Fatty Acid Composition of Milk, Cream, and Butter as Influenced by Feeding Cows Fish Oil, Extruded Soybeans, or Their Combination

Milk was collected from 8 multiparous Holstein and 4 multiparous Brown Swiss cows, which were distributed into 4 treatments in a four-4 week period, arranged in a randomized complete block design. The 4 treatments included a control diet comprising of a 50:50 ratio of forage-to-concentrate; a fish oil diet comprising of control diet with 2% ( on dry matter basis) added fat from menhaden fish; a fish oil extruded soybean diet comprising of control diet with I% (on dry matter basis) added fat from menhaden fish oil and I% ( on dry matter basis) added fat from extruded soybeans; and an extruded soybean diet comprising of control with 2% ( on dry matter basis) added fat from extruded soybeans. Milk from cows fed control, fish oil, fish oil with extruded soybean, and extruded soybean diets contained 3.31, 2.58, 2.94, and 3.47 % of fat, respectively. Treatment milks were processed into cream and butter. Milk, cream, and butter from fish oil and fish oil with extruded soybean diets had a 4-fold increase (P < 0.05) in the concentration of conjugated linoleic acid. Milk, cream, and butter from the fish oil and fish oil with extruded soybean diets had a higher concentration of transvaccenic acid. Unsaturated fatty acids were higher in the fish oil, fish oil with extruded soybean, and extruded soybean diets. Butter made from the extruded soybean diet was the softest at 4°C and 20°C. The sensory panel did not find any difference in flavor characteristics of milk and butter from the diets, and at different storage times. Consumers evaluated the control and fish oil milks and found no flavor difference between the milks.