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Effects of Energy Intake, Cow Body Size and Calf Sex on Composition and Yield of Milk by Angus-Holstein Cows and Preweaning Growth Rate of Progeny

The Pennsylvania State University, University Park ³

Abstract

Twenty-four Angus-Holstein crossbred cows and their calves (sired by one Polled Hereford bull) were measured for body depth at withers, width at hooks and length from shoulder point to pins. The 12 cows with the greatest products of these three measurements were designated large cows and those with the least products, small cows. The products were used to express body size instead of actual weight or W^0.75 since the correlations with condition score were 0.22, 0.64 and 0.65, respectively. The 14 steer and 10 heifer calves averaged 76.3 days of age at the start of the 123-day trial. The cows within each size group were allotted to two isonitrogenous, group-fed rations of 38,640 and 28,650 kcal. DE/head/day (US and 85% of N.R.C., 1963, requirements). Milking machines and oxytocin were used bi-monthly to measure 12-hr, milk production. The objectives were to determine the effects of energy level, cow body size, and calf sex on cow and calf weight changes and cow milk production, and to evaluate the milk yield of Angus-Holstein cows.

Energy level significantly (P<.01) influenced cow weight loss, cow and calf condition and calf conformation scores, calf gain, 12-hr, milk kcal. and SCM yield. Although the cows receiving the 85% energy level lost an average of 54.4 kg., the 115% groups maintained their initial weight.

Cow body size did not significantly affect milk or performance traits although large cows tended to produce lesser total quantities of milk and milk energy. Significant (P<.05) energy level x body size interactions were observed only for retained milk yield and percent protein, indicating that the effects of energy level and body size were essentially linear for the other traits.

The 12-hr, average milk production (4.7 kg.) of the Angus-Holstein cows was appreciably greater than previous reports with straightbred beef cows. Total calf gain was correlated 0.49 (P<.05) with 12-hr, milk kcal. and SCM yield. Amount of milk produced accounted for approximately 88% of the variation in 12-hr, milk kcal.

¹ Present address: Colbert Farms, Washington, Indiana.

² Present address: Department of Animal Science, Virginia Polytechnic Institute, Blacksburg.

³ Department of Animal Science, published with the approval of the Pennsylvania Agricultural Experiment Station, No. 3429 of the Journal Series, June 7, 1968. Appreciation is extended to the Pennsylvania Department of Justice, A. T. Prasse, Commissioner, and the State Correctional Institution at Rockview, A. C. Cavell, Superintendent, for granting permission for use of cattle; to the Leon Falk Family Trust for grants-in-aid; and to W. H. Cloninger and A. E. Branding; Department of Dairy Science, for technical assistance.