Genome-Wide Association Study for Milk Fatty Acids in Holstein Cattle Accounting for the DGAT1 Gene Effect.

Valdecy A R Cruz,Flavio S Schenkel,Steven Larmer,Allison Fleming,Filippo Miglior,Hinayah R Oliveira,Luiz F Brito

doi:10.3390/ani9110997

Abstract

Simple SummaryMilk fat content and fatty acid composition are key traits for the dairy industry, as they directly influence consumer acceptance of dairy products and are associated with the chemical-physical characteristics of milk. In order to genetically improve milk fat composition, it is important to understand the biological mechanisms behind the phenotypic variability observed in these traits. In this study, we used a genomic dataset for 6692 animals and over 770,000 genetic markers distributed across the genome. We compared different statistical approaches to better identify the genes associated with milk fatty acid composition in Holstein cattle. Our results suggest that the DGAT1 gene accounts for most of the variability in milk fatty acid composition, and that the PLBD1 and MGST1 genes are important additional candidate genes in Holstein cattle.The identification of genomic regions and candidate genes associated with milk fatty acids contributes to better understand the underlying biology of these traits and enables breeders to modify milk fat composition through genetic selection. The main objectives of this study were: (1) to perform genome-wide association analyses for five groups of milk fatty acids in Holstein cattle using a high-density (777K) SNP panel; and (2) to compare the results of GWAS accounting (or not) for the DGAT1 gene effect as a covariate in the statistical model. The five groups of milk fatty acids analyzed were: (1) saturated (SFA); (2) unsaturated (UFA); (3) short-chain (SCFA); (4) medium-chain (MCFA); and (5) long-chain (LCFA) fatty acids. When DGAT1 was not fitted as a covariate in the model, significant SNPs and candidate genes were identified on BTA5, BTA6, BTA14, BTA16, and BTA19. When fitting the DGAT1 gene in the model, only the MGST1 and PLBD1 genes were identified. Thus, this study suggests that the DGAT1 gene accounts for most of the variability in milk fatty acid composition and the PLBD1 and MGST1 genes are important additional candidate genes in Holstein cattle.

Highlights

Milk fat composition is directly related to nutritional aspects of milk and dairy products, which account for up to 30% of the total fat intake in the human diet [1]
A ranking of single nucleotide polymorphisms (SNPs) variances when not fitting or fitting the Diacylglycerol O-acyltransferase 1 (DGAT1) gene as a covariate in the statistical model is presented in the Supplementary File 1
Large differences in rank were observed between the two models, and larger variances for the significant SNPs were estimated by model 1 compared to model 2

Summary

Introduction

Milk fat composition is directly related to nutritional aspects of milk and dairy products, which account for up to 30% of the total fat intake in the human diet [1]. Several studies have documented the potential effects of dietary fatty acids on human nutrition, as well as the recommended limit of dietary fat intake [2,3,4]. Saturated (SFA) and 30% unsaturated (UFA) fatty acids [5,6]. Some fatty acids are essential nutrients for human health, such as phospholipids, that are important constituents of cell membranes [7]. The high SFA content in milk is often undesirable, as it has been associated with several diseases, including elevated blood cholesterol, obesity, and cardiovascular problems [2,8,9]. Saturated fatty acids and UFA of different chain lengths have ranging heritability estimates

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