I see a lot of fads in the industry that are wonderful compensation for a lack of skill on behalf of the farrier applying the product. The problem is that many of them violate the fundamentals of the function of the horse’s hoof. Many of these fads are endorsed by the Equine Podiatry movement. I would challenge anyone to find a veterinary college in America that focuses on shoeing horses. You won’t. Many vet schools have made a good effort to mend the vet/farrier relationship by having workshops taught by qualified farriers. However, specialized education cannot be covered in a weekend. Fact of the matter is this trade takes a lifetime to learn. The hoof is a complicated structure and in order for the horse to work properly, all of its structures must work together to be healthy. Each structure has its own property that allows the structure to work correctly. Many of these fads do not take the overall function into account and focus on one small part without regard for the way it affects the overall function.
Let’s begin with an overview of its parts and some necessary definitions.
- Hoof wall– The hoof wall offers protection to the internal structures of the hoof and is responsible for suspension of the bony column. It is made of tubular horn and intertubular horn. This design allows for the function of tensegrity in forming the tensive forces that compensate for the concussive forces of the load. It is made of three layers, stratum externum, stratum medium, and internum. The hoof wall is designed to be weight bearing.
- White Line- the connection of the sole and hoof wall
- Sole- area inside the white line attached solidly to the horny frog. It’s primary function is to protect the coffin bone.
- Frog- a triangular structure of rubber like tissue. Responsible for some traction and expansion of the hoof when it enters the ground during the load phase. It also aids in circulation.
- Digital cushion- fibro fatty tissue fills the space between the frog, deep flexor tendon, and lateral cartilages. Helps create expansion of the heels of the horse.
- Collateral cartilage- hyaline cartilage (no nerve cartilage) extend off the wings of the coffin bone. Define the widest part of the hoof.
- Laminar Attachment- the attachment of the coffin bone to the hoof wall. Dermal lamina (on the bone) and epidermal lamina (on the wall) interdigitate much like velcro. The attachment is through desmosomal bonds at the basal membrane.
- Center of Rotation (COR)- a fixed point to a body undergoing planar movement that has zero velocity at a particular instant of time. At this instant, the velocity vectors of the trajectories of other points in the body generate a circular field around this point, which is identical to what is generated by a pure rotation. Think of a seesaw. In the case of a horse, it’s is dead center of the sphere of the distal end of the short pattern bone. (Fig. 1)
Models for Proper Equine Trimming
Now let’s get into the meat and potatoes. I often say Albert Einstein was not a mathematical genius because he reinvented mathematics. He was a mathematical genius because he had a firm understanding of the fundamentals of mathematics. How does that apply to the farrier? Well, mastering the fundamentals makes a great farrier. That incompasses an understanding of anatomy, biomechanics, locomotion, kinesiology, forging, and linear proportions. Each skill is essential and fundamental to this trade. We have a few fundamental theories on how to properly balance the horse’s limbs in the trim. Each have their strength, but as previously stated focus on one piece of the puzzle and not the overall picture. Another limitation in determining the veracity of each method is they are fundamentally a series of observations and a true scientific approach was not applied. The governing sciences of the farrier trade are geometry and physics.
There are currently four basic models for proper trimming to influence skeletal alignment and optimize biomechanical properties to withstand the concussive forces created by the horse’s movement. The first is the natural approach. This interpretation involves the observation of a limited group of horses in one environment. It promotes a 60:40 ratio around Center of Rotation based on a proportion of two thirds of the bearing border being placed behind the apex of the frog. The aggressive roll of the toe effectively limits the amount of horn that is broken away during the equine trimming cycle; however, may be detrimental when the hoof is in an environment that prevents the hoof from sinking into the ground. The laws of physics accepts that everything follow the path of least resistance. Without resistance from the terrain, the hoof will migrate forward giving the long toe low heel effect. The second approach began in 1990 with Dave Duckett’s research giving linear measurements to balancing the trim. This has proven to be a good system and will allow the farrier to get in the general area of a balance around center of rotation. The drawbacks are the frog is compromised by over trimming, and a linear measurement is impossible because horse feet come in all sizes. Nonetheless, it is a very practical method and revolutionized the farrier’s ability to use external landmarks to obtain balance. The third is the Uniform sole thickness. This trim suggests a balanced hoof will have uniform sole thickness and principally hypothesizes if the hoof is in both static and dynamic balance the sole will maintain a uniform thickness. The fourth is relatively new. I’m not sure there is a name for it yet, but the ideas of proper trimming is centered around proportional measurement allowing a balance around center of rotation. These are the most scientific methods I have found. Mark Caldwell F.W.C.F., PHD was able to do quantified studies with the use of real measurements to accumulate data and interpret that data into where forces are applied through all phases of the stride as well as when standing.
So, what difference does it really make. I say it makes a big difference in determining if a theory is well thought out, or just a magpie regurgitating bad information. We are able to broadcast data freely with the web. Anyone can be an expert, but a true expert can articulate complex arguments in a manner a layman can understand. The late farrier Jack Miller described, “Horseshoeing is Deceptively Simple, Endlessly Complex, and Physical as any Sport.” I believe he hit the nail on the head. The competent farrier can take these complex issues and interpret them in a simple and understandable manner. (Much like Einstein). When someone really has their thumb on the pulse of the topic they don’t need to rely on buzzwords or sophisticated jargon to appear as though they know what they are talking about. In other words I refer to the old adage of either dazzling with brilliance or baffling with bullshit. Let me just say that there is a considerable amount of baffling going on over the internet today. I have seen a rash of competent farriers being challenged with owners forcing theories they found on the web. I would caution each owner if they cannot draw out and articulate the cause and effect of the theory it is best to defer to the judgment of the farrier. At the end of the day, it is his reputation on the line and not the demiconosure that felt it necessary to contaminate the world with bad principles.
Let’s look at some of the myths out there today. First, “Shoes are bad.” A true sign of intelligence is not in the ability to retain information; rather, the ability to ask good questions. Why were shoes invented for horses in the first place. The answer is ancient civilizations devoted significant resources to the technology because horses were essential to civilization. One of the greatest texts I have read is the Dollar and Wheatley Handbook on Horseshoeing. Basically the shoe was developed as a wear plate so that horses could travel long distances and not wear off the toe to the point they became sore. A properly applied shoe should allow the hoof to function within acceptable parameters to maintain health and use of the animal. Competitive horseshoers are frequently chastised by their peers because of their commitment to excellence. Fact of the matter is, they hold themselves to a very high standard and work diligently to perfect their skills. Many of these farriers hold themselves to a tolerance of 1/32 of an inch. No doubt that standard is well within acceptable parameters.
Next let’s look at many of the fad shoes designed to influence “break over.”
First let me ask you, do you twist your ankle falling into a hole, or getting out of a hole? Sound ludicrous? So is the idea that break over influences soundness. The way the hoof leaves the ground will only influence the path it takes in flight. The palmer forces from center of rotation are influenced by distance to Center of Rotation. This will allow influence over the moment arm created by the angles of the interphalangeal joint. What happens dorsally is relatively insignificant. I often see the idea of backing the toe up to the extreme behind the white line. This will not have the effect of printing the hoof into balance around COR if the heels are too close to COR. It will only result in cutting off circulation in the circumflex artery and create a necrotic hoof because of a lack of nutrients. There is a limit to how much a toe can be backed up. In my opinion it is the stratum medium. Remember there are 3 layers of wall. If the dorsal wall is weakened by over rasping, then it will only continue to advance forward. (The path of least resistance). I suggest a better alternative is to buy a horse with conformation suitable for the job you intend it to do. A horse with a long sloping pastern will always have a long sloping pastern. If it is trimmed to look like an upright foot, then it will pop a quarter crack trying to correct itself. The fact of the matter is the horse should be trimmed proportionately around the coffin bone and the shoe should fit that trim. Anything less is unbalanced. Many of the shoes on the market today are made in a fashion that the toe cannot be fit. In these cases their own rhetoric works against them. Length is leverage, and when a horse works on a tight circle there is very limited play in the coffin joint to allow flexibility to absorb the force, however the interphalangeal joint has three points of articulation and a wide range of movement around COR that prevent it from becoming a leverage arm.
Next myth…”I don’t need to learn to make shoes, I can buy any shoe I need.” Let me just say therapeutic and corrective shoeing needs to be left to experts. There is really no magic to it, it is just a really tight job centered around the fundamentals. I can honestly say that I have helped more horses become sound by taking off terribly applied therapeutic packages and just doing a solid shoeing job. That being said there are times I needed to fabricate shoes. Here are some that cannot be purchased. (Fig. 2)
There are two associations in America that provide good education for the farrier. The American Farriers Association and World Championship Blacksmiths have been instrumental in my ability to acquire the skills and knowledge I have, and I would highly recommend getting involved with them.
Another myth, you can grow heel by cutting off toe. At the end of the day, balance is balance. Each horse has its own conformation. The protocol for shoeing should be centered around that fact. If a horse has bad heels, the solution is to repair the heels. Dr. Hood has a great lecture called the architecture of the hoof. In it he explains the buttress and the bars work as a line of movement to counter the line of force created by the radius of the toe. The back half of the hoof needs to be properly organized to repair damaged heels.
This myth is a pet peeve of mine…”Caudal Heel Pain.” Is there such a thing as dorsal heel pain? The fact of the matter is there are very few things that can go wrong in the front of the foot. A farrier can bleed them, or drive a bad nail. Laminitis and pedal osteitis can cause pain in the front of the foot. There are many things that can cause a horse to be lame from the caudal part of the hoof. Caudal heel pain is not a clinical diagnosis. It must first be identified what is causing the heel pain before a treatment plan can be produced.
I hope this helps people think about the things they accept as truth. There is a big difference between fact and opinion. These days those concepts seem to be convoluted. I would like to encourage people to require data supporting the opinions before accepting ideas as truth. In the real world everyone does not get a trophy.