effects of chemical inhibitors on fermentation pattern, methanogenesis and hydrogen emission in ruminal batch cultures

the objective of this meta-analysis was to compare effects of chemical methanogenic inhibitors on fermentation parameters in ruminal batch cultures. nine published in vitro studies including 26 treatment means in which 2-bromoethane sulfonate, bromochloromethane and 9,10-anthraquinone were used as methanogens inhibitor compared in amount of ch4, h2, total volatile fatty acid, actate, propionate and butyrate production. the results showed that all chemical inhibitors reduced methane production significantly (-2.64±0.290) and 2-bromoethanesulfonate was the most effective inhibitor. the inhibitors had a significant negative effect on acetate production (-1.48±0.255), and positive effect on molar proportions of propionate (+0.94±0.309) and butyrate (+0.69±0.125). the reduction in acetate production was not compensated by increase in propionate and butyrate production, therefore total vfa production reduced (-0.42±0.180) significantly. the inhibitors increased h2 production (+2.31±0.540) significantly and it was less than the predicted amount by stoichiometry equation. it was concluded that although the applied methanogens inhibitors were successful in reducing methane emission, but less vfa recorded and energy lost in form of h2 was significant in batch culture systems.