When I give attention to another horse, my horse will pin his ears, lunge at, bite, and kick the other horse. And it's not just while I'm paying attention to the other horse that he does it. He will actually keep doing it for several days. Once he kept it up for several weeks. If given the chance, he would seriously hurt the other horse.
Does anyone have advice about how I can minimize or stop his behavior?
For info, my horse is a 17-18 yr old OTTB Gelding. I've only had him for 3 yrs.