Exploring the adaptive responses to acute heat stress in crossbred calves of Kerala under controlled climatic conditions.

Authors

Balakrishnan Navin, K Karthiayini, Viswanathan Ramnath, Vakayil Beena, Aziz Zarina, S Harikumar, O K Sajana, V L Gleeja

Published in

Tropical animal health and production. Volume 58. Issue 6. Jul 09, 2026. Epub Jul 09, 2026.

Abstract

Climate change associated heat stress is the major global challenge affecting the overall health and production of livestock. If the ambient temperature exceeds the thermo-neutral zone of cattle, they experience heat stress. The study aimed exclusively to explore the adaptive physiological, behavioural, metabolic, endocrine and molecular responses exhibited by crossbred (Holstein Friesian × Sahiwal) calves of Kerala to acute heat stress (treatment) and compared it with the thermo-neutral zone (control) in a climate-controlled chamber. The experimental animals were given an acclimatisation period of 10 days each in the animal holding facility and in the chamber. It was followed by experimental period of 10 days each in both the groups, from 6:00 A.M. to 6:00 P.M. under thermo-neutral zone maintained at 27 °C and acute heat stress where maximum temperature of 40 °C and relative humidity of 55-65 per cent was simulated for three hours a day. Rectal temperature, respiratory rate, heart rate, serum cortisol level, pO₂ level and behavioural parameters such as standing time, water intake frequency and feeding time were significantly increased (p < 0.01) in the treatment group. But mean values of pCO₂, bicarbonate, blood pH, blood sodium, blood glucose, lying time, rumination time and feed intake were significantly decreased in the treatment group (p < 0.01). Respiratory rate exhibited a strong positive correlation with pO₂ level and a negative correlation with pCO₂ and bicarbonate levels in heat stress. Relative quantification of HSP 70 gene expression showed a significant (p < 0.05) upregulation in acute heat-stressed calves. It was evident that crossbred calves of Kerala exhibited physiological adjustments indicative of thermal homeostasis when exposed to a maximum THI of 95.04.

PMID:
42423827
Bibliographic data and abstract were imported from PubMed on 09 Jul 2026.

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