Factors affecting the colour of lamb meat from the longissimus muscle during display: The influence of muscle weight and muscle oxidative capacity

•70% of lambs failed to produce loin meat of sufficient redness after 3 days of display.•Sire selection for increased muscle weight increased R630/R580 by 0.27 units.•Increasing isocitrate dehydrogenase activity reduced R630/R580 by 0.5 units.•Increasing hot carcass weight at a given age increased R630/R580 by 0.5 units.•Increasing pH24 across a range of 5.4 to 6 reduced R630/R580 by 0.88 units.

Spectrophotometric measures were used to determine the redness:browness (R630/R580) of 4238 lamb longissimus muscle after 3 days under simulated display. The results were analysed using linear mixed effects models. Environmental factors represented by effects such as kill group and site of production produced the greatest variation of up to 2.76 units in R630/R580. Isocitrate dehydrogenase activity, reflecting muscle oxidative capacity, reduced R630/R580 by 0.5 units. Selection for high muscling sires increased R630/R580 by 0.27 units, likely due to changes in muscle oxidative capacity. Lamb carcass weight also increased R630/R580 by 0.5 units. Analysis of genotypic factors influencing lamb size and growth rate such as sire type and dam breed further supported that increased growth rate improves meat R630/R580. Our findings suggest that breeding for increased growth rate and increased muscle weight could result in Australian lamb meat retaining its red colour for extended periods whilst on display.