This wasn't mentioned but with behavior that extreme...could he have been a cryptorchid? Did anyone check? could you even check if he was that bad? A few years back, We were given a weanling jack (who we had full intentions of gelding) he was a sweet boy, did his job of guarding the goats very well but he never 'developed' He was always seperated him from our mares (didn't want any possibility of mules on our good broodmares!) and when we realized he just wasn't going to drop we found a new home for him to protect cattle without any horses or other donkeys around (I wasn't wanting to spend the $600+ on a free donkey to have him gelded surgically when his only purpose was livestock protection.)
Having had a crypt horse colt, I do know that it can completely change their behavior, they're in pain. They get aggressive, they do things that normal studs will do but they do it amped up x10! My sweet imprinted well mannered foal, who is now my sweet easy to handle 9 yr old gelding, was becoming an absolute terror during the 3 months it took me to find the right vet. We usually geld as soon as they are developed as yearlings and start to get worked up over the ladies, I brought him to the vet and oops...discovered he only had one. I immediately started researching a vet, and he slowly got worse. By the time I hauled him to the vet, I was embarrassed to unload him he was so uncontrollable. The ladies at the vet office said he wasn't the worse they had seen, in fact they said he was great for them and they could tell I had put the training into him (he stayed at vets for 2 weeks because we had damage from a hurricane and no roof on my barn) but having never experienced this before and always having well mannered horses I was appalled by his behavior. My horses just don't charge and bite and act goofy like that. They don't try to pull my arm out of my socket coming out of the trailer, and they definitely don't turn and try to kick the vet tech. I don't allow things like that but there was no stopping him til after the surgery! He was still a little rough for a few weeks after I brought him home but it was different, his manner was different, he didn't have a sour face and I think most of that was because he was confined so much with only hand walking and then eventually very limited turnout so that he would heal. He was pure energy bursting at the seams. When he finally was cleared for turnout I almost had a heart attack when he went to performing aerial acts of supernatural proportions!
By the time he worked all that energy out, he was back to being my sweet boy. Now don't get me wrong, he's still a forceful personality, and in the pasture he is the boss, even over the donkey, but I'd have hated to see what he'd have been like as a 2 yr old cryptorchid colt!
