title: Non-invasive assessment of adrenocortical function in captive Nile crocodiles (Crocodylus niloticus).
abstract: The occurrence of stress-inducing factors in captive crocodilians is a concern, since chronic stress can negatively affect animal health and reproduction, and hence production. Monitoring stress in wild crocodiles could also be beneficial for assessing the state of health in populations which are potentially threatened by environmental pollution. In both cases, a non-invasive approach to assess adrenocortical function as a measure of stress would be preferable, as animals are not disturbed during sample collection, and therefore sampling is feedback-free. So far, however, such a non-invasive method has not been established for any crocodilian species. As an initial step, we therefore examined the suitability of two enzyme-immunoassays, detecting faecal glucocorticoid metabolites (FGMs) with a 11β,21-diol-20-one and 5β-3α-ol-11-one structure, respectively, for monitoring stress-related physiological responses in captive Nile crocodiles (Crocodylus niloticus). An adrenocorticotropic hormone (ACTH) challenge was performed on 10 sub-adult crocodiles, resulting in an overall increase in serum corticosterone levels of 272% above the pre-injection levels 5h post-injection. Saline-treated control animals (n=8) showed an overall increase of 156% in serum corticosterone levels 5h post-administration. Faecal samples pre- and post-injection could be obtained from three of the six individually housed crocodiles, resulting in FGM concentrations 136-380% above pre-injection levels, always detected in the first sample collected post-treatment (7-15 days post-injection). FGM concentrations seem comparatively stable at ambient temperatures for up to 72 h post-defaecation. In conclusion, non-invasive hormone monitoring can be used for assessing adrenocortical function in captive Nile crocodiles based on FGM analysis.
authors: Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Onderstepoort 0110, South Africa; Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Onderstepoort 0110, South Africa. Electronic address: Stefanie.Ganswindt@up.ac.za.
authors: Stefanie B
authors: SB
authors: Ganswindt
authors: Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Onderstepoort 0110, South Africa. Electronic address: Jan.Myburgh@up.ac.za.
authors: Jan G
authors: JG
authors: Myburgh
authors: Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa; Wildlife Ecology/Conservation, School of Zoology, University of Tasmania, Hobart, TAS 7001, Australia. Electronic address: Elissa.Cameron@utas.edu.au.
authors: Elissa Z
authors: EZ
authors: Cameron
authors: Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Onderstepoort 0110, South Africa; Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. Electronic address: AGanswindt@zoology.up.ac.za.
authors: Andre
authors: A
authors: Ganswindt
mesh_terms: D000302:Adrenal Cortex / Q000378:metabolism* / Q000637:transplantation*; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000489:Alligators and Crocodiles / Q000097:blood / Q000378:metabolism* / Q000502:physiology*; D000818:Animals; D003345:Corticosterone / Q000097:blood; D004777:Environment; D005243:Feces / Q000737:chemistry; D005260:Female; D005938:Glucocorticoids / Q000378:metabolism; D008297:Male; D013312:Stress, Physiological / Q000502:physiology
chemical_list: D005938:Glucocorticoids; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone
keywords: ACTH challenge test; Adrenocortical function; Corticosterone; Enzyme-immunoassay; Faecal glucocorticoid metabolites; Nile crocodile; Post-defaecation hormone stability