Animal feeding and sample analysis: Rumen liquor Due to paucity of studies on the effect of was collected from donor animals fitted with individual EO on rumen fermentation pattern in Indian permanent rumen fistula, before morning feeding into a pre-warmed

Aim: Present study was conducted to examine the modulatory effect of different essential oils on rumen fermentation pattern in vitro using wheat straw based diet (concentrate: wheat straw 50:50). Materials and Methods: Four essential oils i.e. cinnamon, garlic, oregano and rosemary oils were tested at concentration of 0, 30, 300 and 600 mg/litre (ppm) of total culture fluid using in vitro gas production technique. Total gas production, methane production, nutrient degradability, volatile fatty acid (VFA) production and ammonia nitrogen concentration were studied in vitro using buffalo rumen liquor. Results: Results indicated that all four essential oils decreased gas production significantly (P<0.05) at 600ppm concentration. However, in case of garlic oil, 300 ppm concentration was also found to be effective in decreasing total gas production. Reduction in methane production was found maximum (P<0.05) at higher doses in most of the oils. Maximum reduction in methane was noticed with garlic oil at 600ppm dose. Ammonia-N concentration was also decreased significantly (P<0.05) with essential oils and was found minimum with oregano oil at 600 ppm dose. Partition factor was found to be significantly (P<0.05) higher in 600 ppm concentration of garlic and oregano oil. The degradability of dry matter decreased significantly with higher concentration of essential oil in most of treatment combinations. Conclusion: Supplementation with different essential oils on wheat straw based diet modulates rumen fermentation and reduced methane and ammoniaN production and improved utilization of nutrients.