Abstract: [Objective] This study aimed to investigate the effects of adding different doses of Abelmoschus manihot （L.） Medic flavonoids （AMF） to drinking water on immune organ development, serum immune indices, antioxidant indices, and disease resistance in houdan chickens. [Methods] A total of 120 eight-week-old houdan chickens were randomly divided into five groups. The blank control group （Group C） received normal drinking water; the antibiotic control group （Group A） received water supplemented with 0.005% chlortetracycline; and the low-, medium-, and high-dose AMF groups （Groups L, M, and H) received water supplemented with 0.05%, 0.1%, and 0.2% AMF, respectively. After a 42-day feeding trial, immune organ indices, serum immune indices, antioxidant indices, and disease resistance parameters were measured. [Results] Compared with Group C, the thymus index in Groups L and H increased significantly （P<0.05）. Serum IgG and IgM levels in Groups A, L, M, and H were significantly higher （P<0.05）. Serum IL-6 level was significantly elevated in Group A （P<0.05）, while IL-10 level was significantly increased in Group H （P<0.05）. Serum SOD content was significantly decreased in Group A （P<0.05） but significantly increased in Group H （P<0.05）. Serum CAT content was significantly increased in Groups A, L, M, and H （P<0.05）. Serum MDA content was significantly increased in Group A （P<0.05） but significantly decreased in Groups M and H （P<0.05）. Serum TP, ALB, and GLO levels in Groups L, M, and H were elevated, though not significantly （P>0.05）. Compared with Group A, the thymus index in Groups L and H increased, while the spleen and bursa indices decreased. All immune organ indices in Group M decreased, though not significantly （P>0.05）. Serum IgM levels in Groups M and H were significantly lower （P<0.05）. Serum IL-6 levels in Groups L, M, and H were significantly lower （P<0.05）, while IL-10 level was significantly higher in Group H （P<0.05）. Serum SOD content in Group H was significantly increased （P<0.05）, and MDA content in Groups L, M, and H was significantly decreased （P<0.05）. Serum TP, ALB, and GLO levels in Groups L, M, and H were elevated （P>0.05）. [Conclusion] Supplementation of AMF in drinking water can promote immune organ development, increase serum immunoglobulin and anti-inflammatory cytokine levels, enhance antioxidant capacity and disease resistance in houdan chickens, suggesting its potential as an antibiotic alternative.

Key words: Abelmoschus manihot（L.）Medic Flavonoids, houdan chickens, immune function, serum antioxidant capacity, disease resistance