Lamb carcass grading is changing from classification on carcass weight and tissue depth (GR) to yield grading systems such as VIAscan®. Under the VIAscan® system, farmers receive information on the percentage lean meat yield from the hindleg, loin and shoulder primal cuts, and payments are based on these measurements. Genetic improvement programmes for meat have concentrated on producing age-adjusted breeding values for carcass lean and fat weight from live weight and ultrasonic eye muscle measurements. This has worked well for grading using carcass weight and GR, but does not quantify differences in yield between meat cuts. Carcass and VIAscan® yield data collected for the Meat and Wool New Zealand Central Progeny Test were analysed to determine heritabilities and genetic and phenotypic correlations for meat yield traits. The dataset contained around 6,600 progeny from 143 terminal sire or dual purpose rams. Data were analysed using linear mixed models in ASReml. The results showed significant variation between sires for lean yield traits. Heritabilities for age-adjusted lean weight in the hindleg, loin and shoulder were 0.40, 0.37 and 0.42, respectively. Genetic correlations for age-adjusted weight of lean by carcass region were all high (range 0.94 to 0.96), but were lower (0.62 to 0.85) when adjusted to constant carcass weight.
Proceedings of the New Zealand Society of Animal Production, Volume 69, Christchurch, 215-219, 2009
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