Influence of Rumen Protozoa on Volatile Acid Production and Ration Digestibility in Lambs

Abstract

The influence of protozoa on rumen fermentation was studied with in vitro and lamb experiments. The addition of protozoa to bacterial fermentations increased volatile acid and ammonia production. The presence of protozoa in the rumen of lambs fed rations containing 80% roughage as compared with that of defaunated lambs resulted in higher levels of ruminal VFA and ammonia. Faunated lambs fed a ration containing 80% concentrate had a higher level of ruminal propionic acid, but no higher concentration of total acids than the defaunated lambs. There was a narrower acetate-to-propionate ratio in faunated lambs fed either a high- or a low-concentrate ration than in the protozoa-free lambs. No differences were observed in digestibility of rations that could be ascribed to the presence of protozoa.