Abstract: Four male purebred Brahman bulls about 2 years olds were used in a 4x4 Latin square design. Their initial body weight was 151+13 kg (mean±SD). Treatments were 8.0, 10.0, 12.0 and 14.0% crude protein in total diets. Rice straw was used as main roughage sources. Animals were offered in form of total mixed ration. Feed intake was linearly decreased (p<0.05) as increased protein level. Digestion of DM, OM, NDF, ADF and EE were not significantly difference (p>0.05) among treatments. Nitrogen intake was 81.95, 103.0, 115.5 and 147.2 g day-1 in 8.0, 10.0, 12.0 and 14.0% CP in diets, respectively (p<0.05). Fecal nitrogen excretion was linearly enhanced (p<0.05) as increased protein level. Urinary nitrogen and total nitrogen excretions were significantly difference (p<0.05) among treatments. Apparent N digestibility was 67.53, 72.97, 80.60 and 78.78 % in 8.0, 10.0, 12.0 and 14.0% CP in diets, respectively (p<0.05; quadratic). Plasma urea nitrogen was linearly elevated (p<0.05) as increased protein level. In conclusion, it can be concluded that CP level 12.0% did increase apparent total tract N digestibility without any adversely effect on feed intake.