Organic benzoic acid modulates health and gut microbiota of Oreochromis niloticus

The aim of this study was to evaluate the influence of 0%, 0.1%, 0.2%, or 0.3% organic benzoic acid on the intestinal microbiota of Nile tilapia (Oreochromis niloticus). Classical medium-dependent microbiology, histology, and metagenomics analyses used high-throughput sequencing. Fish (n = 320) were divided into 16 tanks, with four fish per group: not supplemented with benzoic acid (BA0%), and supplemented with 0.1% (BA0.1%), 0.2% (BA0.2%), or 0.3% (BA0.3%) benzoic acid. The experimental diets were fed four times daily for 54 d. After the experimental period, in relation to classical microbiology, BA0.3% favored total heterotrophic bacteria (5.17 +/- 0.32) compared to the other treatments. Histological results revealed BA0.1% resulted in the greatest increase in villus length (69.93 +/- 23.84) compared to the control group and villus height (22.93 +/- 6.78) compared to the other supplemented groups, which shows better absorption of nutrients with consequent better growth. In metagenomics results, the main phyla were Actinobacteria and Firmicutes in the BA0.1% and BA0.3% group, respectively, and showed positive modulation with BA0.1% supplementation, consolidates that BA0.1% is beneficial for intestinal health. There was no increase in bacterial richness in the supplemented fish, regardless of the benzoic acid dose, validating the bactericidal and bacteriostatic activities. These results suggest that benzoic acid supplementation in the diet of O. niloticus positively modulates intestinal health at 0.1%. This study also suggests that organic acids are important as an alternative to the use of antibiotics, since several acids have already proven to be efficient in the digestibility of nutrients and a positive modulator of the intestinal microbiota, therefore, knowing the appropriate dose of each acid for each species is extremely important for a more sustainable fish farming.