Evaluationthe effects of different levels of Echinacea purpurea extract on the immunity responses, biochemical and hematological indicesand disease resistance against Streptococcus iniae in rainbow trout (Oncorhynchusmykiss)

240 rainbow trout fingerlings weighting 16 gram were randomly allocated into three treatment groups including 0.5, 1.0and 1.5 gr/kg of Echinacea purpurea extract in food, and a control group (without EPE in food), each intriplicates for 60 days. At sampling times, some of hematological and biochemical parameters including C 3 and C 4 complements, oxygen free radicals, lysozyme activity, and other hemathological parameters were analyzed. Also, at the end of the experiment, fishes challenged with Streptococcus iniae and the mortality was analyzed.