Aim: The present investigation was undertaken to study the impact of heat stress and hypercapnia on physiological, hematological, and behavioral profile of Tharparkar and Karan Fries (KF) heifers.

Materials and Methods: The animals of both the breeds of Tharparkar and KF were exposed at different temperatures and CO₂ levels. Exposure conditions of 25°C, 400 ppm CO₂ level, and 60% relative humidity (RH) were taken as a control condition. The exposure conditions 40°C with two levels of CO₂ 500 ppm and 600 ppm with RH 55±5% and exposure conditions 42°C with two levels of CO₂ 500 ppm and 600 ppm with RH 55±5% were taken as treatments. The exposure period in each condition was 4 h daily for 5 consecutive days.

Results: Physiological responses (respiration rate [RR], pulse rate [PR], and rectal temperature [RT]) were significantly (p<0.01) higher and different during all exposure conditions compared to control condition in both the breeds of cattle. KF heifers had higher RR, PR, and RT than Tharparkar heifers. Hematological parameters, namely, red blood cell, hemoglobin, and packed cell volume were significantly higher and different during all exposure condition than control in both the breeds, whereas no significant changes were observed in total leukocyte count and differential leukocyte count. Blood pH increased with increase in temperature and CO₂ levels and was significantly higher than control conditions. PCO₂ and base excess were significantly (p<0.05) lower, and PO₂ was higher during different exposure conditions than control in both breeds. Restlessness and excitement signs were observed in all the exposure conditions as compared to control condition in both the breeds.

Conclusion: Changes in physiological responses, behavioral pattern, and hematological parameters reflect the current functional status of the body system, and it can be used as an index for assessing the adaptation capacity of cattle to predict changes occurring in climate variables due to increasing CO₂ levels and environmental temperature.

Keywords: behavior, hematological, hypercapnia, hyperthermia, Tharparkar.

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