THE EFFECT OF DIETARY PROBIOTICS IN NILE TILAPIA Oreochromis niloticus HEALTH AND GROWTH PERFORMANCE  

B. T. Standen*, G. A. Santos
Biomin Holding GmbH, Erber Campus 1, 3131 Getzersdorf, Austria
 

Three investigations were conducted in order to investigate the effect of dietary probiotics in tilapia (Oreochromis niloticus) growth performance, intestinal morphology, intestinal microbiology and immunity.

The first experiment demonstrated that probiotic strains in AquaStar® Growout were capable of modulating the intestinal microbial populations in a favourable manner. High-throughput sequencing reported that >99% of 16S rRNA reads in the AquaStar® group belonged to the probiotic genera, predominantly assigned to Enterococcus (52.50%) and Bacillus (45.94%). Tilapia in the probiotic group displayed significantly higher intraepithelial leucocyte (IEL) populations in the mid intestine when compared to the control treatment. The probiotic also improved microvilli density and had a higher absorptive surface area when compared to the control.

In the second trial, after six weeks of supplementing tilapia diets with AquaStar® Growout at 3g kg-1, fish demonstrated significantly higher final weight, weight gain and SGR when compared to that of the control (void of probiotic) treatment. Probiotic supplementation at 3g kg-1 also caused an increase in the abundance of intestinal IELs and goblet cells and an up-regulation in the gene expression of immunity genes TLR2, TNFα, IL-1β, TGFβ and IL-10 when compared with the expression of control replicates.

Trial three revealed that the probiotic had a more discrete effect on the intestinal allochthonous microbiota as 16S rRNA reads assigned to probiotic genera only accounted for 5-10% of total reads. Nevertheless, the supplementation of dietary AquaStar® Growout at 3g kg-1 improved the localised immune response in tilapia, through the regulation of immunity genes TLR2, TNFα, IL-1β, TGFβ and IL-10, larger populations of goblet cells and a higher recruitment of IELs. Furthermore, the probiotic also improved the systemic immune response through the regulation of immunity genes (mentioned above) in the head kidney.

This research demonstrates that AquaStar® Growout can modulate intestinal microbiota, improve intestinal morphology, growth performance and modulate both the localised and systemic immune responses of tilapia.