Donkeys who eat mostly cut hay can get sharp edges on their teeth, causing them to get cuts in their mouths. We asked our vet about ways to avoid the sharp edges. He said that they get the sharp edges from cut hay because this feed causes them to chew up and down with their jaw so the sharp edges don't wear down. But, he said, if they eat living plants -- such as by being in a pasture or in the wild — their mouths chew in more of a circular, grinding way. This keeps the sharp edges worn down. He said we'll know they need their teeth "floated" (filed down) if they start "dropping their feed" (having it fall out of their mouths) or if we see blood in their mouths. He said they sedate them standing up and then file down the teeth. So the best prevention is simply to pasture the donkeys where they've got good plants, shrubs and trees to tug on and chew. (Be careful that there's nothing bad for them in the pasture.)