Thirty-two lactating Karadi ewes, 3-4 years old and 55.80±1.03 kg in body weight were used to study the effect of reducing ruminal degradable protein in concentrated ration on milk yield, composition and some blood metabolites. Ewes were allocated to four groups. The first was control (C), fed on concentrate ration (14% CP) and untreated barley, wheat bran and soybean meal, the second (T1), third (T2) and fourth group (T3) have 15,17 and 20% crude protein and feed ingredients barley, wheat bran and soybean meal was treated with formaldehyde solution. Estimated RDP level in the concentrate ration for all 4 treatments was 99.13, 54.78, 70.64 and 76.48 g/day, while the estimated corresponding undegradable protein levels for the same treatments were 32.46, 89.83, 94.77 and 109.48 g/d, respectively. Results showed that milk production in ewes increased significantly (P<0.05) in 17% CP treatment (1518.5 g/d) compared with control (1097.25 g/d). Milk protein percentage increased significantly (P<0.05) in 20% CP treatment compared with control ration. Milk protein yield increased significantly (P<0.05) in T1 and T2 compared with control. Milk lactose yield increased significantly (p<0.05) in T2 treatment compared with control diet. Blood urea and triglyceride concentrations increased significantly (P<0.05) in T3 compared with control and T1 respectively, whereas Globulin/Albumin ratio increased significantly (p<0.05) in T3 group ewes blood compared with the rest of the treatments