Effects of Partial Myostatin Loss of Function on Carcass Yield and Meat Quality in Pigs Differing in IGF2 Genotype

The objective of this study was to evaluate the effects of partial loss of function (LOF) of MSTN on carcass composition and pork quality and determine whether the phenotype was influenced by the IGF2 genotype (IGF2-G3072A). Pigs (N = 44) segregating for the paternally expressed IGF2 G or A alleles were either wild-type (WT) or heterozygous (HET) for a targeted MSTN LOF allele and were harvested at 175 ± 5 days of age. Carcass composition and loin and belly quality traits were analyzed using linear models. Few significant MSTN × IGF2 genotype interactions were detected, indicating that the heterozygous MSTN phenotype was largely independent of IGF2 status. Relative to WT contemporaries, MSTN HET pigs exhibited greater dressing percentage and loin muscle area (p < 0.01) without differences in hot carcass weight or backfat depth, resulting in increased fat-free lean percentage. However, loins from HET pigs were approximately 5 L* units lighter in color (p < 0.01) and exhibited greater drip loss. Marbling scores and extractable lipid content were reduced in both loin and belly, and belly firmness decreased. The IGF2 genotype had similar muscle-deposition effects. These results indicate that partial MSTN LOF improves lean yield but introduces tradeoffs in pork quality, largely independent of IGF2 genotype.