The present study was carried out to estimate the effect of solanine in potato by-products (PB-P) as a natural toxic component, on milk yeild and its constituents as well as the solanine residue in milk on born lambs of lactating ewes fed on potato by – product as silage (PB-PS) or hay  (PB-PH).  Eighteen lactating Rahmany ewes with an average body weight of 45.4 ± 0.64 kg and aged 2.5 – 3 years and their born lambs with an average weight of 3.53 kg (every ewe with her lamb) were used in this study.  Ewes were divided into three similar groups (6 animals each) and assigned randomly to three experimental rations according to the requirement of NRC (I990) as follows: (1)50% concentrate feed mixture (CFM) + 50% berseem hay (BH) as a control, (2) 50 % CFM + 50 % PB-PS and (3)50% CFM + 50 % PB-PH.  Whereas born lambs were fed on their mother's milk all the experimental period .The experiment lasted for 16 weeks.  Body weight gains were 14.7,13.6 and 10.4 (kg) for the control, PB-PS and PB-PH, respectively.  Solanine values of PB-PS and PB-PH were 8.19 and 24.86 mg/100 g, respectively.  The digestion coefficients of OM and CF significantly (P < 0.05) increased in PB-PH followed by PB-PS than the control.  On the other hand, PB-PH showed lower TDN and DCP values than the other tested diets.  Milk yield and its constituents were lower in PB-PH compared with the other tested groups, but the ME (Mcal/kg) was higher in PB-PH than PB-PS and the con trol.  Milk yield and composition was lower in PB-PH compared with other test groups.  Values of white blood cells count, hematocrit, globulin, AST, ALT, urea, creatinine and bilirubin of PB-PH group were significantly (P < 0.05) higher than the other tested groups.  The water consumption of PB-PH group was higher than PB-PS and control groups, also feed costs of PB-PH and PB-PS were lower than the control group .The PB-PS and PB-PH in lactiting ewes caused decrease in feed cost and the values were 28.37 and 33.02 % for the PB-PS and PB-PH, respectively than the control.  In conclusion, potato by–products as silage could be used safety, successfully and economically in ration of lactating ewes at 50% of nutritional requirements.