Early-life intervention with the host-derived probiotic Bacillus subtilis improves growth and health in hybrid sturgeon (Acipenser schrenckii ♂ × Huso dauricus ♀) fingerlings

This study evaluated the efficacy of Bacillus subtilis Ya3.1 supplementation, administered via feed (BF, 1.0 × 10⁸ CFU g⁻¹) or water (BW, 1 × 10⁷ CFU L⁻¹ every 48 h), on growth performance, intestinal function, hepatic metabolism, and disease resistance in hybrid sturgeon (Acipenser schrenckii ♂ × Huso dauricus ♀) fingerlings. Following a 6-week trial, both treatments significantly improved growth parameters，including final weight, weight gain rate (WGR), specific growth rate (SGR), and viscerosomatic index (VSI)，and reduced the feed conversion ratio (FCR) relative to the controls (CK), with no impact on whole-body composition or nutrient retention. Probiotic supplementation significantly upregulated intestinal digestive enzyme activities (trypsin, α-amylase, and cellulase), with superior efficacy observed in the BF group. High-throughput 16S rRNA gene sequencing indicated that B. subtilis Ya3.1 modulated the intestinal microbiota composition by enriching Bacillus abundance of and suppressing Clostridium sensu stricto 1, despite stable microbial diversity. Untargeted liquid chromatography–mass spectrometry (LC–MS) metabolomics revealed distinct hepatic metabolic profiles in the treated groups, characterized by widespread upregulation of metabolites and pathways indicative of heightened hepatic metabolic activity. Moreover, innate immune parameters (serum complement C3 and C4) were elevated, corresponding to significantly improved survival rates (BF: 83.3 %; BW: 80.0 %) following Aeromonas hydrophila challenge. Collectively, these findings suggest that B. subtilis Ya3.1 may promote growth and health in hybrid sturgeon fingerlings by modulating intestinal microbiota, enhancing digestive and metabolic efficiency, and potentiating innate immunity, with dietary administration yielding superior results. This study underscores the potential of host-derived probiotics for sustainable aquaculture.