Abstract Four rumen-cannulated cows ( Bos taurus × Bos indicus , 631 ± 88 BW) were assigned in a 4×4 Latin Square design to test the effects of different canola oil inclusion levels (CO; 0.0, 0.40, 0.80 and 1.2 g/kg shrunk body weight, SBW = BW×0.96) on the reduction of CH 4 emissions and the energy value of the diet based on Brachiaria sp. under rotational grazing supplemented with a fixed amount of concentrate. The CH 4 emission was analysed by an infrared analyser. Grass consumption and faecal production were estimated using Cr 2 O 3 as external marker. The CO supplementation increased (linear effect, P < 0.05) DM (16.6%), organic matter (OM, 18.0%) and gross energy intakes (26.3%) and decreased the total digestibility of neutral detergent fibre (NDF) by 26% (linear effect, P < 0.05); also increased digestible energy value (Mcal/kg) by 7.1%. In the rumen, the maximum oil inclusion level decreased the total protozoa population by 89%, the acetate: propionate ratio by 25% and the enteric methane production by 18.9%, all without negatively affecting any of the other variables of fermentation and digestion evaluated. It is concluded that canola oil at supplementation levels of up to 1.2 g CO/kg SBW (5.3% of the total diet) for cows grazing tropical forages supplemented with concentrates increases the total and energy consumption and the efficiency of ruminal fermentation, thereby reducing the emission of enteric methane by up to 18.9%.