This is a free online study program by Dr. Andy K. McLean explaining the anatomy of the donkey and some work on mules.
Excellent program explaining the differences between donkeys, mules and horses. Dr. McLean, DVM explains clearly why we must be so very careful with feeding our donkeys and mules to ensure they are not obese. Ensure we do not cut feed back to fast, small meals. She explains the body temperature, vitals, how to give pain medication compared to a horse.
Most importantly she explains how efficient the donkey and mule is with food. She explains the body scoring, physical anatomy differences and much, much more. Absolutely the best medical information I have found to date.