Dietary L-Tryptophan potentiates non-specific immunity in Labeo rohita fingerlings reared under elevated temperature

Abstract

At present environmental scenario global climate change is a reality and its affect all living organism including fish. The aquatic ecosystem is the most affected system as it is the biggest sink for global warming and elevated temperature and obviously affects all the aquatic life forms. With this hypothesis an experiment was conducted to evaluate the effect of elevated temperature on Labeo rohita fingerlings and potential of dietary L-tryptophan (TRP) in mitigating the effects elevated temperature and enhancing the non-specific immunity. Seven hundred and twenty fishes were randomly distributed in three different thermal groups each with three replicates. The thermal groups were ambient temperature (26 °C), 34 and 38 °C. Then each thermal groups were fed with four different formulated diets containing 0. 0.36%, 0.72% and 1.44% TRP. The effect of dietary TRP supplementation was studied on stress responses, such as cortisol, blood glucose, histopathological changes in liver and kidney and immuno-hematological changes such as red blood cell count (RBC), haemoglobin (Hb), white blood cell count (WBC), lysozyme, nitroblue tetrazolium (NBT), total serum protein, albumin, globulin and albumin-globulin ratio. Subsequently the treated fish were subjected to challenge test with Aeromonas hydrophila. In the present study, primary stress markers were noticeably (p < 0.01) elevated with temperature stress and levels were reduced with nutritional supplementation of TRP. Similarly, immuno-hematological parameters were altered with the exposure of temeparture stress and got improved with dietary TRP supplementation. Results of the present study suggest that dietary supplementation of 1.44% tryptophan has definitive role in the mitigation of temperature stress and gives protection against bacterial infection to L. rohita.