Association Analysis Of Candidate SNP With Milk Traits In Italian Holstein Cows

Thanks to the availability of high-throughput genotyping technologies, SNP became the genetic markers of choice for high resolution genetics and genome-wide association studies. The SNP could have direct effects on the phenotypes or act as markers linked to the causal genomic variants. Moreover the estimate of the effects of SNP on production traits has to be verified in any new population in which this information is planned to be used in marker assisted selection. In the first step of a project supported by “Accordo Quadro CNR- Regione Lombardia” a 124 SNP panel was selected to genotype loci involved in milk protein and fat biosynthesis and responsible for genetic disease susceptibility in Italian Holstein breed. Also 13 SNP useful for animal identification and paternity analysis were included in the panel. About 500 cows were collected included both unrelated animals and family trios in order to confirm the described association between SNP and milk traits (milk yield, protein and fat yield and percentage), to check its functionality in paternity analysis, and to find new associations with other phenotypic traits, such as milk fatty acids (FA) composition. DNA was extracted both from blood and milk and genotyped with the Illumina GoldenGate Assay. Of the 124 SNP submitted for scoring by the Illumina assay design tool, 96 (84 for milk protein and fat biosynthesis and 12 for paternity analysis) had a SNP score guaranteeing a successful assay. Statistical tests were applied to detect the associations between SNP and traits also considering the tight linkage between some loci. Their use in marker assisted selection programs could be useful to modify nutritional qualities of milk through genetic selection.