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October 24, 2007

Anatomical Differences in Donkeys

We all know the differences between donkeys and horses by sight. But, the differences that are easily seen, like ears, are not the only differences to be aware of.

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Donkeys have a short, upright mane, usually no forelock and a broomstick kind of tail. Donkeys are not just a “poor man’s” horse. A donkey reacts totally differently than a horse, has a different outlook on life, and different nutritional requirements. For those of us who are familiar with donkeys, we understand that they are a smart, affectionate, unique equine, well worthy of their own respect and appreciation. Obviously, some training methods commonly used for horses won’t work very well for donkeys. That will be another article. For now, let’s just cover some of the major anatomical differences we have in our donkeys.

One of the biggest concerns with donkeys is castration. A normal castration of a horse, the vet clamps the blood vessels until the bleeding stops. Then, he allows the incision site to stay open and drain. Unfortunately, donkeys seem to bleed more than horses, and some can be heavy bleeders. It is recommended that the vet use ligation (this is when the vet places a stitch in the blood vessel to help stop bleeding) in donkeys when castrating. If your vet isn’t aware of the differences in donkeys, a frank discussion with him/her before scheduling the surgery is in order. There are some places that you can find reference materials on the internet that you can print copies of and give to your vet (a few reference sites will be listed at the end of this article). Occasionally, a vet will not take what your saying to heart, our advice to this is to find a vet who will. There have been way too many close calls to leave it up to chance, and a few deaths have been reported.

Another common difference is gestation time. Gestation for horses is generally about 11 months. For donkeys, gestation is usually about 12 months, but anything from 11 ½ to 13 months is normal. Live, healthy twins are also more common in donkeys than horses, by about 100 times. Care still must be taken, and many breeders will have jennets known to have twins ultra sounded early in their pregnancy, and one of the twins pinched off, to give mom and the other twin a better chance of surviving.

Donkeys also have a longer life span than horses, and can live easily in excess of 45 years. Horses average lifespan is 25-30 years.

To find the jugular vein in a donkey is a bit more difficult than in a horse. Blood used for tests such as coggins, or drugs that need to be administered intravenously, such as tranquilizers, are usually drawn or given through the jugular vein. The muscle that covers this area in donkeys is much thicker, and usually hides the middle third of the jugular vein. The jugular farrow in donkeys is obscured by this muscling in comparison to horses. Most vets will use the upper one third or lower one third of the jugular farrow in a donkey.

The nasolacrimal duct is found in a different location compared to horses. In a donkey, the duct is found on the flare of the nostril. In a horse, this duct is found on the floor of the nostril.

Chromosome differences are usually pretty well known. A donkey has 62 chromosomes and horses have 64. For this reason, almost all mules are sterile, since they end up with 63 chromosomes.

In donkeys, the pelvis tips down more vertically than in horses. This is especially helpful to know when a vet is conducting a pelvic exam, or if dystocia occurs.

Also, a jennets cervix is longer and narrower than that of a mare. There is also a large protrusion from the cervix into the vagina. And, dorsal and ventral folds in the vaginal passage that can hinder passage to the cervix.

Male donkeys, or jacks, also have some notable differences. Some jacks have teats on their sheath. Jacks are also notably larger in reproductive areas than horses.

Donkeys do not have chestnuts on their hind legs. They do have ergots on their front legs, which are mainly just a flat pad.

Donkeys hooves are also smaller than horses, and tend to be boxier and more upright.

One primary difference between donkeys and horses is their larynx. Vocal folds and laryngeal saccules were found to be different then horses and account for the braying sound that a donkey makes. One other thing to be aware of when a vet is tubing a donkey, the nasal passage is very narrow, and there is also a recess between the openings of the guttural pouches. For this reason, when passing a tube, a smaller diameter tube is better to be used. Donkeys are known for excessive bleeding during this procedure, and a smaller tube may help the bleeding problem.

There are many other differences between horses and donkeys, such as vertebrae, that are too lengthy and confusing to go into for this article. Just be aware that if the vet needs to give an anesthesia shot in the spine for any reason, it differs from horses and the vet should be aware of this fact.
Of course, there are many other differences besides the physical ones mentioned here. Donkeys are known to be stoic, what many call stubborn is just self preservation, and donkey behavior must be understood to manage them effectively. Subtle differences in behavior or attitude may indicate severe problems.

It’s good to know your animals, it helps with the vet, the farrier, and anyone who may come into contact with them. If you treat a donkey like a horse, you will be disappointed with the results.

Suggested reading:
The Definitive Donkey- A Textbook on the Modern Ass. Hutchins, Betsy and Paul. Hee Haw Book Service, 1999.
The Professional Handbook of the Donkey. Svendsen, Elisabeth D.. Whittet Books, 1997.

Posted by Tanya Tourjee at October 24, 2007 08:48 PM

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