Functional Feeds as Immunostimulants for Aquaculture: A Molecular Perspective.

The development of aquafeeds that enhance immunity in fish represents an effective strategy for disease management in aquaculture. This approach involves incorporating functional ingredients with immunostimulatory properties to improve fish welfare. The use of dietary immunostimulants is considered a suitable, safe, and eco-friendly alternative to mitigate the adverse effects of antibiotics and chemotherapeutics. Hence, there is growing interest among aquaculture stakeholders in immunostimulant sources such as algae, plant derivatives, trace minerals, prebiotics, and probiotics. However, earlier studies have relied on biochemical markers to evaluate the interactions of dietary immunostimulants with the fish immune system, which provide limited mechanistic insights and reduce reproducibility for large-scale applications. Recent advances in molecular approaches, including genomics, transcriptomics, proteomics, metabolomics, and small RNA profiling, have been increasingly applied to elucidate the underlying mechanisms of dietary immunostimulants and to guide the development of species-specific formulations. By integrating these molecular tools, researchers can design sustainable, species-tailored immunostimulant diets that reduce the reliance on antibiotics. This review synthesizes molecular evidence on nutrient-, plant-, microbial-, and algae-based immunostimulants, highlighting how omics tools elucidate their mechanisms and support the design of species-specific functional feeds.