Effects of essential oils from medicinal plants acclimated to Benin on in vitro ruminal fermentation of Andropogon gayanus grass

BACKGROUND: Plants from West Africa commonly used in both human and veterinary medicine contain various secondary metabolites. However, their potential in mitigating ruminal methane production has not been explored. This study examined the effects of seven essential oils (EOs) from plants acclimated to Benin at four dosages (100, 200, 300 and 400 mg L-1), on in vitro rumen microbial fermentation and methane production using Andropogon gayanus grass as a substrate. RESULTS: Compared to control, Laurus nobilis (300-400 mg L-1), Citrus aurantifolia (300-400 mg L-1) and Ocimum gratissimum (200-400 mg L-1) decreased (P < 0.05) methane production (mL g-1 DM) by 8.1-11.8%, 11.9-17.8% and 7.9-30.6%, respectively. Relative to the control, reductions in methane (mL g-1 DM) of 11.4%, 13.5% and 14.2% were only observed at 400 mg L-1 for Eucalyptus citriodora, Ocimum basilicum and Cymbopogon citratus, respectively. These EOs lowered methane without reducing concentrations of total volatile fatty acids or causing a shift from acetate to propionate production. All EOs (except M. piperita) reduced (P < 0.05) apparent dry matter (DM) disappearance of A. gayanus. CONCLUSIONS: The current study demonstrated that EOs from plants grown in Benin inhibited in vitro methane production mainly through a reduction in apparent DM digestibility.