a, b, c, d, e means in the same column with different superscript differ significantly (P < 0.05); B gas = cumulative gas production after 96 h incubation (ml/1 g of DM); C gas = rate of gas production (ml/h/1 g of DM); 24 h = Cumulative gas production after 24 h incubation; 48 h = Cumulative gas production after 48 h incubation; Control = ensiled brewers’ grain without any additive; SEM: Standard error mean.