Additional support for an association between the fat mass and obesity associated (FTO) gene and intermuscular fat deposition in Italian Duroc pigs

In humans, mutations in the fat mass and obesity associated (FTO) gene are associated with the obesity phenotype in several populations. In pigs, we already identified three single nucleotide polymorphisms (SNPs) in the FTO gene that we genetically assigned to porcine chromosome 6 (SSC6), in an imprinted QTL region for fat deposition. Then, using a selective genotyping approach, we showed that an SNP in this gene (g.276T>G) was associated with visible intermuscular fat (VIF, a measure that resembles intermuscular fat content) in Italian Duroc pigs. Here, we refined the mapping of this gene to SSC6 using a radiation hybrid panel and evaluate the effect of the same mutation in two different pig samples. The first was constituted by 157 sib-tested Italian Duroc animals for which estimated breeding values (EBV) for average daily gain, feed:gain ratio, back-fat thickness, lean cuts, ham weight and VIF were calculated. The second group of pigs was constituted by 117 commercial hybrids measured for a total of 31 carcass and fatness traits. In the Italian Duroc pigs the FTO marker was associated only with VIF EBV (P = 0.027). In the second group of pigs, the FTO genotypes showed a tendency to be associated with several fat deposition traits. These results confirm that FTO is an important source of variability for intermuscular fat deposition in Italian Duroc pigs while the effects on fatness traits in commercial pig populations should be further investigated.