Oligosaccharides and Fish Gut Microbiome. Modification of Nile Tilapia Gut Microbiome by Oligosaccharides

Finfish aquaculture is expected to continue to benefit from significantly improved fish diets, which are the source of energy to support the growth and health of fish. Huge efforts have been undertaken to produce fish feed with higher nutrient and energy levels, such as investigation of supplement for fish growth enhancement. However, the addition of these supplements can result in increased costs of fish farming and the loss of nutrients during production. Strategies to enhance the transformation rate of dietary energy and protein to fish growth are greatly desired by fish culturists. Prebiotic compounds can be used as supplements to human, animal, and fish diets to populate beneficial bacteria in the gut. These bacteria are expected to increase the absorption of the food nutrients by the host digestive system. In the present study, several oligosaccharides were evaluated as prebiotics with Nile tilapia (Oreochromis niloticus), one of the most widely aquacultured species in the world. Results indicated that the addition of xylooligosaccharide (XOS), galactooligosaccharide (GOS), or XOS and GOS combination to the basic fish diet significantly decreased the feed conversion ratio (FCR), suggesting improved energy transformation efficiency from fish diet to fish growth. The application of XOS and GOS also elevated the production of glutathione-related enzymes and the enzymatic activity of glutathione peroxidase (GPX), indicating the enhancement of antioxidation processes in fish. These improvements were associated with significant changes in the fish gut microbiota. The microbiome analysis showed the numbers of several bacterial species were increased by XOS and GOS supplements. These identified bacteria can be potentially used as probiotic supplements in the future to improve fish growth and feeding efficiency and create a cleaner environment for aquaculture.