A new perspective on the use of plant secondary metabolites to inhibit methanogenesis in the rumen

Ruminant livestock due to production of methane during normal fermentation in the rumen contributes substantially to the greenhouse effects. Some plants or their extracts with high concentrations of bioactive plant secondary metabolites (PSM) such as saponins, tannins, essential oils, organosulfur compounds, flavonoids and many other metabolites appear to have potential to inhibit methane production in ruminants. Although PSM may negatively affect nutrient utilization, there is evidence that methanogenesis could be suppressed without adversely affecting rumen fermentation. Therefore, there is a need for much systematic research for evaluation of PSM on their effect on rumen methanogenesis and fermentation based on the chemical structures of these PSM and dietary composition, which would not adversely affect nutrient utilization and ruminant production.