Effects of FABP4 variation on milk fatty-acid composition for dairy cattle grazed on pasture in late lactation.

This research communication describes associations between variation in the fatty acid binding protein 4 gene (FABP4) and milk fat composition in New Zealand Holstein-Friesian × Jersey cross dairy cows. After correcting for the effect of the amino acid substitution p.K232A in diacylglycerol O-acyltransferase 1 (DGAT1), which is associated with variation in many milk fatty acid (FA) component levels, the effect of FABP4 c.328A/G on milk FA levels was typically small. For the five genotypes analysed, the AB cows produced more medium-chain fatty acids than CC cows (P < 0.05), and more C14:0 FA than AA and AC cows (P < 0.05). The AA and AC cows produced less C22:0 FA (P < 0.01) than the BC cows, and the AC cows produced more C24:0 FA (P < 0.05) than was produced by the BC cows. Cows of genotype CC produce more long-chain fatty acids than cows of genotype BC (P < 0.05).

Haplotypic variation in the UCP1 gene is associated with milk traits in dairy cows.

Uncoupling protein-1 (UCP1) plays a role in the regulation of body temperature, metabolic rate and energy expenditure in animals. While variation in UCP1 and its phenotypic effect has been investigated in humans and sheep, little is known about this gene in cattle. In this study, four regions of bovine UCP1 were investigated in 612 Holstein-Friesian × Jersey (HF × J) dairy cows using polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP) analyses. In the four regions of the gene analysed, a total of 13 SNPs were detected. Three sequences (a, b and c) were found in Region-2 and three sequences (A, B and C) were found in Region-4, and these were assembled into three (a-B, b-B and c-A) common and three (b-C, c-B and c-C) rare haplotypes. Of the three common haplotypes, b-B and c-A were associated (P < 0·007 and P < 0·043, respectively) with increased milk yield and tended to be associated (P < 0·085 and P < 0·070, respectively) with decreased fat percentage. Cows with genotype b-B/a-B produced more milk (P < 0·004), but with a lower percentage of fat (P < 0·035) and protein (P < 0·038) than cows with genotype a-B/a-B. Cows of genotype a-B/c-A had milk of low fat percentage (P < 0·017), but tended to produce more milk (P < 0·059) than cows of genotype a-B/a-B. This suggests that UCP1 affects milk yield, milk fat percentage and milk protein percentage.