Hypothalamic-pituitary-adrenal axis responses of horses to therapeutic riding program: Effects of different riders

In order to determine whether therapeutic riding could result in higher levels of stress than recreational riding, hypothalamic-pituitary-adrenal (HPA) axis response was evaluated in six horses by monitoring circulating β-endorphin, ACTH and cortisol concentrations. Horses were already accustomed to be trained both for therapy and riding school activity since 2004. Intervention consisted of 60-minute therapeutic sessions, two times per week for 6weeks with different riders: disabled and recreational riders (session A and B respectively). The therapeutic riders' group (A) consisted of six children with psychomotor disabilities; the recreational riders' group (B) consisted of six healthy children without any previous horse riding experience. Horses were asked to perform the same gaits and exercises at all sessions, both with disabled and healthy users. The statistical analysis showed that during both sessions the mean basal β-endorphin and ACTH levels of horses did not show any significant changes, while the one way RM-ANOVA showed significant effects of sessions A on the cortisol (F=11.50; P<0.01) levels. Horses submitted to sessions A showed lower cortisol levels both at 5min (P<0.001) and at 30min (P<0.005) after therapeutic sessions than those after session B. Results suggest that in tested horses and for the variables settled, HPA axis was less responsive to disabled than healthy, recreational riders. Among the endocrine responses, cortisol was one of the indicators of HPA axis stress response.