Dealing with summertime heat is a great challenge for poultry. All types and ages of poultry are susceptible to heat stress, but older poultry face a bigger risk. As poultry get older, they increase in size as well as insulation (feathering). This makes it harder for them to dissipate heat. The most obvious sign of heat stress in poultry is panting. Poultry do not have sweat glands that can cool their skin, so instead they must use evaporation from their throat and respiratory system as a means of cooling themselves. Panting takes a lot of energy which, in turn, generates an appreciable amount of body heat for poultry.