Reproductive and maternal performance of rotational three-breed, and inter se crossbred cows in Florida

Reproductive, calf growth, and cow weight data were collected during a 16-yr period in southern Florida. Data included 1,767 calves at weaning from purebred, F1, backcross, F2, and three-breed crossbred cows of the Angus (A), Brahman (B), and Charolais (C) breeds. The purebred cows primarily produced purebred calves, the F1 and F2 Cows produced inter se crossbred calves, and the backcross cows produced 3/8:5/8 calves. The 1/2 C:1/4 A:1/4 B three-breed crossbred cows were mated to A series, whereas three-breed crossbred dams with breed compositions of 1/2 B:1/4 A:1/4 C, and 1/2 A:1/4 B:1/4 C were mated to C and B sires, respectively. For analysis of additive breed and heterosis effects, pregnancy rate and cow weight were considered to be traits of the dam alone. The A additive breed effect increased (P < .05) pregnancy rate but reduced (P < .001) cow weight. The effects of AB, AC, and BC heterozygosity all increased pregnancy rate, but the advantage was greater for the crosses that involved B. Both AB and BC heterozygosity increased (P < .001) cow weight, whereas AC did not. The additive direct effect of B and C increased birth weight (BWT) and weaning weight (WWT). The additive maternal effect of B reduced BWT. The direct effect of AB heterozygosity increased BWT and WWT, and that of BC increased only WWT (P < .001). A comparable pattern was observed for maternal heterosis on weight traits. A much smaller effect of AC maternal heterosis on WWT was found. Pregnancy rates of F1, backcross, and three-breed dams were similar.(ABSTRACT TRUNCATED AT 250 WORDS)