Heterosis and Breed Maternal and Transmitted Effects in Beef Cattle I. Preweaning Traits2,3,7

This study included data on 1,207 calves born and 1,151 calves weaned in 1973 and 1974 in a four-breed diallel crossing design including Red Poll, Brown Swiss (European and domestic), Hereford and Angus breeds to estimate heterosis and breed maternal and transmitted effects on economic traits of beef cattle. Birth weight, gestation length, calving difficulty, perinatal mortality, calf crop weaned, preweaning average daily gain (ADG), preweaning relative growth rate (RGR) and 200-day weight were analyzed. The effects of heterosis were significant for birth weight, calf crop weaned, preweaning ADG and 200-day weight. The four breeds did not differ significantly in most traits in breed mean heterosis () in their crosses. Breed maternal effects () showed the Brown Swiss breed with the lowest level of calving difficulty. The four breeds did not differ (P>.05) from each other in for calf crop weaned but differed significantly from each other in for ADG and 200-day weight ranking in order (high to low) of Brown Swiss, Red Poll, Angus and Hereford. The difference between Brown Swiss and Hereford breeds in was 48.2 kg for 200-day weight. Calves with Red Poll and Brown Swiss dams averaged 2.4 kg heavier (P<.01) at birth and 35.0 kg heavier (P<.01) at 200 days than their reciprocal crosses with Hereford and Angus dams. Breed transmitted effects ( showed that the Brown Swiss breed was heaviest at birth and had the highest ADG and 200-day weight. Brown Swiss breed showed for highest calving difficulty, highest perinatal mortality and lowest calf crop weaned. Differences in , although significant for several traits, were generally small among Red Poll, Hereford and Angus breeds for most birth and weaning traits; the Angus breed was favored in ADG and 200-day weight. The breeds ranked in order (high to low) of Brown Swiss, Angus, Hereford and Red Poll in for 200-day weight; all differences were significant except those between Hereford and Red Poll and the Angus and Hereford breeds. The difference between Brown Swiss and Red Poll breeds in was 25.5 kg for 200-day weight. The four breeds in crosses did not differ (P>.05) from each other in perinatal mortality and calf crop weaned but differed significantly from each other in ADG and 200-day weight; breeds ranked in order (high to low) of Brown Swiss, Red Poll, Angus and Hereford for ADG and 200-day weight.