Evaluating the role of dietary plant extracts to allow adaptation to thermal stress in a cold stream ornamental fish, Botia rostrata (Günther, 1868).

Increases in ambient temperature affect the biochemical status of fish, and dietary supplementation with bioactive phytoconstituents may promote resilience against environmental stress. This study evaluated the impact of three plant extracts on the biochemical status of a cold stream fish Botia rostrata (Günther, 1868) under high temperatures. After 1 month dietary supplementation separately with Mucuna pruriens methanol extract (0.25 g/kg feed), Tribulus terrestris ethanol extract (0.5 g/kg feed) and Basella alba ethanol extract (1.0 g/kg feed), juvenile fish (Wt. 4.3 ± 0.5g) were exposed to different sublethal heat stress [28 ± 0.5 °C (T1), 32 ± 0.5 °C (T2), 36 ± 0.5 °C (T3)]. Control fish were fed a diet without any plant extract and maintained at 24 ± 0.5 °C. Serum and muscle tissues were collected to measure different biochemical parameters, muscle metabolic enzymes and molecular chaperons before and after heat stress. Before stress, the group fed the Mucuna diet showed significant (P < 0.05) increases in serum glucose [+10.92%], protein [+18.93%], muscle heat shock protein (HSP) 90 [+8.6%] compared to the control group. No significant change (P > 0.05) of stress parameters was observed between control, Tribulus and Basella fed fish. The control group exposed to T3 showed significant differences (P < 0.05) in protein [-26.19%], lactate dehydrogenase [+93.69%], fructose 1,6 bisphosphate [-35.19%], phosphorylase 'a' [+35.72%], HSP60 [+69.54%], HSP70 [+84.85%], HSP90 [+92.07%], heat shock factor (HSF) 1 [+88.48%] suggesting susceptibility of Botia to this temperature. Among the three plant extracts, Mucuna methanol extract was effective to enhance resistance against temperature-induced biochemical alterations. After exposure to T3, only the fish fed Mucuna diet showed no mortality. Fish fed Mucuna diet exposed to 36 ± 0.5 °C showed significantly higher (P < 0.05) glucose [+42.82%], protein [+11.98%], citrate synthase [+59.81%], phosphorylase 'a' [+14.96%], Glucose 6 phosphate dehydrogenase [+60.87%], HSP60 [+34.13%], HSP70 [+41.42%], HSP90 [+65.91%], HSF1 [+61.32%] compared to those in Mucuna fed fish maintained at 24 ± 0.5 °C. These results highlight temperature-induced biochemical alterations in Botia and point towards the potential use of Mucuna in overcoming such adverse high thermal stress.