I have a young jersey bull losing hair down the back. I have seen it on necks from hay rings but never on a cows whole back, this goes almost to his tail. Havent seen him jump through the ring. Any idea if there would be another cause. 2 things different in the last 2 weeks. I sprayed fly spray on all my cattle 2 weeks ago, and I put a new hiefer I just bought a week ago with this jersey and the heifer he was already with.