Abstract

Two groups of 33 Angus steers aged 270 days and weighing 179 ± 2.1 kg were allocated after weaning to 2 pasture regimes designed for high (H) and low (L) mean Liveweight. When the treatments finished after 138 days liveweights were 242 ± 3.7 kg (H) and 218 ± 3.7 kg (L). Both H and L groups were then grazed together on pasture until slaughter at 30 months of age. At slaughter fat depth at the 12th rib, weight of kidney and channel fat, ribeye area, and the trimmed fat, bone and lean (90% visual lean) were measured from the right side of the carcass. Carcass weight was the same for both treatment groups (258 ± 2.5 kg). The L group had faster liveweight gain than the H group for 283 days after treatment, but not thereafter. Steers from the L treatment had more kidney and channel fat (P<0.02). A significant (P<0.01) regression coefficient of 0.05 ± 0.019 for carcass weight on kidney and channel fat weight existed for steers in the H group, but not the L group. Rate of live weight gain before weaning was significantly (P<0.01) related to the weight of trimmed bone and lean at slaughter. Differences between animals in live weight gain at the end of the treatment period affected the weight of kidney and channel fat in the L group (P<0.01), and the weight of trimmed fat in the L group (P<0.05). These results are discussed in context of effects of growth rate on tissue development in cattle.

AB, Pleasants, RA Barton, AJ Ball, and VH Oddy

Proceedings of the New Zealand Society of Animal Production, Volume 58, , 252-255, 1998