Sandrine did her thesis on milk fat composition

Thesis title

Effects of Polymorphisms in DGAT1 and SCD1 on Milk Fat Composition of Summer Milk Samples.

Summary

The aim of this study is to analyze the effects of polymorphism in DGAT1 and SCD1 on milk fat composition of summer milk samples, compare the main differences between winter and summer milk samples and estimate genetic parameters. For this purpose, summer milk samples were retrieved from 1,795 cows belonging to 398 commercial herds in the Netherlands during the period of May and June 2005. Effects of DGAT1, SCD1 and genetic parameters were compared with winter milk samples from the same population. Genotypes for DGAT1 K232A and SCD1 A293V polymorphisms’ were retrieved for most of the cows.

Results pointed out that summer milk samples had lower proportions of C16:0 and SFA, whereas higher proportions of C18:0 and unsaturated C18 FA were found. Effects of DGAT1 K232A polymorphism suggest that the activity or specificity of the 232K allele might be increased due to the higher availability of substrate during the summer when compared to winter milk samples. Effects of SCD1 A293V polymorphism suggests that the activity or the specificity of the A293V alleles might be influenced either by FA originated de novo or from ruminal microbiota activity. Genetic parameters analyses suggested that summer and winter milk samples were similar, but that part of the differences could be explained by herd variation, that includes feeding as well as herd management practices.

Key words

DGAT1 K232A polymorphism, SCD1 A293V polymorphism, milk fat composition, genetic parameters, herd variation.

This work resulted in a scientific publication:

Genetic correlation between composition of bovine milk fat in winter and summer, and DGAT1 and SCD1 by season interactions, S. Duchemin, H. Bovenhuis, W.M. Stoop, A.C. Bouwman, J.A.M. van Arendonk, M.H.P.W. Visker, Journal of Dairy Science, Volume 96, Issue 1, January 2013, Pages 592-604.