Use of essential oils as feed additive for modulation of rumen fermentation and methanogenesis in buffalo

An experiment was conducted to study the effect of dietary supplementation of two essential oils (EOs), namely Trachyspermum copticum (ajwain) seed oil (AjO) and Cinnamomum zeylanicum (dalchini) leaf oil (CiLO) on rumen fermentation, bacterial diversity and methane production in buffaloes. Three rumen-cannulated male buffaloes (Bubalus bubalis) were subjected to three treatments in a 3x3 Latin Square design. The treatments included the feeding of a control (CON) diet with no additive and the CON diet supplemented with AjO (2 g/d) and CiLO (2 g/d). The concentrations of ammonia and lactic acid in the rumen liquor were decreased (P < 0.001), whereas TVFA remained unchanged by EOs supplementation. The activity of carboxymethyl cellulase increased (P<0.05), and that of protease decreased (P<0.01) but xylanase, avicelase and acetyl esterase activities were not affected by EOs supplementation. The population of holotrichs and spirotrichs in the rumen liquor decreased (P < 0.001) by feeding either of EOs. As indicated by the expression of the 16S rRNA gene, the population density of methanogens and Fibrobacter succinogenes decreased in the EOs supplemented groups. Methane emission in terms of 1/d, 1/kg DMI and 1/kg DDMI was reduced (P<0.01) by 10.99, 21.37 and 20.65%, respectively, by dietary supplementation of EOs. Results indicated that the EOs from ajwain seed and dalchini leaf at 2 g/d were equally effective in reducing enteric methane production and positively modulating rumen fermentation.