My son just bought a bull calf recently that is "green" broke. He has been trying to get him ready for our fair and the bull was doing well. He's calm, has been washed and clipped on with no problems. The problem is that he has just learned how to quickly duck his head and gets loose. Any one know how to stop this? The calf is a 7 month old simi and my son is a pretty stout 15 yr old.