Genes that affect meat production, fat deposition and carcass weight in pigs

Muscle growth is a critical trait in the pig industry, as increased muscle growth results in increased meat yield. In this context, the aim of this study was to investigate genes that may be involved in muscle growth and carcass traits in pigs. A total of 474 commercial pigs from New Zealand and Thailand were investigated using polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis to explore variation in nine candidate genes. These genes included: the myogenic regulatory factor 5 gene (MYF5), the myogenin gene (MYOG), the calpastatin gene (CAST), the calpain 3 gene (CAPN3), the myostatin gene (MSTN), the callipyge gene (CLPG), the leptin gene (LEP), the beta-3 adrenergic receptor gene (ADRB3) and the immunoglobulin heavy alpha chain gene (IGHA). These genes have been reported to influence muscle growth rate, meat production and other production traits in animals. Sequence analyses revealed genetic variation at all the loci tested, with the exception of MSTN, which was not variable in the region tested in the pigs studied. There were two variants of MYOG, CAPN3, CLPG and ADRB3, and three variants of LEP and IGHA, including a new variant, that has not been reported previously. The highest level of variation detected was four variants of MYF5 and CAST. The variation in each gene was tested for its association with production traits in the pigs studied. The presence of variant A of MYF5 exon 3 was associated with increased weaning- weight and decreased fat depth. Variant C of CAST intron 5 was associated with increased live weight, average daily gain (ADG) and lean growth rate. Variant D of CAST intron 5 was associated with increased ADG and increased fat depth, while variant B of CAST exon 6 tended (P=0.064) to be associated with increased lean growth rate. The genotype AB of CAST exon 6 tended (P=0.065) to be associated with increased lean growth rate. Variant B of ADRB3 was associated with increased weaning-weight and hot carcass weight.. Absence of variant A was associated with increased fat depth, but this finding is weak since only two individual pigs carried this genotype. Variant B of IGHA was associated with decreased fat depth. Together, these data suggest that genetic variation in MYF5, CAST, ADRB3 and IGHA may be involved in skeletal muscle growth and meat production in pigs. There was no association observed with variation in LEP and some variants of MYOG, CLPG and CAPN3 were at a low frequency, which precluded further analysis. Given that these results could be of benefit to the pig industry, the genes warrant further investigation