To estimate the digestibility coefficients, nutritive values, nitrogen balance and some ruminal and blood constituents of rams fed biologically treated roughages. The obtained results could be summarized in the following: Rice straw (RS) was more digestible for OM, CP, EE, CF, NFE, ADL, cellulose and hemicellulose.  It also was more consumable as DM and different nutrients.  It led to lower drinking water consumption and to higher urine excretion and N-balance. The RS was responsible for higher ruminal ammonia and lower ruminal TVFA and microbial protein concentrations.  It gave also higher blood total protein and globulin and lower blood urea concentrations. Fungus + soybean meal was the best treatment concerning the digestibility of the treated roughage (OM, CP, EE, CF, NFE, ADF, ADL, cellulose and hemicellulose) and their feeding values (TDN, SV and DCP).  It led also to the highest feed and nutrients intake as well as urine excretion and N-balance and to the lowest water consumption. Fungus + soybean meal treatment reflected the highest ruminal pH, ammonia, and microbial protein and the lowest TVFA values.  It gave also the highest blood total protein concentration and the lowest blood serum AST activity. Conclusively, the biological treatment with the white rot fungi, particularly with the fungus Pleurotus ostreatus of the field wastes (roughages) can improve their digestibility, and nutritive value. So, fungal treatment of agricultural by-products can offer unconventional animal feed which is economical and environmentally friend without any negative effects on animal health.