Maternal Productivity of Crossbred Angus × Milking Shorthorn Cows. II. Cow Reproduction and Longevity

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Abstract
Heterosis for maternal productivity was studied in crossbred Angus (A) × Milking Shorthorn (MS) cows beginning with 240 females of A × A, A × MS, MS × A and MS × MS breed groups. Cows were born in the fall over 5 years. Calves were sired by Hereford, Charolais and Red Poll bulls. Traits were percent pregnant, percent calves born and percent calves weaned, all relative to the number of cows placed in breeding pastures; cow retention rate as a percentage of original heifers in each breed group; cumulative calf production per original heifer in each breed group; and calving date. Crossbred cows were superior to purebred cows for all traits. Heterosis (crossbred-pure-bred) contrasts for the first three calf crops, respectively, were 8.4, ×.5 and 13.4 (P<.05) for pregnancy percentage, 7.2, ×1.4 and 14.2 (P<.05) for birth rate and 12.3, 7.0 and 15.2 (P<.05) for weaning rate. Weaning rate contrast always exceeded birth rate contrast, indicating superior survival of calves with crossbred mothers. Heterosis contrasts for percentage cows returning to breeding each successive year of the first 4 were 3.0, 6.4, 20.2 (P<01) and 26.6 (P<.01), respectively, with crossbreds retained 18% (P<.01) more total years. Purebred death losses and reproductive failures exceeded those of crossbreds. Expressed per original cow, over three calf crops crossbreds bore .3 (12.9%; P<.01) and weaned .4 (20.3%; P<.01) more calves, with 102.8 kg (24.5%; P<01) greater total adjusted calf weaning weight, compared to purebred cows. Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.

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