Dietary Fermented Mulberry Leaf Triggers Dose-Dependent Changes in Growth, Antioxidant Immune Status and Intestinal Microecology of Amur Sturgeon (Acipenser schrenckii)

Abstract

Simple Summary Mulberry leaves are a promising plant-based feed material for aquaculture, but raw mulberry leaves contain anti-nutritional factors that limit their use in carnivorous fish. Fermentation can break down these harmful components and improve nutrient availability. In this study, we evaluated the effects of adding graded levels (0%, 2%, 4%, and 6%) of fermented mulberry leaf (FML) to the diets of Amur sturgeon (Acipenser schrenckii) as a partial replacement for fishmeal. Our results showed that moderate FML inclusion (2–4%) maintained growth performance comparable to the control group while improving intestinal structure, enhancing antioxidant capacity, and boosting immune responses without causing intestinal inflammation. High-dose FML (6%) resulted in reduced growth despite favorable effects on gut microbiota. The optimal FML dosage was estimated at 3.66–4.62% based on mathematical modeling. In conclusion, adding 4% fermented mulberry leaf to sturgeon feed offers a balanced improvement in both growth and health, supporting its potential as a sustainable ingredient for carnivorous fish diets. These findings provide practical guidance for the use of mulberry by-products in aquaculture.