Exploring polymorphisms and effects of candidate genes on milk fat quality in dairy sheep

Abstract

Aim of the present study was to investigate the genetic control of the fatty acid (FA) composition in milk from three breeds of sheep: Altamurana, Gentile di Puglia and Sarda. SNP within genes, encoding enzymes putatively involved in the synthesis and metabolism of milk fat, were selected for analysis, and the allele substitution effects were determined for 16 genes, that were polymorphic in the three sheep breeds, upon the milk fat composition. Four genes (alpha-1-antichymotrypsin-2; diacylglycerol O-acyltransferase homolog-2; propionyl Coenzyme A carboxylase, beta polypeptide; insulin-like growth factor-I) play a role in the desaturation of stearic FA into polyunsaturated fatty acids (PUFA). Furthermore, two genes (growth hormone receptor and zona pellucida glycoprotein-2) affect the variability of the total fat content, in addition to the butyric and stearic FA profile, and that the fatty acid synthetase gene has an influence on the medium-chain FA. Milk FA profiles play an important role in dairy sheep farming because they have a large effect on cheese characteristics and also because sheep milk may be marketed as a source of nutraceuticals as it contains higher levels of CLA than milk from other ruminants. The current study evaluated the global effects of a large number of SNP and haplotypes on traits that are not commonly investigated in sheep but that are potentially very useful for improving milk quality.