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Article

Over Time Decay of Cortisol Metabolites in Faecal Pellets of Koalas in Central Queensland

1
Koala Research-Central Queensland and Flora, Fauna and Freshwater Research, School of Health, Medical and Applied Sciences, Central Queensland University, North Rockhampton, QLD 4702, Australia
2
Department of Biomedical Sciences, University of Veterinary Medicine, 1210 Vienna, Austria
3
School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia
*
Author to whom correspondence should be addressed.
Academic Editor: Natasha Speight
Animals 2021, 11(12), 3376; https://doi.org/10.3390/ani11123376
Received: 25 October 2021 / Revised: 22 November 2021 / Accepted: 23 November 2021 / Published: 25 November 2021
(This article belongs to the Special Issue Health and Diseases of Koalas)
Faecal cortisol metabolites (FCMs) are a useful, non-invasive tool for the assessment of stress in koalas. However, FCM stability after defecation is a critical issue. Therefore, we exposed faecal pellets of koalas to three different environmental conditions and measured FCMs with three recently evaluated enzyme immunoassays (EIAs). Because water loss over time exerted the greatest influence on FCMs, we strongly recommend collecting freshly defecated pellets in koalas.
Faecal material can be a valuable source of information for a range of animal health aspects and can be used to measure faecal cortisol metabolites (FCMs). FCM values can relate to physiological stress responses. However, freshly defecated pellets are not always available and environmental conditions, such as temperature and humidity, might affect faecal pellet consistency and FCM levels. Therefore, the impact of environmental conditions on FCMs needs to be evaluated. We collected 107 pellets from two female and two male koalas, exposed them to three types of treatments, and analysed FCMs in these samples with three enzyme immunoassays (EIAs). After analysis, the original FCM values were mathematically corrected for water loss. Results show that the FCMs were more stable when measured using tetrahydrocorticosterone (50c) and 5α-pregnane-3β,11β,21-triol-20-one (37e) EIAs, and were less stable when measured with the cortisol EIA. With 50c, the FCM values did not vary significantly over time either before or after the adjustment with water in the environment treatment group. For samples kept under constant low (25 °C) and high (35 °C) temperatures, the 50c FCM values did not vary significantly over time, after adjustments were made for water loss. Thus, this study highlights the importance of considering the suitability of faecal field samples for FCM analysis. Because water loss was the main driver of FCM changes, we strongly recommend collecting koala pellets that are freshly defecated, despite the effort and time it might take to collect such pellets. View Full-Text
Keywords: koala; Phascolarctos cinereus; glucocorticoid metabolites; faeces; stability; non-invasive monitoring; stress; decay koala; Phascolarctos cinereus; glucocorticoid metabolites; faeces; stability; non-invasive monitoring; stress; decay
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MDPI and ACS Style

Santamaria, F.; Schlagloth, R.; Palme, R.; Henning, J. Over Time Decay of Cortisol Metabolites in Faecal Pellets of Koalas in Central Queensland. Animals 2021, 11, 3376. https://doi.org/10.3390/ani11123376

AMA Style

Santamaria F, Schlagloth R, Palme R, Henning J. Over Time Decay of Cortisol Metabolites in Faecal Pellets of Koalas in Central Queensland. Animals. 2021; 11(12):3376. https://doi.org/10.3390/ani11123376

Chicago/Turabian Style

Santamaria, Flavia, Rolf Schlagloth, Rupert Palme, and Joerg Henning. 2021. "Over Time Decay of Cortisol Metabolites in Faecal Pellets of Koalas in Central Queensland" Animals 11, no. 12: 3376. https://doi.org/10.3390/ani11123376

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