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Heterosis from Crosses among British Breeds of Cattle: Straightbred versus Crossbred Cows. I¹

Virginia Polytechnic Institute and State University, Blacksburg 24061 and and United States Department of Agriculture

Abstract

Records of 604 matings and 567 births were collected over five successive calf crops. All the calves were crossbred.

Crossbred cows were 31.9 kg heavier than straightbred cows (yearly mean differences ranged from 26.8 to 40.7), and the difference was rather consistent through all five calf crops. Calves from crossbred cows performed significantly better than those from straightbred cows for weaning weight. Weaning weight differences were reduced when cow weight effects were taken into account in the analysis.

There were 2.1% more calves born, but .7% fewer calves weaned from the crossbred cows than from the straightbred cows. Calves from Angus cows performed better than calves from Hereford or Shorthorn cows. When differences in calf performance, cow reproductive performance and cow size were all combined (kg of calf/100 kg cow/cow year), the Angus cow ranked first among all breeds and crosses.

Significant differences were found between the kinds of crossbred cows for weaning weight of calf. Comparisons of reciprocal crosses showed cows resulting from matings involving Hereford dams excelled the reciprocals.

The results of this study lead to the conclusion that in a favorable environment such as the one in which this experiment was conducted, it was more important to have the calves crossbred than it was to have the cows crossbred. However, the dams involved in this study represented only one step in a rotational crossbreeding system, so final judgement of the cows will have to await the results of further steps in rotational crossbreeding.

¹ Published with approval of the Director of the Research Division, Virginia Polytechnic Institute and State University. Contribution of the Southern Regional Project S-10, Improvement of Beef Cattle through Breeding Methods.

² Dept. of Animal Science, V.P.I. & S.U., Blacksburg, VA 24601.

³ From a dissertation by this author. Present address: Delaware Valley College of Sci. and Agr., Doylestown, PA 18901.

⁴ Deceased.

⁵ Investigations Leader S-10, 205 Animal Science Bldg., Univ. of Tennessee, Knoxville, TN 37916.