Case Report: Physiological Stress Responses to Repeated, Standardized Short-Distance Transport in a Transport-Experienced Horse.

Overview

• This case report investigated physiological stress responses in a 10-year-old transport-experienced horse undergoing repeated short-distance transports under controlled, standardized conditions.
• The study assessed heart rate and salivary cortisol levels during multiple transport and training sessions to understand stress patterns and habituation over time.

Background and Purpose

• Transport is a common and necessary activity in equestrian sports and training, but it can induce stress in horses.
• While horses with prior transport experience are often assumed to have reduced stress responses, this assumption had not been rigorously tested over repeated short-distance transports with standardized conditions.
• The purpose of this case report was to examine physiological stress markers in a transport-experienced horse over multiple repeated transports, investigating whether habituation occurs and how stress levels change over time.

Methods

• Subject: A 10-year-old Belgian Warmblood gelding with extensive transport experience.
• Transport Protocol:
  • A total of 17 transport events were conducted.
  • The route and conditions were fixed and standardized, involving the same vehicle, handler, and procedures, limiting environmental variability.
• Physiological Measures:
  • Continuous heart rate monitoring was performed to capture cardiovascular responses.
  • Salivary cortisol samples were collected at standardized time points before, during, and after transport and training sessions to assess hypothalamic-pituitary-adrenal (HPA) axis activation.
• Data Collection Points:
  • Preloading baseline values.
  • During transport.
  • During dressage training session.
  • Return transport post-training.

Findings

• Salivary Cortisol:
  • Increased during transport compared to preloading baseline values.
  • Remained slightly elevated throughout the sequence of transport, training, and return transport.
  • After approximately ten transport events, a gradual decline in cortisol concentrations was observed, indicating partial physiological habituation.
  • However, one notable physiological outlier was observed during the fifth transport event, showing a spike in stress markers despite prior experience and habituation trends.
• Heart Rate:
  • Elevated compared to resting values even before loading onto the vehicle.
  • Peaked during dressage training, indicating high exertion or stress during this phase.
  • Remained moderately elevated during transport phases following the training session.

Interpretation and Implications

• Even well-experienced horses display measurable physiological stress responses during routine short-distance transports.
• The gradual decline in cortisol suggests that some habituation occurs with repeated exposures, but this habituation is partial rather than complete.
• The presence of an acute stress outlier event highlights that unexpected stress responses can arise despite habitual exposure and standardized conditions.
• This challenges the assumption that routine transport is minimally stressful for experienced horses and indicates that transport management should be individualized.
• Recommendations include:
  • Allowing adequate recovery periods between transports and trainings.
  • Continued welfare monitoring to detect and address stress responses early.
  • Considering physiological stress markers when planning and managing horse transport routines.

Conclusion

• The study provides evidence that repeated short-distance transport can induce significant physiological stress responses in horses, even those accustomed to transport.
• Partial habituation occurs over multiple transports but does not fully eliminate stress responses.
• Careful transport and training management with attention to individual variability is critical to support horse welfare during routine equestrian activities.