Anatomical Differences of the Donkey and Mule

The donkey is not just a smaller, inferior type of horse. To those who have taken the time to get to know him, the donkey is a unique equine of special qualities. Yet he is an evolutionary relative of the horse and so will forever be compared with the horse. The mule, however, is still a scientific enigma. The mule has been described as the animal without “pride of ancestry, nor hope of posterity” or, by the muleskinners, as “900 lbs of free enterprise” (Fig. 1). Very little of what is known about the mule comes from scientific research. Folklore and muleskinners teach us that a mule is a creature of habit; that mules enjoy a good roll at the end of the day’s work, and that mules recover from a hard day’s work faster than a horse. Muleskinners were men who understood mule behavior and learned to work around their peculiarities without injury. Although their knowledge of mules may not be based on scientific research, we can still benefit from their wisdom. Veterinarians that work around mules need to be wary because mules are very agile; a mule can strike with any other hoof even if a man is holding one up. Veterinarians need to be patient and work quietly and gently around a mule, but they need to work with purpose and conviction. For the veterinarian working on mules, it is not only important to be a good horseman but also to know the ways of a good muleskinner. Because mules vary so much in genetic makeup, they do not make good subjects for research; therefore, for scientific data, we rely on studies of the donkey. What do we know about donkeys and how do they differ from horses? A donkey brays and has long ears, but those are not the only differences. He has a completely different outlook on life, drinks water differently, reacts to frightening situations differently, has very different nutrient requirements, and has unique physiological responses. Many common rules of horse management are detrimental to the donkey. For instance, the normal ration for a horse will make a donkey obese, possibly cause him to founder, and may result in decreased fertility. The horse dosage interval of penicillin does not produce therapeutic blood levels in the donkey. Castrating the donkey or mule by the routine method used in horses, without ligation, may result in such excessive bleeding, and some have died as a result (Fig. 2). It is the purpose of this session, therefore, to demonstrate ways that donkeys and mules differ from horses as far as we know it at this time. Donkeys and mules are exceptionally revered by their owners, and in recent years, in some parts of the world, their value has increased to equal or