Digestibility of hydrogenated tallow, saturated fatty acids and soybean oil-supplemented diets by sheep.

A TOTAL of 28 crossbred wethers were used in two experiments to determine the digestibilty of hydrogenated tallow-, saturated fatty acidsand soybean oil-supplemented diets. Digestibility values for individual fats were determined by subtracting from total dietary lipid and fecal output the dietary and fecal lipids measured with basal diets. In the first experiment addition of 3% flaked, hydrogenated tallow to a basal diet resulted in lower digestibility (34%) for the tallow compared with soybean oil (98%). In the second experiment, hydrogenated tallow was added to a basal diet at approximately the 4.8% level either in dry flaked form or melted and mixed (blended) into the concentrate portion of the basal diet. A further treatment comparison involved addition of saturated free fatty acids at approximately the 4.8% level to the basal diet. Tenday digestion trials were conducted starting at 10 and again at 35 days of this experiment to measure adaptation of sheep to fat-supplemented diets. Melting and mixing the tallow into the diet resulted in significant (P< .01) improvement in digestibility over flaked tallow (40% vs. 30%). Saturated fatty acids were significantly (P<.01) better digested (73%) than either form of tallow. Blood plasma lipid fatty acid levels of sheep reflected these differences in digestibility after 33 days on feed. It is suggested that the hydrogenation process results in tallow with physical form which resists dispersion and hydrolysis in the rumen and solubilization in the small intestine. Additions of soybean oil, saturated fatty acids and hydrogenated tallow tended to lower digestibilities of crude fiber and acid detergent fiber. The decreases were significant