Changes in methane emission, rumen fermentation in response to diet and microbial interactions.

To evaluate relative contributions of different microbial groups in rumen, the mono-culture (i.e. bacteria, protozoa and fungi) and co-cultures (i.e. bacterial-protozoal, fungal-protozoal and bacterial-fungal) were tested in vitro using high and low roughage diets. Total gas and methane were higher in bacterial-fungal and bacterial-protozoal co-cultures, while lower in fungal-protozoal than controls (high and low roughage with complete rumen consortia; control 1 and 2, respectively). Digestibility and total volatile fatty acids were lower in bacterial-fungal co-culture with both high and low roughage diets. Methanogens decreased in bacterial-fungal co-culture with high roughage. With high roughage, counts were lower for bacteria with bacterial-protozoal, protozoa with fungal-protozoal, and fungi with the bacterial-fungal co-cultures. Total gas was higher in bacterial mono-culture with low roughage, but methane was not detected in any mono-culture. Digestibility and total volatile fatty acids were significantly lowered with protozoal mono-culture. Methanogens reduced significantly in mono-cultures with high roughage diet than control 1. Defaunation reduced methanogens without significantly affecting rumen fermentation.