Poults rest more during periods of heat stress. Some birds will stand quietly while others simply crouch near walls or waterers. Usually, their
wings are spread away from the body to promote cooling by reducing body insulation. Within the bird, blood flow is diverted from certain internal body organs such as the liver, kidneys and intestines to dilated blood vessels of the peripheral tissue (skin) in order to facilitate heat loss.
Hyperventilation or "panting" increases during periods of high environmental temperature. Heat loss through evaporative cooling allows the poult to dissipate the heat it is generating. However, panting requires increased muscle activity and these results in an increased energy requirement, which is associated with heat stress. Therefore, decreased energy efficiency also accompanies hot weather. Panting would normally be expected to occur when the room temperature is near or above 86 degrees.
Relative humidity influences evaporative heat loss through panting. Poults, as well as other domestic poultry, cannot tolerate high temperature coupled with high relative humidity. Death due to heat exhaustion will occur very quickly, especially in heavier birds, if both temperature and humidity are high. In normal birds, panting will remove approximately 540 calories per gram of water lost by the lungs.
