Unveiling Genetic Markers for Milk Yield in Xinjiang Donkeys: A Genome-Wide Association Study and Kompetitive Allele-Specific PCR-Based Approach.

Lactation traits are critical economic attributes in domestic animals. This study investigates genetic markers and functional genes associated with lactation traits in Xinjiang donkeys. We analyzed 112 Xinjiang donkeys using 10× whole genome re-sequencing to obtain genome-wide single nucleotide polymorphisms (SNPs). Genome-wide association analyses were conducted using PLINK 2.0 and GEMMA 0.98.5 software, employing mixed linear models to assess several lactation traits: average monthly milk yield (AY), fat percentage (FP), protein percentage (PP), and lactose percentage (LP). A total of 236 SNPs were significantly associated with one or more milk production traits (p < 0.000001). While the two-software identified distinct SNP associations, they consistently detected the same 11, 95, 5, and 103 SNPs for AY, FP, PP, and LP, respectively. Several of these SNPs are located within potential candidate genes, including glycosylphosphatidylinositol anchored high density lipoprotein binding protein 1 (GPIHBP1), FLII actin remodeling protein (FLII), mitochondrial topoisomerase 1 (TOP1MT), thirty-eight-negative kinase 1 (TNK1), polo like kinase 1 (PLK1), notch homolog 1 (NOTCH1), developmentally regulated GTP-binding protein 2 (DRG2), mitochondrial elongation factor 2 (MIEF2), glutamine-fructose-6-phosphate transaminase 2 (GFPT2), and dual-specificity tyrosine phosphorylation-regulated kinase 2 (DYRK2). Additionally, we validated the polymorphism of 16 SNPs (10 genes) using Kompetitive Allele Specific PCR, revealing that TOP1MT_g.9133371T > C, GPIHBP1_g.38365122C > T, DRG2_g.4912631C > A, FLII_g.5046888C > T, and PLK1_g.23585377T > C were significantly correlated with average daily milk yield and total milk yield in the studied donkeys. This study represents the first genome-wide association analysis of markers and milk components in Xinjiang donkeys, offering valuable insights into the genetic mechanisms underlying milk production traits. Further research with larger sample sizes is essential to confirm these findings and identify potential causal genetic variants.