I kind of want a horse so I can try this, dogs kind of don't stay still once they get into a situation of an orgasm they want to go into a humping motion and the dogs I do own are fixed meaning they can't get an erection. But my experience with giving a dog an orgasm I know they kind of having involuntary humping making it harder to stay still, but horses have devices like a breeding mount and a thing that humans can manually stimulate the horse. Horses also have a similar penis to a human, and even when stations get used for breeding breeders usually do it twice a day. But would it truly be abusive to do it to an animal until they got nothing left?