Effects of Clostridium butyricum on growth, body index, nutrient utilization, 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 of discus fish Symphysodon haraldi, C. butyricum was added in basic feed for the fish at concentrations 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 groups. However, crude protein content and digestibility in 1×10⁵ cfu/g group increased significantly. Compared to control, 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 group significantly improved. For intestinal digestive and antioxidant enzymes, the trypsin activity of fish in 1×10⁵ cfu/g group was greatly improved. Furthermore, the malondialdehyde content in 1×10⁶ cfu/g group fish was significantly decreased. Short chain fatty acids (SCFAs) were measured in fish intestinal contents, and it was suggested that acetic acid and propionic acid in 1×10⁵ cfu/g 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, intestinal digestion and antioxidant capacity, and increase intestinal SCFAs secretion and nutrition utilization.