Abstract
Maternal heterosis and its relative influence on weaning traits were estimated for 12 types of singlecross cows of the Angus, Brahman, Brangus and Hereford breeds. Birth weight, weaning weight and weaning condition score of 222 straightbred, 337 singlecross and 401 three-breed cross calves by straightbred sires of these breeds plus Charolais sires were studied. Linear functions of calf breeding constants were employed to estimate maternal heterosis by comparing triple-cross progeny with the average performance of singlecross progeny from the parental breeds of the dam. Within types of singlecross cows, separate estimates were determined for each three-breed cross and a composite estimate for the three possible triple crosses. Estimates of specific heterosis (non-additive effects) of the three-breed cross calves were calculated from the means of straightbred and singlecross calves. The maternal heterotic, non-additive and additive effects were combined to reconstruct the mean for the various three-breed crosses. The relative influence of the three components was expressed as a percent of the breed-of-calf means for weaning weight. Differences between reciprocal dams for maternal heterosis were nonsignificant. Maternal heterosis for birth weight was generally nonsignificant. Brahman-Hereford cross dams provided the largest composite estimate of maternal heterosis for weaning weight of all singlecross dam combinations. Brahman x Brangus and their reciprocal expressed the greatest similarity of any reciprocal combination. Crosses involving Angus-Brangus dams produced the smallest hybrid maternal effect on weaning weight. Singlecross dams revealing significant maternal heterosis for weaning weight generally expressed significant effects for weaning condition score. On the average, maternal heterosis exhibited by the crossbred dam accounted for 6.6% of the weaning weight mean. The additive effects of the breeds involved in the crosses accounted for 84.8% and 8.6% was attributed to non-additive effects. Information on these components should serve as an aid in predicting performance of rotational crossbreeding systems. Copyright © 1972. American Society of Animal Science . Copyright 1972 by American Society of Animal Science.