Digestibility and effects of hydrogenated palm fatty acid distillate in lactating dairy cows.

Five midlactation multiparous Holstein cows fitted with ruminal cannulas were used in a 5 x 5 Latin square design with 14-d periods. Treatments were 1) no added fat (control), 2) 6.1% Ca salts of long-chain fatty acids, 3) 5.0% prilled long-chain fatty acids, 4) 5.2% prilled hydrogenated palm fatty acid distillate, and 5) 5.2% flaked hydrogenated palm fatty acid distillate. Cows were fed for ad libitum intake a total mixed diet (17.0% CP and 18.4% ADF) of alfalfa haylage, corn silage, and concentrate (28:22:50, DM basis). Fat sources were added to supply 5% fatty acids. Diets 2 through 5 contained 53, 83, 87, and 86% saturated fatty acids, respectively. Total fatty acid intake averaged 650, 1551, 1315, 1544, and 1581 g/d. Digestibilities of total fatty acids (81.3, 78.0, 70.0, 67.3, and 68.6%) were higher for the control diet than for fat-supplemented diets and higher for Ca salts of fatty acids than for diets containing hydrogenated distillate. Treatments did not affect ruminal fermentation characteristics or nutrient digestibilities. Production of 4% FCM and milk fat tended to be less for Ca salts of fatty acids than for hydrogenated distillate. The digestibility of fatty acids in hydrogenated distillate was lower than that for Ca salts of fatty acids, but intake and production responses were similar or greater for diets containing hydrogenated distillate.