Precision Nutrigenomics in Cultured Finfish: Dietary Regulation of Gene Expression, Microbial Ecology, Metabolism, and Immunity

Precision nutrigenomics requires a diet–microbiome–host perspective because microorganisms can transform feed substrates, generate bioactive metabolites, compete with pathogens, and modify intestinal and systemic gene regulation. This structured narrative review synthesizes representative controlled feeding trials, transcriptomic and targeted gene-expression studies, microbiome analyses, and complementary multi-omic evidence concerning dietary regulations in cultured finfish. The available evidence is concentrated particularly on soybean-derived proteins, lipid-source replacements, selected amino acids and micronutrients, functional additives, probiotics, and fermented ingredients in a limited range of cultured finfish species; therefore, the synthesis is not intended to provide exhaustive coverage of every dietary intervention or finfish taxon. Recurrent host responses involve intestinal inflammation and barrier integrity, nutrient transport, lipid and bile-acid metabolism, long-chain polyunsaturated fatty-acid biosynthesis, targets of rapamycin/insulin-like growth factor (TOR/IGF) signaling, and nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (Nrf2/Keap1) antioxidant defense. The expanded microorganism-centered synthesis shows that dietary effects depend on microbial niche, substrate availability, community succession, metabolite production, and strain-specific probiotic or pathobiont activity. Lactic-acid bacteria, Bacillus-associated interventions, butyrate-generating strategies, fermented ingredients, and microbial biomass may support digestion, immune balance, and disease resistance, but taxonomic shifts alone do not demonstrate functional benefit. Current evidence is limited by extensive reliance on 16S ribosomal RNA (16S rRNA) relative-abundance data, inconsistent digesta-versus-mucosa sampling, inadequate feed and water controls, and weak causal validation. Future precision aquafeed studies should combine host transcriptomics with absolute microbial quantification, shotgun metagenomics, metatranscriptomics, metabolomics, culturomics, histology, and pathogen challenge. Integrating microbial function with host phenotype can improve sustainable feed design, intestinal health, and resilience.