Relationships of Milk Yield of Dam to Early Growth Rate of Straightbred and Crossbred Calves

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Abstract
Data on milk yields and calf growth rates were collected over a period of 3 years from Angus, Brahman, Brangus and Africander-Angus dams suckled by calves sired by Angus or Brahman bulls. Milk yields and calf growth rates were also determined in Brangus and Africander-Angus dams suckled by straightbred calves. Ten breed groups (four straightbred and six crossbred) were compared. Milk-yield samples were taken in May and June by the weigh-suckle-weigh method with calves being separated from dams for a 16-hr period. Breed differences (P<.01) were observed for milk yield at both periods. The linear partial regressions of milk yield on age of dam were significant (P<.05) for June and for the total milk yield of the two samples. The average of the two milk-yield samples for a 16-hr period for cows suckled by calves of the same breed was: Brangus 3.8 kg, Angus 3.3 kg, Africander-Angus 3.2 kg and Brahman 2.8 kilograms. Brangus dams were higher (P<.05 to P<.01) in milk yield than Angus, Africander-Angus or Brahman darns. Angus and Africander-Angus dams did not differ (P<.05) in milk yield but were higher (P<.05) than Brahman dams. Based on the average of the two samples, crossbred calves obtained .50 kg (P<.01) more milk from Angus and Brahman dams than straightbred calves, which represents a 16% increase in milk yield. Crossbred calves obtained an average of .84 kg (P<.01) more milk from Africander-Angus dams than straightbred calves. No difference was found in the milk yield of Brangus dams suckled by straightbred or crossbred calves. Brahman-sired crossbred calves obtained an average of .68 kg (P<.01) more milk from Brangus and Africander-Angus dams than Angus sired crossbred calves. The average daily gain of all calves from birth to June was .73 kilograms. Five of the six crossbred groups studied gained more rapidly than the straightbreds from birth to mid-July. Milk yield was highly correlated (P<.05 to P<.01) with average daily gain of calves from birth for each breed of dam. The correlation coefficients for May milk yield to calf growth rate from birth to May was: Angus .54, Brahman .42, Brangus .53, and Africander-Angus .52; (all P<.01). One sample of milk taken in May or in June was as highly correlated to growth rate at different periods as two samples. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.