Modulation of innate and adaptive immunity in Atlantic salmon (Salmo salar) fed diets containing commercial-like additives under farming conditions in seawater phase.

Diseases and environmental issues (e.g., increased seawater temperature and algal blooms) threaten Chilean aquaculture by causing salmon mortality. Feed additives can help solve these problems by modulating fish physiological responses, but field-level data is still limited. Our study assessed the potential immunomodulation of innate and adaptive biomarkers (e.g., cytokines, effector molecules and cell-surface markers) in farmed post-smolts Atlantic salmon (Salmo salar). Fish were fed either a commercial diet (CD) or experimental diets containing additives (PS: 0.25 % Pack Salud; FT: 0.1 % Futerpenol®) for 90 days. Results showed that ifng, il-10, inos, il-12, cath2, hepcidin, igm and igt were mainly up-regulated in fish fed PS or FT for 34 days (t1). Furthermore, between t2 (90 days of feeding) and t3 (42 days after finishing functional feeding), a natural algal bloom was reported at the facilities. Hence, our study considered the challenge-induced modulation of fish health. Although the accumulated fish mortality throughout the trial did not show significant differences between dietary groups, in the period related to the algal bloom, PS and FT groups reduced dead fish by 10 % and 61 % (respectively, compared to CD). Also, head kidney from FT group (and to a lesser extent in the spleen) had an enhanced innate immune response at t3 with an up-regulation of inos, hepcidin and cath2, which were coordinated by cytokines (il-1b, ifng, il-12 and il-10) and cell-surface markers (cd86, mhci and mhcii). Thus, since t3 was six weeks after the ending of the functional feeding, FT could induce sustained immunomodulation in Atlantic salmon.