The objective of this study was to evaluate in vitro the effects of three essential oils (EO) [cinnamon leaf (250 mg L-1), garlic oil (100 and 250 mg L-1), and juniper berry oil (20 mg L-1)] and two EO compounds (EOC) [anethol (20 mg L-1) and p-cymene (20 mg L-1)] on proteolytic, deaminative and methanogenic activities of mixed ruminal bacteria. Concentrations of total VFA were similar (P > 0.05) among treatments. With the exception of cinnamon and garlic oils, which reduced (P < 0.05) the proportion of propionate, the other EO and EOC had no effect on the proportions of individual VFA, compared with the control. Proteolytic activity of ruminal bacteria was unaffected (P > 0.05) by treatments; however, bacterial deaminative activity and NH3 concentration were increased (P < 0.05) by the addition of EO (except for cinnamon leaf oil and garlic oil at 250 mg L-1) and EOC. Except for anethol, methanogenic activity of ruminal bacteria was reduced (P < 0.05) by EO and EOC, which was reflected by a marked decrease in methane concentration. This study shows that at the concentrations evaluated, anethol, garlic oil (100 mg L-1), juniper berry oil, and p-cymene may not be beneficial to improve efficiency of N utilization in ruminants because they enhance deaminative activity, while cinnamon and garlic oil (250 mg L-1) could be good alternatives to antibiotics because they reduce methanogenic activity of ruminal bacteria. Key words: Essential oil, proteolysis, deamination, methanogenesis, in vitro
Development and characterization of cinnamon leaf oil nanocream for topical application
