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Exploring synergistic interaction between essential oils in in vitro rumen microbial fermentation.

M. E. Rodriguez-Prado

Abstract:

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Exploring synergistic interaction between essential oils in in vitro rumen microbial fermentation.
R. Temmar1, M. E. Rodriguez-Prado*1, G. Forgeard2, C. Rougier2, S. Calsamiglia1. 1Animal Nutrition and Welfare Service, Universit�t Autonoma de Barcelona Bellaterra, Spain, 2TECHNA France Nutrition Coueron, France.

Mixtures of lemongrass (LEM), coriander seed (COR) and ginger oils (GIN) were screened to explore synergistic effects using an in vitro batch fermentation system. Incubations were conducted in a 1:1 rumen fluid: buffer media with 0.5 g of a 50:50 forage to concentrate diet at a starting pH of 6.6, 38�C and anaerobic conditions. Incubations were done in triplicate and in 2 periods. After 24 h, samples were taken for pH, volatile fatty acids (VFA) and ammonia-N concentration determinations. Doses were: LEM (50, 100 mg/L), COR (50, 100 mg/L) and GIN (75, 150 mg/L) mixed at different proportions. Treatments were: T1 (100% LEM), T2 (100% COR), T3 (100% GIN), T4 (50% LEM, 50% COR), T5 (50% LEM and 50% GIN), T6 (50% COR, 50% GIN), T7 (33% LEM, 33% COR, 33% GIN), T8 (50% LEM, 25% COR, 25% GIN), T9 (25% LEM, 50% COR, 25% GIN), T10 (25% LEM, 25% COR, 50% GIN), T11 (100% LEM, 100% COR, 100% GIN), control (CTR), monensin at 10 mg/L (MON) and a blank. All treatments were diluted in ethanol, and the control and blank were also dosed with the equivalent amount of ethanol (0.2 mL). Using LEM, COR and GIN individually did not modify microbial fermentation. However, mixing together LEM and GIN at 62.5 and 125 mg/L increased (P < 0.05) propionate molar proportion and tended (P < 0.10) to decrease acetate molar proportion and the acetate-to-propionate ratio without changing total VFA and ammonia-N concentration, resulting in a synergistic effect. Mixing together COR and GIN at 62.5 and 125 mg/L increased (P < 0.05) butyrate molar proportion, decreased (P < 0.05) acetate and tended to decrease (P < 0.1) the acetate-to-propionate ratio without changing total VFA and ammonia-N concentration, also resulting in synergistic effect. Careful selection and combination of these EO may result in useful mixtures with synergistic interactions to modulate rumen microbial fermentation.

Keywords: essential oils mixtures, rumen microbial fermentation, synergies.