Composition and flavor of milk and butter from cows fed fish oil, extrudedsoybeans, or their combination

Milk was collected from eight multiparous Holstein and four multiparous Bro wn Swiss cows that were distributed into four groups and arranged in a rand omized complete block design with four 4-wk periods. The four treatments in cluded a control diet of a 50:50 ratio of forage-to-concentrate; a fish oil diet of the control diet with 2% (on dry matter basis) added fat from menh aden fish oil; a fish oil with extruded soybean diet of the control diet wi th 1% (on dry matter basis) added fat from menhaden fish oil and 1% (on dry matter basis) added fat from extruded soybeans; and an extruded soybean di et of the control diet with 2% (on dry matter basis) added fat from extrude d soybeans. Milk from cows fed control, fish oil, fish oil with extruded so ybean, and extruded soybean diets contained 3.31, 2.58, 2.94, and 3.47% fat , respectively. Concentrations of conjugated linoleic acid in milk were hig hest in the fish oil (2.30 g/100 g of fatty acids) and fish oil with extrud ed soybean (2.17 g/100 g of fatty acids) diets compared with the control (0 .56 g/100 g fatty acids) diet. Milk, cream, butter, and buttermilk from the fish oil, fish oil with extruded soybean, and extruded soybean diets had h igher concentrations of transvaccenic acid and unsaturated fatty acids comp ared with the controls. Butter made from the extruded soybean diet was soft est compared with all treatments. An experienced sensory panel found no fla vor differences in milks or butters.