A biometrical evaluation of Heterosis in beef cattle

Abstract

Texas Agricultural Experiment Station beef cattle performance records from Substation 23 at McGregor and the East Texas Pasture Laboratory at Lufkin were analyzed using the least-squares method of fitting constants. Data from Herefords, Brahmans, and their crosses were used in evaluation of breed or cross, environmental, and interaction effects. Cow weight was found to exert large effects upon calf weight. Interaction analyses indicated that uniform correction factors may be inadequate in adjusting weaning weights for age of dam for all breeds and crosses. Heterosis exhibited by firstcross calves was 10.8% for birth weight, 6.1% for vigor score at birth, 15.9% for weaning weight, and 11.0% for feedlot gain. The heterotic effect for weaning weight was increased to 18.8% for backcross calves raised by firstcross dams. Mature firstcross cows were 14.6% heavier than Hereford cows. Heterosis for percentage of calves dropped was negative when based on data from firstcross calves dropped by purebred dams, but the estimate was considered to be biased by non-genetic influences. The estimate based on data from backcross calves dropped by firstcross dams was 9.5%. Heterosis for percentage of firstcross calves which survived until weaning was 15.0%. Heterosis for percentage of cows which weaned calves was 0.3% for purebred dams with firstcross calves but 20.3% for firstcross dams with backcross calves. Crossbreds produced over 20% more total pounds of beef than the better parent breed.