Lactational responses of dairy cows fed unsaturated fat from extruded soybeans or sunflower seeds.

Nine multiparous Holstein cows were used in a replicated 3 x 3 Latin square to evaluate the response to diets containing equal amounts of supplemental fat from extruded soybeans or sunflower seeds. Both fat sources contained about 66% polyunsaturated fatty acids; for soybeans, about 8% was linolenic acid, but sunflower seeds contained mostly linoleic acid. Periods were 5 wk, and data were collected the last 3 wk of each period. Total mixed diets were (DM basis) 25% corn silage, 25% alfalfa hay, and 50% concentrate mix. Control concentrate mix contained primarily corn, barley, and soybean meal; extruded soybeans or rolled sunflower seeds replaced portions of the corn, barley, and soybean meal in isonitrogenous (17% CP) diets. Milk yield was higher for cows fed supplemental fat. Percentages of milk fat and protein and DMI were similar for all three dietary treatments. Milk fat from cows fed soybeans or sunflower seeds contained higher concentrations of unsaturated fatty acids and long-chain fatty acids than did milk fat from cows fed the control diet. Milk yield and composition were similar for cows fed soybeans, or sunflower seeds. Soybeans or sunflower seeds can be used as dietary fat supplements to increase milk yield and the proportion of unsaturated fatty acids in milk fat.