energy levels, respectively ( P < . 0 1 ) . The production from the Angus-Holstein crossbred
cows was greater than reported by Montsma
(1960), Neville (1962), Christian, Hauser
and Chapman (1965) and Melton et al.
(1967), but similar to the amount observed
TABLE
by Dawson, Cook and Knapp ~19o0) irom
beef cows.
Averages of 12-hr. milk consumption, estimated from pre- vs. post-suckling calf weights,
were 3.45 and 3.93 kg for the moderate and
high energy levels, respectively ( P < . 0 5 ) .
The difference between milk yield and consumption should approximate the amount of
retained milk. This difference was 0.76 kg
for the moderate energy level and 1.34 kg for
the high level, compared to actual retained
milk means of 0.53 and 0.64 kg, respectively.
The 12-hr. SCM yield was significantly
( P < . 0 5 ) affected by energy level in both
periods. The 24-hr. kg SCM/kg calf daily
gain for the moderate and high energy levels
were 9.6 and 11.2 in period 1, and 8.8 and
10.0 in period 2, respectively.
Comparing SCM means of periods 1 and
2, there were decreases of 15 and 14% for
cows receiving the moderate and high energy
levels, respectively. The persistency of lactation observed in this study was greater than
previous reports based on beef cows (Drewry,
Brown and Honea, 1959; Melton et al., 1967).
Percents BF, protein and SNF were not significantly affected by the main effects. The
1. E F F E C T S O F M G A , R A T I O N E N E R G Y L E V E L A N D C A L F S E X O N
C O W A N D C A L F W E I G H T S A N D C O N D I T I O N S C O R E S "' b
E n e r g y level
Item
MGA
Calf sex
Moderate
High
None
1.0 m g / h e a d / d a y
Initial
C o w wt., k g
Calf age, d a y s
Calf wt., k g
453.2
18.4
43.8
453.0
20.2
43.9
453.1
19.0
43.0
453.1
19.6
44.7
454.1
19.9
47.4 c
452.1
18.7
40.3 a
Final
C o w wt., k g
Calf wt., k g
430.1 ~
203.1
457.9 a
216.3
442.7
206.5
445.3
212.1
444.9
225.8 c
443.0
193.0 a
-- 100.0
--158.3 c
--126.9 ~
-[-25.5
+28.6 a
+26.9 a
--39.8
--77.4
--57.1
--34.7
--52.4
--42.9
--37.8
--65.5
--50.5
--36.7
--65.5
--50.0
--.3
--.5
--.8 ~
+.4
+.4
+ . 8 '1
--.2
+.1
--.1
-}-.2
--,1
+.1
--.1
+.2
-}-.1
+.1
--.2
--.1
1021 e
934 ~
981
848 ~
828 a
839
C o w w t . change, g / d a y
Period 1
Period 2
Trial ~
C o w cond. score chan~e
Period 1
Period 2
Trial R
Calf gain, g / d a y
Period 1
Period 2
Trial ~
905
837
875
964
925
948
918
870
899
949
887
920
Steers
Heifers
a Means are least-squares estimates from analysis including three main effects and three, two-way interactions; interactions were nonsignificant; moderate and high energy levels were 33,600 and 38,640 keal calculated DE/head/day, respectively.
b Period 1 included first 98 days of trial; period 2 included last 84 days from resumption of MGA feeding to trial termination.
e, a Means in the same row within a main effect with different superscripts differ at 0.05 level.
e, f Means in the same row within a main effect with different superscripts differ at 0.01 level.
959
M E L E N G E S T R O L ACETATE AND E N E R G Y I N T A K E
TABLE
2. E F F E C T S O F M G A , R A T I O N E N E R G Y L E V E L A N D
MILK YIELD, CONSUMPTION
AND COMPOSITION
E n e r g y level
Item
Moderate
CALF SEX
a, b
ON
MGA
C a l f sex
High
None
Steers
Heifers
Retained milk, kg
1 2 - h r . yield, k g
12-hr. consumption, kg
BF, %
Protein, %
SNF, %
0.53
4.21 ~
3.45 ~
3.78
3.20
8.70
0.64
5.27 *
3.93 a
3.68
3.29
8.73
0.59
4.60
3.59
3.70
3.23
8.79
1.0 m g / h e a d / d a y
0.59
4.88
3.79
3.76
3.26
8.65
0.62
4.76
3.65
3.67
3.22
8.72
0.56
4.72
3.73
3.79
12-hr. SCM, kg
Period 1
Period 2
T r i a l f~
4.34 ~
3.69 r
4.04 e
5.40 a
4.63 a
5.01 a
4.80
4.02
4.41
4.94
4.29
4.66
4.85
4.12
4.51
4.89
4.17
4.55
3.27
8.72
a Means are least-squares estimates from analyses including three main effects and three, two-way interactions; interactions were nonsignificant; moderate and high energy levels were 33,600 and 38,640 kcal calculated DE/head/day, respectively.
b Period 1 included first 98 days of trial; period 2 included last 84 days from resumption of MGA feeding to trial termination.
e, a Means in the same row within a main effect with different superscripts differ at 0.05 level.
e, r Means in the same row within a main effect with different superscripts differ at 0.01 level.
3.73% mean BF was lower than the 3.98%
obtained by Dawson et al. (1960) or 4.167o
by Schwulst et al. (1966) but greater than
3.43 % by Wilson et al. (1969a). Milk protein
averaged 3.25% which was greater than the
mean of 3.00% reported by Schwulst et al.
(1966) but less than 3.46% by Wilson et al.
(1969a). Average percent SNF (8.72%) compared closely with results of the latter two
studies.
Neither MGA-treatment, calf sex nor the
two-way interactions significantly affected the
milk traits. Therefore, the suppression of
estrus of open cows maintained with pregnant
cows did not significantly increase calf performance or milk yield.
Correlations Among Milk and Animal
Weight Traits. The correlation coefficients
among certain traits, calculated on a residual
variance basis, are presented in table 3. Retained milk was not significantly related with
TABLE
any of the other traits. Milk yield was correlated 0.67 ( P < . 0 1 ) with 12-hr. calf milk
consumption, --.49 ( P < . 0 5 ) with % BF,
0.91 ( P < . 0 1 ) with 12-hr. SCM and 0.54
( P < . 0 5 ) with calf gain. Milk consumption
was correlated 0.71 ( P < . 0 1 ) with 12-hr.
SCM and 0.63 ( P < . 0 1 ) with calf gain. According to these results, 12-hr. yield and consumption accounted for 29 and 39%, respectively, of the variation in calf gain. The
correlations of yield or consumption with calf
gain were in agreement with values reported
by Gifford (1953), Wistrand and Riggs
(1966) and Wilson et al. (1969a).
Cow weight change was negatively correlated (NS) --.32, --.29, --.30 and --.39
with 12-hr. yield, consumption, SCM and trial
average calf gain, respectively. This indicated
a tendency for cows which lost the most weight
(or which gained the least) to produce more
milk and heavier calves.
3. C O R R E L A T I O N
COEFFICIENTS
AMONG MILK YIELD AND COMPOSITION
AND COW WEIGHT CHANGE AND CALF GAIN a
Trait
12-hr.
yield,
kg
12-hr.
consumption, kg
Retained milk, kg
1 2 - h r . yield, k g
12-hr. consumption, kg
BF, %
Protein, %
SNF, %
12-hr. SCM, kg
Cow wt. change, kg
0.14
0.18
- - . 23
- - . 12
....
0.67**
--.49*
--.40
. . . . . . . .
- - . 32
- - . 27
. . . . . . . . . . . .
0.41
. . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . .
BF,
%
Protein,
%
SNF,
%
- - . 02
--.34
- - . 23
0.51"
0.36
12-hr.
SCM,
kg
Cow wt.
change,
kg
Total
calf
gain, kg
0.13
0.91"*
0.71"*
--.23
- - . 19
--.20
0.03
--.32
- - . 29
--.09
0.03
0.02
--. 30
0.24
0.54*
0.63**
0.02
--.02
0.21
O. 59**
- - .39
. . . . .
. . . . . . . . .
a Correlations calculated from residual variances and covariances; initial cow and calf weight and calf age held constant.
* P~.05.
*~ P < . O I .
960
W I L S O N E T AL.
Summary
Twenty-four Angus-Holstein F1 cows and
their calves (half-sib Angus-sired) were allotted to a trial of moderate (33,600 kcal
calculated D E / h e a d / d a y ) v s . high (38,640
kcal) and control v s . MGA-treated. T h e two
energy levels were isonitrogenous and the animals were group-fed. Each of the four groups
contained three steer and three heifer calves.
Initial calf age averaged 19.3 days and ranged
from 12 to 29 days. Twenty-eight days after
initiation of the trial, the two MGA-treated
lots received 1.0 m g / d a y for 14 days. After
a subsequent 56 days of A.I. breeding (period
1, 98 days) for all lots, MGA-feeding was
resumed and continued to termination of the
182-day trial. Each of the four groups contained two n o n - p r e g n a n t cows (based on a
rectal palpation on the 143rd day of the trial).
Milk consumption and yield were estimated
from pre- v s . post-suckling calf weights and
milking machines, respectively. At the beginnining of each 12-hr. separation period, 40
U.S.P. units of oxytocic principle were injected into the coccygeal vein and the cows
were handstripped. Average weight changes
of cows receiving the moderate and high energy levels were - - 2 3 . 1 and 4.9 kg, respectively ( - - 1 2 6 . 9 and 26.9 g/day, P ~ . 0 5 ) .
Means for calf daily gain of the respective
energy levels were 875 and 948 g / d a y ( N S ) .
Means of the moderate and high energy level
groups were 4.21 and 5.27 kg for 12-hr. milk
yield ( P ~ . 0 1 ) and 3.45 and 3.93 kg for 12-hr.
consumption ( P ~ . 0 5 ) . Milk yield and consumption were correlated 0.67 ( P ~ . 0 1 ) . Calf
gain was correlated 0.54 ( P ~ . 0 5 ) , 0.63 and
0.59 ( P ~ . 0 1 ) with 12-hr. yield, consumption
and SCM, respectively. Percent BF, protein
and S N F were not significantly correlated
with calf gain or milk consumption. Neither
M G A - t r e a t m e n t nor the three, two-way interactions significantly affected cow or calf weight
changes or the milk traits. Calf sex significantly ( P ~ . 0 5 or P ~ . 0 1 ) affected only calf
gain.
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