Growth and carcass characteristics of Wagyu-sired steers at heavy market weights following slow or rapid growth to weaning

摘要

Two groups of Wagyu × Hereford steers grown slowly (slow preweaning group, n = 14, mean average daily gain = 631 g/day) or rapidly (rapid preweaning group, n = 15, mean average daily gain = 979 g/day) from birth to weaning were backgrounded on improved, temperate pasture to equivalent group liveweights (543 v. 548 kg, s.e. = 8.8 kg), then finished in a feedlot for 120 days. At weaning, the slow preweaning group was 79 kg lighter than the rapid preweaning group. They required an additional 43 days of backgrounding to reach the same feedlot entry weight as the rapid preweaning group. The slow preweaning group grew more rapidly during backgrounding (630 v. 549 g/day, s.e. = 13.7 g/day) but tended to grow more slowly during feedlotting (1798 v. 1982 g/day, s.e. = 74.9 g/day) than their rapid preweaning counterparts, with overall growth rates from weaning to feedlot exit not differing between the 2 groups (rapid 763 g/day v. slow 772 g/day, s.e. = 17.5 g/day). At slaughter, following the feedlot phase, carcass weights of the 2 groups did not differ significantly (rapid 430 kg v. slow 417 kg, s.e. = 7.2 kg). There was a tendency for the steers grown slowly to weaning to have a higher dressing percentage (57.6 v. 56.6%, s.e. = 0.33%), but there were no significant differences in carcass compositional characteristics between the 2 groups. The slow preweaning steers did have a greater eye muscle area than the rapid preweaning steers (106.6 v. 98.9 cm2, s.e. = 1.87) when carcass weight was used as a covariate. These findings demonstrate that cattle grown slowly to weaning have similar composition at slaughter as those grown rapidly during the same period when backgrounded on pasture to the same feedlot entry weight. Furthermore, marbling was not adversely affected by slow growth to weaning.