Three healthy Rahmany rams were used. They were fed at 90% of their ad libitum intake during successive metabolism trials. The experimental rations were formulated to be almost iso-nitrogenous and contain about 12%  crude protein recommended by Ærskov et al. (1972) to ensure maximal rate of fermentation in the rumen as follows: 30% rice straw (RS) + 70 % concentrate feed mixture (CFM) 30% maize stalks (MS) + 70 % CFM 40% clover straw (CS) + 60 % CFM 60 % RS + 30% CFM + 10% SBM 60 % RS + 38.8% CFM + 1.2% U 60 % MS + 30% CFM + 10% SBM 60 % MS + 38.8% CFM + 1.2% U 75 % CS + 17% CFM + 8% SBM 75 % CS + 24 % CFM + 1.0% U   The results obtained showed that :                 There were no significant effects on the digestion coefficient of DM, OM, CP, hemicellulose, N-balance and DCP% when feeding on RS or MS and CS. The CF digestibility increased significantly (P<0.05) when feeding on RS than MS or CS (64.04, 52.89 and 50.41%, respectively). The NDF digestibility increased significantly (P<0.05) when feeding on MS or RS than CS (58.69, 54.92 and 48.03%, respectively). The ADF digestibility increased significantly (P<0.05) when feeding on RS than MS or CS (60.09, 54.20 and 41.90, respectively). Cellulose digestibility increased significantly (P<0.05) when also feeding on RS than MS or CS (72.21, 65.85 and 51.31%, respectively). The dry matter intake (DMI) increased significantly (P<0.05) when feeding on CS than MS or RS (905.37, 799.64 and 761.66 g/day, respectively). The TDN% increased significantly (P<0.05) when feeding on RS or MS than CS (60.11, 60.52 and 55.53, respectively).                 The DM digestibility increased significantly (P<0.05) when added CFM than with SBM or urea (64.4, 58.52 and 55.54, respectively) and the OM digestibility was as the same trend (68.40, 61.68 and 58.41%, respectively). The ADF digestibility increased significantly (P<0.05) when added CFM or with SBM than added urea (53.49, 53.89 and 48.82%, respectively) but cellulose digestibility increased when added CFM than with SBM or urea (68.09, 63.09 and 58.19%, respectively). The DMI increased (P<0.05) when added CFM than with SBM or urea (919.20, 737.61 and 809.87 g/day, respectively). The TDN % values were higher (P<0.05) when added CFM than with SBM or urea (63.02, 56.43 and 57.61, respectively).                 In general, there were positive effects on cell wall digestion with N-sources when feeding on RS but there were negative effects on the feeding with MS and there were no significant effect in feeding with CS.