Determination of Salivary Cortisol in Donkey Stallions.
Authors: Bonelli Francesca, Rota Alessandra, Aurich Christine, Ille Natascha, Camillo Francesco, Panzani Duccio, Sgorbini Micaela
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Salivary Cortisol Testing in Donkey Stallions Validating non-invasive stress biomarkers in donkeys has been lacking despite the species' growing use in therapeutic and working roles; this study therefore investigated whether a commercial enzyme immunoassay could reliably measure salivary cortisol in donkeys, an assay already validated in other species. Four accustomed stallions were sampled on 13 separate mornings at 08:30 using a standardised swab technique, with samples frozen and analysed using the commercial kit without extraction. The assay demonstrated robust performance with cortisol recovery of 97.3–99.7%, excellent agreement between diluted samples and standard curves, minimal cross-reactivity with other steroids (ranging from <0.1% for testosterone and progesterone to 10.4% for 11-deoxycortisol), intra-assay variation of 10.7% and interassay variation of 8.0%, and a detectable minimum concentration of 0.01 ng/mL. For practitioners managing donkey stress responses—whether in competition, rehabilitation, or behavioural assessment—this validation now enables reliable, animal-friendly cortisol measurement as a objective physiological marker, avoiding the handling stress associated with blood sampling that would confound results during stress evaluation.
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Practical Takeaways
- •Practitioners can now use commercial salivary cortisol assays in donkeys as a reliable, noninvasive stress indicator without extraction steps required
- •Salivary sampling at 8:30 AM avoids circadian variation and is easily performed in accustomed animals, making it practical for field conditions
- •Results are comparable to equine species, so existing knowledge of cortisol interpretation in horses applies to donkey clinical practice
Key Findings
- •Commercial enzyme immunoassay kit successfully validated for measuring salivary cortisol in donkeys with recovery rates between 97.3% and 99.7%
- •Intra-assay coefficient of variation was 10.7% and interassay variation was 8.0%, demonstrating acceptable assay precision
- •Minimal detectable cortisol concentration of 0.01 ng/mL achieved with acceptable cross-reactivity profile across related steroid hormones
- •Noninvasive salivary sampling via swab method is well-tolerated in donkeys and provides valid measurement of free plasma cortisol concentration