My Stallion has a weird habit please help?

Degraeo is my 6 year old Thoroughbred stallion since he was born he had a weird habit of chasing his tail..funny i know.i thought he had grown out of it, but last week when i went out to his pasture he was doing it again, just around and around in circles.please help.also do u think it will be transferred into his progency?how can i stop him doing it, hes worser than my kelpie dog.

Would he be friendly towards a companion animal, like a goat for instance? Or a miniature donkey gelding, even? Sounds to me like he does this when he's bored. Highly intelligent animals with sensitive nervous systems need to be kept busy or they will get themselves into trouble.