Perinatal Stress in Immature Foals May Lead to Subclinical Adrenocortical Dysregulation in Adult Horses: Pilot Study.
Authors: Clothier Jane, Small Alison, Hinch Geoff, Brown Wendy Y
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Perinatal stress resulting from prematurity or dysmaturity at birth may produce lasting changes to adrenocortical function that persist into adulthood, yet this phenomenon has remained largely unexplored in equine medicine despite documented effects in other livestock. Researchers recruited 10 horses with documented gestational immaturity (gestation <315 days or clinical dysmaturity signs) alongside 7 matched controls and 5 negative controls, administering a low-dose ACTH stimulation test (0.1 µg/kg tetracosactrin) and measuring salivary cortisol responses at baseline and 30-minute intervals over 150 minutes. Whilst baseline cortisol concentrations remained within normal ranges across all horses, case animals demonstrated significantly dysregulated peak and area-under-curve (AUC) cortisol values compared to healthy controls—with some horses mounting exaggerated responses (H-cases) and others showing blunted responses (L-cases), both falling outside the 95% confidence interval of reference populations (P <0.001). No confounding effects were identified for breed, age, sex, season, or location. These findings suggest subclinical adrenocortical dysregulation may develop secondary to gestational immaturity, potentially explaining previously undifferentiated stress responses and metabolic vulnerabilities observed in some adult horses, and warrant larger prospective studies to establish clinical significance and identify affected individuals during the neonatal period.
Read the full abstract on PubMed
Practical Takeaways
- •Horses born prematurely (gestation <315 days) or showing neonatal dysmaturity signs may develop long-term endocrine dysfunction that is not detectable through routine baseline cortisol screening alone
- •Subclinical adrenocortical dysregulation in mature horses with histories of difficult births or prematurity could affect stress responses and may warrant investigation during unexplained performance or behavioural issues
- •Consider obtaining detailed perinatal histories for horses showing unexpected stress responses or atypical cortisol patterns on diagnostic testing
Key Findings
- •Case horses with gestational immaturity showed significantly different salivary cortisol responses (peak and AUC values) compared to positive controls (ANOVA P < 0.001)
- •Dysregulated horses presented either elevated or blunted cortisol responses to low-dose ACTH stimulation despite normal baseline cortisol levels
- •No significant effects of breed, age, sex, test month, or location on adrenocortical response patterns were detected
- •Gestational immaturity may lead to subclinical adrenocortical dysregulation with persistent effects into adulthood