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

Overview

• This study investigated how age affects locomotor activity (movement) in senior horses using short-duration monitoring in a paddock setting.
• Researchers found that older horses tend to move less and slower compared to younger senior horses, but these findings mainly reflect differences between different horses rather than changes within the same horse over time.

Introduction and Rationale

• Locomotor activity during turnout (time horses spend in a paddock) can provide valuable information about the health and welfare of older horses.
• There is limited objective data on how the locomotor behavior of senior horses changes with age in naturalistic field settings.
• The study aimed to use a brief monitoring approach to detect associations between chronological age and locomotor activity among senior horses.

Study Design and Methods

• Single-site observational study involving 28 senior Selle Français horses aged 17 to 35 years.
• Each horse was recorded during multiple turnout sessions, totaling 122 sessions, each lasting 2 hours.
• Locomotor activity was measured with a Polar Team Pro sensor, quantifying total distance traveled and mean speed during each session.
• Linear mixed-effects models were used to analyze data, adjusting for environmental factors such as temperature and precipitation.
• Age effects were partitioned into between-horse effects (differences between different horses) and within-horse effects (changes in the same horse over time) to tease apart cross-sectional from longitudinal patterns.

Key Findings

• Total distance horses traveled ranged widely from 148 meters up to nearly 4 kilometers during each 2-hour session.
• After log-transforming the total distance data to meet modeling assumptions, a statistically significant negative association with age was observed, meaning older senior horses moved less.
• This negative association was primarily due to between-horse differences—older horses as a group were less active than younger senior horses.
• The within-horse analysis, which looks at how individual horses’ activity changed with their aging, was imprecise and did not show a significant effect.
• Mean speed showed similar trends, decreasing with higher chronological age between horses but not reliably within individual horses over time.

Interpretation and Implications

• Brief monitoring sessions in paddocks can effectively capture differences in locomotor activity between horses of different ages in a senior population.
• The data support using paddock actimetry as a group-level tool for welfare assessment in older horses.
• However, the study’s data are insufficient for understanding how locomotor activity changes individually within a horse as it ages or for identifying biological aging markers at the individual level.
• Further research with larger, multi-site studies, more frequent monitoring, and external validation is needed to refine interpretation and assess longitudinal aging trajectories.

Limitations and Future Directions

• The study’s sample size was relatively small and from a single site, limiting generalizability.
• Only cross-sectional age differences were statistically clear; data were not adequate to capture within-animal aging effects over time.
• Environmental and management factors that may influence activity could vary across broader populations and were only partially controlled here.
• Future studies should include more horses, repeated measurements in individuals over time, and different environmental contexts to strengthen findings.
• Ultimately, improved methods could support individualized monitoring of senior horse health and welfare based on locomotor activity patterns.