It is common knowledge that the older a bird gets the more problems hot weather can cause. There are a number of reasons for this. First, older birds produce significantly more heat than younger birds. For instance, 24,000 onepound broilers will produce the same amount of heat as that produced by four conventional brooders operating constantly. But, 24,000 seven pound broilers produce the same amount of heat as 30 conventional brooders. More heat, more problems. Next, older birds are better feat...hered and therefore better insulated than smaller birds making it more difficult for the birds to rid themselves of the heat they are producing. As birds get older there is less space between individual birds. Less space means more heat is trapped between the birds significantly increasing the temperature of the air at floor level. Finally, older birds have less surface area per pound of weight than younger birds and therefore cannot lose heat to surrounding air as easily as small birds. All of these factors add together to make heat stress related problems much more severe as the birds age.