Effect of nutmeg essential oil (Myristica fragrans Houtt.) on methane production, rumen fermentation, and nutrient digestibility in vitro

The study evaluated the effect addition of nutmeg ( Myristica fragrans Houtt.) essential oil as a feed additive on methane production, rumen fermentation parameters, rumen enzyme activity, and nutrient digestibility in vitro. This study was divided into three treatments based on the level addition of nutmeg essential oil, including 0 µL/L (T0), 100 µL/L (T2), and 200 µL/L. The composition of feed substrate was king grass as forage and concentrate with a ratio of 60:40. Feed fermentation was carried out using the Menke and Steingass gas production and two-stapes Tilley and Terry in-vitro digestibility technique. The data obtained from the study were analyzed using one-way ANOVA and If there were differences between means continued by DMRT. Results showed that 200 µL/L nutmeg essential oil addition significantly decreased (P < 0.05) ammonia (NH 3 ) levels, VFA total, acetate, propionate, butyrate, and microbial protein (P < 0.05). Methane production and activity of rumen protease enzyme significantly decreased (P < 0.05) with levels at 100 and 200 µL/L. The addition at 200 µL/L of nutmeg essential oil significantly decreased (P < 0.05) on protein digestibility (IVCPD) in 48h, while IVCPD in 96 h was significantly increased (P < 0.05). on the other hand, the addition of nutmeg essential oil did not affect on the activity of the amylase, carboxymethyl cellulase, and β-glucosidase enzymes and in vitro digestibility of dry matter (IVDMD), crude fiber (IVCFD), and organic matter (IVOMD). The conclusion obtained from this study was the optimum level at 200 µL/L of nutmeg essential oil could reduce methane production and increased crude protein digestibility in 96 h without any negative effect on rumen fermentation and nutrient digestibility.