Effects of Clostridium butyricum on the growth performance, digestion, immunity, and gut microbiota of Rana catesbiana

Aims This study aimed to evaluated the comprehensive effects of dietary Clostridium butyricumon the growth performance, digestion, immunity, and gut microbiota of Rana catesbiana larvae. Methods and Results Six groups (N0-N5), each with three replicates of 45 R. catesbeiana larvae, were established, using the dietary C. butyricum supplementation (0.25%-4%) (N1-N5) and an unsupplemented diet (N0) as control. The growth performance of bullfrog larvae in addition of 2% C. butyricum (N4) was the best. Regarding digestive function, the activities of intestinal lipase and chymotrypsin in the N4 group increased by 299% and 193% compared with the control group (P < 0.05), and the activity of liver amylase increased by 128%. In terms of immune regulation, the serum lysozyme and total nitric oxide synthase activities in the N4 group increased by 75% and 71% than the control group. The key antioxidant enzymes of superoxide dismutase and catalase, showed the highest activities were 46% and 57% higher than those of the control group. Intestinal histology showed that the muscle layer thickness and villus height of the N4 group increased by 22% and 16%. Microbial analysis revealed that the addition of C. butyricum significantly increased the alpha diversity index of gut microbiota. Conclusions 2% C. butyricum supplementation promotes bullfrog larval health through synergistic improvements in nutrient metabolism, immune defence, and intestinal microbiota homeostasis.