Improvement of antioxidant capacity and gut microbiota balance in adult zebrafish (Danio rerio) by addition of fermented distillers' dried grains with solubles (DDGS).

The continuous high price of fishmeal has prompted the aquaculture industry to seek alternative protein sources. Distillers' dried grains with solubles (DDGS) possess significant utilization value as a plant-based protein, yet its substitution ratio is limited due to the anti-nutritional factors. This study aimed to assess the potential of compound bacteria-fermented DDGS as a protein source for aquatic feed. DDGS was fermented using complex bacteria, and the treatment group with the highest crude protein content after fermentation was used as the raw material for the experimental diets. Based on different replacement levels of hatching brine shrimp with DDGS, four dietary groups were established: D0, D10, D20, and D30. Each tank was stocked with 30 zebrafish, with three replicates per treatment group. Fish were fed twice daily, and the experiment lasted for 30 days. The main results are as follows: the inclusion of 10% fermented DDGS in the diet significantly enhanced superoxide dismutase and glutathione activities in both the gut and muscle tissue of zebrafish compared to the control group (D0). The relative abundance of the probiotic Cetobacterium exhibited a significant increase of 38% in the D10 group compared to the D0 group. A PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) study unveiled a substantial augmentation in the abundance of metabolic pathways, encompassing cofactor and vitamin metabolism as well as carbohydrate metabolism. In conclusion, the findings demonstrated that incorporating fermented DDGS into the diet significantly augmented the antioxidant capacity and disease resistance of zebrafish.