This blog post was inspired by an old post card of what must have been a famous horse in England at one time: Norfolk Spider. Look closely! He was known as the six-footed Shire. Vintage post card is © and courtesy of Christine Sutcliffe. (Thank you!).
Please note:the photographs used in this article were loaned to Hoofcare Publishing so you could see them. They are the property and copyright of their owners and may not be used or copied without express written permission under any circumstances. Hoofcare Publishing is most grateful to the photo owners for the loan of these images and thanks readers for respecting their property.
But when the equivalent of a "double paw" shows up on a giant Shire draft horse, people notice.
So it must have been for "Norfolk Spider" back in the early 1900s in England. He carried extra toes on both front feet, which must have occasionally been quite painful when they hit each other. That's quite an interference problem!
|This polydactyl was found in British Columbia by one of the farrier students at Kwantlen College. Gerard Laverty, the instructor at Kwantlen, sent these images to me, which started my collection. Image © Hoofcare Publishing and Gerard Laverty.|
|I think this is a relatively rare photo, showing a polydactyl in motion. Imagine if the horse over-reached from behind--ouch! There wouldn't be much margin for error on this horse's trot. Image © Hoofcare Publishing and Gerard Laverty.|
The extra hoof (or paw, etc.) is called a "supernumerary digit".
This "extra hoof"might not even be noticed if the horse's lower limb hadn't been clipped.
(Image © Hoofcare Publishing for Michael Wildenstein)
|Look very closely at this radiograph. This image is from the Florida Museum of Natural History and the collection of Dr Bruce McFadden, author of Fossil Horses: Systematics, Paleobiology and Evolution of the Family Equidae, and was used in one of the Museum's newsletters. (Used with permission, © University of Florida and Florida Museum of Natural History)|
In evolutionary terms, polydactyls are what some people would call an atavism or a "throwback" to ancestors long ago. There are people who argue about this, of course. A book on my shelf is Hen's Teeth and Horses' Toes by Stephen J. Gould, which you might enjoy reading; it has some good illustrations of how the polydactyl forms in the limb.
Gould updated an old drawing of Dr. Marsh's from Scientific American in the 1800s to demonstrate two of the ways that a horse can grow an extra foot. The first way is for a true second lower limb to form. The second way is for the splint bone to turn into the limb, called the atavistic method. This drawing, from Gould's book, shows you the difference.
This horse is the subject of a paper written by three French authors, and published in The Journal of Veterinary Science; the extra digits were surgically removed and the horse went on to develop into a sound adult horse. You can read the full text of Bilateral Polydactyly in a Foal by Carstanjen, Abitbol, and Desbois online.
I don't think that polydactyl horses are very rare. Unusual, yes. I remember that Dr. Robert Hunt at Hagyard Equine Medical Institute had some photos of polydactyls in one of his presentations on foals at the AAEP's Foot Seminar in 2009. And while researching this article, I found a polydactyl horse for sale in Texas on CraigsList. (Should I have bought him? Is a polydactyl horse more or less valuable?)
I'm hesitant to try to say too much about polydactyls, other than that there are different types of limb formations in horses with the condition, but I hope you enjoy seeing these different examples, and that you'll read more if you're interested. I also hope some natural history professors might chime in.
If you are curious why there are so many double-digited cats in New England, here's the reference:
Todd Neil B. Cats and Commerce. Sci American 237: 100-107 (1977). Ernest Hemingway was a fan of double-pawed cats and his house today in Key West is filled with the descendants of his original double-pawed cat. About half the cats have double digits. If you've never been there, I recommend it. The cats both run and over-run the place.
page on her web site about a polydactyl goat out in New Mexico, complete with radiograph and close-up photographs.
Do you have a favorite polydactyl horse? Usually the extra leg is removed, and you can understand why--poor Norfolk Spider probably hit himself an awful lot.
Some of the better storyteller farriers have told me that they have had been asked to make shoes for the extra toes of polydactyls. I'd like to see a photo of that!
I was imagining a horse show class for polydactyls and can just see them all lined up in the ring.
How often do you have to trim the extra hoof, is the next question, of course. Not being weightbearing, it mightn't grow very quickly, but what, if any, effect would feeding a hoof supplement have?
Finally, I'd like to leave you with the story of one of my favorite polydactyls. Norman Pentaquad (someone had a sense of humor) was a royally-bred son of Riverman who was foaled in 1983 on a Kentucky farm. Not only was he small, he had an extra hoof dangling from his fetlock, which was surgically removed.
Norman amassed lifetime track earnings of $6,255 before being exported to New Zealand to stand at stud. He was bought sight unseen, based on his bloodlines. One son won both the Caulfield Cup and the Melbourne Cup. But in general, he was thought to be too small, and his New Zealand owner was going to turn him out with the bush horses when a buyer made a quite high offer for him because his offspring were turning into tremendous polo ponies.
You can read a great story about Norman Pentaquad in the Australian newspaper, The Age.
Norman moved to Australia and became the new polo stallion at Ellerston, the polo stud farm for Kerry Packer, then Australia's richest human. He went on to become the leading polo sire in the world. In 2010, Norman's offspring represented 11 percent of the horses that played for all nations in the Semi Finals of the Gold Cup.
I'd love to know how many legs they had between them.
If you have images of polydactyls to add to the gallery, email them to firstname.lastname@example.org or send a link if they are somewhere on the Internet and you are the owner and can give permission to download them. You can also upload them to the Hoofcare and Lameness page on Facebook: http://www.facebook.com/hoofcareandlameness.
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