Effects of breed, management and personality on cortisol reactivity in sport horses

Sport horses need to fulfill high physical and psychological requirements during training and competition. These as well as certain conditions of modern husbandry may affect their wellbeing. Here we aimed to (1) evaluate effects of demographic and management factors as well as personality traits on stress reactivity of sport horses, (2) investigate if elite sport horses have elevated stress levels compared to amateur sport horses, and (3) assess whether different equestrian disciplines differentially influence horses' adrenal cortex responsiveness. For this purpose, we visited 149 healthy elite (n=94) and amateur (n=54) sport horses in Switzerland and performed an adrenocorticotropic hormone (ACTH) stimulation test. Additionally, a person who was familiar with the horse completed a questionnaire about demographic and management factors and horses’ personality traits. Linear models were calculated to assess associations between the questionnaire data and salivary cortisol 60 and 90 minutes after ACTH stimulation. While the model at T90 was not significant, post-stimulatory cortisol after 60 min appears most informative in line with a previous study and was significantly affected by the horses’ breed and by three management factors: “number of riders”, “hours spent outside” and “group housing” (adjusted r2 =15%, p