Introduction
Animal health related issues are nowadays the major constraint for aquaculture expansion and sustainability (Adams 2019). Besides vaccination, prophylactic measures such as the incorporation of immunostimulants and prebiotics in feeds (Meena et al. 2013; Song et al. 2014), have also been used to prevent disease outbreaks. To enhance fish disease resistance and general health, diets are often supplemented with β-glucans, which are compounds with known beneficial effects in fish innate immune response (Guzmán-Villanueva et al., 2014). β-glucans show repeating patterns on their structure that are recognized in the gut by cell pattern recognition receptors (PRR), leading to the activation of the host´s innate immune cells enhancing its immune response (Dalmo et al., 2008). The present work aimed to evaluate the effects of both short- and mid-term feeding diets supplementated with microalgae (Phaeodactylum tricornutum) extracted β-glucans on gene expression, oxidative stress biomarkers and plasma immune parameters in gilthead seabream (Sparus aurata) juveniles.
Material & Methods
A practical commercial-like diet was used as control (CTRL), whereas 3 others based on CTRL were further supplemented with a constant concentration of β-glucans, derived from Saccharomyces cerevisiae (diet MG1000) and different extracts of P. tricornutum (diets Phaeo21 and Phaeo37). Diets were randomly assigned to quadruplicate groups of 95 gilthead seabream (initial body weight: 4.1 ± 0.1g) that were fed to satiation three times a day for 8 weeks in a pulse feeding regimen. Therefore, fish were fed the different experimental diets intercalated with the CTRL dietary treatment every 2 weeks. After 2 and 8 weeks of feeding, 3 fish/tank were sampled for blood and tissues collection.
Results & conclusion
All groups showed equal growth performance and no significant changes in plasma innate immune status. Nonetheless, seabream fed β-glucans supplemented diets showed an improved anti-oxidant status compared to those fed CTRL at both sampling points. Furthermore, diet Phaeo37 seems to induce an immune tolerance effect in the gilthead seabream gut, causing a general down-regulation of immune related genes, without compromising systemic immune response. In conclusion, results suggest that the dietary administration of a P. tricornutum 37% enriched-β-glucans extract might be relevant in a context of gut inflammation due to its immune tolerant and anti-oxidative effects.
Acknowledgements
This work has received funding from the Bio Based Industries Joint Undertaking (BBI JU) under the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 745754 (project MAGNIFICENT). This output reflects the views only of the author(s), and the European Union and BBI JU cannot be held responsible for any use which may be made of the information contained therein. BR and BC were supported by FCT - Foundation for Science and Technology (PD/BDE/129262/2017 and IF/00197/2015, respectively).
References
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