Measurement of plasma corticosterone and fecal glucocorticoid metabolites in the chicken (Gallus domesticus), the great cormorant (Phalacrocorax carbo), and the goshawk (Accipiter gentilis).
A method for the non-invasive measurement of glucocorticoid metabolites in feces of chickens was established and validated. After high-performance liquid chromatography (HPLC) the presence of at least two fecal immunoreactives was demonstrated, one co-eluting with authentic corticosterone, whereas the second substance migrates close to corticosterone sulphate. We investigated the relationship between corticosterone in blood plasma obtained by a vena brachialis catheter and fecal samples in groups of five chickens after an ACTH and a dexamethasone injection to stimulate and to suppress adrenal activity. A control group received a saline injection. After ACTH plasma cortisol concentrations increased 16-fold after 1.5 h to levels between 19 and 38 ng/ml and dropped to pre-treatment levels (1.1-2.5 ng/ml) 4h after stimulation. Dexamethasone did not result in a distinct suppression of adrenocortical activity and plasma corticosterone dropped only slightly below pre-treatment levels. The concentrations in fecal metabolites corresponded to the changes in the levels of biological active hormone in plasma. Fecal peak excretion (105-295 ng/g) was obtained with a delay of approximately 4 h compared to plasma. The profile obtained after ACTH challenge reflected a broader and dampened pattern of glucocorticoid secretion and provided a more integrated measure of adrenal activity. Dexamethasone treatment did not induce a measurable decrease in fecal metabolites and concentrations fluctuated around a mean of 30.0+/-9.9 ng/g, almost identical to those obtained from the saline treatment group (29.4+/-13.9 ng/g). In a separate experiment the effect of an alternative capture method (remote-controlled injection system) was investigated in cormorants. Plasma corticosterone measurements revealed a significantly diminished stress reaction compared to traditional trapping (1.24+/-0.78 vs. 10.9+/-12.1 ng/ml). Investigations whether goshawk nestlings infected with Trichomas gallinae differ in fecal corticosterone metabolite concentrations compared to healthy subjects revealed no significant changes. However, a significant correlation was found between the glucocorticoid metabolite concentrations and the number of nestlings per nest. The demonstration that adrenal activity can be detected by the assay is a prerequisite that ecologically meaningful levels of imposed stress can be validated. Therefore, non-invasive measurements of fecal metabolites are a promising perspective to monitor stress in birds.[1]References
- Measurement of plasma corticosterone and fecal glucocorticoid metabolites in the chicken (Gallus domesticus), the great cormorant (Phalacrocorax carbo), and the goshawk (Accipiter gentilis). Dehnhard, M., Schreer, A., Krone, O., Jewgenow, K., Krause, M., Grossmann, R. Gen. Comp. Endocrinol. (2003) [Pubmed]
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