Evaluation of a blend of essential oils in the in vitro fermentation of marandu grass

ABSTRACT The aim was to evaluate the effects of doses of a blend of essential oils (BEO) on in vitro fermentation. The experimental design used was a 2x4+1 factorial arrangement, with two samples of Marandu grass (from the rainy and dry season), four doses of BEO (zero, 133, 266, and 350mg animal day-1), and monensin (MON: 83mg animal day-1). The variables analyzed were total GP, digestion rate (kd), ruminal in vitro dry matter (IVDMD) and neutral detergent fiber (IVNDFD) digestibility, ammonia (NH3) and volatile fatty acid (VFA) concentrations, and methane (CH4) production. BEO doses or the addition of MON did not affect total GP, GP rate, IVDMD, total VFA production, and NH3 concentration. Higher values of kd, IVDMD, and NH3 were found for forage obtained in the rainy season. The doses of BEO caused a quadratic effect on IVNDFD, with no interaction effect between additive and roughage. The lower CH4 production estimated for rainy forage might be explained by its higher nutritive value and faster passage rate compared to dry season forage.