Abstract

A trial was undertaken in which 11 meat company lamb drafters estimated the GR carcass fatness, hot carcass weight and carcass class on 26 live lambs. In addition the Phillips Fat Displacement Meter (PFDM) was used to estimate GR fatness these live animals. The average hot carcass weight of the lambs was 21.9kg and mean GR on the left and right sides were 14.2mm and 14.5mm respectively. The best two drafter estimates correlated more highly (0.89 and 0.83) than the PFDM (0.81) with lamb carcass GR (mm) on the left sides of these carcasses. On the right sides these two drafters correlations were respectively 0.91 and 0.84 while the PFDM correlation was 0.85. The correlations of the poorest drafter were 0.62 and 0.57 for the left and right sides, respectively. While the best drafters were accurate in ranking live lambs for fatness, in absolute terms all drafters underestimated GR on average by 2.2mm whereas the PFDM underestimated by 1.1mm on the left side and 0.8mm on the right. So for actually drafting lambs for slaughter, the PFDM is less likely to select lambs in the penalty payment ranges, or is more likely to select lambs before they reach these penalty fatness levels than the company drafters. These results highlight the need for drafter training courses with feedback on their results. On average the drafters underestimated carcass weight by 4.0kg.

NA, Thomson, ML Barnes, and R Prestidge

Proceedings of the New Zealand Society of Animal Production, Volume 51, , 277-282, 1991