Effects of dietary cecropin on growth, non-specific immunity and disease resistance of tilapia (Oreochromis niloticusxO.aureus)

摘要

An 8-week feeding trial was conducted to evaluate the effect of dietary cecropin on growth performance, non-specific immunity and disease resistance of hybrid tilapia (Oreochromis niloticusxO.aureus). A basal diet was supplemented with 0 (control), 75, 150 and 225mgkg(-1) cecropin to formulate four experimental diets. The results showed that final body weight and specific growth rate obtained with diet 150mgkg(-1) cecropin were significantly higher (P0.05) than that obtained with diets 0 and 75mgkg(-1), whereas there was no difference between 150 and 225mgkg(-1). Feed conversion efficiency was improved by increasing the dietary cecropin content (P0.05). However, feeding intake was reduced as dietary cecropin increased. Serum lysozyme, alkaline phosphatase, catalase and superoxide dismutase activity were significantly increased with the increased levels of dietary cecropin (P0.05), and reached a maximum at level of 150mgkg(-1) cecropin, then those values no longer increased. Moreover, the dietary cecropin supplementation level also exhibited a decrease in the cumulative mortality rates compared with the controls when challenged with Aeromonas veronii. The results suggested that the dietary supplementation of cecropin could improve the growth, non-specific immunity indicators and resistance of hybrid tilapia against A.veronii.