The effect of thermal manipulations during embryogenesis of broiler chicks (Gallus domesticus) on hatchability, body weight and thermoregulation after hatch

The significant developments in the genetic selection of fast-growing broiler chickens cause difficulties for broilers in coping with extreme environmental conditions. This study was conducted to elucidate the effect of repetitive short-term increases. in incubation temperature on hatchability and chick's body weight (BW) and thermoregulation immediately after hatch. Thermal manipulation (TM) had no effect on hatchability when the three trials were combined for statistical analysis, and had no effect on chick's BW. It caused a significant reduction in chicks T-b, and significant decline in plasma thyroid hormones concentration, but had no effect on plasma corticosterone concentration. It can be concluded that TM did not affect BW but had a positive effect on thermoregulation, most probably in reducing metabolic rate. (C) 2004 Elsevier Ltd. All rights reserved.