You should definitely take the advice of the people who posted before me. I have a Newfoundland, Golden Retriever, German Shepherd mix (aka a big dog) who was taught to do that. He digs his nails into my thigh every time I get near him if he's sitting directally in front of me. And not only does he do it, but a few of our Border Collies who were never taught to picked up on it. Dx I imagine with a horse it would be even more dangerous. Especially if your horse starts doing it wanting treats or attention.