Transcriptome analysis reveals the effect of fermented feed on the growth, antioxidant capacity, and immune function...

The capacity of fermented feed to improve the nutrient consumption, water quality, and immunological health of cultured species has drawn increased interest in aquaculture. This study aimed to establish the ideal supplementation ratio of fermented feed by analyzing its effects on growth metrics, antioxidative potential, and immunological function in juvenile Eriocheir sinensis. Five trial diets containing 0, 10, 20, 30, and 40% fermented feed were administered for 60 days under controlled pond conditions. Growth indices, hepatopancreas histology, antioxidant enzyme activities, immune parameters, and transcriptomic profiles were analyzed. Crabs fed 30% fermented feed exhibited the highest final weight, weight gain rate, and specific growth rate, accompanied by improved hepatopancreas structure characterized by increased fibrillar cells. The expression levels and activities of enzymes and genes linked to antioxidants and immunity were markedly upregulated in this group relative to the control group. Transcriptome sequencing of hepatopancreas showed 148 differentially expressed genes, mainly enriched in steroid hormone biosynthesis, Hippo, TGF, and Toll and Imd signaling pathways, indicating activation of immune and antioxidant mechanisms. Feeding with 30% fermented feed upregulated key immune genes such as Relish, MyD88, and DREDD while downregulating Cactus, confirming stimulation of Toll and Imd signaling. Overall, an appropriate proportion of fermented feed, particularly 30%, improved growth, enhanced antioxidant defense, and strengthened innate immunity in juvenile E. sinensis. These results demonstrate that optimized fermented feed can promote health and sustainability in crab aquaculture through nutritional and immunological enhancement.