Dietary pyridoxine enhances thermal tolerance of Labeo rohita (Hamilton) fingerlings reared under endosulfan stress

A preliminary experiment was carried out to study the effect of dietary pyridoxine (PN) on thermal tolerance of Labeo rohita fingerlings exposed to endosulfan (1/10th 96 h LC₅₀=0.2 ppb) stress, reared at 26.0±0.5 °C to assess its culture potential in different agro-climatic zones. Two hundred seventy fingerlings were randomly distributed into six treatment groups in triplicate. Five iso-caloric and iso-nitrogenous purified diets were prepared with graded levels of pyridoxine. Six treatment groups were T₀ (10 mg PN+without endosulfan), T₁ (0 mg PN+endosulfan), T₂ (10 mg PN+endosulfan), T₃ (50 mg PN+endosulfan), T₄ (100 mg PN+endosulfan) and T₅ (200 mg PN+endosulfan). After feeding for 60 days, critical temperature maxima (CTmax), lethal temperature maxima (LTmax), critical temperature minima (CTmin) and lethal temperature minima (LTmin) were determined in each group. There was significant (P<0.05) effect of dietary pyridoxine on temperature tolerance (CTmax, LTmax, CTmin and LTmin) of the groups fed diets supplemented with 100 and 200 mg PN/kg diet compared to other experimental groups. Positive correlations were observed between CTmax and LTmax (R²=0.85) as well as between CTmin and LTmin (R²=0.97). The effect was more prominent on lower thermal tolerance limit (CTmin and LTmin). The overall results obtained in this preliminary study indicated that pyridoxine supplementation at 100 mg PN/kg diet enhances the thermal tolerance of endosulfan exposed L. rohita fingerlings.