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Equine September/October 2007 (Vol 2, No 5)

Understanding Behavior: "Transportation-Related Behavior Problems in Horses"

by Sharon L. Crowell-Davis, DVM, PhD, DACVB

    Although the current horse-show season will soon be over and it may seem too soon to start preparing for the next season, now is the time to begin preparing horses to be comfortable when they are transported in trailers and vans. As any visit to a stable, show ground, or parking lot of an equine veterinary hospital will confirm, the fear of entering a trailer or van is an extremely common problem among horses. This is unfortunate because this problem can be easily prevented or treated if the time is taken to properly train the horse.


    The first and most important thing to remember is that it is not natural for horses to walk up a ramp into a small, enclosed "box" and then cope with the inertial forces generated as a trailer or van accelerates and decelerates. Ideally, naive horses should be gradually habituated to trailers: first to seeing them, then to entering them, and, finally, to standing in them while they are moving. This is most easily accomplished with foals, especially if the mother has been trained to comfortably enter trailers or vans. If the mother is led in and begins quietly eating some food placed in the front of the vehicle, the foal may hesitate but will soon follow. If a weanling or yearling is being trained, it should be led close to the vehicle, but not right up to it, and given treats (e.g., apple slices or carrots) while standing calmly near the vehicle. Without a signal from its mother that the vehicle is safe, a weanling or yearling may require several visits to the vehicle before becoming comfortable walking all the way up to it, sniffing it, and touching it with its nose or hoof. Offering highly palatable food at the vehicle entrance can facilitate development of the idea that the vehicle is a "good" place.

    Although it may be very tempting to force the horse close to the vehicle and even into it, this urge should be resisted. While short-term success may be achieved (i.e., the horse goes into the trailer), this is a counterproductive approach in the long term. Association of the vehicle with forceful handling, yelling, whipping, and other aversive stimuli will increase the horse's fear of trailers and vans. Time and patience during the early stages of training can be beneficial in the long term. The number of sessions needed to get a young horse to walk up to a trailer or van and eat food placed at the entrance varies widely, depending on the temperament of the horse.

    Once a naive horse is comfortable being around a trailer or van, the next step is to get it to step inside. This process has multiple phases and, therefore, is likely to require multiple sessions.

    Clicker Training

    Clicker training can be beneficial in training many horses. In this method of training, the sound of a click is associated with immediate presentation of a highly palatable treat. In time, the click becomes a secondary reinforcer, facilitating exact timing of reinforcement for desired behaviors. In the early phases of training, the treat always follows the click as soon as possible. As a horse progresses in its training, the frequency of the treats gradually becomes more sporadic so that the horse cannot predict when a click will be followed by a treat. This form of reinforcement, called variable ratio reinforcement, produces very strong and persistent responses when done correctly.

    Target Training

    Once a horse is clicker trained, it can be target trained without a trailer or van. Commonly used targets in horse training include paper plates with a vivid bull's eye painted on them or dowels with a ball on the end. Initially, the horse is reinforced for touching the target with its nose. Then the target is steadily moved, and the horse learns that it will be reinforced if it follows the target or a series of targets and touches them with its nose. Once the horse has mastered following a target, the target can be used to lead the horse into a vehicle. However, it is important to know that the target must be moved more slowly and for shorter distances to give the horse time to adapt to the major change of walking on the unusual surfaces of the ramp and vehicle and into a small, enclosed space.

    Acclimation to the Vehicle

    When the horse has entered the vehicle for the first time, the back door should be secured while the horse experiences being in the vehicle and explores it through sight, smell, sound, and touch. To associate being in the vehicle with a pleasant experience, the trainer should offer the horse highly palatable food, and the first session in the trailer should last only 1 or 2 minutes. Over subsequent days, the length of time the horse stays in the vehicle should be gradually extended.

    The horse also needs to master the skill of exiting the vehicle comfortably and smoothly. It is important to remember that the horse is moving backward and is not yet familiar with stepping down. While some horses rush out of the trailer, many are hesitant. It is important to be patient while the horse determines how to best step backward and down, and the horse should be rewarded with treats and praise once it has successfully exited. This session should conclude by allowing the horse another look into the "cave" that it has just experienced.

    While initial sessions may be done with a stand-alone trailer (i.e., unattached to a truck), the last training sessions before beginning exposure to a moving trailer should be conducted with the trailer hitched to a truck. This allows the horse to see the truck and experience the slightly different way that the trailer floor moves when it is hitched rather than free-standing or on blocks. If the horse is likely to be transported in a variety of types of vehicles, it is best to expose the horse to as many types of vehicles as feasible during the early training period. Once the horse calmly stands and eats for 15 to 20 minutes, the process of becoming familiar with a moving trailer can begin.

    Transporting the Horse

    A common mistake made by people who are only interested in riding and showing horses is to take the horse on its first ride in a vehicle when it has to be driven 1 hour or more to a show ground, where it undergoes a variety of novel and sometimes frightening experiences. This approach is likely to result in a horse that does not want to go into vehicles because they are predictive of stress and excessive novelty. Instead, a horse's first ride should be only a few minutes and very smooth, with the driver remembering that the horse has to learn how to balance and stand on a floor that accelerates and decelerates. After a short drive, the horse should be returned to its home, given a treat, and allowed free time in a familiar paddock or pasture. In this way, rides will become predictive of pleasant consequences. By ending frequent, short rides in pleasant, familiar surroundings, the owner will teach the horse to be comfortable with the vehicle.

    Trailer Phobia

    The following experiences can cause horses to become trailer phobic through the process of classical conditioning:

    • Being forced into a vehicle with ropes and whipping
    • Being taken on long, exhausting trips for which the horse has not been prepared
    • Riding in a trailer with mechanical problems that cause excessive shaking or noise
    • Being in an accident
    • Riding in a trailer pulled by a thoughtless driver who accelerates and brakes rapidly and switches lanes frequently
    • Any other experience that causes the horse to associate vehicles with fear- and pain-inducing stimuli

    Horses that have become trailer phobic can be rehabilitated using techniques almost identical to those used in familiarizing a naive horse with vehicles, but the process takes much longer.

    If a horse has had a strongly aversive experience with a particular vehicle, it may be easiest, in the long term, to change the vehicle in which the horse will be transported, even if this means selling a current trailer and buying a different one. If the vehicle will be replaced, the following issues regarding the horse's comfort should be carefully considered:

    • The size of the trailer or van (width, length, height)
    • The padding and sturdiness of the floor
    • The sounds that are created when walking in the vehicle
    • Adequate shock absorption
    • Appropriate ventilation to ensure that fresh air enters at a reasonable rate and that exhaust from the towing vehicle does not enter the trailer

    Some horses that have become very trailer phobic will be more comfortable in and accepting of vans, or vice versa.

    If the horse has developed a very strong phobia of vehicles, it may be necessary to medicate the horse before it is transported. If the horse is a show horse, the handler and veterinarian need to know which medications are not allowed for the particular competition in which the horse is involved. If anxiolytics are not allowed, the horse must be rehabilitated during the off season, and sufficient time must be allowed for the medication to be completely eliminated from the horse's body before competition is resumed. Selective serotonin reuptake inhibitors (SSRIs) provide good anxiety control with less sedation than benzodiazepines, but because they have very long half-lives, several weeks are required for SSRIs and their metabolites to be eliminated from the body. Currently, fluoxetine is one of the most economical SSRIs on the market; it is given at a dose of 0.25 to 0.5 mg/kg q24h and can be readily consumed when mixed with the horse's grain. Fluoxetine may require 4 to 6 weeks of administration before full efficacy is achieved. A benzodiazepine, such as diazepam (10 to 30 mg), given 30 to 60 minutes before a treatment session can also alleviate anxiety and may be useful during the early phase of treatment. While antipsychotics, such as acepromazine, may tranquilize the horse sufficiently to facilitate getting it into a vehicle, they are not good anxiolytics and, therefore, are unsuitable for long-term resolution of a problem.

    Systematic desensitization and counterconditioning may be necessary for severely trailer-phobic horses. In desensitization, the horse is exposed to the fear-inducing stimulus, but at such a low level that fear is not induced. During repeated treatment sessions, the intensity of the stimulus is slowly and gradually increased, ideally at a pace that never induces fear. Desensitization generally proceeds more rapidly if it is paired with counterconditioning, in which a response that is behaviorally, physiologically, and emotionally incompatible with the undesired (fear) response is induced. For most animals, including horses, highly palatable food is a good counterconditioner. For some horses, food is not very motivating, so other responses, such as a relaxation response generated by massage or gentle currying, are more useful. As with training a naive horse, clicker training may be useful with trailer-phobic horses. Individual treatment sessions should be short (i.e., 5 to 30 minutes), depending on the horse. The goal is to keep the horse relaxed or focused on the treats while gradually increasing the intensity of exposure to and interaction with the vehicle. The horse must never be forced inside the vehicle.


    Entering and standing in a vehicle is not a natural behavior for horses. Learning to calmly enter, ride in, and exit a vehicle is a critical part of routine horse training that is as important as teaching a horse to respond to pressure applied by a bit or heel. When horses are properly trained to enter and ride in vehicles, traveling can be easy and stress free for the horse and owner.

    See the Key Points box.

    Crowell-Davis SL, Murray T: Veterinary Psychopharmacology. Ames, IA, Blackwell Publishing, 2006.

    Downloadable PDF

    *Dr. Crowell-Davis discloses that she has received financial support from CEVA Animal Health and Merial.

    NEXT: Abstract Thoughts—Immunocompetency: The Long and Winding Road


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