Molecular markers located on the DGAT1, CAST, and LEPR genes and their associations with milk production and fertility traits in Holstein cattle.

The objective of the present study was to investigate single nucleotide polymorphisms (SNPs) located in three candidate genes previously reported to have effects on fertility and milk production traits in a population of 123 Holstein cows. The milk production traits evaluated included lifetime averages of milk yield, protein concentration, and fat concentration. Fertility traits evaluated included lifetime averages of services per conception and days-open. Candidate genes included those encoding diacylglycerol acyltransferase (DGAT1), leptin receptor (LEPR), and calpastatin (CAST). A total of 60 SNPs were selected (20 per gene) at equidistant locations on each candidate gene to identify potential linkage with causative mutations. Four SNPs were identified as being significantly associated with the evaluated fertility traits. Specifically, SNPs rs109663724 and rs137673193 were significantly associated with lifetime average days-open, while rs109663724 and rs135560721 were significantly associated with lifetime average number of services per conception. Five SNP (rs109663724, rs132699547, rs135423283, rs135576599, and rs13675432) were significantly associated with lifetime averages of milk protein concentration and milk fat concentration, with only one SNP (rs109663724) being significantly associated with the average lifetime milk yield. Although multiple SNPs were identified in the current study as being significantly associated with milk production and fertility traits, it is essential that these SNPs are validated in larger populations, under more diverse environments, and that additional SNPs and candidate genes are evaluated prior to their implementation into selection strategies.