Effects of dietary spirulina pacifica on innate immunity and disease resistance against edwardsiella tarda in olive flounder paralichthys olivaceus

Abstract

We tested the effects of short-term dietary supplementation of Spirulina pacifica on non-specific responses and disease resistance to Edwardsiella tarda in olive flounder, Paralichthys olivaceus. Four isonitrogenous (46% crude protein) and isocaloric (17.3 MJ/kg dry mass) experimental diets were formulated to contain 0, 3, 6 or 9% S. pacifica (designated SPI0, SPI3, SPI6 and SPI9, respectively). Three replicate fish groups (30 fish/tank) were fed one of the experimental diets for 15 days. After 15 days, healthy fish (30 per dietary treatment) of similar size were injected with 1 mL of E. tarda suspension to evaluate disease resistance. Dietary supplementation with spirulina resulted in significantly enhanced non-specific immune responses compared to the control groups. Cumulative mortality in the challenge test with E. tarda was significantly lower in fish fed diets containing spirulina compared to that of fish fed the control diet. These results indicate that dietary supplementation of spirulina can enhance non-specific immune responses and disease resistance of olive flounder even over a relatively short feeding period.