Originally Posted by Spirithorse
Your horse has a very strong herding instinct. Horses that have a lot of 'cow' usually show this behavior. It's also a very dominant behavior. It's just who he is, so the best thing to do is to keep small animals away from him as best you can. Because he's so young, he's coming into his own, which is why this behavior is pretty new.
Agree... I have one of these at home. He's now 17 and for his entire life if a dog, cat, deer or even a bunny came into his pasture or paddock the chase was on.
I've watched him in the pasture when a deer comes over the fence. He'll turn so he can keep an eye on them and wait ..... once they are close enough off he goes hell bent for leather after it.