The effect of Ala293Val single nucleotide polymorphism in the stearoyl-CoA desaturase gene on conjugated linoleic acid concentration in milk fat of dairy cows
The objectives of this study were to determine the effects of the Ala293Val single nucleotide polymorphism in stearoyl-CoA desaturase (SCD) on the concentration of cis-9, trans-11 conjugated linoleic acid (CLA) in milk fat of dairy cows, and to identify a phenotypic indicator of cows with a greater genetic capability to produce CLA that is not affected by dietary lipid content. In Study 1, 12 cows, four of each Ala293Val SCD genotype, were fed either a control or an oil-supplemented diet in a cross-over design to examine effects of diet, genotype and their interaction. The CLA concentration in milk fat was greater for cows fed the oil-supplemented (4.4%) vs. the control diet (0.6%), but was not affected by the Ala293Val SCD genotype. In Study 2, the Ala293Val SCD genotype of 215 dairy cows at a commercial dairy did not affect milk yield, composition, or CLA concentration in milk fat. However, in both studies, C14:1 desaturation index was greater for the AA genotype compared with the others. The Ala293Val SCD genotype may not affect CLA production although the SCD Ala293 allele is associated with a higher C14:1 desaturation index possibly because effects of the SCD genotype vary depending on fatty acid chain length or origin.