Abstract: 【Objective】 This experiment was conducted to investigate the effects of complex enzymes and Bacillus subtilis on growth performance,meat quality and liver function of Yellow-feathered broilers.【Method】 A total of 1 200 1-day-old fast large Yellow-feathered cocks were randomly divided into 5 groups with 6 replicates per group and 40 chickens per replicate.The birds in control group were fed basal diet,and the birds in other four groups were fed the basal diet supplemented with 20 mg/kg virginiamycin (antibiotic group),500 mg/kg complex enzymes (complex enzymes group),200 mg/kg Bacillus subtilis (Bacillus subtilis group) and 500 mg/kg complex enzymes＋200 mg/kg Bacillus subtilis (combined group),respectively.The experiment lasted for 63 days.At 21,42 and 63 days of age,broilers were weighed with fasting and feed intake was calculated to calculate growth performance.Two chickens from each replicate at 21 and 63 days of age were slaughtered.Blood and liver tissue samples were collected and biochemical parameters were determined.At 21 days of age,cecum contents were collected to determine the number of microflora.Breast muscle was taken at 63 days of age to evaluate meat quality.【Result】 Compared with the control group,there were no significant differences in the growth performance of Yellow-feathered broilers in complex enzymes group,Bacillus subtilis group and the combined group (P＞0.05),but the liver index at 21 days was significantly increased (P＜0.05),and the muscle dripping loss at 63 days of age was significantly decreased (P＜0.05) in three groups.Compared with the control group,the supplementation of complex enzymes or Bacillus subtilis alone significantly decreased Enterococcus microflora in cecum of Yellow-feathered broilers at 21 days of age (P＜0.05),significantly decreased plasma urea nitrogen (BUN) level at 63 days of age (P＜0.05),and significantly increased the activities of T-superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) in liver (P＜0.05).Compared with the control group,the plasma BUN level of Yellow-feathered broilers at 21 days of age was significantly decreased by complex enzymes supplementation alone (P＜0.05).And the supplementation of Bacillus subtilis alone significantly increased the activity of choline esterase(CHE) in liver of 21-day-old Yellow-feathered broilers (P＜0.05).Compared with antibiotic group,the combined supplementation of complex enzymes and Bacillus subtilis had no significant effect on liver index of 63-day-old Yellow-feathered broilers (P＞0.05),but significantly increased the meat yellowness value at 24 h (P＜0.05).Compared with the combined group,the supplementation of complex enzymes or Bacillus subtilis alone significantly increased GSH-Px and succinate dehydrogenase (SDH) activities in the liver of 63-day-old Yellow-feathered broilers (P＜0.05),but had no significant effect on the composition of cecal microbiota (P＞0.05).【Conclusion】 Dietary supplementation of complex enzymes or Bacillus subtilis alone could enhance the antioxidant capacity and metabolic function of liver,improve meat quality and reduce the number of harmful bacteria in cecum of Yellow-feathered broilers.However,there was no synergistic effect of the supplementation of complex enzymes and Bacillus subtilis.

Key words: complex enzymes; Bacillus subtilis; growth performance; meat quality