Abstract
BackgroundThe milk fat profile of the Danish Holstein (DH) and Danish Jersey (DJ) show clear differences. Identification of the genomic regions, genes and biological pathways underlying the milk fat biosynthesis will improve the understanding of the biology underlying bovine milk fat production and may provide new possibilities to change the milk fat composition by selective breeding. In this study a genome wide association scan (GWAS) in the DH and DJ was performed for a detailed milk fatty acid (FA) profile using the HD bovine SNP array and subsequently a biological pathway analysis based on the SNP data was performed.ResultsThe GWAS identified in total 1,233 SNPs (FDR < 0.10) spread over 18 chromosomes for nine different FA traits for the DH breed and 1,122 SNPs (FDR < 0.10) spread over 26 chromosomes for 13 different FA traits were detected for the DJ breed. Of these significant SNPs, 108 SNP markers were significant in both DH and DJ (C14-index, BTA26; C16, BTA14; fat percentage (FP), BTA14). This was supported by an enrichment test. The QTL on BTA14 and BTA26 represented the known candidate genes DGAT and SCD. In addition we suggest ACSS3 to be a good candidate gene for the QTL on BTA5 for C10:0 and C15:0. In addition, genetic correlations between the FA traits within breed showed large similarity across breeds. Furthermore, the biological pathway analysis revealed that fat digestion and absorption (KEGG04975) plays a role for the traits FP, C14:1, C16 index and C16:1.ConclusionThere was a clear similarity between the underlying genetics of FA in the milk between DH and DJ. This was supported by the fact that there was substantial overlap between SNPs for FP, C14 index, C14:1, C16 index and C16:1. In addition genetic correlations between FA showed a similar pattern across DH and DJ. Furthermore the biological pathway analysis suggested that fat digestion and absorption KEGG04975 is important for the traits FP, C14:1, C16 index and C16:1.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1112) contains supplementary material, which is available to authorized users.
Highlights
The milk fat profile of the Danish Holstein (DH) and Danish Jersey (DJ) show clear differences
This is supported by a genome wide association study (GWAS) that has been published on milk fatty acid (FA) in Dutch dairy cattle showing that medium chain and unsaturated FA are strongly influenced by DGAT and stearoyl-CoA desaturase (SCD) respectively, but other regions showed significant association [9]
The aim of this study was two-fold 1) perform a genome wide association scan (GWAS) using the bovine HD SNP array in both the DH and DJ breed in order to identify genomic regions in both breeds and identify similarities and differences between the breeds in the genetic regulation of milk FA and 2) identify the biological pathways underlying the FA biosynthesis based on the SNP markers
Summary
The milk fat profile of the Danish Holstein (DH) and Danish Jersey (DJ) show clear differences. Polymorphisms in major genes like diacylglycerol O-acyltransferase 1 (DGAT1) and stearoyl-CoA desaturase (SCD) have a large influence on the milk fat composition [4,5,6,7], it has been shown that the biosynthesis of milk fat is a complicated process regulated by many genes [8] This is supported by a genome wide association study (GWAS) that has been published on milk FAs in Dutch dairy cattle showing that medium chain and unsaturated FA are strongly influenced by DGAT and SCD respectively, but other regions showed significant association [9]
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