Abstract
Angus (A), Brahman (B), and Charolais (C) cattle were striaghtbred and reciprocally crossed in a study involving an average of 121 matings during 11 years for each of the nine possible combinations of the parent breeds. Overall least squares means for pregnancy rate, calf survival, and weaning rate were 78.6, 94.3 and 74.1%, respectively. Pregnancy rate was significantly influenced by breed of sire and was 74.4%, 82.3% and 79.1% for cows bred to Angus, Brahman and Charolais bulls, respectively. Effects due to breed of dam and sire × dam interactions were nonsignificant. Pregnancy rate for all cows crossbred (77.1%) was lower (P<.05) than for cows straightbred (81.5%). Calf survival was not significantly affected by breed of sire. However, breed of dam had a highly significant effect with Angus, Brahman and Charolais dams having calf survival rates of 88.7, 97.2 and 96.9%, respectively. The low calf survival rate for Angus dams was the result of a high death loss of F1 progeny sired by Brahman (13%) and Charolais (13.5%) sires. Average survival rates for straightbred and F1 calves were similar, 94.3 and 94.2%. Weaning percent was influenced (P<.05) by breed of dam and averaged 69.8, 76.5 and 75.9% for Angus, Brahman and Charolais cows, respectively. A highly significant sire × dam interaction resulted from Charolais sire × Angus dam matings having the lowest (63.8%) and Charolais sire × Brahman dam matings having the highest (82.2%) weaning rates. There was a nonsignificant advantage in weaning rate for straightbreds (76.9%) vs crossbreds (72.7%). Average weaning percentages for reciprocal combinations were 70.0% for AB + BA, 67.7%for AC + CA, and 80.2% for BC + CB (P<.05). Heterosis levels for pregnancy, calf survival and weaning rates were negative for the AC and AB reciprocals while for the CB combinations they were −2.1% for pregnancy rate but 4.0% for calf survival and 2.0% for weaning rate. These data indicate that mating of cows of the smaller breeds with sires of the large breeds may result in a net decrease for weaning rate Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.