Instructions
Give the horse time to acclimate itself to the trailer and get comfortable with entering it. Plan to get the horse into the trailer at least half an hour before you need to move it. Rushing a horse or urging it on too quickly can make it skiddish and resistant to get into the trailer.
Show the horse that the trailer is a safe place. If possible, leave the trailer in the horse's lot with the doors open on occasion. Place a salt lick or treat in the trailer so the horse can explore the trailer on its own terms and recognize it as nonthreatening. Entering the trailer first and leading the horse can work for larger trailers, but be careful if your horse is spooked or especially nervous.
Stay calm and resist the temptation to crop the horse or yell. Maintain close proximity to the horse and pat it on the neck or haunches to reassure it and calm the horse down. Let the horse step back from the trailer if it wishes, but stay close and soothe the horse as best you can.
Place blinds on the horse and, using a short lead rope, guide the horse into the trailer. This will not work for all horses, but it can limit the horse's fears and keep his focus on your commands.
Consult a professional horse trainer for tips or private lessons to get your horse prepared for the trailer. If the horse has been injured in a trailer accident, it may take a professional to break it of its nervousness.
How to Get an Unwilling Horse Into a Trailer
If you are a horse owner, it's frequently necessary to get your horse into a trailer for travel, trips to the veterinarian or out-of-town shows. No matter how well-trained your horse, though, sometimes it is a battle of wills. Horses naturally do not like enclosed or constricting spaces, so you must overcome a horse's instincts to get it into the trailer. An unwilling horse can be convinced, however, with patience and reassurance.