Abstract: [Objective] To investigate the effects of Astragalus membranaceus stem and leaf powder and Codonopsis pilosula stem and leaf powder, as feed additives, on growth performance, antioxidant capacity, and serum biochemical indices in chicks. [Methods] Forty healthy 1-day-old Sanhuang chicks were selected and randomly divided into four groups. The control group （Group A） received a basal diet, while the experimental groups （Groups B, C, and D） were fed the basal diet supplemented with 1% A. membranaceus stem and leaf powder+1% C. pilosula stem and leaf powder, 2% A. membranaceus stem and leaf powder+1% C. pilosula stem and leaf powder, and 3% A. membranaceus stem and leaf powder+1% C. pilosula stem and leaf powder, respectively （all addition ratios were calculated as mass percentages of the basal diet）. The trial lasted 18 days and was divided into two phases （days 1-9 and days 10-18）. Growth performance indicators, serum antioxidant parameters, and biochemical indices were measured and analyzed across groups. [Results] The final body weight and average daily gain of chicks in all experimental groups were significantly higher （P<0.05） than those in the control group, while the feed-gain ratio was significantly lower （P<0.05）; among them, Group C （supplemented with 2% A. membranaceus stem and leaf powder+1% C. pilosula stem and leaf powder） exhibited the most significant growth-promoting effect. Regarding antioxidant capacity, compared to the control group, only Group D （3% A. membranaceus stem and leaf powder+1% C. pilosula stem and leaf powder） showed a significant increase in serum total superoxide dismutase （T-SOD） activity （P<0.05）; no significant differences （P>0.05） were observed in total antioxidant capacity （T-AOC） or malondialdehyde （MDA） content between Groups B, C, D and the control group, although a beneficial trend of improvement was evident overall. Serum biochemical indices detection revealed significant inter-group differences only in urea nitrogen content: compared with Group A, serum urea nitrogen concentrations in Groups B, C, and D showed a decreasing trend, with those in Groups B and D being significantly lower than that in Group A （P<0.05）, suggesting that supplementation with A. membranaceus and C. pilosula stem and leaf powders may enhance protein metabolic efficiency in chicks. No significant differences （P>0.05） were found among groups in total protein, albumin, globulin, albumin-to-globulin ratio, creatinine, or glucose levels. [Conclusion] The results demonstrate that A. membranaceus stem and leaf powder ; C. pilosula stem and leaf powder can effectively promote growth, improve feed conversion efficiency, and enhance antioxidant function in chicks, with the optimal effect achieved at a supplementation level of 2% A. membranaceus stem and leaf powder+1% C. pilosula stem and leaf powder in the basal diet.

Key words: Astragalus membranaceus stem and leaf powder, Codonopsis pilosula stem and leaf powder, chicks, growth performance, antioxidant capacity, serum biochemical indices