De-rinded sugar cane bagasse (the pith) was subjected to high steam pressures (18.3, 19.0, 19.7 and 20.4 kg/cm2) during 4, 5, 8and 10 minutes. In vitro digestibilities and JD. situ degradabilities were significantly improved by the treatments. The steam pre-digested bagasse pith-SPBP (0,20, 40, 60 y 85.42%) acceptability were lowand the results showed very high weight losses of steers teed 60 and 80% SPBP of their diet. No statistical difference (P < 0.05) was observed for average daily gains of steer fed on high levels of SPBP supplemented with high levels of urea, using three treatment: restricted amount of king grass (T1) whole raw bagasse (T2) and cane molasses(T3); the exclusion of the long fiber (T3) did not effect animal performance. Furfural levels below 1% SPBP (fresch basis) were detected; spectrometric analysis (UV, RI and FMN) registered the presence of carboxil and hidroxil groups indicating the probable existence of phenols.