Effect of blend of essential oils as feed additive on rumen metabolites and rumen microbial status of buffaloes

Three adult rumen cannulated buffaloes (average body weight of 279±9.3 kg) were fed on wheat straw and concentrate mixture for maintenance requirement in 3x3 Latin square designs. The three dietary groups were as control with no additive (group 1), groups 2 and 3 with diet supplemented with blend of essential oils (BEO; ajwain oil, garlic oil, and cinnamon leaf oil in equal proportion) @ 0.15 and 0.30 ml/kg dry matter intake (DMI), respectively. The daily DMI was similar (P>0.05) in all the groups. There was no significant effect of BEO on ruminal pH, but ammonia-N was significantly lower in group 3 as compared to other two groups. There was a significant reduction (P<0.001) in lactate concentration in BEO supplemented groups as compared to the control. Total volatile fatty acid concentration, molar proportion of acetate and propionate and acetate: propionate ratio were similar in all the groups, whereas, butyrate proportion was significantly higher (P<0.001) in BEO supplemented groups. There was decreased xylanase activity in group 3, whereas, carboxymethyl cellulase, avicelase and protease remained unaffected. The BEO feeding did not exert any significant influence on the gene expression of methanogens, Fibrobacter succinogens, Ruminococcus flavefaciens, R. albus and fungi. However, gene expression of ciliate protozoa in group 3 was significantly lower (P<0.01) as compared to Groups 1 and 2. Analysis of mcrA gene library revealed a shift within various groups of methanogens without any change in the overall community of methanogens. The supplementation of BEO did not change rumen environment and the microbes very much. Reduction in protozoa population favors nutrient utilization hence the BEO can be used as rumen modifier.