Analysis of association between the MUC4 g.8227C>G polymorphism and production traits in Italian heavy pigs using a selective genotyping approach.

In pigs, susceptibility to enterotoxigenic Escherichia coli (ETEC) K88 strains (locus F4bcR) is determined by a dominant allele, with the recessive allele determining resistance. The susceptible allele also appeared to be associated with higher growth rate even with discordant results. A single nucleotide polymorphism (SNP) in exon 7 of the mucin 4 (MUC4) gene (DQ848681:g.8227C>G), shown to be in close linkage disequilibrium with the F4bcR locus, has been used as marker to identify susceptible pigs, substituting invasive villous adhesion tests. We herein analyzed this SNP in Italian local breeds and applied a selective genotyping approach in Italian Large White, Italian Landrace, and Italian Duroc comparing allele frequency distribution in groups of pigs with extreme estimated breeding values (EBV) for average daily gain (ADG) and backfat thickness (BFT) to evaluate if this marker is associated with these traits. Allele G (associated with susceptibility to ETEC) was associated with higher ADG and BFT in Italian Large White (P=6.66E-04 and P=0.012, respectively) and higher ADG in Italian Landrace (P=7.23E-12). This polymorphism was poorly informative in Italian Duroc. Antagonistic associations of the MUC4 g.8227C>G alleles on susceptibility to ETEC and growth performances evidence the complexity of applying marker assisted selection in pig breeding.