This study was conducted to evaluate the effect of partial substitution of corn grain by discarded dates on silage quality and their effect on digestibility, milk production and composition. Sixteen crossbreed lactating Friesian cows were assigned to four balanced groups and fed individually for 90 days on experimental rations whereas: all the groups were received a basal diet with one of four kinds of silages as follows:  100 % crushed corn grain (T1), 75 % crushed corn grain + 25% discarded dates (T2), 50 % crushed corn grain + 50 % discarded dates (T3) and 25 % crushed corn grain + 75 % discarded dates (T4) on gross energy based, respectively. Results found that there was slight tendency to increase silage DM content with increasing the entry level of discarded dates. Silages containing discarded dates displayed OM and ash contents nearly identical to those of the control diet. The pH values of the tested silage samples ranged from 3.89 in S1 to 3.72 in S4. The ammonia nitrogen (NH3-N) concentration in silage was decreased with increasing proportion of discarded dates in the silage.  The digestibility coefficient of DM and OM were significantly (P<0.05) higher in the diets containing discarded dates than in the control diet. However, there was insignificant (P>0.05) increases in the digestibility of CP, CF, NDF and ADF for dietary treatment T2, T3 and T4 compared to the control (T1). Also, no significantly (P>0.05) different of dry matter intake was observed among dietary treatments. The highest actual milk and 4% fat corrected milk yield were recorded with T4 (10.87 and 10.24, respectively), while the lowest values for these items were corresponding to T1 (10.06 and 8.56, respectively) but the differences were not significant. Regarding of milk pH value, milk protein and ash contents have the same trend among groups with nonsignificant different among groups. However, there were significant differences in the milk percentages of fat, solid not fat (SNF), lactose and total solids between T1 (the lowest one) and each of T2, T3 and T4. Results of this study indicated that partial replacement of yellow corn grains by discarded dates up to 75% as a source of energy in silage did not show any negative effect on digestibility, feed efficiency, milk yield and composition in crossing Friesian cows.