Dietary β-1,3/1,6-glucans improve the effect of a multivalent vaccine in Atlantic salmon infected with Moritella viscosa or infectious salmon anemia virus

The immunomodulatory properties of beta -glucans are well documented for several animal species. However, little is known on their use as enhancers of non-specific and specific responses against Moritella viscosa and infectious salmon anemia (ISA) virus, which are two major pathogens affecting the Atlantic salmon aquaculture industry. The present study assessed the effects of dietary beta -1,3/1,6-glucans (MacroGard (R)) and vaccination on the survival of Atlantic salmon (Salmo salar) post-smolts challenged with M. viscosa or ISA virus. Dietary supplementation decreased mortality in both unvaccinated (55.4%; RPSend 19.9) and vaccinated (9.3%; RPSend 86.6) M. viscosa-challenged fish compared to the non-supplemented groups (69.1% and 28.3% mortality in unvaccinated and vaccinated fish, respectively; RPSend 59 for vaccinate non-supplemented fish). Similarly, mortality of ISA virus-challenged fish decreased from 87.5% in vaccinated fish without supplementation (RPSend 9.2) to 70.9% in the supplemented and vaccinated group (RPSend 26.4). In summary, these findings show that dietary beta -glucans increase Atlantic salmon resistance and improve the protective effect of vaccines against the tested pathogens.