Effect of essential oils and aqueous extracts of plants on in vitro rumen fermentation and methane production

ABSTRACT

The objective of this study was to evaluate in vitro rumen fermentation and methane production under the influence of two sources of phytochemicals essential oils (EOs) and aqueous extracts (AEs). Treatments were set up in a completely randomized block design, with 4×2+1 factorial arrangement of four species, S (garlic, G; cinnamon, C; rosemary, R; eucalyptus; EU) × two types of presentation, P (essential oil, EO; aqueous extract, AE) and a basal diet, BD (50% concentrate, 20% alfalfa and 30% corn silage). Rumen fermentation was evaluated using the in vitro gas production technique. All experimental units were incubated with 500 mg of BD for 72 hours. Treatments were added at a single dose of 900 mg/L of rumen inoculum. Gas pressure was recorded at 0, 2, 4, 6, 8, 10, 14, 18, 24, 30, 36, 42, 48, 60 and 72 h postincubation. There was an interaction effect (P × S) between plant extract presentation (P) and plant species (S) for all variables. Treatments GEO, CEO, REO decreased volatile fatty acids (mmol/200 mg), microbial mass production (mg/g), CH4 production (mL/g), in vitro dry matter digestibility (P < 0.05), and total gas production at 24 and 72 h post-incubation (P < 0.05; mL/g DM, mL/g OM). No differences (P > 0.05) were observed between AEs and BD. In conclusion, the use of EOs negatively affected rumen fermentation parameters and the production of CH4. Garlic and cinnamon EOs effectively reduced methane emissions; however, they also reduced in vitro dry matter digestibility.