Probiotic effects of the fungi, Aspergillus niger on growth, immunity, haematology, intestine fungal load and digestive enzymes of the common carp, Cyprinus carpio

The present study was conducted to investigate the probiotic role of the unicellular fungi, Aspergillus niger on growth performance, immunity, haematology and digestive enzymes in common carp, Cyprinus carpio. One non-supplemented group (T0) was considered as control and two groups fed the fungi including T1 (fish supplemented with diet containing 1 × 103 A. niger) and T2 (fish supplemented with diet containing 1 × 106 A. niger) considered as the experimental treatments in three replicates. Fish were fed experimental diets for 60 days. The survival rate and growth parameters (final length and weight, weight gain (%), thermal growth coefficient (TGC), protein efficiency ratio and lipid efficiency ratio) significantly increased in A. niger supplemented fish compared with control (p < 0.05). The values of FCR (feed conversion ratio) and CF (condition of factor) significantly decreased after feeding experiment in fish of T2 and T1 compared with control (p < 0.05). The plasma levels of lysozyme and total immunoglobulin significantly elevated in A. niger supplemented groups compared with control (p < 0.05). The RBC (red blood cell) counts, Hb (haemoglobin) concentrations, MCH (mean corpuscular haemoglobin) and MCV (mean corpuscular volume) values significantly increased in A. niger supplemented fish compared with control (p < 0.05). The WBC (white blood cell) and Hct (haematocrit) value were higher in fish of T2 compared with control (p < 0.05). The number of neutrophils significantly increased in the treatment, T2 compared with control (p < 0.05). Furthermore, the lymphocyte counts significantly increased in A. niger supplemented fish compared with control (p < 0.05). The body composition of fish showed increases in the fish dry matter and protein content and decreases in lipid content of T1 and T2 groups compared with control (p < 0.05). The digestive enzymes (protease, trypsin, amylase, lipase and alkaline phosphatase), apparent protein ad lipid digestibility significantly increased in response to dietary level of 1 × 106 A. niger compared with control (p < 0.05). The supplementation of fish with A. niger also prompted the load of the fungi in intestine (p < 0.05). The results of the present study confirmed the probiotic role of A. niger in common carp, since it improved growth, immunity, digestion and the fish haematology.