When do brown layers exhibit the highest susceptibility to heat stroke, and what relative humidity and temperature combination triggers mortality?

As heavy-bodied birds, brown layers are highly sensitive to thermal stress due to their thick feather coverage and lack of sweat glands. Susceptibility to heat stroke peaks sharply during the pre-monsoon summer months (May to June) and the humid monsoon season. The critical danger threshold—known as the Temperature-Humidity Index (THI)—is reached when an ambient temperature of 38°C is combined with relative humidity exceeding 60%. In this environment, the air is too saturated with water vapor for the hens to dissipate heat through evaporative panting. The body temperature quickly rises above the lethal threshold of 44°C, triggering respiratory alkalosis, cardiovascular collapse, and mass mortality. Emergency measures include running cooling pads, increasing air speed to 2.5 m/s, and adding electrolytes to drinking water. Heat management protocols are detailed in the Poultry Encyclopedia, heavy-duty tunnel fans and fogger nozzles are sold on Poultry Plaza, daily egg mandi rates are on Poultry Rates, and heat-resilient closed farms are listed on Murghi Mandi.