Evaluation of fatigue level in endurance horses : development of a composite scale for grading facial expressions and posture ; Évaluation du niveau de fatigue chez le cheval en course d'endurance : construction d'une échelle composite de gradation des expressions faciales et de l'attitude générale

Equestrian endurance is a discipline that requires long-lasting effort and places significant demands on horses'bodies. In endurance racing, the veterinarian, responsible for animal welfare, assesses the level of fatigue in horses and stops them before they develop major issues. Facial expressions and general demeanor are described in literature as indicators of pain in horses. A veterinary thesis studied the significance of facial expressions in endurance horses. The facial expression score proved to be valuable in evaluating fatigue levels but was imprecise due to a limited study population and relatively uniform and undemanding race conditions. The objective of our study is to develop a grading scale for facial expressions and posture to assess fatigue levels in endurance horses. The scale was applied to 744 recordings from three different endurance races. Facial expression and posture scores were analyzed based on individual data collected during the races. The results show a gradual increase in the overall score throughout the race. From the 1st to the 4th veterinary check, scores were higher in eliminated horses compared to those that finished. From the 1st to the 3rd veterinary check, scores predicted elimination at the subsequent veterinary check. Additionally, scores were higher at the beginning of the race for horses in the first quartile and higher at the end of the race for horses in the last quartile. Finally, scores were influenced by age but not by breed or the clinical fatigue criteria studied during the race. The obtained results are promising. However, the main limitation encountered is the lack of reproducibility. Further studies with better evaluator training will be necessary to validate the use of the scale. ; L'endurance équestre est une discipline qui demande un effort de longue durée et sollicite très fortement l'organisme des chevaux. En course d'endurance, le vétérinaire, garant du bien-être animal, a pour rôle de juger le niveau de fatigue des chevaux et de les arrêter avant qu'ils ne ...