Characterization of biological types of cattle (cycle III). IV. Postweaning growth and feed efficiency.

Postweaning growth and feed efficiency data were analyzed on 769 F1 crossbred steers out of Angus and Hereford dams and sired by Pinzgauer, Tarentaise, Brahman, Sahiwal, Hereford and Angus sires. Breed groups were fed in replicated pens and slaughtered serially at three different dates in each of 2 yr. Quadratic regressions of pen mean weight on days fed and of cumulative metabolizable energy consumption (ME) on days fed were used to estimate gain, ME consumption and efficiency (Mcal ME/kg gain) over time (0 to 213 d on feed) and weight (250 to 470 kg) intervals, and from d 0 to a small degree of marbling (corresponds to USDA low Choice quality grade) and an 18.9% fat trim end point. Brahman-sired crosses were significantly heavier at weaning than all other breed groups. However, during the postweaning period, which included winter months, and while being fed a moderately high concentrate diet, average daily gain of Brahman-sired crosses tended to be less than Angus- or Hereford-, Tarentaise- and Pinzgauer-sired crosses and that of Sahiwal-sired crosses was significantly less than all other breed groups. Differences among breed groups were not significant for feed efficiency in the time constant interval from 0 to 213 d. In a weight interval from 250 to 470 kg, only Sahiwal-sired crosses differed significantly, requiring more Mcal ME/kg gain than other breed groups. Hereford-Angus crosses were more efficient than all other breed groups (P less than .05) to the marbling end point and to the 18.9% fat trim end point, primarily because of fewer days on feed and thus less net energy required for maintenance. Pinzgauer-sired crosses were significantly more efficient than Tarentaise-, Brahman- and Sahiwal-sired crosses to the marbling end point (P less than .05).