The rapid growth and intensification of the aquaculture sector had led to various constrains such as stresses and disease, which reflects on a weakened immune capacity. Researchers have prompted innovation for new solutions and methodologies aiming to improve animal immune capacity. The use of vaccines, antibiotics, and non-specific immunostimulants are three possible methods of farmed fish protection against disease. The present work aims to evaluate the efficiency of microalgae-derived ß-glucan on modulate fish systemic immune response through improved nutrition.
A benchmarking test was done with a commercial diet as control (CTRL), the same diet was supplemented with yeast-derived ß-glucan (commercial use) and microalgae-derive ß-glucan (P. tricornutum). Post-larvae Senegalese sole and juvenile seabream were fed the experimental diets and exposed to inactivated Photobacterium damselae subsp. Piscicida, which would trigger the host immune system to react. A panel of immune parameters were analysed, from oxidative parameters (total proteins, catalase, lipid peroxidation, total glutathione and superoxide dismutase activities) to immune parameters (lysozyme, peroxidase and bactericidal activities).
Both experimental trials presented no significant differences on growth performance and feed conversion. On the other hand, diet supplementation with microalgae-driven ß-glucan, significantly increased thrombocytes cells as well as SOD activity, in juvenile seabream. Regarding post-larvae S. sole, ß-glucan supplementation significantly increased lysozyme activity after bacteria exposure. Further analysis is underway.
β-glucan mode of action is mainly in the gut, by the cell pattern recognition receptors (PRR), leading to the activation of the host´s innate immune cells, enhancing its immune response. Further analysis on gut gene expression may lead to more detailed answer on β-glucan capacity to modulate fish immune response.
Furthermore, this work intends to develop a preliminary method to evaluate animal’s short-immune response, as an alternative to the conventional challenge tests.