dietary cirsium arvense essential oil enhances immunity and disease resistance in rainbow trout

Background: fish diseases are among the main challenges in the aquaculture industry. feed additives are promising agents to control fish diseases by improving their innate immunity. objectives: the present study was conducted to assess the effects of dietary supplementation with cirsium arvense essential oil (caeo) on immunological responses and disease resistance in rainbow trout, oncorhynchus mykiss.methods: the fish (mean weight: 31.31±0.15 g) were fed diets containing 0 (cont), 2 (caeo2), 4 (caeo4) and 6 (caeo6) ml/kg caeo for 60 days at a daily ration of 5% of biomass (n=3), followed by an experimental infection by yersinia ruckeri. results: after 60 days of rearing, dietary caeo significantly increased serum total protein, total immunoglobulin (ig), lysozyme, alternative complement (ach50), respiratory burst activity (measured by nitroblue tetrazolium [nbt] test), skin mucus lysozyme, protease, total ig, and alkaline phosphatase (alp). dietary caeo significantly decreased post-challenge mortality; cont, caeo2, caeo4, and caeo6 showed 100%, 58%, 68%, and 48% post-challenge mortalities, respectively. the highest total ig, nbt, ach50, mucus protease, and alp, and post-challenge survival were observed in caeo6 treatment; whereas, the highest serum total protein, mucus lysozyme, and total ig were observed in caeo4 and caeo6 treatments. serum lysozyme significantly increased in all caeo-treated fish.conclusion: caeo can be used as a feed additive for the aquaculture of rainbow trout, as it improves immunity and disease resistance of the fish at a concentration of 6 ml/kg.