1 College of Life Science and Engineering, Northwest Minzu University, Lanzhou 730030, China; 2 College of Animal Science and Technology, Ningxia University, Yinchuan 750021, China; 3 Gansu Provincial General Station of Animal Husbandry Technology Extension, Lanzhou 730030, China
Abstract：Milk fat and protein percentages are critical indicators of milk quality in dairy cows (Bos taurus). Acyl-CoA synthetase long chain family member 6 (ACSL6) is a key enzyme involved in fatty acid metabolism and is considered a promising candidate gene influencing milk production traits. This study aimed to investigate single nucleotide polymorphism (SNP) in the ACSL6 gene and their association with milk production traits in Chinese Holstein cattle. A total of 1 152 cows with clear pedigrees and complete production records were genotyped. Ten SNPs within the ACSL6 gene were identified through PCR amplification and Sanger sequencing, and subsequently genotyped using Sequenom mass spectrometry. Associations between SNPs and 5 traits—milk fat percentage, milk protein percentage, milk fat yield, milk protein yield, and 305-day milk yield—were analyzed using a general linear model. The result showed that all SNPs were in Hardy-Weinberg equilibrium (P>0.05) and exhibited moderate polymorphism (0.25<PIC<0.5) in the studied population. Association analysis revealed that the SNP locus g.22501195 C>T significantly influenced milk fat percentage (P<0.05), with the CC and TT genotypes exhibiting higher milk fat percentage. The SNP locus g.22502247 T>C showed significant correlation with milk fat percentage (P<0.05), and individuals with CC genotype demonstrated significantly higher milk fat percentage compared to those with TC and TT genotypes. The SNP locus g.22527204 C>T had significant effects on both milk fat percentage and milk protein percentage (P<0.05), with CC genotype individuals exhibiting elevated levels in both traits. The SNP locus g.22532788 A>T significantly influenced milk protein percentage (P<0.05), and AA genotype individuals demonstrated significantly higher milk protein percentage. These 4 loci formed 2 haplotype blocks (Block1 and Block2): Block1 showed significant association with milk fat percentage (P<0.05), while Block2 exhibited significant association with milk protein yield (P<0.05). The results of this study revealed a potential association between ACSL6 gene polymorphisms and milk production traits in Chinese Holstein cattle, suggesting that this gene could serve as an important candidate gene for screening molecular markers associated with high-yield and high-quality milk. This study provides a theoretical basis for molecular breeding and genetic improvement of high-quality milk traits in dairy cows.
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