Effects of heat stress on day-old broiler chicks.

Short-term heat stress can occur when chicks are transported from the hatchery to growing facilities. Two experiments were conducted to determine the possible effects of short-term heat stress on growth and feed conversion of broiler (Hubbard X Hubbard) chicks. The heat stress was accomplished by placing chicks in Jamesway 252 incubators at dry bulb temperatures ranging from 40 to 45 C for variable times. Growth, feed consumption, and mortality were measured for 16 days following the heat stress. Short sublethal heat stress significantly reduced growth rate to 16 days in these experiments without any effect on feed conversion ratio. The results indicate that the hatchery industry should avoid overheating chicks even for periods as short as 1 hr.