Influence of dietary plant oils on mammary lipogenic enzymes and the conjugated linoleic acid content of plasma and milk fat of lactating goats

A feeding experiment with 15 lactating goats and 3 dietary treatments was conducted to investigate supplementation of safflower or linseed oil on milk production and the fatty acid (FA) profile of blood plasma and milk, and to measure the mRNA abundance of stearyl CoA desaturase (SCD), lipoprotein lipase (LPL), acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) in mammary biopsies. Goats were randomly assigned to one of three treatment groups with five goats per treatment consisting of a basal diet supplemented with chopped alfalfa hay at a level of 299.9 g/kg (dry matter (DM) basis) as the control (CON); CON diet mixed with safflower oil (50 g/kg of TMR DM) as a source of C18:2 (SO) or linseed oil (50 g/kg of TMR DM) as a source of C18:3 (LO). The experiment lasted 8 wks which included a 2 wk adjustment period. Milk fat yield (P<0.01) and milk fat content (P<0.01) increased with oil supplementation, and oil supplemented TMR increased concentrations of glucose and triglyceride (TG) in blood plasma. While supplementing oils decreased the proportion of short- to medium-chain FA, they increased the C18 unsaturated FA including conjugated linoleic acid (CLA) in plasma and in milk. The SO and LO treatments increased the mRNA abundances of both SCD and LPL. Oil supplementation is a useful way to alter the milk fat and FA profile of goat milk. An increase in the fat content of goat milk due to the supplemented oils was accompanied by increased LPL and abundance of ACC mRNA. Induction of a substantial increase of CLA in milk by supplementing these oils suggests that they may have an effect on some mammary lipogenic enzymes.