عنوان مقاله [English]
The immune system improvement of fishes, especially in valuable species such as the Caspian brown trout (Salmo caspius), is one of the main needs of fish culturists. Therefore, the selection of appropriate immune stimuli that do not adversely affect fish growth while promoting immunity is one of the most important approaches of researchers. In order to investigate the effect of levamisole on the Caspian brown trout, 240 cultivated juvenile with mean weight of 12.46±0.15 g, were fed a diet containing levamisole at concentrations of 300, 600 and 1200 mg/kg diet for 60 days. The control group was fed with a diet without levamisole. At the end of the experiment, in addition to biometry of fish, blood samples were taken for comparison of cellular, biochemical and immunological parameters. The results showed that levamisole had a positive effect on the growth of the Caspian brown trout. In fact, all three concentrations improved the growth performance of fish and the highest percentages of weight gain and specific growth rate were obtained in 1200 mg/kg levamisole. As the amount of levamisole increased, the feed conversion ratio decreased significantly and the protein efficiency ratio increased significantly (P<0.05). The highest number of white and red blood cells and the highest amount of hemoglobin were observed in 1200 mg/kg levamisole. However, the differences amongst treatments were not significant in term of hematocrit (P>0.05). There was no significant difference in total protein, albumin, aspartate aminotransferase and alanine aminotransferase activities between different groups. Maximum lysozyme enzyme activity and the highest IgM amount were measured in 1200 mg/kg levamisole. The highest C3 and C4 complement amounts were observed in 600 and 1200 mg/kg levamisole without any significant difference (P>0.05). Therefore, the addition of levamisole as a dietary supplement to the Caspian brown trout diet to 1200 mg/kg can be suggested to improve the growth and immunity of the Caspian brown trout.