Abstract: The purpose of this experiment was to study the effect of rutin on the ileal tissue morphology, immunity, antioxidant and barrier function of broilers. A total of 256 1-day-old AA broilers were selected and randomly divided into 4 groups, with 8 replicates in each group and 8 chickens in each replicate, and were fed the basal diet supplemented with 0 (control group), 250, 500 and 1 000 mg·kg^-1of rutin, respectively. The experiment was divided into early stage (1-21 d) and late stage (22-42 d), and the experiment lasted for 42 days. The results were showed as follows:1) Dietary rutin significantly increased the mRNA expression levels of Bcl-2 and ZO-1 in ileum mucosa of broilers at 21 d (P_Q<0.05), and linearly increased the villus height (VH) of ileum and the mRNA expression levels of Bcl-2, ZO-1 and Mucin2 in ileum mucosa of broilers at 42 d (P_L<0.05). Moreover, 500 mg·kg^-1 rutin supplementation significantly increased the expression of ki67 mRNA in ileal mucosa and the ileal VH at 42 d (P<0.05). 2) The addition of rutin to the diet linearly and quadratic increased the content of secreted immunoglobulin (sIgA) in the ileal mucosa at 21 d (P_L<0.05; P_Q<0.05), and decreased the mRNA expression of interleukin-2 (IL-2) in ileum mucosa at 42 d (P_L<0.05; P_Q<0.05), also linearly decreased the mRNA expression of tumor necrosis factor -α (TNF-α) (P_L<0.05). At the same time, compared with the control group, the addition of 250 and 500 mg·kg^-1 rutin decreased the expression of nuclear factor-κB (NF-κB) mRNA in the ileal mucosa at 21 d, while the addition of 500 mg·kg^-1 rutin decreased the mRNA expression level of NF-κB in ileal mucosa at 42 d (P<0.05). 3) At 21 d, dietary rutin supplementation increased the T-AOC in ileum mucosa linearly and quadratic (P_L<0.05; P_Q<0.05), as well as GSH-Px activity (P_L=0.096;P_Q<0.05) and HO-1 mRNA expression (P_L<0.05; P_Q<0.05). Also linearly increased the expression level of NQO1 mRNA (P_L<0.05), quadratic decreased the content of MDA in ileum mucosa (P_Q<0.05), and increased the expression level of Nrf2 mRNA (P_Q<0.05); Compared with control group, the expression level of HO-1 mRNA in ileum mucosa in rutin treatment group were significantly increased (P<0.05), the content of MDA in ileum mucosa in 250 and 500 mg·kg^-1 rutin groups were significantly decreased (P<0.05), and the activity of GSH-Px in ileum mucosa was increased (P<0.05). T-AOC and the mRNA expression of NQO1 in ileum mucosa of 500 mg·kg^-1rutin group were also significantly higher than those in control group (P<0.05). At 42 d, the supplementation of rutin linearly and quadratic decreased the content of MDA in ileum mucosa (P_L<0.05; P_Q<0.05), the mRNA expression levels of Nrf2 and HO-1 increased quadratic (P_Q<0.05), and compared with the control group, the supplementation of 500 mg·kg^-1 rutin significantly decreased the content of MDA in ileum mucosa (P<0.05). The activity of T-SOD and mRNA expression levels of Nrf2 and HO-1 were increased (P<0.05). In summary, supplementation of rutin in the diet could improve the ileal morphology and structure of broiler chickens, improve intestinal immunity and barrier function, and improve its antioxidant capacity by enhancing the Nrf2 signaling pathway in ileal tissue. Under the conditions of this experiment, considering the effect of rutin on the whole period of broilers, the recommended amount of rutin in the diet was 500 mg·kg^-1.

Key words: rutin, broiler, antioxidant, immunity, intestinal barrier, intestinal function