Originally Posted by smrobs
Another method to use is to make away from the trailer a place where he doesn't want to be. Lead him toward the trailer and the instant that he refuses, put him to work. Lunge him back and forth between you and the trailer, lots of direction changes, make him breath hard. When he's sucking a bit of air and is focused on you, lead him toward the trailer again. So long as he is looking/investigating or coming forward just let him come and keep lightly encouraging him. If he is obviously scared and he wants to stop and look, give him plenty of time to do that, so long as he doesn't move away. The instant that he backs up or moves away from the trailer, put him to work again. Repetition will make him realize that being on the ramp or in the trailer is where he gets to rest and away from the trailer means he has to work. He should be loading up in no time.
^ this is what I would impliment... make the right thing easy, the wrong thing difficult. In this way, you are also making loading into the trailer 'his' idea, since he will want to be in there after a while of having to work outside of it.
I don't like tactics that "pull" a horse into the trailer (using a long line around the butt), simply because if your horse is one of those that DOES decide to put up a fight, you could both be seriously hurt before you can even think about releasing the rope all the way.
Bribery usually will not work with a horse since he can simply choose not to eat; they are not so easily food motivated like dogs. Even when they are hungry, if they don't feel 'safe' with a situation, they will not eat...they are prey animals, so that makes them alot different than dogs; predators will usually eat at any time, a prey animal will forgo food, for safety if he has to. Something to think about, when using food, or "lack of food" to motivate a horse into any situation.