Exploring the association between stress-related hormonal changes, behaviours and facial movements after an interval training exercise in French Standardbred.
Authors: Hennes Noémie, Tutin Léa, Foury Aline, Vancassel Sylvie, Bourguignon Hélène, Duluard Arnaud, Ruet Alice, Lansade Léa
Journal: PloS one
Summary
# Editorial Summary Exercise-induced stress in racehorses remains poorly characterised, yet understanding individual variation in response to training is crucial for optimising welfare and performance in French Standardbreds. This study examined 14 horses performing interval training, measuring salivary cortisol, serum adrenaline and serotonin at four timepoints (pre-exercise, immediately post, 1 hour, and 24 hours post-exercise), whilst simultaneously recording behaviours and facial movements before and after exertion. All three hormones increased significantly post-exercise with peak concentrations immediately after the trotting session; cortisol and adrenaline remained elevated at the one-hour mark—a pattern consistent with normal physiological adaptation rather than pathological stress. Notable inter-individual variation in hormonal responses revealed that horses experienced the exercise differently, and increased serotonin and adrenaline correlated positively with heightened agitation behaviours (pawing, head turning) and mouth movements, suggesting these observable signs may serve as practical non-invasive indicators of exercise-induced arousal. For practitioners, monitoring increased facial movements and agitation-related behaviours alongside known training intensity could help identify horses requiring modified conditioning protocols or management adjustments, though the authors appropriately caution that post-exercise handling practices (such as cross-tying) require investigation as potential confounding stressors before behavioural indicators can be reliably interpreted in clinical settings.
Read the full abstract on PubMed
Practical Takeaways
- •Monitor increased mouth movements and agitation (pawing, head turning) after interval training as non-invasive indicators of exercise stress—these behaviours correlate with elevated stress hormones
- •Recognize that horses respond individually to the same training intensity; use behavioural and facial cues to assess whether a horse is coping well rather than assuming uniform responses
- •Post-exercise management matters: be aware that practices like cross-tying immediately after exercise may compound frustration signals shown through mouth movements and agitation
Key Findings
- •All three stress hormones (cortisol, adrenaline, serotonin) increased significantly immediately post-exercise, with cortisol and adrenaline remaining elevated at 1 hour
- •Increased facial movements (particularly mouth movements) and agitation-related behaviours (pawing, head turning) occurred post-exercise
- •Positive associations found between serotonin/adrenaline concentrations and agitation behaviours plus mouth movements
- •Substantial inter-individual variability in hormonal responses suggests horses experienced the same exercise stimulus differently