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

Abstract

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 equine 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 their horses’ personality traits. Linear models were calculated to assess associations between the questionnaire data and salivary cortisol 60 (T60) and 90 (T90) minutes after ACTH stimulation. While the model at T90 was not significant, post-stimulatory cortisol after 60 minutes appears most informative in line with a previous study and was significantly affected by the breed and by three management factors: “number of riders”, “hours spent outside” and “group housing” (adjusted r2 = 15%, p<0.001). Thoroughbred and Warmblood horses displayed an increased adrenal response compared to Franches-Montagnes horses. Horses with several riders had a less pronounced reaction than horses with one rider, and horses that spent more time outside had a decreased response compared to horses that were stabled most of the time. Horses living in groups showed higher post-stimulatory cortisol values than horses that were housed singly. However, no significant associations of cortisol responsiveness with personality traits were found, and neither the use as elite or as amateur sport horses nor the discipline had an effect on the cortisol response. This suggests that optimizing husbandry conditions may be more important for improving equine welfare than changing their use.

The effect of stress and exercise on the learning performance of horses

“…In common with the other breeds used in the study, the TB/WB horses were a mixture of horses that were either in active training for eventing competitions or horses that had been in low to moderate exercise for at least the month prior to the experiment. In comparison to our data, Sauer et al, 102 reported that warmblood and thoroughbred sport horses had higher salivary cortisol concentrations in response to ACTH challenge than French-Montagne breed horses. Cortisol responsive phenotypes have been identified in Japanese quail 103 , mice 104 and cortisol reactivity in humans is associated with some psychiatric disorders 105 .…”

Does Experience Make Hucul Horses More Resistant to Stress? A Pilot Study

“…As reported by Sauer et al [ 47 ], stress resistance may be related to the animal breed as well as maintenance and use of the animal. The high level of cortisol in the examined horses may be related to these indicators, which suggests a need for further research in this field.…”

Habit Formation and the Effect of Repeated Stress Exposures on Cognitive Flexibility Learning in Horses

“…Smeets et al [ 114 ] reported impaired cognitive flexibility in humans with higher salivary cortisol concentrations irrespective of stress exposure. To date, while breed differences in salivary cortisol have been identified [ 115 ], there is little data on whether cortisol genotypes per se exist in horses. Further research evaluating cortisol reactivity and cognition in horses is required to confirm our finding as other studies have reported either no relationship between salivary cortisol and task performance [ 116 ] or a transient increase in performance in an appetitive task acquisition in horses [ 117 ].…”