Endocrine response of crossbred calves to acute heat stress in a climate-controlled environment

Abstract

Heat stress in cattle due to global climatic change affects their overall health and production. Cattle are homeotherms and initiate thermoregulatory responses to heat stress. Hypothalamo-pituitary-adrenal axis is one of the principal endocrine regulators of stress responses in livestock. The activation of this axis as a response to heat stress might lead to enhanced production and release of cortisol into circulation. Several studies reported that the rise in serum cortisol concentration was temperature-dependent and is considered as a most reliable and primary physiological index for determining heat stress response in animals. Hence the present study was conducted to assess the endocrine response of crossbred calves to acute heat stress (Treatment) and compared it with thermo-neutral zone (Control) in a climate-controlled animal chamber. Venous blood samples without anticoagulant were collected on days 0, 1, 5 and 10 of the experiment in both control and treatment groups for serum cortisol estimation by radio immunoassay. It was evident from the findings that rise in serum cortisol was temperature-dependent. Furthermore, the results demonstrated cortisol acclimation pathway in acute heat-stressed crossbred calves under controlled climatic conditions. The study also thrown light on declined level of this stress hormone under thermo-neutral zone.