Genetic parameters for meat quality and carcass traits and their correlation with wool traits in Australian Merino sheep

Estimates of genetic parameters for carcass traits in Merino sheep are presented, including muscle pH and colour, which are indicators of meat quality. The inclusion of these in the parameter set for genetic evaluation will provide the basis for more accurate estimated breeding values and the design of better breeding programs for improving meat traits in straightbred Merino sheep and crossbred lamb production. Data from 1045 nineteen-month-old Merino rams, the progeny of 125 sires from 3 strains that are representative of the industry, were used. Heritability and genetic correlations were estimated by fitting an animal model using a REML procedure in univariate and multivariate analyses. The traits included fasted pre-slaughter liveweight; dressing %; carcass tissue depth at the GR site (FATGR); fat depth at the C site (FATC); eye muscle depth (EMD), width (EMW), and area (EMA); ultimate pH and colour (L*, a*, b*) of the eye muscle. Multivariate analyses were used to estimate genetic correlations among meat traits and between wool traits (clean wool weight and mean fibre diameter) and selected carcass and meat traits. Estimates of heritability were: liveweight 0.51 (+/-0.10), dressing % 0.39 (+/-0.10), FATGR 0.33 (+/-0.09), FATC 0.20 (+/-0.08), EMD 0.27 (+/-0.08), EMW 0.15 (+/-0.07), EMA 0.23 (+/-0.08), muscle pH 0.27 (+/-0.09), and 0.14 (+/-0.07), 0.02 (+/-0.06), and 0.04 (+/-0.06) for the meat colour measurements L*, a*, and b*, respectively. There was a favourable genetic correlation between muscle pH and colour L* of -0.56 (+/-0.23). There were also significant genetic correlations between wool weight and FATGR (-0.34 +/- 0.16) and between mean fibre diameter and muscle colour L* (-0.66 +/- 0.27). The study indicates that there is genetic variation for carcass traits, including indicators of meat quality, with scope for selection to improve meat production and quality in Merino sheep.