Metabolic and biochemical changes during heat stress in relation to the feathering degree of the domestic hen

Abstract

Rhode Island Red layers, consisting of four genetically different feathering types—fully feathered (nanaff), fully frizzled feathered (nanaFf), naked neck (Nanaff), naked neck frizzled type (NanaFf)— were exposed to heat stress, and the physiological and metabolic responses were evaluated according to the feathering degree. Heat stress conditions (34°C and relative humidity of 45%) were maintained for 8 weeks. Body temperature measured at different points, body characteristics and blood gas and electrolytes were determined and related to the environmental heat conditions. A plumage reduction led to higher body surface temperature, improved heat loss and, consequently, lower body-core temperatures. This was accompanied by a reduced polypnoea as reflected by higher blood levels of CO2, and smaller increases in blood pH and alkalosis with better stabilization of acid-base balance and elecrolytes homeostasis. Reduced plumage seems to contribute to a greater resistance to hyperthermia caused by high ambient temperatures. © 1995 Avian Pathology