Donkey hurting Miniature Horse

Question
Hi, I have a 1year old gelded Miniature Donkey and a 5month old Miniature Horse (female). My Donkey bites at her back legs and pushes her all the time. He will also do this if I have the horse on a lead. If I move him to a separate fenced area so I can work with my horse, he runs, calls and tries to jump the fence, even though he can still see her. Will he always do this and how can I stop this behavior? Thanks so much, Debbie

Answer
Hi Debbie,
              Your donkey is displaying all the behaviors of a Jack. It sounds as though when he was gelded that they did not get everything. Have your vet pull some blood and have his testosterone level tested. If his levels are high then they should be, you may have to get him regelded. For now, you should continue to keep them separated as he can severely hurt her.

Lisa