Exogenous enzymes improve growth, antioxidant capacity, and gut health of zebrafish ( Danio rerio ) fed DDGS-based diets

Distillers’ dried grains with solubles (DDGS) are promising in aquafeeds, but recalcitrant non-starch polysaccharides limit their utilization. This study evaluated six diets with three DDGS substitution levels (15%, 25%, and 35%) with or without xylanase and β-glucanase (XB) supplementation. Adult zebrafish (Danio rerio) were allocated to these treatments across three replicate tanks (30 fish/tank) for 30 days. Across all levels, XB supplementation significantly improved growth performance compared with non-supplemented diets (p < .05), with specific growth rate peaking in DXB15 (2.89 ± 0.03%/day). Furthermore, DXB15 achieved peak enhancements in hepatic glutathione (+96.5%), total antioxidant capacity (+43.3%), protease (+140%), and amylase (+22.1%), whereas hepatic superoxide dismutase peaked in DXB25 (+13.3%) (all p < .05). Additionally, DXB15 enriched beneficial Cetobacterium (+13.3%) and Firmicutes (+65.4%) (p < .05). Overall, XB supplementation mitigates high-DDGS dietary stress by improving antioxidant status, digestion, and gut micro-ecology.