Twenty lactating Friesian cows at the peak of lactation curve and in their first to third parity were used to study the effect of  feeding diets containing different levels of  orange waste silage on the nutrient digestibility coefficients  and nutritive values of feeds, ruminal  and some blood parameters  and   productive performance of  Friesian cows .Friesian cows  were chosen and divided into  four   similar groups (5 cows each)  according to body weight, milk yield and number of  lactations.  Animals were fed  on the following rations: First group was fed a control ration (R1) which consisted of 50% concentrate feed mixture (CFM), 45%,  berseem  hay (Trifolium alexandrinum) and 5% rice straw . Groups R2, R3 and R4 were fed the same formula of control with replacing 25, 35 and 45% of berseem  hay by orange waste silage, respectively. Results indicated that  cows fed R4 recorded significantly (P<0.05) higher  digestibility coefficients of CP ,CF and EE than that of (R1) and showed higher DM and OM digestibility coefficients with no significant differences, while ration (R2) appeared to the highest (P<0.05) significant in CP digestibility, TDN recorded significantly (P<0.05) increased with increasing orange waste silage level, showing the highest TDN %with (R4) , while highest DCP%was found with (R2) . Cows fed R4 recorded the highest ruminal TVFA's concentration .While , NH₃-N concentration in rumen liquor decreased significantly with increasing level of orange waste silage in the rations. Concentration of total protein , albumin and globulin significantly (P<0.05) increased with R2 , while activities of GOT and GPT were   significantly (P<0.05)  lower with  level 25% of orange waste silage .Cow fed R4 recorded significantly (P<0.05) the highest yield of actual milk and  4% FCM ,while those fed R3 recorded significantly (P<0.05) the highest of  milk contents  .Cow fed R4 showed the highest feed and economic efficiencies , while those fed the control ration had the lowest values. It could be concluded that, using orange waste silage as a source of roughage is more efficient especially during summer season under Egyptian conditions to replace berseem hay . Using 25% , 35% and 45%  orange waste silage as a roughages replacement in the rations of lactating Friesian cows resulted in higher milk production and improve feed utilization and economic efficiencies, especially using 45% orange waste silage as a roughages replacement in the rations of lactating cows .