Aquaculture Reports (Jun 2024)
Probiotic breakthrough: Clostridium butyricum improved the intestinal SCFAs content, digestive enzymes and antioxidant activities, gut morphology and microbiota composition of largemouth bass
Abstract
The intestinal tract plays an important role in digestion and absorption, nutrient metabolism, and immune anti-stress. At the same time, the intestine is also the major site for pathogens and various harmful substances to invade. Probiotics, as living microbial agents, improve animal health by maintaining the microecological balance of the host's intestinal flora. To explore the protective effect of Clostridium butyricum (CB) on the gut, we investigated the changes in digestion, antioxidant, and gut microbiota in juvenile largemouth bass. The fish were fed with diets containing 0 (control, CB0), 4.3×108 (CB1), 7.5×108 (CB2), 1.5×109 (CB3), and 3.2×109 (CB4) CFU/kg Clostridium butyricum for 56 days. After 56 days of dietary supplementation with 4.3×108 and 3.2×109 CFU/kg of CB, significant growth promotion and feed utilization improvement were observed in largemouth bass (P < 0.05). The activities of digestive enzymes (trypsin, protease and amylase) and intestinal functional indicators (sodium-potassium ATP, γ-GT and CK) were significantly increased in the intestine of largemouth bass (P < 0.05). The contents of intestinal short-chain fatty acids (acetic acid, propionic acid, isobutyric acid, N-butyric acid and isovaleric acid) in largemouth bass were significantly increased (P < 0.05). CB significantly increased the activities of antioxidant enzymes (T-AOC, CAT, POD, GSH-Px and SOD) and decreased the content of MDA in the intestine of largemouth bass (P < 0.05). It was also observed that CB significantly increased the activities of immune-related markers lysozyme and alkaline phosphatase (P < 0.05). High-throughput sequencing of the 16 S rRNA gene in largemouth bass revealed a significant increase in gut microbial richness. KEGG pathway analysis showed that CB had significant effects on intestinal microbiota functions, such as nutrient metabolism and energy conversion. The results showed that CB could stimulate intestine to produce the organic product butyric acid, which was customized in the gut to enhance digestive performance, promote nutrient metabolism, and protect microbial homeostasis in the intestinal tract of largemouth bass. These results provide new insights into the protective effects of CB on the intestinal tract of aquatic animals.
