In vivo responsiveness of the broilers' adrenocortical system

The possible interaction of circadian rhythms in serum concentrations of corticosterone (B) with the response of broiler cockerels to heat stress (HS) and adrenal manipulation with adrenocorticotropic hormone (ACTH) and dexamethasone acetate (DA) was investigated. Adrenocortical response, as indicated by corticosterone concentrations, was greater early in the photoperiod in cockerels exposed to HS or injected with ACTH. A single injection of DA tended to be more inhibitory on B when administered later in the photoperiod.