Effect of plant extracts on in vitro methanogenesis, enzyme activities and fermentation of feed in rumen liquor of buffalo

The extracts of pods of Acacia concinna (Shikakai), seed pulp of Terminalia chebula (harad), Terminalia belerica (bahera), Emblica officinalis (amla) and seed kernel of Azadirachta indica (neem seed) in different solvents (ethanol, methanol and water) were evaluated for their effect on methane production, enzymes activities and rumen fermentation in in vitro gas production test. Gas production per gram dry matter (DM) of substrate (wheat straw and concentrate mixture in 1:1 ratio) was significantly (P<0.05) higher with extracts of A. concinna, E. officinalis and T. belerica as compared to control. Among the extracts tested only methanol extract of T. chebula suppressed in vitro methane production significantly (P<0.05). Specific activities of carboxymethylcellulase (CMCase) and xylanase were similar (P>0.05) among the extracts at both the levels tested, whereas, the activity of acetylesterase was reduced significantly (P<0.05). Total volatile fatty acids (TVFA) were significantly (P<0.05) decreased with extracts of T. chebula and A. indica. There was a decrease (P<0.05) in acetate to propionate ratio due to addition of the extracts of A. concinna and A. indica in incubation medium as compared to control. In vitro dry matter and organic matter degradabilities of feed (g/g) were decreased significantly (P<0.05) with all the extracts compared to that of control. The extracts of A. concinna and A. indica at 0.25 and 0.50 ml levels and extracts of T. chebula at 0.50 ml level reduced total protozoa counts significantly. Similar trends were observed for small and large entodiniomorphid protozoa counts. However, no effect (P>0.05) was found on holotrich protozoa numbers. The results indicated that methane emission is not essentially associated with protozoa activity since among three seed pulps with high antiprotozoal activity, only T. chebula (methanol extract) had antimethanogenic activity. The methanol extract of seed pulp of T. chebula appears to have a potential to be used for mitigation of enteric methane production, but the level of feeding will have to be evaluated so that there is minimum adverse effect on the degradability of feed in the rumen.