Shinder, D., Department of Poultry Sciences, Institute of Animal Science, ARO, The Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel
Luger, D., Department of Poultry Sciences, Institute of Animal Science, ARO, The Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel
Rusal, M., Department of Poultry Sciences, Institute of Animal Science, ARO, The Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel
Rzepakovsky, V., Department of Poultry Sciences, Institute of Animal Science, ARO, The Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel
Bresler, V., Department of Poultry Sciences, Institute of Animal Science, ARO, The Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel
Yahav, S., Department of Poultry Sciences, Institute of Animal Science, ARO, The Volcani Center, P.O. Box 6, 50250 Bet Dagan, Israel

The influence of short repetitive cold exposure at an early age (cold conditioning-exposure to 15°C for 3 h at 3 and 4 days of age) on chickens' thermotolerance during cold challenge (15°C) at 21 days of age was examined. The first cold exposure elicited a dramatic decline in body temperature (Tb) and a significant elevation in stress response (plasma corticosterone concentration); the second cold exposure resulted in moderate Tb and stress responses. Thereafter, the corticosterone concentration remained at a significantly lower level. Acute cold challenge of conditioned broilers at 21 days of age revealed better Tb and stress recovery during the first 24 h, and a significantly lower mortality rate thereafter. Conditioned chickens exposed to optimal conditions (22°C) achieved significantly higher body weights than others. It may be concluded that early cold conditioning improves thermotolerance in broiler chickens in later life. © 2002 Elsevier Science Ltd. All rights reserved.