Using a CD hunting on horses!!!

I started my catchdog about 2 months ago. i snap a leash to a collar around the tree, i am using a shock collar to speed things up and for when the dog might try to nip at the horse. the dog every now and then trys to go under the horse, around the legs, and up and under the head of the horse. all in all has worked out allright for me. i took a buddy huntin the other night and had a small rodeo. i got off my horse and asked this feller to hold him while i tracked my dogs, he said ok. so i walked to the four wheeler and started trackin. i looked back and seen that the bulldog had went under the horse, but since they were just standing there and no one was horseback i thought to myself it will be allright. well i turned my back to them and in a second i heard the horse blowin hard. i turned and seen the horse buckin, but the bulldog leash had gotten around the back leg on the horse. the leash held for the first kick but the second it broke. i finally got everything settled down. well come to find out this city boy tried to get on my horse, needsless to say i was none to happy. but all in all came out with a few sratchs, a broke collar, and a city boy who knows not to get on somebody elses horse.