Acclimatization of the fowl to intermittent acute heat stress.

The acclimatization of poultry to a hot, dry climate was assessed by studying changes in rectal temperature (Tr) during regular daily exposure to an ambient temperature of 38 degrees C and 26% RH. Laying hens of two strains, young chicks, growing broilers and broiler breeders were able to acclimatise, in varying degrees, to these conditions. Acclimatization was characterised by a progressive reduction in the rate of increase in Tr over the period of exposure and the ability to survive conditions that initially would have been fatal. Laying hens could acclimatise if prevented from displaying their normal postural responses to heat stress. Acclimatization was accompanied by a decrease in oxygen consumption when measured at either the acclimatization temperature or at a thermoneutral temperature.