The objective of this study was to evaluate the effects of two levels of maize silage and extruded soybeans supplementation on fatty acid profile in milk fat of dairy cows. Eight Holstein cows were distributed in a double 4x4 Latin Square design with a factorial arrangement. The treatment groups were: high maize silage and low lipid, high maize silage and high lipid, low maize silage and low lipid and low maize silage and high lipid. The experimental periods lasted 21 days. Milk samples were collected on days 18 and 19 of each experimental period. The increase of lipid contents in high and low maize silage diets decreased short chain fatty acids concentrations (C4:0 - C12:0). The conjugated linoleic acid content (cis-9 trans-11 C18:2) increased from 3.72 to 4.85, and 4.6 to 5.89mg/g, when extruded soybeans was used in high and low level of corn silage, respectively. The increase in dietary lipids content resulted in higher trans-11 C18:1 fatty acid concentration. Fatty acid trans-10 C18:1 tended to increase with the elevation of the lipids content in the diet. There was significant correlation between trans-10, cis-12 C18:2 and milk fat percentage. The extruded soybeans supplementation decreased shortchain fatty acids and palmitic acid in milk. In addition, this oilseed enhanced the concentration of conjugated linoleic acid (C18:2 cis-9 trans-11) and vaccenic acid, which improved the milk quality for the human health.
CLA; concentrate; lipids; rumenic acid; vaccenic acid