Genotype by Environment Interaction in Australian Maternal and Terminal Sheep

Genotype by environment interactions (GxE) for economically important traits in Australian maternal and terminal sheep were investigated by both sire by flock interactions and multi-trait methods for performance data observed in eight flocks (sites) across Australia. The traits included growth traits: birth weight (bwt), weaning weight (wwt), post-weaning weight (pwt); carcass composition traits: carcass eye muscle depth (cemd), carcass fat (ccfat), lean meat yield (lmy) and dressing percentage (dressperc), and meat quality traits: intra-muscular fat (imf) and shear force (sf5). Univariate analyses showed that variation between genetic groups was relatively large compared to direct genetic variance and that maternal effects were significant for growth traits. The estimates of heritability were low for growth traits (from 0.08 to 0.11), moderate for most carcass composition traits (except for lmy) and sf5 (from 0.24 to 0.26), and high for lmy (0.44) and imf (0.50). Significant sire by flock interactions were found for growth traits and sf5. The average genetic correlations over pairs of flocks for each trait were 0.35 (bwt), 0.44 (wwt), 0.43 (pwt), 0.78 (cemd), 0.70 (ccfat), 0.77 (dressperc), 0.83 (lmy), 0.91 (imf) and 0.72 (sf5), respectively. Both the interaction term and multi-trait methods demonstrate that significant GxE existed for growth traits. The industry genetic evaluation should account for GxE for these traits.