Citrus extracts are increasingly used in aquaculture production, due to the benefits they provide to animals. Such a process is driven by the market demand for natural products. However, depending on their origin, Citrus extract can vary a lot in terms of composition and concentration of active compounds. The present study was undertaken to study the effect of graded inclusion levels of a standardized natural citrus extract (SNCE) in the feed of Nile tilapia. In parallel, the SNCE has been characterized in order to identify its active compounds.
This study was performed at the University of Vale do Säo Francisco experimental station in Brazil. 380 juvenile Nile tilapias (mean initial weight: 12.8 ± 0.17 g) were randomly divided into 6 groups with 3 replicates. Each treatment was fed with a standard diet supplemented with SNCE at different doses described in Table 1 for 60 days.
Final weight was evaluated at the end of the experiment. statistical analysis was performed using ANOVA. Then, 30 fish per treatment were randomly selected and inoculated with Aeromonas hydrophila (0.2ml of a 1*10 7 CFU/ml solution) and mortality was assessed 8 days post challenge. In parallel, 5 batches of SNCE have been analyzed using HPLC-UV-DAD-DEDL and HPLC-UV-MSMS analyzers to characterize the SNCE.
Results show a positive effect of the increasing inclusion of NSAB on growth (Fig. 1)
Survival after the challenge with A. hydrophila was also positively influenced by the increased inclusion rate of the citrus extract (Fig. 2).
Regarding SNCE characterization, analysis performed on 5 batches didn’t show any difference between the 5 DEDL profiles of the SNCE. Pectic oligosaccharides, eriocitrin, and hesperidin were identified as SNCE’s major components.
Our results demonstrate the positive effects of the graded inclusion of a standardized natural citrus extract on zootechnical performances on juvenile Nile tilapias grown in unchallenging conditions. They also underline its interest when fish are challenged with a pathogenic bacteria. These results may be explained by the modulation of Nile tilapias’ intestinal microbiota. In fact, some compounds of SNCE such as hesperidin and POS are well known for their beneficial effect on intestinal microbiota. More studies will be necessary to confirm these hypotheses.