Validation of a Commercial ELISA Kit for Non-Invasive Measurement of Biologically Relevant Changes in Equine Cortisol Concentrations
by
, , and
Elizabeth R. Share
1,*,
Sara L. Mastellar
2,
Jessica K. Suagee-Bedore
3
and
Maurice L. Eastridge
1 1
Department of Animal Sciences, The Ohio State University, Columbus, OH 43210, USA
2
Agricultural Technical Institute, The Ohio State University, Wooster, OH 44691, USA
3
Department of Animal and Poultry Sciences, Virginia Tech University, Blacksburg, VA 24061, USA
*
Author to whom correspondence should be addressed.
Animals 2024, 14(19), 2831; https://doi.org/10.3390/ani14192831
Submission received: 20 August 2024
/
Revised: 26 September 2024
/
Accepted: 27 September 2024
/
Published: 1 October 2024
(This article belongs to the Section Equids)
Simple Summary
Cortisol is a very common hormone measured when studying the stress response. While plasma cortisol is commonly utilized, concerns regarding stress caused by the sampling procedure and whether that sample represents acute vs. chronic stress have paved the way for measuring fecal cortisol metabolites (FCMs). The measurement of FCMs can be costly, and some reagents used require special permission. Commercial ELISA kits have become popular as a cost-effective method of cortisol measurement, but it is crucial to validate if these kits can detect a biologically significant change in the hormone being measured within the animal being studied. In our work, we conclude that the Arbor AssaysTM DetectX® Cortisol ELISA kit (K003-H1, Ann Arbor, MI, USA) is a reliable, economic option for the measurement of biologically relevant changes in cortisol in equine plasma and FCMs. This work helps to provide another potential tool for researchers who want to evaluate horse stress and well-being.
Abstract
The measurement of fecal cortisol/corticosterone metabolites (FCMs) is often used to quantify the stress response. The sampling method is relatively non-invasive, reduces concern for elevation of cortisol from the sampling method, and has been shown to measure cortisol more consistently without the daily diurnal rhythm observed in blood. Commercial ELISA (enzyme-linked immunoassay) kits offer benefits over previously validated immunoassay methods but lack validation. The objective of this study was to evaluate a commercial ELISA kit (Arbor AssaysTM DetectX® Cortisol ELISA kit, K003-H1, Ann Arbor, MI, USA) and provide analytical and biologic validation of equine fecal and plasma samples. Horses (4 male, 4 female, mean ± SD: 4 ± 5 yr) were transported for 15 min with limited physical and visual contact via a livestock trailer. Blood and fecal samples were collected pre- and post-transportation. Parallelism, accuracy, and precision tests were used to analytically validate this kit. Data were analyzed using PROC MIXED in SAS 9.4. Plasma cortisol concentrations increased in response to trailering (254.5 ± 26.4 nmol/L, 0 min post-transportation) compared to pre-transportation (142.8 ± 26.4 nmol/L). FCM concentrations increased 24 h post-trailering (10.8 ± 1.7 ng/g) when compared to pre-transportation (7.4 ± 1.7 ng/g). These data support that changes in FCMs can be observed 24 h post-stressor. In conclusion, the Arbor AssaysTM DetectX® Cortisol ELISA kit is a reliable, economic option for the measurement of biologically relevant changes in cortisol in equine plasma and FCMs.
