Effects of growth path and post-slaughter chilling regime on carcass composition and meat quality of ewe lambs

Abstract

Sixty-five Poll Dorset x (Border Leicester/Merino) ewe lambs. were grown at pasture on one of four growth paths commencing at mean age of 24 weeks and a mean liveweight of 37-5 kg. These were, continuous growth between 24 and 34 weeks (HH), maximum possible growth for 6 weeks followed by weight loss for 4 weeks (HL), no gain for 6 weeks followed by rapid gain for 4 weeks (LH) and weight maintenance (LL). Lambs were slaughtered as soon as possible after LH and HL lambs were the same full weight. There were significant differences between treatments in average growth rate, liveweight, hot carcass weight (HCW) and dressing percentage. After adjustment for HCW, LH had significantly (P < 0.05) less omental and kidney fat than HH, and there was a strong tendency for less subcutaneous fat, intermuscular fat and a lower tissue depth over the twelfth rib (at the GR site). Eye muscle area was significantly larger in LH than HH, but this did not translate to a significant difference in dissectible 'soft tissue' measurement. The Warner Bratzler shear value for LL in the M. longissimus dorsi was significantly higher than LH and HH. There were no differences between treatments for pH, Warner Bratzler shear values of the M. semimembranosus, cooking loss, or the colour measurements using a Minolta chromameter of L* (lightness) or b* (yellowness). The difference in a* (redness) between HL and LH was significant. Warner Bratzler shear values for M. longissimus dorsi and M.semimembranosus were significantly higher at 4¦C than 10¦C. The a* was significantly higher at 10¦C, but there were no differences between L* and b*. There were no interactions between the post-slaughter chilling regime and the pre-slaughter nutritional management. It was concluded that the growth path had little effect on meat quality unless the lamb had been continuously on a restricted diet. Therefore there was some potential for the use of growth paths to manipulate carcass composition, and further research into management systems at pasture is recommended.