Seaweed residue hydrolysate enhances the intestinal health, immunity and disease resistance in northern snakehead (Channa argus)

Abstract

Seaweed residue hydrolysate (SRH), produced by the acid hydrolysis of seaweed processing residues, is rich in bioactive compounds. The development and utilization of SRH as an aquatic immune enhancer not only achieves high-value utilization of waste but also promotes green and healthy aquaculture. In this study, northern snakehead (Channa argus) juveniles fed a compound feed supplemented with SRH (treatment group) exhibited a significant enhancement in intestinal microbial diversity and the proliferation of beneficial bacteria after eight weeks. After Edwardsiella tarda infection, the survival of the treatment group (70 %) was significantly higher than that in the control group (30 %). Histological analysis revealed that SRH alleviated tissue damage incurred by bacterial infection. Compared to the control group, the treatment group demonstrated an increase in the activities of non-specific immune enzymes and antioxidant enzymes, as well as a decrease in malondialdehyde (MDA). Furthermore, SRH influenced intestinal gene expression, with differentially expressed genes (DEGs) being enriched in various immune-related pathways, including cAMP, intestinal immune network for IgA production, and NF-κB signaling pathways. The present study has elucidated the potential efficacy of SRH in mitigating oxidative stress, enhancing the immunity and disease resistance of northern snakehead, providing valuable insights into the high-value utilization of SRH as a sustainable and eco-friendly immune enhancer in aquaculture.