Effect of genes related to meat quality traits on progeny of selected bulls of Italian Limousine breed

The aim of this study was to analyze polymorphisms in candidate genes for meat quality traits in the Italian Limousine beef breed. Chemical (proximate analysis and fatty acid profile) and physical (sample cut, colour, pH, cooking loss, shear force and free water) traits from steaks of 97 steers progeny of 9 selected bulls were recorded. DNA was extracted from the same animals and analysed at 10 SNP mutations in 7 different genes: myostatin (MSTN), dyacilglycerol-acyltransferase (DGAT), calpain (CAPN), calpastatin (CAST), leptin (LEP), thyroglobulin (TG), fatty acid binding protein (FABP). Allele and genotype frequencies, heterozygosity, and Hardy-Weinberg equilibrium for each SNP were estimated. Haplotype reconstruction through Phase software was also performed for SNPs located on the same chromosome. The association among SNPs or haplotypes and the recorded traits has been performed through a linear mixed model incorporating the effect of the pedigree with the pedigreemm package in R. Two SNPs at myostatin gene (F94L and Q204X) and one located in the thyroglobulin gene (C422T) were fixed whereas the other SNPs presented a MAF .05. Fixation of the first two SNPs might be either the result of the selection program developed so far or the bias due to the small sample size. No significant departures from Hardy-Weinberg equilibrium were identified for the genotypes, except for the CAST282 located in the calpastatin gene where a moderate excess of heterozygous genotypes was observed. Accounting for haplotypes did not change the association results in any of the traits analyzed. Two out of three SNPs of the CAPN gene (CAPN316 and CAPN530) and one at CAST gene (CAST282) were associated with meat tenderness, free water content and fatty acid profile. Thus the combined effect of favourable alleles for CAPN and CAST markers resulted in improved meat quality traits providing further evidence that selection based on these markers might be feasible. There are also evidence that SNPs at FABP, DGAT and CAST genes were associated with fat traits confirming the important role of these genes in lipid metabolism of intramuscular fat. No significant association between LEP gene and meat quality traits has been found. Due to the moderate size of the sample is not possible to draw final conclusions but the result suggests to deepen the studies at the final aim of incorporating markers information in the selection criterion of Italian Limousine breed.