Progressive Changes in the Physiological Responses of Heat-stressed Broiler Chickens

The present experiment was designed to study progressive changes in the physiological responses of broiler chickens (Gallus gallus) exposed to different durations of acute heat stress. Male broiler chickens (n = 8) at 16 days of age, were exposed to acute heat stress of 34°C for 6, 12 or 18 h while control chickens were kept at 25°C. Exposure to different durations of heat stress resulted in significant decreases in the levels of blood HCO3~ and pCO2, while pH and pO2 were not changed. Hemoglobin, hematocrit and Na+ values were reduced after 6 h while no such change was observed after 12 or 18 h of heat stress. In contrast, K+ levels were lowered by 6 or 12 h of heat stress and no differences in blood calcium levels were observed between the control and heat-stressed groups. In conclusion, there is evidence that exposure of broiler chickens to different durations of acute heat stress resulted in distinct time-dependent physiological responses. Data set from this experimental model could provide an overview of physiological state in the typical acute heat-stressed birds.