Oxidative stability of milk and expression of oxidative stress response, lipogenic-related, and IGF-1 genes in early-lactation cows supplemented with peanut and sunflower oils

Context. Feeding dairy cows with plant oils rich in unsaturated fatty acids is a recommended strategy for increasing the proportion of polyunsaturated fatty acids in milk for human consumption. Aims. We evaluated the effects of supplementation with peanut oil (high oleic acid content) and sunflower oil (high linoleic acid content) on the fatty acid profile and oxidative stability of milk and the expression of oxidative stress response, lipogenic-related and insulin-like growth factor 1 (IGF-1) genes in pasture-fed Jersey cows in early lactation. Methods. Twenty-four cows were distributed in a randomised block design. Treatments were four dietary supplements of concentrate alone, or concentrate plus oil (59.6 g/kg dry matter): peanut oil, sunflower oil, or a 1:1 (v/v) mixture of peanut and sunflower oils. Analyses were performed at 30 and 60 days in milk. Key results. Both peanut oil and mixed oil diets increased the hypocholesterolemic/hypercholesterolemic ratio (P < 0.001) and health-promoting index (P < 0.001) of milk. The sunflower oil diet increased the thrombogenicity index (P = 0.005) and conjugated diene production (P < 0.001). mRNA abundance of fatty acid synthase (P = 0.003), acetyl-CoA carboxylase alpha (P = 0.001), and stearoyl-CoA desaturase (P < 0.001) decreased with the sunflower oil diet. mRNA abundance of superoxide dismutase decreased (P = 0.01) with sunflower oil and mixed oil diets. The control diet tended (P = 0.08) to reduce IGF-1 mRNA abundance. Conclusions and implications. Supplementation with peanut oil increases the health-promoting index of milk, whereas supplementation with sunflower oil increases susceptibility to lipid peroxidation. Supplementation with sunflower oil reduces the expression of lipogenic and antioxidant enzyme genes, and supplementation with unsaturated fats may reduce IGF-1 gene expression in early-lactation cows. The relatively small sample size means that more studies are needed.