Toxicity effect of silver nitrate on some hematological indices of Nil tilapia (Oreochromis niloticus) fed with different levels of prebiotic oyster mushroom (Pleurotus ostreatus)

The aim of this study was to investigate the effect of different prebiotic levels of oyster mushroom (Pleurotus ostreatus) on hematological indices of Nil tilapia exposed to silver nitrate. For this purpose, 120 juveniles of tilapia were fed with diet containing 0 (treatment 1, control), 0.05 (treatment 2), 0.1 (treatment 3) and 0.2% (treatment 4) prebiotic oyster mushroom) for 42 days. Then, 0.5ppm of silver nitrate was added to each group for 16 days. Before and after exposing to silver nitrate, fish blood indices were evaluated. Prebiotics alone had no significant effect on RBC, MCV, hematocrit and hemoglobin (P<0.05). But, treatments fed with prebiotics and exposure to silver nitrate toxin showed an increase in WBC, MCHC (in 0.1 and 0.2 treatments), MCH indices compared to the control group. According to the results, oral prebiotics stimulated nonspecific immunity in tilapia and using mushroom prebiotics reduced the destructive effects of the silver nitrate toxin on blood indices. In conclusion, levels of 0.1 and 0.2% of prebiotic oyster mushroom in treatments which exposed to 0.5ppm silver nitrate toxin could improve the blood factor status of tilapia.