Abstract
Simple SummaryThe monitoring of a horse’s endocrine status can provide valuable information of its welfare and sexual and health conditions. The use of non-invasive matrixes for hormonal monitoring, as alternatives to blood samples, are being increasingly used. Among them, the measurement of hormones deposited in the hair shaft has been widely used as a retrospective hormonal biomarker. In the present study, we aimed to evaluate the seasonal variations in hair C, T and DHEA-S in horses for a whole year, as well as to assess the variations between seasons of C/DHEA-S and T/C ratios as a retrospective measure of the hypothalamic–pituitary–adrenal and hypothalamic–pituitary–gonadal axis activity. The results showed how cortisol, testosterone and dehydroepiandrosterone sulphate and their ratios were significantly affected by season. Therefore, as shown in this study, season should be considered when analysing sexual and stress hormones in stallion hair.The monitoring of stress physiology includes studying a wide range of endocrinological mechanisms, which can be assessed using multiple tissue samples. This study aimed to evaluate the seasonal variations of hair C, T and DHEA-S in horses for a whole year, as well as to assess the variations between seasons of C/DHEA-S and T/C ratios as a retrospective measure of the hypothalamic–pituitary–adrenal and hypothalamic–pituitary–gonadal axis activity. Ten pure-breed Menorca stallions were included in the study. The hair samples were collected approximately every two months following the shave-reshave method caudally to the sternum. After a methanol-based extraction, samples were analyzed by enzyme immunoassay for cortisol, testosterone, and dehydroepiandrosterone sulphate. Following our findings, we detected that cortisol, testosterone and dehydroepiandrosterone sulphate were significantly affected by seasonality, with the highest values of cortisol during summer and the lowest values of testosterone during spring. Dehydroepiandrosterone sulphate concentrations were increased in autumn compared to the other studied periods. Additionally, the studied hormone ratios showed variations between seasons. To conclude, season should, therefore, be considered when assessing sexual and stress hormones in stallion hair, since this variable can be a potential influencing factor and led to misinterpretations.
Highlights
The monitoring of a horse’s endocrine status can provide valuable information of its welfare, sexual and health conditions [1]
We aimed to evaluate the seasonal variations in hair C, T and DHEA-S in horses for a whole year, as well as to assess the variations between seasons of C/DHEA-S and T/C ratios as a retrospective measure of the hypothalamic–pituitary– adrenal and hypothalamic–pituitary–gonadal axis activity
As far as we know, there is no literature available on how environmental factors, such as temperature, humidity or daylight duration, affect HCC in the adult horse. These factors have been studied in foals during the perinatal period, and no significant effect on the hair cortisol concentrations measured at birth or at 30 days of age was found [36]
Summary
The monitoring of a horse’s endocrine status can provide valuable information of its welfare, sexual and health conditions [1]. Assessing simultaneously hormones that are thought to co-regulate to each other, such as those secreted by HPA and HPG activation, would be postulated as a better approach to physiological stress measurements [2,3]. With the activation of the HPA axis, other components, such as dehydroepiandrosterone (DHEA) and its sulfate ester (DHEA-S), are released into bloodstream [3]. Both DHEA and DHEA-S have been characterized as glucocorticoid antagonists, and are considered as indicators of resilience, because of their anti-aging, immune-enhancing and neuroprotective functions [3]. C/DHEA ratio has been used as a more complete picture of the HPA activity and as a potential biomarker tool of resilience and allostatic load in livestock animals, including horses [3,8,9,10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
