摘要Background Growth-promoting antibiotics have been banned by law in the livestock and poultry breeding industry in many countries.Various alternatives to antibiotics have been investigated for using in livestock.Epimedium(EM)is an herb rich in flavonoids that has many beneficial effects on animals.Therefore,this study was planned to explore the potential of EM as a new alternative antibiotic product in animal feed.Methods A total of 720 1-day-old male broilers(Arbor Acres Plus)were randomly divided into six groups and fed basal diet(normal control;NC),basal diet supplemented with antibiotic(75 mg/kg chlortetracycline;CTC),and basal diet supplemented with 100,200,400 or 800 mg/kg EM extract for 6 weeks(EM 100,EM200,EM400 and EM800 groups).The growth performance at weeks 3 and 6 was measured.Serum,intestinal tissue and feces were collected to assay for antioxidant indexes,intestinal permeability,lactic acid and short-chain fatty acids(SCFAs)profiles,microbial composition,and expression of intestinal barrier genes.Results The average daily feed intake in CTC group at 1-21 d was significantly higher than that in the NC group,and had no statistical difference with EM groups.Compared with NC group,average daily gain in CTC and EM200 groups increased significantly at 1-21 and 1-42 d.Compared with NC group,EM200 and EM400 groups had significantly decreased levels of lipopolysaccharide and D-lactic acid in serum throughout the study.The concentrations of lactic acid,acetic acid,propionic acid,butyric acid and SCFAs in feces of birds fed 200 mg/kg EM diet were significantly higher than those fed chlortetracycline.The dietary supplementation of chlortetracycline and 200 mg/kg EM sig-nificantly increased ileal expression of SOD1,Claudin-1 and ZO-1 genes.Dietary supplemented with 200 mg/kg EM increased the relative abundances of g_NK4A214_group and Lactobacillus in the jejunal,while the relative abundances of Microbacterium,Kitasatospora,Bacteroides in the jejunal and Gallibacterium in the ileum decreased.Conclusion Supplementation with 200 mg/kg EM extract improved the composition of intestinal microbiota by regulating the core bacterial genus Lactobacillus,and increased the concentration of beneficial metabolites lactic acid and SCFAs in the flora,thereby improving the antioxidant capacity and intestinal permeability,enhancing the function of tight junction proteins.These beneficial effects improved the growth performance of broilers.