Identification of Genetic Polymorphisms of PI, PIII, and Exon 53 in the Acetyl-CoA Carboxylase-α (ACACα) Gene and Their Association with Milk Composition Traits of Najdi Sheep

SIMPLE SUMMARY: The acetyl-CoA carboxylase gene (ACACα) plays a role in facilitating the delivery of fatty acid precursors to the mammary glands during lactation. The purpose of this study was to identify single-nucleotide polymorphisms (SNPs) for promoter I (PI), promoter III (PIII), and Exon 53 in the ACACα gene to determine whether SNPs are associated with milk composition (MC) and the fatty acid profile (FA) in Najdi sheep milk. An analysis and alignment of the PI, PIII, and Exon 53 sequences for the ACACα gene identified twenty SNPs. The homozygous ewes with PI, PIII, and Exon 53 SNPs were associated (p < 0.05) with essential fatty acids (EFAs) (α-linolenic acid (ALA, n3), linoleic acid (LA, n6), and conjugated fatty acid (CLA)) in their milk fat. These results suggest that ACACα genes are involved in PUFA synthesis, which modifies the compositional properties of Najdi sheep milk, resulting in healthier dairy products. ABSTRACT: Recently, increasing attention has been paid to sheep milk products, which are high in saturated fatty acids (SFA), and the extent of their impact on human health. This study aimed to identify SNPs for PI, PIII, and Exon 53 in the ACACα gene and their association with the MC and FA profiles in Najdi sheep milk. A total of 76 multiparous Najdi ewes were used, and they were maintained using the same feeding system. Milk and blood samples were collected during the first lactation. A genetic polymorphism analysis identified 20 SNPs: 4 SNPs on PI, 6 SNPs on PIII, and 10 SNPs on Exon 53. In PI, the SNP g.4412G > A was associated (p < 0.05) with palmitic acid (C16:0), palmitoleic acid (16:1 n-7) and linoleic acid (LA), while SNP g.4485C > G was associated with CLA and vaccenic acid (VA) (p < 0.05). Furthermore, in PIII, two SNPs (g.1168A > G and g.1331G > T) were associated with milk protein (p < 0.05), while the SNP g.6860G > C in Exon 53 was associated with milk fat (p < 0.05). SNPs in the Najdi breed have been shown to be strongly related to milk fat and EFA contents. This could support a genetic selection program and the control of milk traits in the Najdi breed of high-quality dairy sheep.