Effect of dietary chitosan on non-specific immune response and growth of Cyprinus carpio challenged with Aeromonas hydrophila.

This study was conducted to investigate the effect of dietary chitosan on the non-specific immunity, growth and survival of common carp. Common carp with an average weight of 45 ± 2 g and total length of 31 ± 2 cm were fed diets containing 0 (control), 1%, 2% and 5% chitosan for a period of 70 days. Sixty fish in all treatments were challenged with Aeromonas hydrophila on day 30 and 58, in order to monitor the response of the chitosan fed fish against the bacterial challenge. Phagocytic index, phagocytic ratio and serum bactericidal activity were increased in the chitosan fed (2 and 5%) groups, compared to the control group (P < 0.05). After the fish in all treatments were challenged intra-peritoneally with Aeromonas hydrophila, the relative percentage survival (RPS) (82.78 %) was higher in chitosan (2%) group (P < 0.05), when compared to other treatments. Feed conversion ratio (1.81) and specific growth rate (SGR) (2.67) were higher in chitosan fed (2%) group, when compared to other treatments. The control group displayed the decreased performance in all the assays of non-specific immune response with the coincidental decrease in the survival and growth rates. Thus, the incorporation of chitosan at a level of 2% in the diet of fish enhanced the non-specific immunity, reduced the fish mortality and enhanced the growth of fish under stress conditions.