The Stylosanthes ‘Campo Grande’ (Stylosanthes capitata + S. macrocephala) is adapted to tropical conditions and exhibit a nutritional value comparable to other high efficiency feeds being used in the tropics. The objective of this study was to evaluate the nutrient intake, total apparent digestibility, ruminal pH and ammonia concentration and the microbial efficiency of beef cattle fed Stylosanthes ‘Campo Grande’ (StS) or corn silages (CS) with 2 dietary protein levels (PL). Four Nelore rumen cannulated, average (BW) of 449.8 ± 9.47 kg were assigned to a 4 × 4 Latin square with a 2 × 2 factorial design of treatments with 4 16-d periods. The treatments were StS and CS with 2 PL (11% and 13% CP on DM basis). Data were analyzed including in the model the fixed effects of silage (S), PL and the interaction S × PL, and the random effects of animal and period. The intake and digestibility were not affected (P > 0.01) by the interaction S × PL. However, the diets containing StS showed lower (P < 0.01) TDN intake than CS (4.52 vs. 6.01 kg/d). Similar pattern was observed for DM, OM, CP and NDF digestibilities. The ruminal pH and ammonia concentration were affected (P < 0.01) by S and PL, respectively. The microbial efficiency estimated from urinary purine derivatives was not affected (P > 0.01) by treatments (average of 75.77 g/kg TDN). The StS resulted in lower TDN intake and lower total apparent digestibility of DM, OM, CP and NDF without affecting the microbial efficiency. Supported by Fapemig, CNPq and INCT-CA.