|...the ultimate source for horse enthusiasts|
Your goal when loading a scared horse is not to get him into the trailer, but rather to show him that he has nothing to fear from the horse trailer. This is a very important distinction to make, and actually runs contrary to the natural instincts of may horsemen. As humans we tend to be linear and results-oriented; success is defined by the horse entering the trailer and anything less is failure. Put this type of thinking out of your head – a successful session with a nervous horse might result in the horse not loading onto the horse trailer.
Obviously given the above, it's best to train a nervous horse to load onto a horse trailer long before you actually need to transport him anywhere. If you wait until the "moment of truth" to expose your horse to something he fears, you have failed him.
Establishing a bond of trust between you and your horse is a huge benefit for you both. Remember that when horses become frightened they look towards the herd leader to lend them strength and guidance. If you have already established yourself as a trustworthy and loved leader, your horse will react far less strongly to the object of his fears than he would otherwise.
The next key to keep in mind is that you should always take things slow. Don't just try and bully your horse into the trailer – allow for prolonged sessions such that when your horse finally loads the trailer, he did so because he wanted to rather than because he was forced to.
If your horse hesitates or jerks away from the horse trailer, let him. This is contrary to what many horse owners do – they think allowing the horse to shy from the trailer will actually make the horse worse. They want to dominate the horse until they win the battle of wills.
This would be a correct approach (sorta) if your horse was being defiant, but if your horse is actually afraid of the request or the trailer then this would be the worst thing you could do. You wouldn't toss a person afraid of water into the middle of a raging river, would you? Because if you did the victim might get over his fear, but it's more likely that he'll instead drown or become even more traumatized.
In other words, do not meet fear with force! When your horse jerks away from the horse trailer he's telling you that he's not ready for your request yet. Give him the time he needs to gain confidence.
Now that we have the basic ground rules laid out for loading a scared horse into a trailer, let's move on to Part 2 of Horse Trailers: Loading A Nervous Horse.