Effects of Essential Oils on In Vitro Methanogenesis and Feed Fermentation with Buffalo Rumen Liquor

Seven essential oils (EOs): garlic ( Allium sativum ), clove ( Syzygium aromaticum ), lemongrass ( Cymbopogon citratus ), wild turmeric ( Curcuma aromatica ), turmeric ( Curcuma longa ) and cinnamon ( Cinnamomum zeylanicum ) were evaluated as rumen modifier to mitigate methane emission. The lowest level of EOs tested in this experiment (167 μl l −1 of incubation medium) was the most appropriate level of inclusion as higher doses were detrimental for feed digestibility and fermentation. At this level, methane inhibition was maximum (38.5 %) with garlic oil (GO) followed by cinnamon bark oil (CiBO; 34.9 %), wild turmeric oil (15.5 %), clove bud oil (CBO; 12.9 %), clove leaf oil (8.0 %), lemongrass oil (7.3 %) and turmeric oil (no effect). Feed digestibility was significantly hampered by CBO and CiBO. The response of GO was different from that of other oils as inclusion of GO at 167 μl l −1 of incubation medium resulted in 38.5 % decrease in methane production, significant increase in total volatile fatty acids and propionate production, a decrease in acetate to propionate ratio and had no effect on feed digestibility. All the oils suppressed ammonia production. Partitioning factor, which indicates efficiency of microbial biomass production, was also increased by inclusion of all the seven oils. The CiBO was detrimental for feed fermentation even at the lowest dose of 167 μl l −1 of incubation medium. The data indicated that GO was the most promising feed additive which caused maximum methane inhibition and had the minimum adverse effect on feed digestibility.