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Non-invasive assessment of adrenocortical function in captive Nile crocodiles (Crocodylus niloticus)
journal contribution
posted on 2023-05-18, 02:38 authored by Ganswindt, SB, Myburgh, JG, Elissa Cameron, Ganswindt, AThe 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 5 h post-injection. Saline-treated control animals (n = 8) showed an overall increase of 156% in serum corticosterone levels 5 h 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.
History
Publication title
Comparative Biochemistry and Physiology Part AVolume
177Pagination
11-17ISSN
1095-6433Department/School
School of Natural SciencesPublisher
Elsevier Science IncPlace of publication
360 Park Ave South, New York, USA, Ny, 10010-1710Rights statement
Copyright 2014 Elsevier Inc.Repository Status
- Restricted