Thanks for the great input, everyone! A mechanical cow would be a great option and I'll consider it, but it's out of question right now due to financial reasons. We don't have goats, but we have a dog, which Snickers tried cutting just last evening. And we have a filly, which has also been cut one time, when she was trying to escape the arena and Snickers went to the rescue. For now, I love the idea to train with another horse&rider - I have a friend who might be interested. Also, I will maybe try to find someone who will mimic the run-stop-rollback-turn-run move, so I can trot Snickers along this pattern. Gotta give it a try, he sure seems to enjoy such activities. :)
I have come a long way, to surrender my shadow to the shadow of my horse.