Effect of fat supplementation on voluntary food intake and rumen metabolism in sheep.

1. In an experiment in which a high-fat supplement was given in the dry form to lambs offered dried grass ad lib., both the voluntary intake and digestibility of the dried grass were reduced. When the high-fat supplement was given in a liquid suspension so that the rumen was by-passed, the voluntary intake and digestibility of the dried grass were not significantly altered. 2. The effect of injecting an emulsion of tallow into the rumen of sheep on rumen metabolism was studied in another experiment. Increasing the fat supplementation lowered the rate of digestion of both dried grass and cotton thread, lowered markedly the concentration of rumen ammonia, and raised the proportion of propionic acid in the rumen.