Straightbred and crossbred weaner steers bred in north-eastern New South Wales and grown on Victorian foodlots and pastures

Abstract

Weaner steers of 6 breed types were procured from 82 herds from the North Coast of New South Wales and grown in feedlots and on pastures in Victoria over a 3-year period. Growth and carcass traits were compared when adjusted to a common initial liveweight (204 kg), and breed type effects were tested using the between-herd (of origin) mean square as error. Steers comprised Hereford; first-cross Angus x Hereford (A x H); first-cross Brahman x Hereford (B X H); Braford; an outcross A x (B x H); and a backcross H x (B x H). Initial liveweight was significantly and positively correlated with final liveweight, carcass weight, dressing percentage, muscle score, subcutaneous fat depth [except for B x H and A x (B x H)], and eye muscle area [except for H x (B x H)]. There was no significant relationship between initial liveweight and daily gain. Feedlot steers grew faster than pasture steers (1159 v. 741 g/day) and were slaughtered earlier (after 144 v. 268 days) at similar carcass weights (202 kg) and subcutaneous fat depths at the 12-13th rib (6.6 mm). Muscle colour was significantly lighter for the younger feedlot steers, but all other fat and muscle measurements were unaffected by feed type. The A x H and B x H steers had the highest carcass weights (204 and 206 kg, respectively), while Braford and H x (B x H) steers had the lowest (both 199 kg). The A x H steers had the highest muscle score and greatest subcutaneous fat depth (5.6 units and 8.2 mm), while Braford steers ranked lowest for these measures (4.9 units and 5.5 mm) when adjusted to the same initial liveweight. Underlying these differences were significant breed effects on daily gain (range 71 g/day), final liveweight (range 10.8 kg), and dressing percentage (range 1.6%). There was a significant breed type x feed type interaction for muscle colour: on feedlot, A x (B x H) were significantly lighter than Hereford; and on pasture, H x (B x H) and A x H were lighter than B x H and A x (B x H), and Hereford were lighter than B x H. The range in producer effects (origin) on daily gain was 80-124% of the overall mean, with a repeatability of 0.47. Except for fat depth, breed differences were small, but first-cross steers were generally superior to progeny of first-cross cows. This indicates a conflict in the choice of breed type between that which performs best for rowers (first-cross cattle) and that which performs best for North Coast store weaner producers (calves from first-cross dams). There were large differences in growth rate between steers from different producers that could not be attributed to any 1 factor.