Breed and heterosis effects of American Zebu cattle.

Abstract

The Brahman (American Zebu) has been evaluated in numerous crossbreeding studies throughout the Southern United States. Brahman females producing straightbred calves have usually been found to have a lower calving percentage, calf survival rate and weaning rate than other contemporary straightbreds, although they have been reported to be superior or competitive in some studies. Birth weights of Brahman calves have been larger than those of Angus, smaller than Charolais and comparable to those of Herefords. Brahman steers generally have had lower postweaning daily gains, lower carcass grades, less backfat and higher Warner-Bratzler shear values than other contemporary straightbreds. Heterosis estimates for reproduction have been small and variable in producing F1 calves, but larger and positive for reproductive traits of F1 cows. Birth and weaning weight heterosis estimates averaged 3.3 and 21.7 kg for F1 calves and 1.9 and 31.1 kg for calves of F1 cows. Small and variable heterosis estimates have been found for all carcass traits.