Three digestibility trails were conducted using three cows (in each ) with on average SW 480 kg. to the present study. the experimental rations were formulated as follows: R 1: ration 1: 59 % concentrate feed mixture l, CFl‘vl) + 31 % rice straw (RS) as a control. R 2: ration 2: 82 % CFM +'r' % ground corn grains (GCG)+31% (RS). R 3: ration 3:: 55 % CFM +14 “/6 (606) + 31 % ( RS). These proportions were chosen to achieve lac-nitrogenous diet containing about 12.2-13.0 % crude protein necessary for optimal utilization and fermentation of roughages of in the rumen @rskov ef al. (1872). The target of 12-13% CP in each experimental diets were achieved in all diets since the ingredients were analysis before formulating the experimental diets. The apparent digestibility of crude fiber (CF) was significantly {P<0.05) higher with R3 than the other ones, while the nitrogen free extract (NFE) and available neutral detergent fiber (ANDF) were significantly (P<0.05) higher with R1 than the others. The cellulose digestibility was increased (P<0.05) with R1 than R2, but there were no significant effect between R1 and R3 or R2 and R3 while acrd detergent lignin (ADL) digestibility was increased with R3 {P<0.05) than R1, and there was no significant effect between R1 and R2 or R2 and R3. The total digestible nutrient (TDN) to crude protein (GP) ratio (TDN: GP) was higher tP<0.05) with R3 than R1 or R2 (5.1, 4.?1 and 4.?8 respectively ). The mean values of the ruminal pH was increased (P<0.05) with R1 or R2 than R3. the mean values of the ruminal pH were 8.33, 8.3 and 8.13 respectively. The same trend was observed on the effective neutral detergent fiber (eNDF) values (21.48, 20.89 and 16.75% for R1, R2 and R3 respectively). The mean values of the buffering capacity (BC) was the lowest   (P<0.05) with R1 or R3 than R2. While the mean values of the total VFA concentration was significantly (Ps005) higher with R3 than R1 or R2. The mean values for TVFA' s were 12.5, 13.0 and 2?.8? ml eq f 100ml with R1, R2 and R3 respectively. The ruminal NH3—N concentrations were ranged from 5.8? to '34? mo i' 100 mi RL with different rations, but without significant effect. "