Explained by Dr. Stephen O’Grady Palm Beach Equine Clinic (PBEC) of Wellington, FL, proudly offers advanced services to referring veterinarians and clients in equine podiatry with the expertise of Dr. Stephen O’Grady. As the show season continues on, some horses may be experiencing foot soreness or new lameness that could be related to their farriery.
The importance of good quality hoof care in the competition horse can’t be denied. The equine hoof is unique, as it is comprised of a group of biological structures that follow the laws of biomechanics (Figure 1). The farrier is a major asset during the show season as he or she can be proactive in maintaining the health of your horse’s feet and thus preventing lameness.
There are three very important aspects of farriery science that the farrier will use to keep your horse sound, which are trimming the foot in conjunction with the size and placement of the horseshoe. Typically, a farriery session will begin with an evaluation of the conformation of each hoof from the front, side, and behind to observe the height of the heels. Next, the farrier should observe the horse in motion to see whether the horse’s foot lands heel first, flat or toe first. All this information is considered and evaluated before the farrier begins shoeing.
Regarding the trim, many farriers no longer use the term ‘balance the foot’ – which has no meaning – and have begun to use guidelines or landmarks when approaching the trim. The guidelines used are trimming to achieve a straight hoof-pastern axis, using the widest part of the foot which correlates to the center of rotation, and trimming the palmar foot (heels) to the base of the frog or to the same plane as the frog (Figure 2, 3).
A closer look at these three guidelines, which are all interrelated, will help to show their importance. If the dorsal (front) surface of the pastern and the dorsal surface of the hoof are parallel or form a straight line, then the bones of the digit (P1, P2, P3) are in a straight line, and the force from the weight of the horse will go through the middle of the joint. Furthermore, and equally important, if the hoof-pastern axis is straight, the weight will be distributed evenly on the bottom of the foot.
The second guideline is the center of rotation (COR), and as the COR is located a few millimeters behind the widest part of each foot, it allows the farrier to apply appropriate biomechanics to each foot. The foot is trimmed in approximate proportions on either side of the widest part of the foot, which provides biomechanical efficiency.
Lastly, one should trim the palmar section of the foot to the base of the frog or trim 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 are necessary to absorb concussion and dissipate the energy of impact.
We must remember that heels do not grow tall, they grow forward. If we allow the heels to migrate forward, the soft tissue structures will be forced backward out of the hoof capsule. Furthermore, as the heels migrate forward, the weight is placed on the bone and lamellae, thus bypassing the soft tissue structures of the foot. Allowing the heels to migrate forward also decreases the ground surface of the foot. An example of this guideline is shown in Figures 4A & 4B, where the palmar foot was trimmed appropriately and a size larger shoe was applied to properly distribute the weight.
These three guidelines can be applied to any foot and they 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 5A & 5B will illustrate a hoof where all three of these guidelines have been applied.
Many horses are given a rest from competition, which includes their feet, following a heavy competition load such as Wellington’s Winter Equestrian Festival. Many horses arrive with very reasonable foot conformation, but upon arrival the farriery can change and many horses are 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 increases, the sole thickness starts to decrease and the feet become softer from multiple baths; now the farriery that was applied for protection may be causing pressure on the thinner, softer structures of the foot, thus becoming somewhat detrimental. Furthermore, the horses continue to be trimmed and shod on a monthly basis and the change in the integrity of the hoof structures without investigating can cause horses to be over-trimmed. Additionally, as the season starts into March, the structures of the foot deteriorate further as a result of the workload, and many horses become foot sore. At this point, the farrier options are limited because they may have been used at the beginning of the season.