Excreted corticosterone metabolites differ between two galliform species, Japanese Quail and Chicken, between sexes and between urine and faecal parts of droppings

Japanese Quail (Coturnix japonica) are a common avian laboratory model, and measuring corticosterone metabolites (CM) non-invasively from Quail droppings would be of broad interest. Using the enzyme immunoassay suitable for measuring CM in droppings of Chicken (Gallus domesticus) and other galliform species, we tested the CM measured in Quail droppings after stimulation with adrenocorticotropic hormone. An ACTH challenge indicated that the assay did not detect major amounts of CM in Japanese Quail excreta. Therefore, we aimed at testing whether steroid metabolism and clearance differed between closely related species. We compared the CM excretion patterns in male and female Japanese Quail and Chicken. After intravenous injection with [H-3]-labelled corticosterone, we collected all droppings for 24 h, including caecum excreta. Males and females of both species excreted radioactive CM with two peaks. The first radioactivity-peak presumably was from uric acid (Quail 45/55 min; Chicken 120/75 min post-injection, males/females respectively), whereas the second peak probably represented faecal excretion (180/210 min; 240/140 min, respectively). Several highly polar radioactive CM, but no corticosterone, was separated by chromatography in droppings of both species. Number and identity of CM considerably differed between males and females, as well as between urine and faecal excretion. The nature of excreted CM in Quail droppings remains unresolved. However, we show that knowing the effective time for dropping collection is essential for interpreting stimulus-specific CM responses, and mixing samples from rapid urine and slower faecal excretion should be avoided.