|First Posted Feb 12, 2010|
Jul 22, 2010
Horse Feet and Shoeing/Ducket's Dot
You will hear many different thoughts from vets as well as farriers about how to shoe a horse. One of the major problems is that no two horses are alike! You cannot just slap on a shoe and drive in nails. Secondly, remember that your horse is not naturally wearing down his hoof in the wild. He is being used for purposes that are not really part of his natural design. Wild horse do not bear the unbalanced weight of a rider and tack, nor are they asked to do the many feats that we ask of our horses. It is important to take into consideration many different aspects of the horse from the overall conformation, specific medical problems, use, hoof and surrounding structures, rate of growth, etc. We have all heard the saying "No feet, no horse." It is imperative to maintain a sound hoof and horse, protect the foot and horse's limbs, adjust for pathological problems, and enhance the horse's way of going and natural ability. It is also imperative to do NO HARM in the process.
What A Farrier Should Know
"Although we as horse owners pay for a farrier's professional service, it is advisable that we at the very least have a basic understanding of what a well-shod horse is,'" Dave Duckett stated at the 52nd Annual Convention of the American Association of Equine Practitioners, held in San Antonio, Texas.
Duckett, a Fellow of the Worshipful Company of Farriers in London, England, and a member of the International Horseshoeing Hall of Fame, developed a system for evaluating hoof balance and shape more than 20 years ago (you might have heard of Duckett's Dot and Duckett's Bridge), and his work fundamentally changed how many farriers evaluated feet. He believes that farriers, owners, and veterinarians need to have a consistent, reproducible way to evaluate foot shape and balance, and that his system gives us this. At the convention, he presented a discussion of his system and its implications for foot care during the standing-room-only "Putting Science into Farriery" session.
"Why do we need this system?" he asked the audience. "Owners, farriers, and equine health care practitioners need to be able to accurately appraise a horse's foot. We all have a basic need for accurate hoof evaluation, and a need to communicate using the same terminology. Using this information (hoof shape and balance relative to Duckett's Dot and Duckett's Bridge), we can:
"The basic concept of using Duckett's Dot and Duckett's Bridge is to measure the foot from the center to its peripheral borders, rather than using traditional methods of calibrating the exterior, which would perpetuate the errors of the past (with distorted feet)," Duckett explained.
So where is the center of the foot, and how do you find it? Duckett explained that the center of the foot is the center of the third phalanx bone, which is often termed the coffin bone.
"The third phalanx is the physical, dynamic foundation of the foot," he stated."Therefore, knowing its position within the confines of the hoof capsule is crucial. The external landmark of the center of the third phalanx is noted by Duckett's Dot. This is a consistent external reference point situated 3/8" behind the apex of a trimmed frog on the average-sized horse. This is proportionate from the Shire to the Shetland (the point is slightly further back from the apex on a Shire, and slightly closer on a small Shetland)."
"From the position of the Dot, the third phalanx can be balanced by measurement and weight mass," he went on, showing a photo of a coffin bone balanced on the point of a pencil at the Dot to illustrate its physical balance.Using the Dot
Optimal toe length "Understanding that there's an equal amount of tissue (wall) attached to the third phalanx bone, we can scribe around the hoof wall to gain maximum toe length (with a compass like the one we used to draw perfect circles in school)," he said. "From the Dot to the medial wall, scribe to the toe. This will assure maximum toe length (anything outside that line means the toe is too long)."
If the horse's toe is very long, he advised a cautious approach: "Radical reformation of the hoof capsule at one time is not necessarily a good thing, it has to come over time. You're only doing a little at a time, don't overdo the job to emphasize the work."
"For the working farrier, a better perspective on the foot's internal structures can be gained when using these external reference points," he said, noting that the third phalanx on most horses toes in an average of four degrees.
Dubbing the toes "We don't have to rasp the toe off to conform with the traditional type of shoeing," he commented. "If the hoof wall is long, rasping it back to match an ideal is not necessary. The foot is a conical (cone) shape, and its strength is in its shape. If you rasp the toe back, you are rasping away the cortex and strength of the foot. If the foot loses that strength, it will collapse onto that shoe, creating lameness. This has been witnessed by many horseshoers attempting to create a short toe and in following the 'natural craze.'"Duckett's Bridge
The Bridge is a line rather than a point like the Dot, and it lies behind the Dot. It is a horizontal line running from medial (inside) to lateral (outside) sides of the foot. The Bridge is directly beneath the center of rotation of the distal interphalangeal joint, also called the coffin joint. Externally, you can see this as the widest part of the foot, which corresponds to this horizontal line. Therefore, the Bridge can be used to separate the foot into halves.
"The anterior or cranial (front) half of the foot includes tendon attachments on the third phalanx for movement, among other things," he said. "This half holds the bone and laminar attachments. The caudal or rear half is made up primarily of softer, elastic tissue. The separation of these occupations is an area named the Duckett Bridge, which is also considered to be the central biomechanical balance point of the foot."
When the foot is properly balanced, Duckett says, the bridge is exactly halfway between breakover at the toe and the heel end of the shoe. And if it's not, he noted that the heel bearing areas of the foot will be under great stress, resulting in collapsed, underrun heels. But the heels will collapse no further forward than the bridge.Shoe Placement and Size
"When a horse is shod, he is no longer standing on his feet--he's standing on his shoes," Duckett stated. "Therefore, it is imperative that the shoe is placed with biomechanical congruency (to match the biomechanical needs of the foot). The shoe should be placed central to the Bridge (with equal ground surface length in front of and behind the Bridge) and in harmony with the horse's movement, regardless of the hoof shape."
The distance between breakover (the forwardmost point of the shoe's ground contact) and the Bridge should equal the distance from the Bridge to the heel end of shoe, he clarified. Breakover is not centered on the toe, he added; as mentioned earlier, most horses' bony columns toe in slightly. "The anatomy and its mechanics determine where the breakover is," he said.
Using this technique also gives you a basis on which to evaluate an existing shoeing job. Duckett gave case examples in his presentation and challenged the audience to "raise their conscious awareness to such a level that you see what you are looking at. This may be a simple statement, but it has a important meaning," he said.
Using radiographs to complement the information on a particular case, he noted: "If the front half of the foot is for tendon attachments, laminae, and bone, and the back half is for weight bearing, how much shoe is there to support that limb (i.e., how much shoe is there under the rear half of the foot bearing the horse's weight)? Just the little bits at the ends of the branches. It's not nearly enough."Take-Home Message
"Think about what you've learned today and place it into practice when appraising a horseshoeing job," he concluded. "Some schools of thought view the art and science of farriery as merely covering the preparation of a horse's foot and the application of a shoe. But it's a little more than just slapping a shoe on. We all must appreciate that the foot is the foundation of the horse, and we must also become aware that it's the art of horse shoeing, not FOOT shoeing."For More Information and Images of Ducket's Dot:
"Landmarks for Evaluating, Trimming, and Shoeing the Equine Foot," Bumbaugh, Sue. "Buzz Words and Brainstorms to Decode Duckett's Dot." Buzz Words and Brainstorms to Decode Duckett's Dot/first published in slightly different form in Hoofcare & Lameness, Summer 1992