Sodium alginate supplementation modulates gut microbiota, health parameters, growth performance and growth-related gene expression in Malaysian Mahseer Tor tambroides

This study investigated the effects of sodium alginate supplementation on gut microbiota composition, health parameters, growth performances and growth-related gene expression of Malaysian mahseer. Five test diets were formulated by supplementing 0%, 0.1%, 0.2%, 0.4% and 0.8% sodium alginate. Triplicate groups of juvenile Tor tambroides (2.19 +/- 0.05 g) were stocked in 15 aquaria (20 individuals per aquarium) and fed at 3.0% body weight per day for 60 days. PCoA and UPGMA analysis showed that gut bacterial community were more convergence in higher sodium alginate-supplemented diets. The percentage of Porphyromonadaceae, Bacteroides, Plesiomonas and Shewanella were substantially higher and Aeromonas, Entomoplasmatales and Prevotellaceae were drastically lower in higher sodium alginate (0.2%-0.8%) diets. Sodium alginate supplementation (>= 0.2%) significantly improved the haematocrit value and respiratory burst activity of T. tambroides. Growth performances and feed utilization were significantly higher in 0.2%-0.4% sodium alginate-supplemented diets. The increased growth rate of T. tambroides was governed by both hyperplastic and hypertrophic muscle growth. Real-time PCR data demonstrated that most of the growth-related genes were significantly upregulated in 0.2%-0.4% sodium alginate-supplemented diet. Finally, it can be concluded that sodium alginate should be supplemented at 2 g/kg in practical fish feed formulation.