Sixty minutes of daily solitary turnout improved physiological and behavioral indicators of stress and welfare in stall-housed horses.

Overview

• This study investigated how different daily durations of solitary turnout (0, 15, or 60 minutes) affect stress and welfare indicators in stall-housed horses.
• The findings show that a 60-minute daily turnout significantly improves physiological and behavioral stress markers compared to no turnout or just 15 minutes.

Introduction

• Horses in stalls have limited movement, restricting natural roaming behavior.
• This restriction leads to increased stress and development of stereotypic (repetitive, abnormal) behaviors.
• Providing daily turnout—time outside the stall for voluntary exercise—is commonly used to reduce stress.
• Optimal duration of turnout sessions is not well established and requires scientific investigation.

Objective

• To evaluate how minimal (15 minutes) versus moderate (60 minutes) daily solitary turnout impacts physiological and behavioral stress markers in stall-housed horses.
• To determine if moderate-duration turnout improves welfare compared to minimal or no turnout periods.

Methods

• Subjects: Eleven adult Quarter horses housed in stalls.
• Experimental Design:
  • Latin-square design to control for individual and period effects.
  • Three turnout treatments given in 12-day periods: 0, 15, or 60 minutes of solitary turnout per day.
• Measurements:
  • Behavioral assessments conducted on day 6 of each period, including in-stall behavior and 24-hour time budgets.
  • Heart rate variability (HRV) recorded daily during and after turnout to assess autonomic nervous system activity.
  • Blood samples collected on days 2, 4, and 12 for complete blood count.
  • Inflammatory markers (TNFα, IL6), insulin, and glucose assessed on day 2.

Key Findings

• Heart Rate Variability (HRV)
  • HRV metrics associated with vagal parasympathetic tone—such as NN intervals, pNN, and LF/HF power ratio—were significantly higher during 60-minute turnout.
  • This indicates lower physiological stress and improved autonomic regulation when horses had 60 minutes turnout.
• Immune and Inflammatory Markers
  • Circulating lymphocyte counts and plasma IL-6 concentrations were significantly reduced in horses receiving 60-minute turnout compared to those with 15 minutes.
  • Lower IL-6 suggests reduced systemic inflammation and immune stress with longer turnout.
• Behavioral Observations
  • The 60-minute turnout group tended to show less locomotor activity inside the stall on day 6, implying calmer behavior.
  • Stereotypic and aggressive behaviors did not significantly differ across turnout durations, though there was a trend towards improvement.

Conclusions and Implications

• Daily solitary turnout of moderate duration (60 minutes) effectively reduces both physiological and some behavioral indicators of stress in stall-housed horses.
• Minimal turnout duration (15 minutes) resulted in only marginal or no significant improvements, highlighting a dose-dependent effect.
• The study emphasizes the importance of providing horses with adequate turnout time to support their welfare and reduce stress-related health issues.
• These findings can inform better management practices in equine care by encouraging at least one hour of daily turnout for stall-kept horses.

Study Limitations and Future Directions

• The study involved only adult Quarter horses, so generalization to other breeds or age groups should be done cautiously.
• Longer-term welfare impacts and effects on stereotypic behaviors over extended periods were not assessed.
• Future research might evaluate turnout in group settings or explore variations in exercise type and environment.