Age-Associated Differences in Paddock Locomotor Activity Among Senior Horses: A Pilot Observational Study

Turnout locomotor activity is a potentially informative indicator of health and welfare in older horses, yet objective field data in seniors remain limited. We examined whether a brief turnout recording could detect associations between chronological age and locomotor activity in senior horses under routine conditions. In this single-site observational study, 28 senior Selle Français horses (17–35 years) contributed 122 paddock sessions (2 h each), with total distance and mean speed quantified using a Polar Team Pro sensor. Associations with age were assessed using linear mixed-effects models adjusted for temperature and precipitation. Age was decomposed into between-horse and within-horse components. Log-transformed total distance was negatively associated with age (β = −0.062 per year, 95% CI −0.094 to −0.032; P < 0.001), driven by the between-horse component (β = −0.063; q = 0.003), with no within-horse association (P = 0.75). Mean speed showed a similar pattern, with a significant between-horse association (β = −0.060; q = 0.003) and no within-horse effect (P = 0.87). These findings suggest that brief paddock actimetry may help characterize between-horse heterogeneity and support group-level welfare monitoring. Larger multi-site cohorts with denser follow-up and external validation are needed before individual trajectories or clinical interpretation can be established.