Influence of Melengestrol Acetate and Energy Intake upon Weight and Milk Yield and Composition of Angus-Holstein Cows and Progeny Growth Rate

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Abstract
Twenty-four Angus-Holstein F1 cows and their calves (half-sib Angus-sired) were allotted to a trial of moderate (33,600 kcal calculated DE/head/day) vs. high (38,640 kcal) and control vs. MGA-treated. The 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 mg/day 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 non-pregnant cows (based on a rectal palpation on the 143rd day of the trial). Milk consumption and yield were estimated from pre-vs. post-suckling calf weights and milking machines, respectively. At the begin-nining 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 −23.1 and 4.9 kg, respectively ( − 126.9 and 26.9 g/day, P<.05). Means for calf daily gain of the respective energy levels were 875 and 948 g/day (NS). Means of the moderate and high energy level groups were 4.21 and 5.27 kg for 12-hr, milk yield (P<.01) and 3.45 and 3.93 kg for 12-hr, consumption (P<.05). Milk yield and consumption were correlated 0.67 (P<.01). Calf gain was correlated 0.54 (P<.05), 0.63 and 0.59 (P<.01) with 12-hr, yield, consumption and SCM, respectively. Percent BF, protein and SNF were not significantly correlated with calf gain or milk consumption. Neither MGA-treatment nor the three, two-way interactions significantly affected cow or calf weight changes or the milk traits. Calf sex significantly (P<.05 or P<.01) affected only calf gain. Copyright © 1970. American Society of Animal Science . Copyright 1970 by American Society of Animal Science

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