The role of the rumen ciliate protozoa for methane suppression caused by coconut oil

Diets containing either coconut oil or rumen-protected fat (54 g kg⁻¹ dry matter each) were supplied to Rumen Simulation Technique fermenters filled with faunated and defaunated rumen fluid in a 2 × 2 factorial design. Defaunation immediately reduced methane formation by about 40% with each diet. With coconut oil, methane gradually declined in faunated and defaunated rumen fluid. Finally, the extent of methane suppression was similar, both with coconut oil and with defaunation. Independently of the status of protozoa, the population of methanogens in rumen fluid was significantly reduced by coconut oil. The results suggest that defaunation and coconut oil independently and additively suppress rumen methanogenesis.