Short- and long-term effects of a dietary yeast β-glucan (Macrogard) and alginic acid (Ergosan) preparation on immune response in sea bass (Dicentrarchus labrax)

Over the long-term period, no significant differences were observed in innate and specific immune parameters, survival, growth performances and conversion index in treated and control fish. A dramatic decrease of both innate and acquired immune parameters was observed during the winter season in all groups, followed by a partial recovery when water temperature increased. Reduction in complement and lysozyme activities was significatively correlated (p < 0.01) to water temperature variation. The results suggested the potential of alginic acid and β-glucans to activate some innate immune responses in sea bass, and particularly under conditions of immunodepression related to environmental stress.