Genetic variation of C18:1 and C18:2 isomers in sheep milk fat

The aim of the present study was to evaluate the genetic variation of milk fat CLA, together with the variation of CLA precursors, including the individual PUFA that are potentially involved in the metabolic pathway of CLA. The allelic substitution effect, upon these FA, was estimated for a number of polymorphisms, that are located within 9 candidate genes known to influence milk FA partitioning. Sheep milk was chosen because it contains higher total fat percentage, and higher CLA levels per gram fat, than milk of other ruminants. Milk FAME analyses were performed on individual milk samples of sheep from three different breeds. Our results reflect the association of three genes (alpha-1-antichymotrypsin; diacylglycerol O-acyltransferase homolog-2; and zona pellucida glycoprotein-2) with the values of both linolenic FA and CLA; of three more genes (insulin-like growth factor I; lecithin-cholesterol acyltransferase and propionyl coenzyme A carboxylase, beta polypeptide) with the variability of linolenic FA; and of one gene, the fatty acid synthetase with the variability of CLA and stearic FA. The current study might contribute to the understanding of the metabolic pathway of PUFA in sheep milk, providing suggestions to modify milk fat composition through selection.