Persistence of defaunation effects on digestion and methane production in ewes

The effect of defaunation on feed digestion and on methane production of ewes was determined 10 and 25 weeks after defaunation. When fed a lucerne diet (800 g/day), the absence of protozoa did not change the apparent digestibility of dry matter, excretion of macro-minerals, or methane production 10 or 25 weeks post-treatment. Defaunation did, however, increase microbial protein flow by 22% (estimated from allantoin excretion) and the molar proportions of acetate and butyrate in the rumen, while decreasing excretion of copper and manganese. The fermentation data contrasts with previous studies that found defaunation reduced methanogenesis and rumen acetate proportions, but supports the hypothesis that a reduction in rumen acetate percentage is required to achieve reduced methanogenesis through defaunation.