Transport Stress in Horses: Could Melatonin Offer a New Tool for Travel Welfare?

Transportation is a routine part of equestrian life, whether moving horses between yards, travelling to competitions or attending veterinary appointments. Yet for horses, travel represents far more than a logistical exercise. Research increasingly shows that transport acts as a significant physiological stressor, triggering hormonal and metabolic changes that can compromise welfare.

A recent study has explored whether transdermal melatonin could help reduce some of these stress responses, offering a potential non-invasive tool to support horses during transit.

What happens inside a horse’s body during transport

When horses are transported, their bodies activate the hypothalamic-pituitary-adrenal (HPA) axis, a central component of the stress response system. This activation leads to an increase in circulating cortisol, a hormone that mobilises energy but, when elevated repeatedly or for prolonged periods, can negatively affect immune function, metabolism and musculoskeletal health.

Alongside rising cortisol levels, transport has been shown to trigger metabolic disturbances. Cortisol stimulates gluconeogenesis, increasing blood glucose, while markers associated with muscular strain such as creatinine and bilirubin may rise as horses work to maintain balance during prolonged confinement.

Transportation also affects hydration and electrolyte balance. Horses commonly show reduced potassium and elevated sodium levels following travel, shifting the sodium-to-potassium ratio towards values seen in pharmacological diuresis. This pattern raises concerns around post-transport risks such as dehydration, colic and metabolic disruption, particularly after longer journeys.

Together, these physiological changes reflect the cumulative toll of travel, combining physical effort, confinement and psychological stress.

Exploring melatonin as a welfare support tool

Against this backdrop, researchers investigated whether transdermal melatonin could help attenuate some of these stress responses. Melatonin is best known for regulating circadian rhythms, but it also has recognised antioxidant and anti-inflammatory properties, making it a candidate for moderating physiological stress.

In the study Effect of transdermal melatonin on circulating cortisol and blood chemistry in horses exposed to transport stress, researchers applied melatonin through the skin prior to transport and monitored cortisol and blood chemistry parameters.

The findings showed that horses receiving transdermal melatonin had lower circulating cortisol levels compared with untreated controls, suggesting reduced activation of the HPA axis. While melatonin did not eliminate all transport-induced metabolic changes, its ability to dampen cortisol release indicates potential for reducing the hormonal burden associated with travel.

This aligns with broader veterinary research in other species, where melatonin has been shown to moderate stress-related physiological responses and oxidative damage. Within equine science, complementary approaches such as antioxidant supplementation and acclimatisation protocols have also been explored to support horses facing physical or environmental stressors.

Important limitations and next steps

While the results are encouraging, the researchers also highlight important limitations. The study involved a relatively small sample size and focused on short-term physiological responses rather than longer-term outcomes. In addition, the horses were not elite competition animals, meaning further research is needed to understand how transdermal melatonin may perform in high-performance horses or those that travel frequently for sport.

As with many emerging welfare interventions, wider trials across different populations, journey durations and transport conditions will be essential before firm conclusions can be drawn.

What this means for riders, owners and professionals

Melatonin is not a cure-all for transport stress. Travel remains a complex challenge affecting multiple body systems, and effective welfare management will continue to rely on good practical foundations: appropriate ventilation, careful driving, regular rest periods, access to water, thoughtful journey planning and close monitoring of individual horses.

However, transdermal melatonin offers an intriguing addition to the welfare toolkit. By targeting one of the body’s core stress pathways, it may help support horses in situations where transport is unavoidable, potentially reducing cumulative hormonal strain and supporting recovery. For riders and professionals, this research reinforces an important principle: transport should be treated as a physiological event, not simply a logistical one. Even short journeys can trigger measurable stress responses, and repeated exposure may have longer-term implications for health and performance.

Editorial perspective

This study represents an early step rather than a definitive solution. Its real value lies in highlighting the biological cost of transport and encouraging evidence-based discussion around how horses are supported during travel.

As equestrian science continues to evolve, integrating emerging tools like transdermal melatonin with established management practices may help improve resilience and welfare. But responsible adoption requires continued research, critical evaluation and an understanding that no single intervention replaces good horsemanship. Ultimately, improving transport welfare is about reducing cumulative stress wherever possible, through preparation, management and informed care. Studies like this move the conversation forward by reminding us that every journey matters.