Validation of an enzyme immunoassay for the measurement of faecal glucocorticoid metabolites in Eurasian (Lynx lynx) and Iberian lynx (Lynx pardinus)

• Six different enzyme immunoassays (EIA) were tested for fGM measurement in lynx.
• Assay comparison was carried out based on two ACTH challenges.
• Radiometabolism study confirmed 11β-hydroxyetiocholanolone as one of the major fGM.
• The 11β-hydroxyetiocholanolone assay was found to be the most appropriate EIA to monitor fGM in lynx.
• Husbandry interventions resulted in pronounced increases in fGM levels in Iberian lynxes.

Stress hormone levels are important indicator of an animal’s well-being, as stress has harmful effects on reproduction, growth and immune function. The development of enzyme immunoassays (EIA) to monitor faecal glucocorticoid metabolites (fGM) contributes a powerful tool to assess an animal’s adrenal status non-invasively. We aimed to identify a suitable EIA for monitoring fGM by assessing the suitability of six different EIAs for detecting quantitative changes in fGM concentrations in response to an ACTH challenge test in Eurasian lynx. FGM were characterised in a male Eurasian lynx that received an injection of 3H-cortisol. Using HPLC analyses radiolabeled metabolites were compared with immunoreactive metabolites. The second aim was to biologically validate the established EIA for monitoring adrenocortical activity of captive Iberian lynxes after a translocation to new enclosures in relation to behaviour. Additionally faecal samples of ten pregnant Iberian lynxes from the peripartal period were analysed. The ACTH challenge revealed an 11β-hydroxyetiocholanolone EIA as the most sensitive assay to reflect acute fGM elevations in the Eurasian lynx. HPLC immunograms demonstrated that the 11β-hydroxyetiocholanolone EIA measured significant amounts of immunoreactivities corresponding to radiolabeled metabolites with strong similarities across both lynx species. Additionally, HPLC and GC–MS analyses confirmed the presence of 11β-hydroxyetiocholanolone in faeces of both, the Eurasian and the Iberian lynx. Longitudinal fGM profiles of Iberian lynx revealed increases in concentrations associated with management events. During the peripartal period, however, fGM concentrations were not significantly elevated. Our results show that the 11β-hydroxyetiocholanolone EIA is a reliable tool to assess fGM in both lynx species.

We developed an enzyme immunoassay (EIA) based on an antibody directed against 11β-hydroxyetiocholanolone which is a reliable tool to monitor faecal glucocorticoid metabolites (fGM) in lynxes. FGM concentrations were measured with the 11β-hydroxyetiocholanolone assay after an ACTH challenge in a male and a female Eurasian lynx.Figure optionsDownload as PowerPoint slide