Abstract
Meat colour was measured in 7732 lambs produced at 8 sites across Australia over a 5 year period (2007-2011) and slaughtered in 125 groups as pari of the Sheep Cooperative Research Centre's information nucleus flock experiment. Lambs were the progeny of sites of different types (merino, maternal and terminal) selected for a diverse range in Australian Sheep Breeding Values for post weaning eye muscle depth (PEMD). 24 hours post slaughter them. longissimus was cut at the 12th rib, a probe was used to measure pH and the meat surface was allowed to bloom/oxygenate for 30 minutes before fresh colour measures of lightness (L*), redness (a*) and yellowness (b*) were captured using a Minolta colorimeter. These measures were analysed in a multivariate analysis before least square means were produced for L *,a* and b* using a linear mixed effects model in SAS. The base model included fixed effects for site, year of birth, slaughter group, sex and dam breed within sire type as well as random effects for sire and dam by year. In a second analysis sire PEMD estimates were included in the model as a covariate. Increasing sire PEMD across a range of -2 to 4 was associated with an increase (P<0.01) in the predicted means for L*, a* and b* by 1.15, 0.38 and 0.55 units respectively. When pH measured 24 hours post-m01iem was accounted for in the model, the impact of sire PEMD estimates on L *, a* and b* were halved. This suggests that selection for sires based on PEMD may impact meat colour via changes in muscle metabolism that affect the extent of glycolysis and pH decline post slaughter. Our findings suggest that using sires with high PEMD will improve the lightness and redness of the meat produced.