Influence of supplementation of tropical plant feed additives on in vitro rumen fermentation and methanogenesis

Tropical plants rich in secondary metabolites have the potential to modulate rumen fermentation for more efficient food production with reduced environmental impact. In the present study after extensive screening, three tropical tree leaves (Bahunia variegata, Psidium guajava and Cannabis indica) and three herbs (Cinnamomum zeylanicum, Trachyspermum ammi and Cinnamomum tamala) were selected to evaluate their effect on buffalo rumen fermentation. Total gas production, substrate degradability, volatile fatty acid pattern and enzyme activities were not affected by any of the plants tested in this study. However, methane production was lowered (P <= 0.05) due to inclusion of P. guajava leaves. Anti-methanogenic/anti-protozoal metabolites present in tropical plants seem to be better extracted by ethanol solvent and accordingly the best performing plant i.e. different levels of P. guajava extract was used for further evaluation. Both the methane inhibition and defaunating action of ethanol extract of P. guajava were found to be dose dependent. In conclusion, leaves of P. guajava appear to be a promising plant feed additive for decreasing methane production without affecting feed degradability in the rumen.