Post-weaning growth of cattle in northern New South Wales - 3. Carry-over effects on finishing, carcass characteristics and intramuscular fat

The effects of prior growth on subsequent growth and body composition of ca ttle potentially affect the profitability of growing cattle to meet specifi cations based on weight and fatness. The effects of different growth rates and patterns of growth between weaning (about 230 kg) and entry to finishin g (average 400 kg) on growth rate, carcass characteristics and intramuscula r fat content of steers finished on pasture and in a feedlot on a predomina ntly grain ration to 2 liveweights (520 kg, Korean and >600 kg, Japanese) a re reported here. Over a period of 4 years (1994-1997), 1095 Bos taurus ste ers of 4 breeds (Angus, Hereford, Murray Grey and Shorthorn), were allocate d to 1 of 3 grow-out pathways from weaning until entry into finishing. The pathways were based on introduced pasture (P1), with different animal growt h rates induced by strategic supplementation with a pelleted concentrate fe ed (P2), or a forage crop (P3) (Ayres et al. 2001; Dicker et al. 2001). In general, the mean growth rate of steers from the different growth pathwa ys during finishing was inversely related to mean growth rate during grow-o ut. However, where the difference in liveweight at the end of grow-out was greater than 15 kg, increased growth rate during finishing was insufficient to permit complete catch up of liveweight by the end of finishing. There w as no further compensation beyond 520 kg liveweight. Steers with better nut rition during grow-out tended to have more intramuscular fat at Japanese ma rket weights, but lower retail meat yield. Steers finished on pasture had l ess fat thickness and intramuscular fat content than those finished on the grain based ration. Compared with P3 steers, there was a tendency for steer s from pathways P1 and P2 to have lower intramuscular fat content in their M. longissimus at Japanese market weights.