Effect of DGAT1 K232A polymorphism on Milk Production Traits in Iranian Holstein Cattle

Acyl-CoA: diacylglycerol acyltransferase-1 (DGAT1) gene has been mapped at centromeric end of bovine chromosome 14 and is known as a factor affecting fat content of milk. Our objective was to determine the relationship between the K232A polymorphism at the gene and milk traits in Holstein cattle of Iran. A 411 bp fragment including this polymorphism was amplified and digested with the enzyme CfrI to determine the genotypes of 206 Holstein cows. The estimated allele frequencies were 0.66 and 0.34 for the A (alanine) and K (lysine) alleles, respectively. Average allele substitution effects of the K allele for all traits in the first and second lactations were estimated, separately. The statistical analyses showed positive and significant effects of the K allele for fat and protein content traits, as well as for the fat yield in both lactations. In contrast, negative and significant effects were found for milk and protein yield. The relatively lower frequency of the K allele than the A allele may be due to selection for milk yield in recent years. Our results showed that the DGAT1 K232A polymorphism can be a source that underlies the reported quantitative trait loci for fat content trait in the proximal region of bovine chromosome 14.