Abstract: [Objective] To investigate the effects of dietary supplementation with Clostridium butyricum culture on the production performance, serum biochemical indices of lactating Hu ewes producing twin lambs, and the growth performance of lambs. [Methods] Twenty-four lactating twin-bearing Hu ewes （7 days postpartum） from the same production batch with similar age and body weight, together with forty-eight of their healthy twin F1 Dorper × Hu crossbred lambs with similar average birth weights, were selected and randomly assigned to four groups （6 ewes and 12 lambs per group）: a basal diet （CK）, a basal diet supplemented 0.1% C. butyricum culture （CB1）, a basal diet supplemented 0.2% C. butyricum culture （CB2）, and a basal diet supplemented 0.4% C. butyricum culture （CB4）. The experimental period lasted for 53 days. Production performance indices of ewes and growth performance indices of lambs were measured on days 9, 24, 39, and 53, respectively. The body weight of ewes was measured at the start and end of the experiment. Serum biochemical indices of ewes were determined at the end of the experiment. [Results] ① C. butyricum culture had no significant effects on body weight and average daily gain of ewes （P>0.05）, but dry matter intake in the CB4 group was extremely significantly higher than that in the other groups （P<0.01）. ② C. butyricum culture had no significant effect on milk yield and milk composition of ewes （P>0.05）. ③ C. butyricum culture significantly improved growth performance of lambs （P<0.05）; body weight of lambs in the CB4 group during 24-53 days was extremely significantly higher than that in the CK group （P<0.01）, and starter feed intake of lambs in the CB4 group during the whole experimental period was significantly higher than that in the CK group （P<0.05）. ④ Interleukin-2 （IL-2） content in the CB1 group was significantly higher than that in the CB4 group （P<0.05）, and interleukin-6 （IL-6） content in the CB4 group was extremely significantly lower than that in the CK group （P<0.01）. The total antioxidant capacity （T-AOC）, superoxide dismutase （SOD） activity, and glutathione peroxidase （GSH-Px） activity in the CB4 group were extremely significantly higher than those in the CK, CB1, and CB2 groups （P<0.01）. C. butyricum culture had no significant effects on serum total protein （TP）, albumin （ALB）, globulin （GLB）, total cholesterol （TC）, triglyceride （TG）, blood urea nitrogen (BUN), aspartate aminotransferase （AST）, alanine aminotransferase （ALT）, glucose （GLU）, or prolactin （PRL） levels （P>0.05）. However, progesterone （P） content in the CB4 group and estradiol （E2） content in the CB2 group were significantly higher than those in the CK group （P<0.05）. [Conclusion] Dietary supplementation with C. butyricum culture does not significantly improve body weight, milk yield, or milk composition of ewes; however, it extremely significantly increases dry matter intake during the middle and late experimental stages through multi-component synergistic effects （P<0.01）, regulates immune and antioxidant functions of ewes, and significantly improves growth performance of lambs （P<0.05）. Considering all indices, 0.4% is the optimal supplemental level of C. butyricum culture.

Key words: Hu ewes, production performance, milk yield, serum biochemical indices, growth performance of lambs