Effect of protein-protected fat on ruminal and total nutrient digestibility of sheep diets.

Experiments were conducted to determine the effects of supplementing chopped ryegrass hay with 0, 5, 10, or 20% fat coated with ruminal bypass protein (Prolip on ruminal digestion by cows and nutrient digestibility by sheep. Ruminal disappearances of DM, ADF, and NDF were measured by the in sacco technique using a cannulated cow. Degradation of DM, ADF, and NDF was not affected by protected fat supplementation at the 5, 10, or 20% level during the first 16 h in the rumen. In addition, supplementation with Prolip did not influence in vitro fermentation characteristics such as pH and VFA patterns. A digestibility experiment with six mature sheep in a switch-back design showed no decrease in feed intake or other undesired effects between unsupplemented (basal) and Prolip-supplemented diets. Whatever the diet fed to sheep, fiber digestibility was similar; however, DM and nitrogen digestibilities were significantly higher relative to the basal diet when ryegrass hay was substituted at 20% (64.2 vs 59.0% and 74.1 vs 71.1%, respectively). Ether extract digestion was enhanced by increasing level of Prolip; the corresponding values were 48.0, 64.9, 74.6, and 84.6% at 0, 5, 10, or 20% Prolip. Likewise, Prolip supplementation at the 10 or 20% level augmented digestibility of energy (62.7 or 65.9 vs 59.2%). Nitrogen and energy retentions were improved due to the decreases in fecal and(or) urinary excretion(s).