Dutch Milk Genomics Initiative

Dutch Milk Genomics Initiative Reveals Large Genetic Variation in Milk-fat Composition

Anke Schennink1, W. Marianne Stoop1, Marleen H. P. W. Visker1, Jeroen M. L. Heck2, Henk Bovenhuis1, Hein J. F. van Valenberg2, Toon Van Hooijdonk2, Johan A. M. van Arendonk1,
1Animal Breeding and Genomics Centre, Wageningen University, the Netherlands; and 2Dairy Science and Technology, Wageningen University, the Netherlands

Milk and milk-derived foods contribute substantially to dietary fat, but have a fat composition that is not optimal for human health. The aim of our study is to identify possibilities for selective breeding to improve the composition of cow’s milk and to characterize genes involved in milk-fat synthesis and milk-fat metabolism. We measured the fat composition of milk samples in 1,933 Dutch Holstein Friesian cows in their first lactation. Substantial genetic variation in milk-fat composition was found: heritabilities were high for the short-chain fatty acids C4:0-C12:0 (0.59) and for the medium-chain fatty acids C14:0 (0.59) and C16:0 (0.43). Heritabilities for the saturated and unsaturated long-chain fatty acids C18 were moderate (around 0.25), except for the conjugated fatty acid C18:2 cis-9 trans-11 (0.42). We genotyped polymorphisms in several genes involved in fatty acid and triglyceride synthesis and fat metabolism to study associations with milk-fat composition traits. The K232A polymorphism in diacylglycerol acyltransferase 1 (DGAT1) for example, is known to affect milk-fat percentage. Our analysis revealed that this polymorphism also has a clear influence on milk-fat composition. The A allele of DGAT1 is associated with less saturated fat; a smaller fraction of C16:0; and larger fractions of C14:0, unsaturated C18, and CLA. The large genetic variation shows that selective breeding can make a significant contribution to improve dairy quality, which offers opportunities to meet consumer’s demands. Polymorphisms such as DGAT1 K232A can be used as markers in genetic selection.