Hoof Neglect: A donkey's hooves should be trimmed every 10-12 weeks using the proper equipment (consult a ferrier rather than trying it yourself). If there is a curvature (upward or downward) to the hoof, this means they are too long. This makes it difficult and painful for the donkey to walk. Likewise, a donkey's hooves can be trimmed too short, making it very uncomfortable to support all of their weight.
Weight: Donkeys grow fat in pockets (a little bit like cellulite). It is alright for a donkey to have a few pockets, however, excessive weight is not healthy. Again, likewise, a donkey should not be malnourished (are the hip bones and shoulders prominent?). Healthy weights for donkeys are as follows.
Miniature: 200 lbs - 350 lbs
Standard: 400 lbs - 700 lbs
Mammoth: 900 lbs - 1400 lbs
Founder: By eating too many rich grains, a donkey can develop a condition called founder. This means that the insides of the legs and hooves are growing in an incorrect and painful way. If you notice a donkey's gait is stilted, uneven, or very slow, consult a veterinarian as soon as possible. If you are aware of a problem with the donkey's legs and do not consult a vet, this is neglect.
Teeth: A donkey's teeth need regular attention from a veterinarian. They are continuously growing, and therefore it is easy for them to grow improperly. If a donkey seems to be favouring one side of his mouth, this could mean there is a dental issue (teeth should not be left to grow uneven or too sharply - sharp teeth require floating as they can lead to cuts or other mouth discomforts - consult your veterinarian). It is difficult to tell if there is a problem, so it is a good idea to make sure your regular vet checkups include the teeth!