Supplementation with extruded linseed cake affects concentrations of conjugated linoleic acid and vaccenic acid in goat milk

The aim of the research was to determine what effect adding extruded linseed cake to the dry diet of goats had on the concentrations of conjugated linoleic acid (CLA) and trans vaccenic acid (VA) in milk fat. Thirty crossbreed dairy goats were divided into three groups. They had their diet supplemented with 0% (control group, C), 5% (low group, L) or 10% (high group, C) of extruded linseed cake (ELC). This supplied 0, 16 and 32 g/d of linseed fat to groups C, L and H respectively. The milk fat percentage (overall mean 3.5%) and yield did not differ with the different diets, but fatty acid composition was affected by the ELC supplements. The inclusion of ELC in the diets did not influence the concentration of FA from C6:0 to C12:0. The concentrations of C14:0 and C16:0 decreased as the quantity of ELC supplements increased. The concentrations (mg/100 mg of total fatty acids methyl ester; FAME) of VA (0.70, 1.23 and 1.39 in C, L and H groups respectively) and cis9, trans11 CLA (0.63, 0.96 and 1.05 in C, L and H groups respectively) were increased by ELC supplements. The milk fat content of VA and cis9, trans11 CLA were closely correlated (R2 = 0.82). Desaturation of VA in the mammary gland to produce cis9, trans11 CLA was higher in C group than in the groups with ELC diets. The ELC supplementation to lactating goats may enhance the nutritional profile of milk lipids.