Ten Genetic Loci Identified for Milk Yield, Fat, and Protein in Holstein Cattle

The production of high-yield and high-quality milk is the direct economic goals of dairy industry breeding. Understanding the genetic architecture underlying milk-related traits is beneficial so that genetic variants can be targeted toward the overall improvement. In this study, we measured five traits related to milk production and components in Holstein cattle population from China. These traits included milk yield, protein yield, and fat yields; fat percentage and protein percentages. We used the estimated breeding values as dependent variables to conduct the genome-wide association study (GWAS). Breeding values were estimated through pedigree relationships by using a mixed linear model for individuals with and without phenotypic data. Genotyping was carried out on the individuals with phenotypes by using the Illumina BovineSNP150 BeadChip. The association analyses were conducted by using the Fixed and random model Circulating Probability Unification (FarmCPU) method. A total of 10 SNPs was detected above the genome-wide significant threshold, six were located in previously reported QTL regions. We also found 8 candidate genes each is within a distance of 120 kb upstream and downstream to an associated SNPs, the most significant SNP affecting milk fat and protein percentage is in the DGAT1 gene. These genetic variants and potential candidate genes would be valuable resources to enhance dairy cattle breeding.