The effect of a candidate feed additive derived from the essential oils of Pinus merkusii (jungh. & de vriese) and Melaleuca leucadendra (l.) on the kinetics of gas production and methane emitted during in-vitro ruminal fermentation

The study was designed to determine the effect of a candidate natural feed additive on the kinetics of gas production as a representation of feed degradability and methane produced during rumen fermentation. Three blends of essential oil (BEO) as candidates for feed additives were formulated using pine and eucalyptus essential oils in the following ratios: 75:25, 50:50, and 25:75 for BEO1, BEO2, and BEO3, respectively. Every BEO was added to the batch fermentation system at dosages of 0, 100, and 200 l/l in the medium. Furthermore, an in vitro gas production technique was used to simulate rumen feed fermentation. According to the gas production kinetics, all BEO additives did not affect the total potential gas produced, as well as the potential gas produced from the soluble and insoluble substrate. The rates of gas production were similar among treatments. Furthermore, the addition of BEO did not affect the total volume of gas produced during fermentation. Meanwhile, BEO1 at 200 l/l dose and BEO 3 at 100 l/l dose significantly reduced methane production (P0.05). In conclusion, the BEO1 and BEO 3 at dosages of 200 and 100 l/l, respectively, had the potential as a feed additive to reduce methane production without a negative effect on nutrient digestibility. © The Authors, published by EDP Sciences.