In contrast, rumen molar proportions for acetate, propionate and butyrate were unaffected by feeding glycerol to beef cattle at levels up to 120/kg of concentrate DM (Mach et al., 2009). Roger et al. (1992) reported that the addition of glycerol at 0.05 (v/v) to the in vitro media greatly inhibited the growth and cellulolytic activity of rumen bacteria and fungi.