| Abstrakt: |
We conducted a multiyear study in two phases to determine preweaning performance traits of Senepol (S × S), Hereford (H × H), and reciprocal (S × H and H × S) F1crossbred calves and feedlot performance and carcass characteristics of steers. In Phase I, from 1985 to 1989, data from S × S (n = 194), H × H (n = 383), and S × H (n = 120) calves were used. Numbers of S × S cows were increased during Phase I so that data from H × S (n = 74) calves could be included in Phase II (1990 to 1992) in addition to S × S (n = 118), H × H (n = 130), and S × H (n = 56) calves. Also during Phase II, feedlot performance and carcass characteristics were determined for S × S (n = 30), H × H (n = 26), H × S (n = 36), and S × H (n = 26) steers. In Phase I, S × S calves had heavier (P< .01) birth weights and heavier (P< .01) 205-d adjusted weaning weights than H × H calves. Birth weights of S × H calves were heavier (P< .01) than the mean of the purebred calves, but 205-d adjusted weaning weights did not differ (P> .10). In phase II, direct heterosis was 3.5% for birth weight (P< .05) and 5.1% for 205-d adjusted weaning weight (P< .01). Senepol maternal breed effects were 1.9 kg for birth weight (P< .10) and 37.9 kg for 205-d adjusted weaning weight (P< .01). Levels of direct heterosis, Senepol maternal breed effects, and Hereford direct breed effects were significant for most feedlot performance traits of steer calves that were fed to a common end point. Breeds did not differ (P> .10) for USDA yield and quality grades, and direct heterosis was not significant for Warner-Bratzler shear force. These results demonstrate significant levels of heterosis in preweaning performance between S × S and H × H calves and in feedlot performance of steers. Levels of heterosis were smaller and nonsignificant for most carcass traits including meat tenderness, which did not differ between S × S and H × H steers in this study. |
