Effects of dietary scFOS and lactobacilli on survival, growth, and disease resistance of hybrid tilapia

The present study was aimed to select gut adhesive Lactobacillus strains and evaluate the combined effects with scFOS on the growth performance, gut adhesive bacteria and disease resistance of juvenile hybrid tilapia. Firstly, the adhesive property of Lactobacillus strains in the gut of tilapia, and effect of scFOS on the adhesion of Lactobacillus were determined by rpoB PCR-DGGE. Fish were fed with diet supplemented with seven probiotic Lactobacillus strains at equal amounts (2.0 × 107 cells/g basal diet) for 2 weeks, followed by basal or scFOS supplemented diet for 4 weeks. Results showed that strain JCM 1170 and JCM1149 was the most highly-adhesive strains and scFOS increased their relative abundance. In another experiment, fish were fed a diet containing 108 cells/g feed of JCM1170 OR JCM1149 with or without scFOS for 5 weeks. No significant differences in survival rate, weight gain, or feed conversion were observed in the different treatments. 10 predominant phyla were identified from gut samples by 454 pyrosequencing, and Proteobacteria, Firmicutes, Fusobacteria and Actinobacteria were the most predominant group. The composition of gut adherent microbiota was affected by probiotics/synbiotics. The challenge test showed that synbiotics of JCM 1149 and scFOS protected fish against A. hydrophila (P < 0.05). In conclusion, L. plantarum JCM 1149 at 108 cell/g feed and scFOS at 1 mg/g may be recommended as a synbiotics formulation for tilapia.