EFFECT OF EXOGENOUS ADRENOCORTICOTROPIC HORMONE ADMINISTRATION ON PLASMA-CORTICOSTERONE CONCENTRATIONS IN AMERICAN BLACK DUCKS (ANAS RUBRIPES)

A protocol for the adrenocorticotropic (ACTH) stimulation test in Amer ican black ducks (Anas rubripes) was established with synthetic ACTH, cosyntropin (Cortrosyn(R)); ACTH stimulation testing was conducted on 31 adult ducks (14 males, 17 females) in September 1993. Plasma cortic osterone concentrations were measured on heparinized blood samples col lected 30 min, and 1, 2, and 4 hr post-injection. In comparison with s aline controls, cosyntropin (0.25 mg/duck) produced a two- to three-fo ld increase in corticosterone 30 min after administration. Maximal con centrations ranged from 132 to 312 ng/ml and occurred between 1 and 2 hr post-injection. Corticosterone concentrations declined to basal, pr e-injection values after 4 hr. Endogenous ACTH release in response to handling stress was evident in control ducks after saline injection bu t did not interfere with interpretation of the stimulation test. Recom mendations for the ACTH stimulation test in black ducks include a 30 m in acclimatization period for recently captured or relocated ducks and determination of plasma corticosterone concentration 1 to 2 hr follow ing intramuscular injection with 0.25 mg cosyntropin.