Effects of Dietary Astaxanthin on Innate Immunity and Disease Resistance against Edwardsiella tarda in Olive Flounder Paralichthys olivaceus

Abstract

We report on the non-specific immune responses and disease resistance against Edwardsiella tarda in olive flounder fed diets supplemented by astaxanthin. Four experimental diets were formulated to be isonitrogenous (45% crude protein) and isocaloric (17.1 MJ/kg, dry matter). Astaxanthin was added to the diets at 0 (control), 1%, 2%, and 3%. Three replicate fish groups (30 fish/tank) were fed one of the experimental diets for 15 days. After 15 days, 30 healthy fish per dietary treatment were selected and injected with 1 ml E. tarda suspension to evaluate the disease resistance of the fish. Dietary supplementation of astaxanthin resulted in significantly higher non-specific immune responses than in fish fed the control diet. Cumulative mortality in the challenge test with E. tarda was significantly lower in fish fed the astaxanthin-supplemented diets than in fish fed the control diet. Results indicate that dietary supplementation of astaxanthin can enhance non-specific immune responses and disease resistance of olive flounder against E. tarda, and that a relatively short feeding period of astaxanthin can improve immunity in fish.