<i>In vitro</i> screening of the ruminal methane and ammonia mitigating potential of mixtures of either chestnut or quebracho tannins with blends of essential oils as feed additives

Tannins and essential oils (EOs) have been previously described for their properties to mitigate ruminal methane ammonia. Their combination might be even more efficient, as they different modes of action on rumen pathways. This study aimed screen in vitro the mitigating variously combining tannins with EO a total 48 treatments: 12 single additives, 10 mg or 20 tannins/g diet, establish basal efficiency; 36 combinations + 10–15 EO. Quebracho (Q) chestnut (C) defined C, Q C/Q groups mixtures blends, formulated oregano, thyme clove EO, citrus peel, carvacrol, thymol, eugenol, α-pinene, bornyl acetate. Supplements were added control which was also incubated alone basis comparisons supplemented treatments, six runs. Effects pH, protozoal count, proportions individual volatile fatty acids (VFA) limited. The extracts seemed cause most effects by suppressing ammonia up 31% yield 15%, highest reductions obtained tannins-based supplements. However, this occurred contemporary affecting feeding value substrate, indicated VFA organic matter digestibility. Overall, C efficient need further studies understand mechanisms actions synergistic occurring among compounds.HighlightsCombinations oil compounds screened vitroSome lowered formation 15 31%Essential enhanced