Effect of soya oil hydrolysate on rumen digestion in defaunated and refaunated sheep

Abstract

The effects of soya oil hydrolysate (SOH) supplementation on the kinetics of rumen contents and on in sacco rumen degradabilities of various feeds were studied using two defaunated and refaunated sheep. This allowed us to investigate the relative importance of protozoa depletion in the overall effect of oil feeding on rumen metabolism. The addition of 7% SOH to the diet lowered protozoal numbers from 1.6 10 6 ml −1 to 6 10 5 ml −1. SOH supplementation significantly enhanced rumen fluid volume and rumen dry matter, and this effect was partly connected with protozoa depletion. The addition of SOH did not modify the amount of volatile fatty acids in the rumen, but shifted the fermentation patterns to a greater proportion of propionate, while decreases in butyrate and acetate were observed. SOH supplementation did not affect in sacco degradabilities of maize grains and soya-bean meal in the rumen of refaunated animals, but strongly enhanced them in defaunated sheep (respectively, 57% DM vs. 37% and 64% DM vs. 48% after 8 h incubation). SOH lowered in sacco degradabilities of straw (25% DM vs. 46% after 48 h) and cellulose (43% DM vs. 65% after 24 h) in refaunated animals, but only in sacco degradability of straw in defaunated animals (31% DM vs. 44% after 48 h). Coating of cellulose by SOH did not affect its in sacco degradability in the rumen. An estimation of SOH fatty acid kinetics in the rumen seemed to indicate that the variation of rumen content kinetics during the adaptation period to SOH favoured a decrease by 25% in the concentration of SOH fatty acids in the rumen.