Crude glycerine (CG) is an abundant biodiesel byproduct and an alternative material for livestock diets. The objective of this study was to evaluate the effects of glycerol supplementation on the digestibility and microbial protein synthesis in Nelore steers. Five ruminally cannulated Nelore breed steers (522±43 kg) were used in a replicated 5◊5 Latin Square design to evaluate 0 (control), 3, 6, 9 and 12% of CG in total dry matter of diets during ˚� ve experimental periods of 21 days. The dry matter intake (DMI), ruminal apparent digestibility (RAD), intestinal apparent digestibility (IAD), total apparent digestibility coef˚� cient (TAD) of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent ˚� ber (NDF) and non-˚� ber carbohydrates (NFC) were not affected (P > 0,05) by CG inclusion. Fecal ˚� ow of ether extract (EE) decreased linearly (P 0.05) effect on microbial protein synthesis. It is concluded that CG may be used in the diet of beef cattle up to 12% and can be considered a good alternative energy.