Effect of Caspian Sea Red Macroalgae, Laurencia caspica powder on growth, hematological parameters, serum and immune responses of common carp (Cyprinus carpio) fry infected with Aeromonas hydrophila

The aim of this study was to investigate the effects of Caspian red algae (Laurencia caspica) as natural originated immunostimulant in common carp fry. Algae were collected from Caspian sea and supplemented to diet in different levels of 0, 1, 2, 3 and 4 percent for 60 days. Results of growth parameters indicated an increase in final weight, and specific growth rate in fish fed 2, 3 and 4% algae powder (AP) comparing to control (P<0.05). The numbers of white blood cells and red blood cells were higher in diet containing 3 and 4% AP than those of control and 1% AP. The highest levels of hemoglobin and hematocrit were found in fish fed diet containing 3 and 4% AP. Moreover, fish fed 2, 3 and 4% AP demonstrated lower cholesterol and higher total protein among groups. Hepatic enzymes such as aspartate transaminase, alanine transaminase and alkaline phosphatase displayed a decreasing trend by addition of AP. Alternative complement pathway improved by increasing AP level as the highest value observed in 3 and 4% AP. Also, diet containing 3% AP led to significantly increase lysozyme when compared to other diets. Fish bacterial challenging with A. hydrophila showed increasing survival (more than 40%) in fish received 2, 3 and 4% AP. Overall, administration of 3% L. caspica powder to diet of common carp fry is advised in order to improve growth performance, hematological and immune indices and resistance against A. hydrophila.
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