Effects of microencapsulated probiotics-supplemented diet on growth, non-specific immunity, intestinal health and resistance of juvenile Nile tilapia challenged with Aeromonas hydrophila

The present study evaluated the use of two microencapsulated probiotic additives in extruded diets for juvenile Nile tilapia (Oreochromis niloticus). For this purpose, 630 juvenile tilapias were distributed in nine experimental units (70 fish per unit), conditioned to three treatments (SACCH with Saccharomyces cerevisiae; BACIL with Bacillus amyloliquefaciens and B. subtilis; and control), all in triplicate. Zootechnical, intestinal microbiota, haemato-immunological, as well as histological and histomorphometric analysis were performed. At the end of the experimental period, the fish were exposed to the pathogen Aeromonas hydrophila. After 45 days of dietary supplementation, we verified greater survival, improvements in feed conversion, as well as in the specific growth rate in fish that received diets containing probiotics. In the intestinal histomorphology, both probiotic treatments expressed greater length and width of the intestinal folds. Furthermore, a significant differentiation of intestinal microbiomes was observed between treatments in the metagenomic evaluation. In the experimental challenge against A. hydrophila both probiotic treatments showed lower cumulative mortality (10% SACCH and 15% BACIL) than the control (45%). We conclude that the use of probiotics, as presented in this study, microencapsulated in extruded diets for juvenile Nile tilapia improves the zootechnical and health aspects of fish, demonstrating probiotic action as an immunomodulator.