INFLUENCE OF STRESS ON THE SECRETION OF CORTICOSTERONE IN THE DUCK (ANAS PLATYRHYNCHOS)

The influence of stress on the secretion of corticosterone has been investigated by radioimmunoassay in domestic ducks (Anas platyrhynchos) of 6–8 weeks of age. Intravenous and i.m. injections of synthetic ACTH (Synacthen, 25 i.u./bird and Synacthen Depot, 100 i.u./bird respectively) markedly increased (2·7- to 10-fold) basal concentrations of corticosterone in plasma (3–6 ng/ml) in comparison with those in birds injected with 0·9% saline (1 ml/bird). Maximum levels of 30–40 ng/ml plasma were reached after 30 min and 5 h respectively. Increased levels of corticosterone in plasma were also seen within 5 min of i.v. administration of saline and remained as high as those in birds treated with Synacthen for at least 20 min after injection. Blood sampling (from the brachial vein) was, by itself, sufficient to increase levels of corticosterone in plasma; a large (twofold) rise being observed as soon as 1 min after initial handling and bleeding, with concentrations of 30–40 ng/ml being found in birds bled 15 times during a period of 14 min. However, in a flock of birds, the alarm created in unhandled birds while others were being bled had no effect on concentrations of corticosterone in plasma. Deprivation of food or water for 24 h also enhanced levels of corticosterone in plasma, as did 24 h of adaptation to 0·2 m-NaCl drinking water. These results have demonstrated the lability of the secretion of corticosterone in response to stress and demonstrated its usefulness as a physiological indicator of stress in ducks.