Probiotics ameliorate chromium-induced growth retardation and stress in Indian major carp rohu, Labeo rohita

Chromium (Cr) is one of the most prominent contaminants due to its cumulative negative effects on fish. Probiotics may be able to mitigate the unfavorable effects of Cr in fish. In this study, the rohu Labeo rohita (3.02 +/- 0.37 g) were exposed to Cr with or without probiotics, representing control (C; without Cr or probiotics), treatment one (T1; Cr at a dose of 4 mg/L), treatment two (T2; probiotics at a dose of 1 ml/L) and treatment three (T3; Cr at a dose of 4 mg/L + probiotics at a dose of 1 ml/L) for 42 days. The results showed that weight gain (WG) and specific growth rate (SGR) were inhibited significantly in T1, while those substantially increased in T2 (probiotics) compared to C. On the other hand, WG and SGR were regained as compared to C in T3. The significantly lowest feed conversion ratio (FCR) was found in T2, and moderate FCR was recorded in C and T3, while it was significantly highest in T1. No mortality was observed in C and T2, while 20 % mortality was recorded in T1, and decreased mortality was recorded in T3 (10 %). Exposure to Cr (T1) caused lower hemoglobin and higher glucose levels; however, the use of probiotics reversed these effects in T3 (Cr + probiotics). The frequencies of nuclear (notched nuclei, nuclear bridges, and karyopyknosis) and cellular (tear drop shaped, fusion, and twin) abnormalities of erythrocytes increased in the Cr-exposed group (T1); however, these were recovered after probiotic administration (T3). The findings of the present study suggest that probiotics play a beneficial role in reducing the toxicities of Cr in rohu.(c) 2023 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).