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This experiment aimed to study the effects of dietary supplementation of chitosan and levamisole on the growth performance, non-specific immune responses and disease resistance of Nile tilapia in earthen-pond cage culture. Fish were divided into 4 groups before being fed for 12 weeks with unsupplemented commercial diet as the control, 1% of chitosan, 250 mg/kg feed of levamisole and 1 % chitosan plus 250 mg/kg feed of levamisole. Results showed dietary supplementation of chitosan and levamisole enhanced the growth with better feed conversion ratio of all treated fish significantly. Lysozyme and complement activity were significantly enhanced in fish fed with 1 % of chitosan, 250 mg/kg levamisole and 1% chitosan plus 250 mg/kg diet, in correlation with higher survival rate of experimental fish challenged with Streptococcus agalactiae, compared to the control. These results suggest that administration of 1 % chitosan or 250 mg/kg feed of levamisole in the diet can enhance growth performance and improve resistance of Nile tilapia to Streptococcus agalactiae.
Keywords: chitosan; levamisole; growth performance; immune response; Nile tilapia
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