Effects of Clostridium butyricum on growth, body index, nutrient utilization, and intestinal structure and function of discus fish Symphysodon haraldi

To determine the effects of Clostridium butyricum on growth, body index, nutrient utilization, and intestinal structure and function, C. butyricum was added in basic feed for discus fish Symphysodon haraldi with concentration of 0 (control)、1×10⁴、1×10⁵、1×10⁶、1×10⁷ and 1×10⁸ cfu/g, respectively. After 8-week culture, no significant difference was showed on growth and body index of fish in C. butyricum-added group. However, crude protein content and digestibility in 1×10⁵ cfu/g addition group increased significantly. Compared to control one, height and width of midgut villi in fish fed with C. butyricum was apparently increased and mucopolysaccharide secretion level of fish in 1×10⁵ cfu/g addition group significantly improved. For intestinal digestive and antioxidant enzymes, the trypsin activity of fish in 1×10⁵ cfu/g addition group was greatly improved. Furthermore, the malondialdehyde content in 1×10⁶ cfu/g addition group fish was significantly decreased. Short chain fatty acids (SCFAs) were measured in fish intestinal contents, it suggested that acetic acid and propionic acid in 1×10⁵ cfu/g addition group was significantly higher than that in the control group, and the total acid content reached the maximum in this addition group, which was significantly higher than other groups. Studies have shown that under the conditions of this experiment, adding 1×10⁵ cfu/g C. butyricum to the discus fish bait can improve intestinal structure, improve intestinal digestion and antioxidant capacity, and increase intestinal SCFAs secretion and nutrition utilization.