Dietary supplementation of Bacillus amyloliquefaciens and β-glucan, both individually and in conjunction effected growth performance, skin mucosal immunity, mRNA expression, and disease protection against Aeromonas hydrophila in striped snakehead, Channa striata (Bloch 1793).

Abstract

Probiotics offer a promising strategy to enhance aquaculture sustainability. A 60-day trial evaluated the effects of dietary Bacillus amyloliquefaciens, β-glucan, and their synbiotic on growth, immunity, gene expression, and Aeromonas hydrophila protection in striped snakehead, Channa striata. Four dietary treatments were formulated: a non-supplemented basal diet; basal diet augmented with B. amyloliquefaciens (10 CFU g); basal diet augmented with β-glucan (5 mg g); and basal diet augmented with both supplements as a synbiotics. The isolated B. amyloliquefaciens H23 strain (Genbank ID: PP776582.1) tolerated to wide pH, bile, and salt levels, and survived gastric and intestinal fluids, supporting its suitability as a probiotic. By the end of the trial, fish fed with the B. amyloliquefaciens-β-glucan synbiotic showed significantly improved growth indices and feed efficiency, along with the highest digestive enzyme activities. serum and mucosal immune parameters were strongly elevated, antioxidant capacity increased, and cortisol levels declined. Synbiotic feeding also upregulated key antioxidant, growth-related, and cytokine genes and improved survival against A. hydrophila by 27.7 %. Overall, the synbiotic (10 CFU gB. amyloliquefaciens + 0.5 % β-glucan) produced the best health outcomes, indicating its potential as an effective aquafeed supplement.