Transitioning to Flexible Shoes

Transitioning to Flexible Horseshoes
Monique Craig, EponaShoe

Introduction

Switching to the use of flexible shoes is not a big deal.  Generally, there are no problems.  However, here we give a few pointers that may be helpful in some cases.

What are the mechanical properties of hoof keratin, composite material and metals?

The diagram of figure 1 shows that the mechanical properties of metals (steel and aluminum) have little in common with those of hoof keratin. Young’s Modulus is a fundamental measurement of elasticity of a material.  It is measured in “psi” – pounds per square inch.  Using knowledge of the Young’s Modulus of a material, along with the geometric shape the material has been formed into, one can compute how stiff (or flexible) it will be.

Let’s make an analogy concerning the relative flexibility of the materials in figure 1:   Imagine a tall skyscraper, where each floor represents 100,000 psi of Young’s Modulus – then both the hoof keratin and man-made synthetic plastics and elastomers are found within the first 10 floors. Aluminum is up on floor 100, and steel is on floor 300! 

  

Figure 1:  Stiffness versus Strength for Keratin, Plastics, Aluminum, and Steel

What Happens when a Hoof is Shod?
One constraint with using metal to shoe horses stems from the fact that metal does not have mechanical properties similar to hoof keratin (see figure 1.) 

Therefore, it seems reasonable to say that any metal shoe will alter the natural mechanical behavior of the hoof capsule.   When a less-flexible

material is attached to a more-flexible material, the combination results in system of intermediate flexibility.  That is to say, the nearly-rigid metal impedes the flexing of the natural hoof.  Unlike the hoof keratin, metal is not a fibrous composite material and does not exhibit viscoelastic behavior (except in its molten stage!)  A cautionary note: I do not think that metal shoes are at the root of all hoof problems -- poor trimming methods are far more detrimental to the hoof than any particular choice of shoe.

 

Figure 2:  ‘Before’ photos on the left (A), and ‘after’ photos on the right (B).

The hoof in the example of figure 2 went from a metal shoe to being barefoot. The change in the hoof, due to both the trim style and the lack of metal constraint, was followed for six months. What you are seeing is a hoof regaining its natural flex. Metal shoes do not allow the hoof to flex and it tends to stiffen and compress the entire hoof capsule regardless of the trim.

How Does the Hoof Behave as it Adapts to a Flexible Shoe?
Hooves can change very fast once they are allowed to flex again. As the hoof expands and regain more flexibility, you will notice quite a bit of change in the hoof capsule.

 

  

Figure 3: The nature of the hoof wall changes as it grows out when it is now shod with a flexible shoe.  The portion below the red curve is the older horn as it grows out.  The images above cover a 4 month period.

Obviously, the changes have also something to do with trimming methods not just the shoe. The trim comes first not the shoe!

How does the Horse Feel when it is First Shod with Flexible Shoes?

Most horses transfer from metal to plastic shoes very smoothly. Horses may walk a bit awkwardly the first few minutes after being shod (with anytype of shoe) but in general this is the extent of it.

However, there are situations where horses will not instantly feel comfortable depending on pre-existing hoof problems and shoeing conditions. In my opinion, it is a bit absurd and somewhat dishonest to claim that a type of shoe, trimming method, drugs or surgeries can truly help a hoof regain optimal health overnight!

Suggestions for Best Success when Applying Flexible Shoes.
A flexible shoe can only help restoring the natural flex of the hoof capsule but not necessarily help correct other problems.  Assessing the existing hoof situation and adjusting your trim to it, is truly pivotal to avoid trouble and to help the hoof regain optimal health whenever possible. I also strongly recommend working with x-rays whenever you are dealing with hoof problems and/or corrective trimming and shoeing.

It is likely that you will see rapid changes in the hoof with flexible shoes (see figure 3.)  My advice is to re-set flexible shoes a bit sooner after the first shoeing. You may lose a shoe if you wait too long to reset the shoes.

Unless the horse has serious capsular deformities and/or other hoof problems, this is generally no longer an issue after the first or second shoeing.

Hooves with Capsular Deformities

In general, I like to re-shoe these horses a bit more often. Also I like to use glue when I work with this kind of hoof. It may add to the price of the shoeing but you get faster results. 

 

Figure 4: Changing from metal & wedge to plastic, packing and glue.

Horses that have Been Shod Too Tight

I would not re-shoe such a horse right away. I would remove the shoe, support the sole and arch with packing and wrap the hoof and let it stand for a day or two in a stall or paddock with a soft surface. An hour prior to the shoeing I would unwrap the hoof and let it dry for a while, especially if you are going to apply glue with the shoes.

Horses with Thin or Bruised Soles

In cases like this, I prefer to use glue for the first shoeing or two depending on the existing problem. The glue is more flexible than the shoe and the horn and it creates a buffer between the shoe and the sole.

Horses with Overly High Heels
Lower the heels! This will also help the longevity of the shoe since the wear is more likely to happen at the caudal part of the shoe not the toe.

Horses with Prolapsed Frog

These are excellent candidates for the use of glue.  The glue is used to make up the difference between the heel and the frog, so that the frog and walls at the heel can each bear some weight.  Over a shoeing or two, this condition will often correct itself.

 

  

Figure 5: Using glue to deal with a “prolapsed” or “descended” frog.

Note that the whole hoof plays a part in bearing weight, not just the sole, or the frog or the walls.

When a Horse Should Not be Shod

In a few special cases, horses should be left barefoot until their situation stabilizes or resolves itself somewhat.  For example… 

  • Horses during the acute stage of founder (get veterinary assistance)
  • Horses with fresh hoof wounds (get veterinary assistance)
  • Horses with shoes embedded in their soles. If you can remove the existing shoes, do it. In this case, there is a potential for bruising or worse. (This situation may need veterinary assistance.)

 

 

Comments on Shoes and Wear

The ability for a plastic shoe to wear, to change the bevel at the toe and other places, is a good thing.  This lets the horse “make its own adjustments” instead of being stuck with something for 6 weeks that is not right for it.  Obviously, we don’t want shoes to wear out too soon, for economic reasons, but some limited wear is a helpful thing.  In therapeutic shoeing with flexible shoes, some wear is fundamental – it prevents the stresses from again causing deformities in the hoof capsule – rather, the shoe wears down in reaction to the stress.