Effect of polymorphisms in the goat DGAT1 gene on milk fat traits

Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) plays a key role in lipid metabolism, catalyzing the final stage of triacylglycerol synthesis. In cattle, a non-synonymous substitution in DGAT1 influences enzyme activity with a major effect on milk composition. This aspect makes DGAT1 an interesting candidate gene to explain the phenotypic variation of milk related traits in other species such as goats. Aim of this work was to identify polymorphisms in the goat DGAT1 gene and to study their association with milk fat and other milk related traits. The goat DGAT1 gene was screened for polymorphism in 12 animals of 6 breeds. Sequence analysis of the gene from exon 3 to 17 revealed the presence of 4 single nucleotide polymorphisms (SNPs) in introns 7, 12, 14 and 16. No SNP was identified in the coding regions of our sequences, confirming a low level of polymorphism of this gene in goat. The SNPs genotyping, of 109 Alpine and 84 Saanen bucks, revealed high frequencies of the major alleles (from 0.82 to 0.99). To evaluate the effect of single SNPs an association analysis on about 28.000 records of milk (kg/d), fat (kg/d and %) and protein (kg/d and %) of 1900 daughters was performed using a mixed linear model, with bucks genotype (from 59 Alpine and 55 Saanen bucks) as fixed effect among others, followed by permutations. Results showed significant associations of the SNP in intron 12 with fat % in the Alpine breeds, and of the SNP in intron 14 with fat kg/d and % in the Saanen breed.