Competition and stereotypic behavior in Thoroughbred horses: The value of saliva as a diagnostic marker of stress.
Authors: Bazzano Marilena, Marchegiani Andrea, La Gualana Francesca, Petriti Begi, Petrucelli Marina, Accorroni Lucrezia, Laus Fulvio
Journal: PloS one
Summary
# Editorial Summary Stereotypic behaviours in Thoroughbreds reflect underlying stress responses to restrictive management systems, yet identifying which horses are truly struggling has proven challenging for practitioners. Researchers compared salivary biomarkers—cortisol, alpha-amylase (sAA), and butyrylcholinesterase (BChE)—across three groups: ten non-stereotypic competition horses, eleven stereotypic competition horses, and five non-stereotypic leisure horses, collecting resting saliva samples to establish baseline stress signatures. Surprisingly, resting cortisol was highest in non-stereotypic competition horses rather than stereotypic ones, whilst sAA activity was significantly elevated in leisure horses compared to both competition groups; BChE showed no meaningful variation. These findings suggest that stereotypic behaviour may represent a coping mechanism rather than a direct marker of acute stress, and that high-level competition itself induces measurable physiological stress responses even in horses without visible stereotypies. For equine professionals, this implies that the absence of stereotypic behaviour should not be interpreted as evidence of effective stress management, and that resting saliva biomarkers warrant further investigation as objective diagnostic tools to identify at-risk individuals and refine training protocols—though additional research is needed to clarify the temporal relationship between stress exposure, behavioural adaptation, and salivary markers.
Read the full abstract on PubMed
Practical Takeaways
- •Salivary biomarkers (cortisol and alpha-amylase) may help identify stress responses in competition horses, but their absence or presence does not necessarily indicate welfare problems — stereotypic behavior cannot be reliably diagnosed by saliva alone
- •High-level competition non-stereotypic horses showed higher cortisol, suggesting some stress is normal in racing; use behavioral observation alongside any biomarker assessment
- •Further research needed before using saliva testing as a clinical diagnostic tool for stress in racing Thoroughbreds — current findings are preliminary and based on small sample sizes
Key Findings
- •Salivary cortisol was significantly higher in high-level competition non-stereotypic horses compared to other groups
- •Alpha-amylase (sAA) activity was significantly elevated in leisure non-competition horses versus competition horses
- •Butyrylcholinesterase (BChE) activity showed no significant differences between stereotypic, non-stereotypic competition, and leisure horse groups
- •Stereotypic horses in competition did not show the expected elevated cortisol response, suggesting possible habituation or altered stress response mechanisms