Feeding hydrogenated fatty acids and triglycerides to lactating dairy cows.

Effects of feeding hydrogenated tallow fatty acids and triglycerides to lactating dairy cows were studied using five primiparous Holstein cows in a 5 x 5 Latin square design. A control diet with no supplemental fat and diets containing either hydrogenated tallow fatty acids or triglycerides at 2 and 5% levels were fed for ad libitum intake. Diets were isonitrogenous but not isocaloric. Each treatment period consisted of 28 d; the last 14 d were used for data collection. Fat-supplemented diets had no effects on DM intake, milk fat percentage, milk protein percentage, and BW compared with the control diet. Energy intake and milk yields were higher for cows fed fat-supplemented diets. Adding fatty acids to diets increased milk fat percentage above that in milk from cows fed triglyceride diets. Apparent digestibilities of DM and OM were lowered by the addition of fat, mainly in response to fatty acid additions. Feeding fatty acids reduced ash digestibility compared with feeding triglycerides, and NDF digestibility also tended to be lower for cows fed fatty acid diets. Fat addition to diets reduced fatty acid digestibility; digestibility of added fat averaged 37.7%. Although of similar saturation, the triglyceride supplement was more ruminally inert than the fatty acid supplement. Esterification and degree of saturation are features of importance when processing tallow for use in ruminant diets.