Originally Posted by tsaleska
Why do horses do the biting thing... is it dominance or what??? Dumb question I know... but the problem is I don't know.....
Dominance has some to do with it, yes.
Dominant animals will bite others that are lower on the totem pole if they are too close to their personal space, are eating out of turn or are overall just seen as a bother. My mares do it to my gelding all the time for seemingly no reason.
Your best bet is to NEVER let him get away with it. I don't really like crops, but in this case, it may be a wise idea to keep one, but I really suggest training rather than just smacking an animal. I don't know much about donkeys, so I really couldn't give you much advice on training him, but I would definitely geld him.
Also, worming is as easy as holding the horses nose down with one hand, as if you were bridling, and then sticking the tube in the corner of the mouth and squirting the paste in :)