Date of Award
Master of Science
The effects of essential oils (EO) and condensed tannin (CT) on methane production and fermentation were evaluated under in vitro conditions. Experiment one screened the effects of ten different EO at 500 mg/L of culture fluid on methane production in a 24 hr rumen batch culture. Based on the results from experiment one, four EO (clove oil (CLO), cinnamon oil (CNO), white thyme oil (WTO), and anise oil (ANO)) were selected and tested at three different dose levels (125, 250, and 500 mg/L of culture fluid) for their effects on methane production and fermentation in a 24 hr batch culture (experiment two). Methane production was significantly reduced with the four EO at the 500 mg/L dose but at 250 mg/L; only CLO and CNO reduced methane production. The reduction in methane production with the 500 mg/L dose was also associated with reductions in dry matter (DM) digestibility and total volatile fatty acids (VFA). In the third experiment, the effect of CT at 2.5, 5 and 7.5% of diet DM on methane production was also tested in a 24 hr batch culture. Results from this experiment showed no effect of CT on methane production although methane production tended to be lower at 7.5% CT. In conclusion, the reduction in methane production with EO most likely resulted from EO negative effects on DM digestibility and fermentation.
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