Clostridium butyricum WF4-2 in Enhancing Growth and Immunity of Red Claw Crayfish (Cherax quadricarinatus)

A total of 600 four-week-old C. quadricarinatus juveniles (0.26 ± 0.02 g) were randomly assigned to five groups based on the dietary supplementation levels of lyophilized C. butyricum strain WF4-2: C0 (0 g/kg), C1 (0.002 g/kg), C2 (0.02 g/kg), C3 (0.2 g/kg), and C4 (2 g/kg). Each group included three replicates, with 40 crayfish per replicate, and the feeding trial lasted for eight weeks. Results demonstrated that supplementation with 0.02 g/kg of WF4-2 significantly enhanced both weight gain rate (P = 0.038) and specific growth rate (P = 0.040) in C. quadricarinatus. Broken-line analysis indicated that the optimal supplementation level for growth promotion was 0.02 g/kg. In terms of digestive enzyme activities, trypsin activity was significantly elevated in groups C1 and C2 (P