Abstract: The aim of this experiment was to study the effects of Bacillus subtilis,oligomeric chitosan,sodium butyrate added alone or in pairs instead of antibiotic on growth performance,immune function,carcass performance and meat quality of Yellow-feathered chickens raised in cages.Seven hundred and twenty 1-day-old rapidly growing Lingnan Yellow-feathered male chickens were randomly assigned to eight groups according body weight (each group consisted of six replicates with 15 broilers per replicate),and they were control group (antibiotic-free),antibiotic group (200 mg/kg 4% eramycin),probiotics group (500 mg/kg Bacillus subtilis),oligomeric chitosan group (50 mg/kg oligomeric chitosan),sodium butyrate group (500 mg/kg sodium butyrate),antibiotic-free combination group 1 (500 mg/kg Bacillus subtilis＋30 mg/kg oligomeric chitosan),antibiotic-free combination group 2 (30 mg/kg oligomeric chitosan＋300 mg/kg sodium butyrate),antibiotic-free combination group 3 (500 mg/kg Bacillus subtilis＋300 mg/kg sodium butyrate).The experiment was carried out in three stages,and the experimental period was 63 days.The results showed:1 to 21 days,there was no significant difference in growth performance and plasma immune parameters among all treatments (P > 0.05).Bursa of Fabricius index of oligomeric chitosan group was higher than control and antibiotic groups (P > 0.05).The ileum pH in probiotics and sodium butyrate groups were significantly lower than antibiotic group (P < 0.05).22 to 42 days,there was no significant difference in growth performance among all treatments (P > 0.05).Spleen index of antibiotic-free combination group 3 was significantly higher than control group(P < 0.05).The jejunum pH in probiotics group was lower than antibiotic group (P > 0.05).Plasma IgG content in sodium butyrate,antibiotic-free combination groups 1,2,and 3 were significantly lower than control and antibiotic groups (P < 0.05).IgA content in antibiotic-free combination group 2 was significantly lower than control and antibiotic groups,and IgM content was significantly lower than antibiotic group (P < 0.05).Plasma IgM content in antibiotic-free combination group 1 was significantly higher than control and antibiotic groups (P < 0.05).IgA and IgG contents in probiotics group were higher than control and antibiotic group (P > 0.05),and IgM was significantly higher than control group (P < 0.05).43 to 63 days,ADG of antibiotic-free combination group 3 was significantly higher than antibiotic group (P < 0.05).The duodenum pH in probiotics group was significantly lower than antibiotics group (P < 0.05).Abdominal fat rate of antibiotic-free combination group 1 was significantly lower than control and antibiotic groups (P < 0.05).There was no significant difference in meat quality and plasma immune parameters among all treatments (P > 0.05).According to the results of growth performance,intestinal pH,immune performance and carcass performance in three stages,it was recommended to add 500 mg/kg Bacillus subtilis and 300 mg/kg sodium butyrate for improving growth performance,add 500 mg/kg Bacillus subtilis and 30 mg/kg oligomeric chitosan for improving carcass performance,and add 500 mg/kg Bacillus subtilis alone for improving intestinal health of rapidly growing Lingnan Yellow-feathered male chicken aged from 1 to 63 day.

Key words: Bacillus subtilis; oligomeric chitosan; sodium butyrate; Yellow-feathered chickens; growth performance; immunefunction