Preconditioning to heat stress by a nontemperature stressor.

Three experiments were conducted in which 3-week-old chickens were subjected to a handling procedure for 4 days (21 to 24 days of age) and subjected to heat stress on either the 5th or 7th day (25 or 27 days of age). The heat stress episode consisted of exposure to 50 C for up to 240 min in a forced-draft chamber. In two experiments in which broiler chickens were studied, the heat stress survival time, determined at 25 days of age, was increased by the handling procedure. The same phenomenon did not occur in Leghorn chicks or broiler chickens heat stressed after a 3-day adjustment period.