Bioremediation of chromium-induced toxic effects in Nile tilapia (Oreochromis niloticus) using probiotics

Chromium (Cr) is one of the major heavy metal pollutants and its toxicity causes an adverse impact on body physiology of aquatic organisms including fish. Probiotics may be able to degrade toxic effects of Cr, thereby mitigating its adverse effects on the fish body. In this study, Nile tilapia (35.29 ± 1.21) was subjected to: control (without Cr or probiotics), hexavalent Cr (potassium dichromate) treatment (10 mg/L), probiotics treatment (1 ml/L), and combination of Cr and probiotics treatment (10 mg Cr/L and 1 ml probiotics/L) for a period of six weeks (42 days). The results showed that growth performance (weight gain; WG, specific growth rate; SGR) and feed utility (feed conversion ratio; FCR) were inhibited significantly in Cr-treated group compared to the control, while those parameters were found to be regained in probiotics-treated group as to control. In case of hemato-biochemical parameters (hemoglobin and glucose), Cr-exposed fish showed lower hemoglobin and higher glucose levels; however, the use of probiotics showed their level as to control. The number of cellular (teardrop, twin, spindle, and echinocyte shaped) and nuclear (notched nuclei, nuclear buds, nuclear bridges, and karyopyknosis) abnormalities in erythrocytes were higher in the Cr-exposed group. However, probiotic addition leading to a notable decrease these abnormalities. Similarly, higher deformities were observed in the gills and intestine of the fish exposed to Cr, while the administration of probiotics reduced these abnormalities. Overall, probiotics appear to have the potential to mitigate the negative physiological effects of Cr on Nile tilapia. • Probiotics improved growth and physiological responses in Cr-exposed fish. • Cellular and nuclear abnormalities due to Cr exposure decreased by probiotics. • Administration of probiotics reduced Cr-induced internal organ abnormalities. • Probiotics might be useful to relieve Cr-induced growth retardation in Nile tilapia.