Effect of eucalyptus (Eucalyptus globulus) oil on in vitro methanogenesis and fermentation of feed with buffalo rumen liquor.

The effect of inclusion of eucalyptus (Eucalyptus globules) oil (EO) at the levels of 0, 0.33, 0.66, 1.0, 1.33 and 1.66 μl/ml of incubation medium on methane production and rumen fermentation was studied in in vitro gas production test. The gas production decreased linearly with the increasing level of EO. At the highest inclusion level (1.66 μl/ml) there was 39.7% decrease in gas production. Methane emission was reduced by 10, 17, 35, 46 and 56% at 0.33, 0.66, 1.0, 1.33 and 1.66 μl/ml levels of EO inclusion, respectively. The total volatile fatty acids were reduced (P<0.05) by inclusion of EO at higher levels, whereas at 0.33 μl level there was no effect. The butyrate content increased significantly (P<0.05) with increasing EO level at the cost of acetate as it decreased linearly. In vitro true digestibility decreased linearly only upto 1.0 μl level of EO. The numbers of holotrichs and spirotrichs decreased (P<0.05) by increasing level of EO. The results indicated that EO had a potential to inhibit methane production but further in vivo trials are required to standardize the dose which inhibits methane production without adversely affecting feed digestibility.