A Donkey is Not a Horse: The Differences from a Practical Veterinary Standpoint. Stephen R. Purdy, D.V.M  [Back to Article List]

         Terminology associated with donkeys and mules:

§         Donkey- worldwide common name for the ass family

§         Jack, Jack Ass, or Jackass- an intact male of the ass family

§         Jennet, Jenny- the female of the ass family.

§         Burro- the smaller member of the ass family, usually of Mexican or Spanish descent.  Usually gray in color and commonly thought of as feral asses.

§         Donkey Gelding, or Gelded Jack- castrated male of the ass family; the hybrid cross resulting from breeding a jack to a mare.

§         Hinny- the hybrid cross resulting from breeding a stallion to a jenny.

§         Mare Hinny- a female hinny.

§         Horse Hinny- a male hinny.

§         Mule- the hybrid cross resulting from breeding a mare to a jack

§         Mare Mule- female mule, also referred to as a Molly Mule.

§         Horse Mule- male mule, often referred to as a John Mule.

§         Mule Mare- a mare used to raise mules.

§         Miniature Donkey- member of the donkey family that stands at 36 inches or less at the withers at maturity.

§         Standard Donkey- between 36 and 54 inches at the withers at maturity.

§         Mammoth Donkey- greater than 54 inches at the withers at maturity.

§         Jack Stock- indicative of multiple animals of mammoth size regardless of sex; similar to the term cattle for cows.

·        Genetic makeup

§         Domestic horses- 64 chromosomes

§         Domestic ass- 62 chromosomes

§         Mule- female horse bred to a male ass- 63 chromosomes

§         Hinny- male horse bred to a female ass- 63 chromosomes also

§         Both crosses are considered sterile even thought there are documented cases of fertility in the female mule (Mare Mule or Molly Mule).

§         No documented cases of fertility in the female hinny or male of either hybrid cross

§         Spermatozoa are not produced in the testes of male mules as a result of incompatibility between paternal and maternal chromosomes resulting in a block in meiosis

§         Same chromosomal incompatibility causes partial meiosis arrest in female mules and hinnies with subsequent severe depletion of oocytes at birth

§         Female mules and hinnies can be used as embryo recipients

§         Female mules and hinnies do cycle- most often erratic

§         Male mules are not seasonal in behavior

·        Can be used as a teaser

·        Train mares to accept pasture breeding by a jack

·        May not work in mares

§         Mules and hinnies are difficult to differentiate by conformation

·        Anatomic Differences

§         Ear length- donkeys>mules>horses

§         Most donkey and many mule withers cannot hold a saddle well

§         Donkey mane and tail hair is stiff

§         Donkey tails have short hair- mules may be more like horses

§         Donkey croup muscles are usually less developed than those of horses

·        Modern mules are more like horses

§         The donkey pelvis tips down more vertically than the horse

·        Important during reproductive exams and dystocias

§         Hooves are smaller than those for equal sized horses

·        Frog is set more caudally than that for the horse

·        Pastern angles are greater

§         Donkeys do not have chestnuts in the rear

·        May be absent in mules or smaller on the rear legs than horses

§         Donkey ergots are more prominent than for horses

·        Often look more like a digital pad

·        May be up to 2 inches in diameter on mammoth donkeys

·        Mules more like horses

§         Donkey inferior check ligaments

·        Have an extension from the deep flexor tendon to the superficial flexor tendon in the front legs (not found in the mule)

·        No ICL in the rear

§         Laryngeal anatomy slightly different

§         Donkey and some mule nasal passages smaller than equal sized horses

·        Smaller NG tubes required

§         Castration

·        Larger scrotal vessels and thicker scrotal skin than the horse

·        More prone to bleeding

·        Use ligation along with emasculation

·        Sedative/anesthetic drug doses approximately 25% higher in donkeys than equal sized horses

·        Early castration at less than 3 months may increase chances of evisceration

¨      Wait until after weaning

¨      Include the common vaginal tunic in the ligation if performing at < 3 months

·        Behavioral Differences

§         Donkeys very stoic

§         Colic

·        May go undetected longer

·        Assume severe problem with mild pain signs

·        Treat with decompression of the stomach, analgesics, and antacids

·        Increased pulse rate may not be reliable

·        Look for subtle changes in behavior or attitude

§         Laminitis

·        May progress without severe signs

·        Less responsive to hoof testers than horses

·        Radiograph early to look for rotation/sinking

·        Analgesic medications important

§         Tolerance of Medical Procedures

·        Donkeys need to see what is going on for a while

·        Best to perform with other animals nearby

·        Stubbornness is evaluation of the situation

·        Twitch works well in most animals

·        Go slow and stay quiet

·        Reverse and stop are the best gears for donkeys

·        Sedation with xylazine, butorphanol, detomidine (diluted to increase the volume)

§         Donkeys are highly social animals

·        Form strong attachments to others

·        Jacks aggressive towards newly introduced jennets

¨      May occur after being brought back after a short separation

¨      May need to wear a breeding muzzle on first introduction

¨      Can be removed after things calm down

¨      Kicking, biting, and chasing are the norm

·        Vocalization very common- braying

¨      Greeting

¨      Hungry

¨      Horny

¨      Calling out to other jacks

·        Pecking order important for feeding time and availability to feed

¨      They need space to eat

·        Mothers correct foals early in life with mild kicking and biting

·        Foals play fight with mothers on day of birth

·        Mothers move off from the herd to foal

¨      Keep newborns away from others initially

¨      Will stay out in the rain/snow with a new foal (normally they would be inside)

§         Hauling and drinking

·        Prefer to ride backwards

·        Leave loose in a stock trailer

·        May not drink when hauled, even for 12 to 18 hours and for hours afterwards if in a new place

·        Can keep loaded if trip is less than 24 hours

·        Stop to rest animals for an hour every 4 to 6 hours

·        Stop and unload every 12 hours if hauling more than 24 hours

·        Donkeys can dehydrate and lose 30% of body weight without adverse affects

·        Can rehydrate by drinking within 5 minutes

·        May refuse to drink for 48 to 96 hours if removed from their normal water supply

¨      Common for hauling, showing, and hospitalization

¨      May have to go home to resume drinking and eating

·        Drug Metabolism

§         Research is limited

§         Differences among horses, donkeys, and mules

§         Possibly among different sizes of donkeys

§         Difficult to make specific dosage and frequency recommendations

·        Use horse specs

·        What we do know:

¨      Phenylbutazone- clearance after a single IV injection (4.4 mg/kg) is rapid; compared to horses, miniature donkeys may require more frequent administration to achieve therapeutic efficacy

Ø      Suggestion:  4.4 mg/kg IV or orally BID/TID or possibly 8.8 mg/kg SID

¨      Trimethoprim-sulfamethoxazole- dosing intervals for IV administration of trimethoprim (2.5 mg/kg)-sulfamethasoxazole ( 12.5 mg/kg) in horses may not be appropriate in donkeys and mules; donkeys eliminate the drugs rapidly compared with horses

Ø      Suggestion:  oral or IV TS at same levels BID

*3*. Summary

¨      Donkey/mule specific terminology must be understood to speak intelligently to owners

¨      Genetic makeup of donkeys and mules and horses is different

§         Some interbreeding is possible

§         Most donkey/horse hybrids are sterile but females cycle like horses

¨      Several clinically important anatomical differences exist between donkeys and horses

¨      Donkey behavior must be understood to handle them effectively and safely

§         Stoicism is manifested by disguising pain

§         Subtle differences in attitude and behavior may be the only indicators of even severe problems

§         Social interaction is very important to donkeys with regards to nutrition and reproduction

¨      Donkeys may go long periods of time without drinking during travelling, hospitalization, and when moved to new surroundings

¨      Drug metabolism is different among donkeys, horses, and mules

¨      Much more research is needed to define correct dosage levels and intervals in these species

*4*. References/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.

¨      Taylor TS, Matthews NS, Blanchard TL.  Introduction to Donkeys in the US. New England Journal of Large Animal Health; 1(1): 21-28, 2001

¨      Peck KE, Matthews NS, Taylor TS, Mealey KL.  Pharmacokinetics of Sulfamethsoxazole and Trimethoprim in Donkeys, Mules, and Horses.  American Journal of Veterinary Research, 63(3): 349-353, 2002.

¨      Matthews NS, Peck KE, Taylor TS, Mealey KL.  Pharmacokinetics of Phenylbutazone and Its Metabolite Oxyphenbutazone in Miniature Donkeys.   American Journal of Veterinary Research, 62(5): 673-675, 2001.

¨      Donkey Organizations:

§         American Donkey and Mule Society, PO Box 1210, Lewisville, TX  75067  www.lovelongears.com

§         National Miniature Donkey Association, 1450 Dewey Road, Rome, NY 13440 www.matrixdm.com/nmda

§         Canadian Donkey and Mule Association, Julie Taylor, Box 341, Nanton, Alberta, Canada, TOL1RO

§         American Council of Spotted Asses, Box 121, New Meile, MO 63365

§         New England Animal Health Institute, PO Box 1160, Chester, VT 05143 www.NEAHI.org

¨      Donkey Publications

§         The Brayer Magazine, American Donkey and Mule Society

§         Asset, National Miniature Donkey Association

§         New England Journal of Large Animal Health, New England Animal Health Institute

§         Mules and More Magazine, PO Box 460, Bland, MO 65014 www.mulesandmore.com

§          

Subject:  Miniature Donkey and Horse Medicine

Author: Stephen R. Purdy, D.V.M.; New England Animal Health Institute, Chester, Vermont, USA   Email: steve@purdyvet.com

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