Digital video analysis reveals gait parameters that predict performance in the jumping test phase of three-day eventing

In international equestrian sport, visual inspections assess gait and lameness to protect the welfare of performance horses during competition. Horses competing internationally in three-day eventing must pass two mandatory inspections (pre-competition and post-cross country) before attempting the final phase: the jumping test (JT). We hypothesized that digitally quantifying objective gait parameters captured during the two mandatory inspections will identify locomotor characteristics that predict success during the jumping test. Utilizing the DeepLabCut (DLC) software package for labeling of anatomical landmarks and a custom analysis pipeline we calculated gait parameters for 194 competition horses at the trot. During the pre-competition inspection, relative trot speed was significantly associated (P = 0.0060, GLMM), and the forelimb travel trended towards significance (P =0.0800, GLMM), with achieving a clear round in the later jumping test. Post-cross country, the forelimb travel significantly predicted JT results (P = 0.0188, GLMM). As our parameters are scaled for body size, these parameters may indicate conformational characteristics for superior jumping ability and overall athletic fitness. Within each competitive effort, comparisons of the post-cross country and precompetition observations revealed that the change in speed and duty factor were significantly different in the group that accrued jumping faults (P = 0.00376 and P = 0.02430, GLMM), perhaps capturing locomotor signs of exercise fatigue. Further work employing these approaches to better understand competition performance will encourage the use of objective measures to protect sport horse welfare, as well as provide an advantageous tool for gait evaluation in the horse.