Does your horse resist going in the trailer or show signs of stress after being unloaded at your destination?

You may need to trailer your horse for many reasons, such as seeing a veterinarian, competing, breeding or for recreational purposes.

Trailer stress can make it more difficult to load your horse, increase the dangers of transit, and negatively impact health and performance. Trailering also increases the risk of gastric ulcers, colic, dehydration, heat stroke, and shipping fever.

Trailer transport is sometimes unavoidable, but trailer stress and the risks that come with it can be minimized. Preparing for a trip should start well before the day you leave.

You can support your horse’s well-being during trailering by ensuring they are comfortable and accustomed to the trailer and by implementing some of the management practices recommended in this article.

Why Won’t my Horse Load in their Trailer?

Horses are locomotory prey animals, meaning they will try to escape unfamiliar or frightening situations.

If your horse isn’t used to riding in a trailer, it can trigger their “fight or flight” response and increase the risk of injury. [1]

There are many aspects of trailering that your horse may find stressful or uncomfortable, but these triggers are not always intuitive.

Consider the following potential stressors before and during a trailer ride: [2][3][4][5]

  • Anxiety from a previous trauma during trailering
  • Being isolated or apart from their social group; horses are herd animals and may resist leaving their companions to enter a trailer/li>
  • Unfamiliar feel and hollow sound of walking up a ramp
  • Dark interior of a trailer, especially on a bright sunny day
  • Stress of confinement
  • Poor air quality
  • Inability to lower their head to clear mucus from the airways if their head is tied
  • Lack of water and feed
  • Unfamiliar vibrations during transport
  • Exertion of maintaining balance
  • Uncomfortably high or low temperature and humidity
  • Difficulty urinating and defecating while maintaining balance

These stressful circumstances can promote a physiological response in your horse that result in undesirable or dangerous behaviours and an increased risk of injury.

Physiological Stress Responses to Trailering

Defecating, sweating, pawing, head swinging, ear pinning, and restless behavior during loading or transit are all signs of stress.

These external signs are often accompanied by the following physiological changes during and after travel: [6][7][8][9]

  • Elevated heart rate
  • Increased breathing rate
  • Increased cortisol levels
  • High lactate caused by muscle activity
  • Oxidative stress
  • High white blood cell count
  • Increased serum creatine kinase activity indicating muscle stress

Some of these signs are outwardly apparent, while others require a blood test to assess. If you notice your horse is sweating profusely, is breathing rapidly, or has a fast heart rate, they are likely stressed.

Health Issues Associated with Trailering

The most common risks of trailering include physical injuries, shipping fever, heat stroke and gastrointestinal problems.

While trailering poses some inherent risks, careful management can minimize negative outcome and their severity.

Physical Injury

Injuries can occur during loading, transit, or unloading, but most horse injuries occur during transit. [8][10]

Injuries may be caused by behaviours or movement of the horse during transit, items in the trailer that are not securely fastened, or transport vehicle accidents due to mechanical failure or collision with another vehicle. [9]

Before beginning a journey with your horse, check the trailer and the hauling vehicle for signs of wear or damage that could cause an accident. [11]

Self-inflicted trailering injuries, such as kicking or rearing, usually occur within the first hour of travel. [5][12] Horses typically become habituated to trailer stressors within the first hour of travel, at which point the risk of injury decreases. [10]

The most common trailer-related injuries are:

  • Scrapes
  • Cuts
  • Bruises
  • Fractures
  • Joint damage

The hindlimbs are the most frequently injured area, followed by the forelimbs and poll, but trailering injuries can affect any part of your horse. [11][13]

In some cases, horses may fully recover from transport-related injuries. One survey found that 3.2% of horses injured during trailer transport had to be euthanized. [13]

It is important to manage horses carefully during transport to minimize the risk of physical injury.

Gastrointestinal Issues

The stress of transportation can lead to gastrointestinal issues such as colic, colitis, and ulcers. One study of Australian horses found that gastrointestinal issues accounted for 27% of cases requiring veterinary attention following transportation. [14]

The risk of gastrointestinal issues is substantially increased in the springtime and on trips longer than 20 hours. Factors such as dehydration, lack of food and water, and diet change upon arrival at the destination increase gastrointestinal complications.

Colic

Colic is a commonly observed gastrointestinal issue associated with transportation.

The combination of stress and dehydration during transportation can decrease blood flow to the gut, and lead to impaction colic of the colon. [14]

When transporting your horse, be vigilant for signs of colic such as pawing, looking at the flank and kicking at the abdomen. Contact a veterinarian immediately if your horse exhibits colic symptoms after being transported.

Colitis

Enterocolitis occurs when harmful bacteria and fungi in the gut proliferate rapidly, causing inflammation and death of tissue of the gastrointestinal tract.

Stress, inadequate food and water intake, dietary changes, and antibiotic or anthelmintic treatments may increase the risk of colitis.[14]

The most common symptoms of enterocolitis are diarrhea and colic. [15] Monitor your horse for changes in behavior and fecal output, and contact a veterinarian if you suspect your horse has colitis.

Ulcers

Ulcers can develop as a result of stress, changes in stomach pH, and changes in gut motility during and after transportation.

The severity of ulcers is greater in horses that more frequently lose their balance, are more reactive, or are more stressed during transportation. [16]

Shipping Fever

Longer transport periods may habituate horses to trailer stressors, but also increase the risk of respiratory issues, including shipping fever. Shipping fever occurs when bacteria and particles from the air get trapped in the mucus that lines the upper airways of the lungs.

Because horses are grazing animals, they are adapted to spending ample time with their heads lowered.

The horse’s airways are lined with small hairs called cilia. When their head is lowered, the cilia push mucus and trapped debris back up the airways. This prevents debris from travelling deeper into the lungs.

Unfortunately, common trailering practices can interfere with a horse’s natural ability to clear her lungs and increase the risk of shipping fever.

Tying a horse’s head during transport inhibits them from lowering their head to clear the mucus from their lungs.

Air Quality

Poor air quality can also contribute to shipping fever. This can arise from:

  • Dust from hay
  • Exhaust from the vehicle
  • Inadequate ventilation in the trailer

Pneumonia

This combination of factors allows bacteria and other irritants to accumulate in the lower parts of the lungs, where they cause infection and pneumonia.

The most common form of pneumonia associated with transportation is called pleuropneumonia, and it is often referred to as shipping fever.

Horses shipped for a short duration are unlikely to develop shipping fever, but the risk increases significantly on trips lasting six or more hours. [17][18][19]

Signs

Signs of shipping fever include:[21]

  • Laboured breathing
  • Wet coughing
  • Elevated heart rate
  • Fever
  • Stiffness and lethargy
  • Depressed mood

Racehorses have a particularly high rate of shipping fever, although the reasons for this are unclear. A genetic predisposition or the combined stress of transport and intense exercise may make them more vulnerable.

While shipping fever is sometimes fatal, horses can recover with treatment. Contact your veterinarian if your horse has recently been trailered for two or more hours and is displaying symptoms of respiratory infection. [20]

If you are planning a long trip with your horse, check their temperature during each stop to detect fever and possible pneumonia early. [1]

Heat Stroke

Temperatures inside the trailer can be 5 – 10oC hotter than outside. During the summer, higher temperatures and humidity leave horses susceptible to heat stroke. [1][22]

Dehydration can occur during transportation because of low water intake, increased energy expenditure, and increased sweating due to stress or exertion.

Dehydration impairs a horse’s ability to sweat to maintain a stable body temperature. Even in comfortable weather, transportation stress can raise the horse’s core temperature and increase the risk of heat stroke. [1][23]

Good ventilation can help reduce the risk of heat stroke because airflow can help to cool the horse during transit.

There are no standards or guidelines for horse trailer ventilation, making it difficult to know if your trailer has sufficient ventilation. [1][22]

Other Risks

Although injuries, shipping fever and heat stroke are some of the most common risks of trailer transportation, there are several other risks to consider:

  • Exposure to infectious diseases during transport with other horses, on layovers, or at the final destination.[23]
  • Shifting to maintain their balance in a moving vehicle can cause muscle strain, resulting in muscle fatigue which can impair performance. [1]
  • Stress-induced diarrhea or weight loss [1][25]

Common Risk Factors

Various elements of trailer transport may increase your horse’s stress level and their likelihood of being injured or developing an illness.

Knowing these factors and how to mitigate them will give your horse the best trailering experience possible.

Inexperienced Drivers

Inexperienced drivers are more likely to rapidly accelerate and decelerate and take turns quickly, making it harder for horses to stay balanced.

More experienced drivers who are familiar with handling horses will have a lower risk of getting in an accident and will be more likely to drive calmly.

Experienced horse transport drivers are also better able to recognize signs of stress in horses and intervene if necessary. [8][11]

If you are learning how to drive a trailer, ensure that you get ample practice without a horse in the trailer.

When you do start hauling horses, always leave a safe following distance, and accelerate, brake, and turn slowly and smoothly.

Driver Fatigue

Sleep deprivation lowers awareness and reaction time, raising the probability of an accident.

If you are taking a long trip, be sure to get plenty of rest before you depart, and plan to stop at least every 4 hours to give yourself and your horse a chance to rest

Bad Weather

Rain, snow, or strong winds can result in poor driving conditions and decreased visibility, increasing the risk of accidents. Check the weather before travelling to avoid dangerous road conditions.

If you are travelling at a warmer time of year, choose a cool time of day or wait for a lower temperature day to minimize the risks of heat stroke in your horse.

Previous Transport Trauma

Horses that have previously been traumatized during transport are more likely to resist loading. If your horse panics during transport, she will have a higher risk of injury.

Make sure to work with your horse before planning a trip to increase their comfort with loading, standing calmly in the trailer, and unloading.

Before travelling with any horse, secure loose objects in the trailer to avoid your horse being spooked or injured during transport.

Analgesics

Horses that are sedated for transport are more likely to lose their balance. Avoid sedating horses before traveling to minimize the risk of slips and falls.

Aggressive Behavior

Shipping horses with a buddy can decrease their stress. However, having multiple horses in a trailer increases the chance of an accident or aggression between horses.

Be sure to transport horses with appropriate companions to minimize aggression and the risk of injury.

Isolation During Travel

Horses shipped alone are more likely to perform stress behaviours such as pawing and kicking.

If your horse will be travelling alone and becomes distressed when separated from other horses, consider hanging a shatter-proof mirror in the trailer.

Research shows that some horses are comforted by seeing a horse in the mirror. [3]

Tying During Transit

Tying a horse’s head in cross-ties is sometimes done to secure a horse in a trailer and prevent them from biting other horses.

However, trying prevents the from lowering her head to clear bacteria and mucus from the lungs, which can result in shipping fever.

It is important to carefully weigh the risks and benefits of tying for each journey. [1]

Dehydration Prior to Travel

Dehydration during transport is common, and horses that are dehydrated before transport can become even more severely dehydrated en route. This can make your horse more susceptible to heat stroke and colic.

Ensure your horse is healthy and well-hydrated before travel to lower the risk of serious adverse reactions. [1]

Always provide your horse with adequate salt in their diet and consider feeding electrolytes to promote water intake on hot days or after exercise.

Poor Footing

Your horse’s risk of slipping is increased during trailering. Avoid applying loose bedding to the floor that your horse may slip on.

Instead, opt for a non-slip rubber mat or dust-free, absorbent bedding. [4]

Trailer Partitions

Trailer partitions prevent horses from biting or fighting in the trailer and may help them stabilize themselves during transport.

However, during an accident or a bout of panic, limbs and tails can easily be hit or caught on the partition, resulting in injury.

Weigh the risks of aggression between horses against the possibility of trailer partition injuries.

Long-Duration Trips

The probability of injury or complication increase as the length of time in the trailer increases. Ensure your horse is healthy before a long trip and ideally give them some experience with short trips first.

Consider having a veterinarian evaluate your horse before you leave for trips that will last longer than a day. Transportation stress may exacerbate preexisting conditions. [1]

During travel, plan to stop every four hours to allow your horse to urinate, eat, and drink.

Horses urinate approximately six times per day and it is difficult for them to assume a position to urinate while maintaining balance in a moving trailer. Stopping gives your horse a chance to comfortably urinate.

You should leave your horse in the trailer during stops to avoid the stress of unloading and reloading. [1][11][23]

Performance horses travelling for three or more hours should arrive at their destination several hours before their competition to allow muscles to recover and reset their stress level. [12]

8 Tips to Reduce Trailer Stress

You can support your horse’s welfare while trailering by following these seven feeding and management practices.

1) Training

Training your horse to load and stand relaxed in the trailer is critical to transporting them safely. There are many different training methods you can research.

The goal of any training program should be to desensitize your horse to the unfamiliar sounds and sensations that they will experience in transit and to make them comfortable with being trailered. [27]

2) Hydration

Horses should have unlimited access to fresh, clean water, especially leading up to a trip. Ensure your horse is well-hydrated before departure to reduce the risk of dehydration and heat stroke.

Add 1-2 tablespoons of salt to your horse’s feed every day and provide free-choice plain salt. Consider adding an electrolyte supplement to their feed or water. [23]

Water may taste different when you are travelling to new regions. If your horse is hesitant to drink when travelling, additives such as apple or peppermint flavouring can encourage water intake. [28]

However, not all horses like the smell or taste of additives. Get your horse used to the flavour of your electrolytes before travelling.

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3) Soaking Hay

Provide soaked hay in the trailer to improve hydration and reduce dust inhalation.

Ideally, hay should be placed on the ground to encourage low, natural head carriage and limit the risk of shipping fever.

Alternatively, use low-hanging hay bags with small holes that your horse cannot get tangled in.

4) Orientation

Horses have better balance if they are not facing directly forward in the trailer. Some horses may balance better facing away from the direction of travel (backwards) or at an angle to the direction of travel.

Depending on your trailer design, consider loading your horse backwards or at an angle to make it easier for them to balance during transport. [29][30][31]

5) Bandages and Protectors

Boots, leg bandages, tail bandages, and poll protectors are generally safe during transport. However, studies show these devices may not protect them from injury during transport. [13]

6) Gut Health

Gastrointestinal issues are one of the most commonly observed health complications following transportation. Horses that are trailered experience higher rates of ulcers and hindgut issues.

Feed a gut health supplement that targets the foregut and hindgut. Ingredients such as probiotics, yeast, immune nucleotides, and lecithin can be beneficial.

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7) Antioxidants

Your horse may also benefit from additional anti-inflammatory and antioxidant support to minimize muscle damage and the risk of infection.

Organic trace minerals and vitamin E support your horse’s antioxidant capacity to protect muscles from oxidative stress associated with trailer transportation. [9][14]

Oils that are high in the omega-3 fatty acid DHA may also decrease inflammation to support muscle recovery.

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8) Balanced Diet

Considering the stress of trailering, ensure that your horse is healthy before your trip. Provide a balanced diet and adequate veterinary care to maintain your horse’s well-being.

All horses benefit from a forage-based diet with hay or pasture that matches their physiological needs.

Your horse’s diet should allow appropriate free-choice forage intake to support gut health and expression of foraging behaviours without affecting body condition.

Performance horses may require additional calories beyond what they can obtain from forages. Highly digestible fibre sources such as beet pulp or soy hulls are suitable, cost-effective options. Adding oil, rice bran and/or ground flax can also effectively increase the calorie density of the diet.

Horses on a forage-only diet will typically not meet their vitamin and mineral requirements, which can increase the risk of illness and disease.

All horses should receive a comprehensive vitamin and mineral supplement to balance the diet, avoid deficivies and support optimal health.

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Consult with an equine nutritionist to develop a feeding program that supports performance while minimizing the negative effects of trailer stress.

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Identify gaps in your horse's nutrition program to optimize their well-being.

References

  1. Padalino, B. et al. A survey on transport management practices associated with injuries and health problems in horses. PLoS One. 2016.
  2. Houpt, K. Stable Vices and Trailer Problems. Veterinary Clinics of North America: Equine Practice. 1986.
  3. Kay, R. et al. The use of a mirror reduces isolation stress in horses being transported by trailer. Appl Anim Behav Sci. 2009.
  4. Riley, C. B. et al. Horse injury during non-commercial transport: findings from researcher-assisted intercept surveys at southeastern Australian equestrian events. Animals (Basel). 2016.
  5. Padalino, B. et al. Risk factors in equine transport-related health problems: a survey of the Australian equine industry. Equine Vet J. 2017.
  6. Stull, C. L. Responses of horses to trailer design, duration, and floor area during commercial transportation to slaughter. J Anim Sci. 1999.
  7. Padalino, B. Effects of the different transport phases on equine health status, behavior, and welfare: a review. J Vet Behav. 2015a.
  8. Yorke, A. et al. How to minimise the incidence of transport-related problem behaviours in horses: a review. J Equine Sci. 2017.
  9. Latham, C. M. et al. Complexed trace mineral supplementation alters antioxidant activities and expression in response to trailer stress in yearling horses in training. Sci Rep. 2021.
  10. Hall, C. et al. A retrospective survey of factors affecting the risk of incidents and equine injury during non-commercial transportation by road in the United Kingdom. Animals (Basel). 2020.
  11. Padalino, B. et al. A survey-based investigation of human factors associated with transport related injuries in horses. Front Vet Sci. 2018a.
  12. Tateo, A. et al. Transport stress in horses: effects of two different distances. J Vet Behav. 2012.
  13. Riley, C. B. et al. A survey-based analysis of injuries to horses associated with transport by road in New Zealand. Animals (Basel). 2022.
  14. Padalino, B. et al. Health Problems and Risk Factors Associated with Long Haul Transport of Horses in Australia. Animals. 2015b.
  15. Uzal, F. A. et al. Bacterial and viral enterocolitis in horses: a review.J. Vet. Diagn. 2022.
  16. Padalino, B. et al. Effects of transport conditions on behavioural and physiological responses of horses. Animals (Basel). 2020.
  17. Racklyeft, D. J. et al. Influence of head posture on the respiratory tract of healthy horses. Aust Vet J. 1990.
  18. Raidal, S. L. et al. Inflammation and increased numbers of bacteria in the lower respiratory tract of horses within 6 to 12 hours of confinement with the head elevated. Aust Vet J. 1995.
  19. Raidal, S. L. et al. Effect of transportation on lower respiratory tract contamination and peripheral blood neutrophil function. Aust Vet J. 1997.
  20. Racklyeft, D. J. et al. Towards an understanding of equine pleuropneumonia: factors relevant for control. Aust Vet J. 2008.
  21. Leadon, D. P. Transport stress and the equine athlete. Equine Vet Educ. 1995.
  22. Purswell, S. et al. Air exchange rate in a horse trailer during transport. Trans ASABE. 2006.
  23. Weeks, C. A. et al. Welfare issues related to transport and handling of both trained and unhandled horses and ponies. Equine Vet Educ. 2011.
  24. Boden, L. S. et al. An online survey of horse-owners in Great Britain. BMC Vet Res. 2013.
  25. Stull, C. L. Responses of horses to trailer design, duration, and floor area during commercial transportation to slaughter. J Anim Sci. 1999.
  26. Knowles, T. G. et al. The response of untamed (unbroken) ponies to conditions of road transport. Anim Welf. 2010.
  27. Shanahan, S. et al. Trailer loading stress in horses: behavioral and physiological effects of nonaversive training (TTEAM). J Appl Anim Welf Sci. 2003.
  28. Mars, L. A. et al. Water acceptance and intake in horses under shipping stress. J Equine Vet Sci. 1992.
  29. Waran, N. K. et al. Effects of transporting horses facing either forwards or backwards on their behaviour and heart rate. Vet Rec. 1996.
  30. Gibbs, A. E. et al. Horse preference for orientation during transport and the effect of orientation on balancing ability. Appl Anim Behav Sci. 1999.
  31. Clark, D. K. et al. The effect of orientation during trailer transport on heart rate, cortisol and balance in horses. Appl Anim Behav Sci. 1993.