Genetic effects of stearoyl-coenzyme A desaturase (SCD) polymorphism on milk production traits in the Chinese dairy population.

Stearoyl-CoA desaturase (SCD) is a multifunctional complex enzyme important in the cellular biosynthesis of fatty acids. The present study was to investigate the association of the SCD gene with milk production traits in dairy cattle. Two single nucleotide polymorphisms (SNPs) (g.6926A>G and g.8646A>G) in introns 3 and 4, and three SNPs (g.10153A>G, g.10213T>C and g.10329C>T) in exon 5 were identified with pooled DNA sequencing and genotyped using matrix-assisted laser desorption/ionization time of flight mass spectrometry assay in 752 Chinese Holstein cows. Polymorphism g.10329C>T was predicted to result in an amino acid replacement from alanine to valine in the SCD protein. With a mixed animal model, the significant associations of the five SNPs with 305-day milk, fat and protein yields and protein percentage were determined. We further demonstrated cows with heterozygous genotypes (A/G or C/T) had highest 305 day milk yield, fat yield, protein yield and lowest protein percentage. Heterozygous cows with genotype AG at the g.6926A>G locus showed the greatest milk yield (P < 0.0001), fat yield (P < 0.0001) and protein yield (P < 0.0001) among other heterozygous genotypes at any of the loci. Dominance effects of all identified SNPs on milk, fat and protein yields and protein percentage were significant. Moreover, significant allele substitution effects at g.6926A>G locus on milk yield and at g.10213T>C on protein yield were observed. Five-locus haplotypes and strong linkage disequilibrium (D' > 0.9) between the five SNPs were also observed. The results suggest that identified polymorphisms could be potential genetic markers to improve the production performance of Chinese Holstein.