Abstract:The beneficial Clostridium butyricum,which synthesizes short-chain fatty acids such as butyric acid,can be added to feed to improve animal production,feed utilization efficiency,and the antioxidant ability of animals.[Objective] This paper explored effect of C.butyricum as a replacement of chlortetracycline on quality and antioxidant function of broiler leg muscle.[Methods] A total of 360 healthy 1-day-old Arbor Acres broilers were randomly selected and classified into three groups,with 8 replicates each group.Negative control group (CON) was fed with basal diet,antibiotics group (ANT) basal diet supplemented with 75 mg/kg chlortetracycline,and C.butyricum group (CB) basal diet supplemented with 500 mg/kg C. butyricum(viable bacteria,109 CFU/g).The experiment lasted 42 days.[Results] Compared with CON group,CB significantly increased weight,24h redness (a*),pH45 min,pH24 h,crude protein content,and ether extract,decreased 24 h brightness (L*),drip loss,cooking loss,and malondialdehyde (MDA) content,improved the total-antioxidant capacity (T-AOC),and the activity of catalase (CAT),total superoxide dismutase (T-SOD),and glutathione peroxidase (GPx),and up-regulated the expression of nuclear factor erythroid 2-related factor 2(Nrf2),GPx-1,SOD-1,and SOD-2 of broiler leg muscle (P<0.05).ANT raised the weight and pH45 min,reduced the drip loss and MDA content,and up-regulated the expression of Nrf2,GPx-1, and SOD-1 of broiler leg muscle compared with CON group (P<0.05).CB group demonstrated lower drip loss and L* after 24 h and higher ether extract and CAT activity of broiler leg muscle than the ANT group (P<0.05).[Conclusion] C. butyricum can replace chlortetracycline for broiler feed,activate the expression of Nfr2 signaling pathway related genes,and which improves the quality and antioxidation of broiler leg muscle.