Effects of Spirulina microalgae (Spirulina sp.) and acidifier citric acid on the hematological and immune indices in common carp fry, Cyprinus carpio

The study was designed to evaluate the effects of spirulina algae and the acidifying impacts of citric acid on the variation of hematological and immune indices in common carp, Cyprinus carpio. The study was completely random in design with nine treatments, 3 replicates and the control, which included using basic diet without any additives. The treatments included T1: basic diet supplemented with 0.5% citric acid; T2: basic diet supplemented with 0.1% citric acid; T3: basic diet supplemented with 0.2% spirulina extract; T4: basic diet supplemented with 0.3% spirulina extract; T5: basic diet supplemented with 0.2% spirulina extract and 0.05% citric acid; T6: basic diet supplemented with 0.3% spirulina extract and 0.01% citric acid; T7: basic diet supplemented with 0.2% spirulina extract and 0.01% citric acid; and T8: basic diet supplemented with 0.3% spirulina extract and 0.05% citric acid. For this purpose, 270 juvenile carp fish (mean weight: 11.35 ± 1.21 g) were fed with the experimental diets for 8 weeks. At the end of the trials, the number of white blood cells (WBCs), red blood cells (RBCs), Hb, HCT, differential white cells (lymphocyte, eosinophil, neutrophil and monocytes) were measured. The mean volume of red blood cells (MHC), mean concentration of cellular hemoglobin (MEHC) and immune indices of fish blood including Lysozyme, GM, and immunoglobulin were also measured. The results indicated significant differences in certain blood factors (i.e., HCT, neutrophil and lymphocyte) between experimental diet groups and the control (p < 0.05). In addition, certain immune indices in the experimental groups were at healthier levels than those in the control (p < 0.05). Finally, the study showed that spirulina algae combined with citric acid acidifier could enhance the body immune system of juvenile carp fish.