Reproductive Performance of Angus, Brahman, Charolais and Crossbred Dams

Breed and heterosis effects on reproductive performance were examined by the mating of Angus (A), Brahman (B) and Charolais (C) sires to A, B, C, AB, AC and BC dams, each sire mated to all dam groups. Reciprocals for each of the three F1groups of dams were combined. Contrasts between least-squares group means were used to evaluate breed of sire, breed group of dam and maternal heterosis effects on calving rate, calf survival and weaning rate. The most important influences on calving rate were breed of sire (90, 83 and 80% for B, C and A sires, respectively, P<.01) and class of dam (88 vs81% for crossbreds vspurebreds, P<.01). Breed of sire × breed group of dam interactions were negligible for this trait. The highest calving rate among dam groups was 92%, for reciprocal AB crossbreds; the lowest 82%, for A and AC dams. Survival rate of calves from A dams was 86%, compared with values of 92 to 96% for other breed groups of dams (P<.01). Calf survival rates were 94, 93 and 91% for A, B and C sires, respectively. The most important influence on weaning rate was breed group of dam. Means varied from 70% for A to 87% for AB dams. The mean weaning rate for F1dams was 82% vs75% for purebreds (P<.01). Among the crossbred cows, the two groups of B crosses, AB and CB (86%), excelled the AC crosses (76%) (P<.01).