Broiler chickens are highly susceptible to heat stress during the time at which their growth rates ought to be highest. In order to overcome the deleterious effects of heat stress, consideration has to be given to ways in which the heat production of the bird and its ability to dissipate heat are brought into balance whilst still permitting the birds to eat and grow rapidly. Methods for adjusting this balance include changes in the micro environment of the birds, alterations to heat output by variations in the timing, quantity and quality of food and enabling the bird to maximise its use of fluids for evaporative cooling.