The importance of good quality hoof care in competition horses cannot be denied. Farriery can be a major asset during the show season and beyond. The farrier can be proactive in keeping the horse’s feet healthy and thus preventing lameness. Learn more as Dr. Stephen O’Grady of Palm Beach Equine Clinic in Wellington, FL, explains the philosophy behind correct basic farriery in sport horses.
The equine hoof is unique as it is comprised of a group of biological structures (anatomy) that follow the laws of biomechanics. Therefore, if the veterinarian and farrier know the anatomy of the equine foot combined with an understanding of the biomechanics and good basic farriery principles, proper physiological farriery can be consistently applied (see Figure 1A and 1B). There are three important aspects of farriery used to keep the horse sound, beginning with the appropriate foot trim, along with the correct size and placement of the horseshoe.
The farrier session begins with an evaluation of the conformation of each foot. This means viewing the foot from the front, the side, and behind to observe the height of the heel bulbs (see Figure 2). It is important for the clinician to observe the horse in motion to see whether the horse’s foot lands flat or slightly heel first, which is desired. If the horse lands markedly heel first with a toe flip, it is a sign the heels have migrated dorsally (toward the front), decreasing the ground surface in the palmar section of the foot, or the size of the shoes is too small. The foot that lands toe first is an indication that the musculotendinous unit of the deep digital flexor tendon is shortened or the horse is experiencing palmar foot pain. Lastly, the foot should be observed for an asymmetrical landing pattern that is dictated by limb conformation because, if severe, a heel bulb can be displaced proximally resulting in the foot conformation termed “sheared heels.”
The use of guidelines or landmarks when approaching the trim provides consistent, repeatable results that can be used on each foot regardless of the conformation. The three guidelines used are: 1. Trimming the foot to achieve a straight or parallel hoof-pastern axis, 2. using the widest part of the foot, which correlates closely with the center of rotation, and 3. trimming the palmar foot (heels) to the base of the frog or to where the heels of the hoof capsule and the frog are on the same plane (see Figure 3A and 3B). A closer look at these three guidelines, which are all interrelated, will help to show their importance.
1. If the dorsal (front) surface of the pastern bone and the dorsal surface of the hoof are parallel or form a straight line, then the bones of the digit (in the hoof) are in a straight line, and the force from the weight of the horse will go through the center of the joint. Furthermore, and equally important, if the hoof-pastern axis is straight, the weight will be distributed evenly on the bottom or the solar surface of the foot.
2. The second guideline is the center of rotation (COR). The COR is located a few millimeters palmar (behind) the widest part of each foot. This guideline allows the farrier to apply the appropriate biomechanics to each foot. The foot is trimmed in approximate proportions on either side of the widest part of the foot, which addresses the moments on either side of the COR and provides biomechanical efficiency.
3. Lastly, the palmar section of the foot is trimmed to the base of the frog or trimmed such that the heels of the hoof capsule and the frog are on the same plane. Adherence to this guideline keeps the soft tissue structures (frog, digital cushion, ungula cartilages) within the hoof capsule, which is necessary to absorb concussion and dissipate the energy of impact (see Figure 4). It is important to remember that heels do not grow tall; they grow forward. If the heels migrate forward, the soft tissue structures will be forced in a palmar direction out of the hoof capsule. Furthermore, as the heels migrate forward, the weight is placed on the bone via the lamellae thus bypassing the soft tissue structures of the foot. Allowing the heels to migrate forward also decreases the ground surface of the foot. Two examples of this guideline are shown in Figures 5A, 5B and 6A, 6B where the palmar foot was managed appropriately, and a size larger shoe was applied.
The three guidelines described here can be applied to any foot and can serve as a basis for maintaining a healthy foot and a basic starting point for applying farriery to a horse with poor foot conformation or one with a distorted hoof capsule. Figures 7A and 7B illustrate a hoof where all three of these guidelines have been applied.
Thoughts From Dr. Stephen O’Grady
Most competition horses now show year-round instead of on a seasonal basis. My observation is based on years of experience regarding the farriery performed on these horses. Many of these horses are given a rest from competition prior to leaving for Wellington for the winter show season. Many horses arrive with very reasonable foot conformation. However, upon arrival, horses are often shod with various specialty shoes, wedges, pads, pour-ins, etc., as a means of protection and perhaps to enhance their performance.
As the season progresses and the workload becomes more intense, the sole thickness starts to decrease, and the feet become softer from multiple baths. Now the farriery that was applied for protection at the onset may be causing pressure on the thinner, softer structures of the foot, thus becoming somewhat detrimental. The horses continue to be trimmed and shod on a monthly basis, and the farrier may not be aware of the change in the integrity of the hoof structures, especially the sole, and perhaps some horses may be over-trimmed. As the season progresses into March, the structures of the foot deteriorate further as a result of the workload. Many horses begin to become foot sore. At this point, the farrier options become limited because all the protective methodology was already used at the beginning of the season.
One recommendation would be to refrain from trimming the sole (trade the hoof knife for a wire brush), create ground surface in the palmar foot with a rasp, and decrease toe length vertically from the dorsal section of the foot to preserve mass. Always remember that adequate breakover in the shoe is important, as it decreases the stress in the deep digital flexor tendon and decreases the moment about the distal interphalangeal joint, both of which preserve sole thickness.
I remember the words of Joe Pierce when I was an apprentice learning the farrier trade many years ago, “No one will know if you leave the last few rubs of the rasp on the foot, but everyone will know if you take a few too many rubs!”
Palm Beach Equine Clinic offers a farriery consultation service to both veterinarians and farriers. This unique service provides a second opinion or simply “another set of eyes” available to both professions when treating difficult farriery cases. Please call 561-793-1599 or visit equineclinic.com for more information.