Effect of a Blend of Essential Oils on In Vitro Methanogenesis and Feed Fermentation With Buffalo Rumen Liquor

Essential oils (EOs) are effective antimethanogenic agents but some of them have adverse effect on feed digestibility. Therefore, a blend of ajwain (Trachyspermum ammi) oil, garlic (Allium sativum) oil and cinnamon (Cinnamomum zeylanicum) leaf oil (BEO) having anti-methanogenic activities was used at lower concentrations to avoid adverse effect on digestibility of feed in an in vitro gas production test. Inclusion of the BEO at graded levels of 0.66, 1.0, 1.33, 1.66 and 2.0 μl/ml of incubation medium resulted in a linear depression (P<0.001) in total gas and methane production with a maximum reduction of 28.9 and 22.1 per cent at 1.33 μl/ml level. The in vitro true dry matter and organic matter digestibility of feed was also inhibited (P<0.001) by 25.70 and 24.17 per cent at this level. The levels of total volatile fatty acids in the fermented medium were not affected, however, the proportion of acetate was significantly increased and that of propionate and butyrate decreased, resulting in increased acetate to propionate ratio. The results indicated that the blend of EOs comprising of low levels of individual EOs suppressed methane production, however, there was also a simultaneous reduction in in vitro true degradability (IVTD) of feed.