Understand that treats are not the most effect way to reward your horse. Horses are creatures of habit and instinct. They do not posses any logical thinking abilities. They can not understand cause and effect. Any reward given for performing a task or exhibiting a desired behavior must occur immediately at the time of the desired action. For example, if you stopped your horse and gave him a carrot every time he jumped a fence nicely, he could not associate the way he jumped the fence with carrot. He would however, develop the habit of stopping after every jump and looking for a carrot, regardless of whether he jumped well or not. He may even start stopping and looking for treats when you are not even jumping. What he does understand is that when he jumps correctly you don't get off balance and jerk on his mouth. The reward is that it physically feels good when he jumps correctly. He knows that he has jumped correctly when you stroke his neck immediately upon the landing. By the time you bring him to a halt, he will not associate anything else with that jump. The same immediacy is essential for effective correction or punishment also. If a treat is consistently given as a reward for any desired behavior, the horse will eventually become more focused on the reward than on performing the desired behavior or task you are asking him to do.
There are many good ways to use treats in your training. One example is when teaching a horse to load in the trailer. In this position, being over-focused on a treat is not necessarily a bad thing. You are also asking him to do something that is completely against of his natural instincts (be alone and confined). Most importantly, the reward comes immediately after the desired behavior. And there is no reason he can't be rewarded with a treat every time he performs this command, especially since most horses will have a nice full hay bag to munch on when the treat is gone.
Treats can be useful when introducing your horse to any strange, unfamiliar object such as walking over a bridge or tarp. Instead of pulling and pushing and hitting to make you horse step up on the obstacle, try putting a small amount of grain or other treat on it and wait--eventually his desire for the treat will probably win over his fear of the obstacle. The lowering of his head and chewing action will also help him relax.
