Stress and nutritional quality of broilers

Broiler chicks were reared in environmental chambers. All birds were starte d under ideal conditions, i.e., 30.6 C with 35% RH. Beginning at Day 36, ha lf of the chicks were maintained at 24 C and 35% RH. The other half were su bjected to a cyclic temperature-RH regime that approximated a typical Augus t day in central Mississippi (heat treatment). Half of each of the describe d groups received implants of osmotic pumps that released adrenocorticotrop in (ACTH) at 8 IU/kg BW/d for 7 d. The remaining birds received placebo pum ps. The main effects of ACTH and heat treatments were similar. Both treatme nts caused reductions in BW, carcass weight (CW), carcass protein (CP), and muscle calorie (C) content. ACTH, but not heat, reduced carcass moisture ( M). Carcass fat and ash, however, were not affected. Most changes were not reversed after 1 wk of recovery. Although visible signs of pale, soft, exud ative muscle (PSE) were present, "white" areas of muscle were absent. The d ecreased meat yield and detrimental changes in meat quality suggest that st ress, whether induced hormonally or by exposure to over-heating, caused los ses that were as severe as those associated with PSE under field conditions .