SUMMARY The aim of this study was to evaluate changes in nutritive values of sugarcane bagasse when treated with fungus and to evaluate performance of growing lambs at partial replacement of CFM with treated sugarcane bagasse. Nine local Ossimi rams were used to evaluate the effects of replacing 15 or 30% of concentrate feed mixture with biologically treated Sugarcane bagasse on nutrients digestibility and nutritive values in terms of total digestible nutrient (TDN) and digestible crude protein (DCP). Ruminal pH, NH3-N and TVFA's were measured CP and ash contents were increased in biologically treated sugarcane bagasse while, NDF, ADF, cellulose and hemi-cellulose were reduced.  Control group recorded (P<0.05) the highest digestibility coefficients for all nutrients and nutritive values compared with 15% and 30% replacement groups. Control group had higher value of ammonia nitrogen and total volatile fatty acid in rumen liquor at 4 hrs after feeding. Acetic and Propionic acids were higher in control group than treated groups while butyric acid was higher in treated groups than control group. The maximum total fungi counts and microbial protein were observed in control group followed by 15 and 30% replaced ones, respectively. Serum urea, total protein, albumin, globulin, albumin/globulin ratio, GOT and GPT were not significantly changed.
Eighteen Rahmany lambs with average body weight 20.00±0.30 kg/head were distributed into three similar groups. Groups were fed, for 120 days, Animals were weighed monthly to determine total and daily gain and feed conversion. The highest total body weight gain, daily gain and lowest feed conversion efficiency were recorded for control group, while medium values were recorded with 15% replacement one. The highest feed cost per head per day and lowest relative economical efficiency were obtained with control group. Controverslly, the lowest feed cost per head per day and highest relative economical efficiency were obtained with 30 % replacement group. The most efficient economical efficiency synchronized with moderate growth rate was obtained with 15 % replacement.