The hoof wall is the armor and support of a horse’s hoof capsule. Hoof wall growth is generated at the coronet band and from there keratinizes into hoof horn, which we call hoof wall. This keratinized growth takes form partially through a collection of tubules. “The hoof is designed to bear weight. The hoof tubules have a spiral, columnar structure that makes them resistant to compression and flexion. The conical shape of a hoof provides a strong structural support.”¹ If these tubules maintain their linear profile, they remain very strong.
Figure 1 is a collection of straws (tubules) under a load. When the straws remain straight, they can easily handle this load. However, since the hoof wall is malleable and adapts to force, these tubules do not always remain straight.
Figure 2 is the same collection of straws but, once distorted, they cannot handle half of the original weight without some additional support.
Figure 3 is a real hoof example of the same situation. Notice in Figure 3, the hoof wall is giving in to the forces in the outside heel and has folded in upon itself. This has created a very weak structure. So, even though this hoof has a poor hoof angle, the natural inclination to trim toe only and preserve the heel isn’t a strategy that will benefit this horse. Trying to shorten the toe length in order to increase the hoof angle without trimming the heels, or worse yet adding heel wedges, will only compromise the heels of this hoof further. The resulting increase of hoof angle will never be sustained. Trimming those heels down to solid (and straight) hoof wall is the only way to improve this hoof. Once down to solid hoof wall we can address the low angle situation. (See Figure 4.)
Hoof capsule integrity is compromised by the distortion of hoof wall. The natural shape of a hoof is defined by the shape of its coffin bone (P3). The hoof wall shape is formed by the laminar attachment between the hoof wall and P3. This attachment happens in the upper third of the hoof capsule so that any variance from that shape in the lower two thirds of the hoof is distortion. Keeping in mind that the upper third of the hoof is its natural shape, distortion then becomes easy to identify.
Some degree of distortion is evident in most hooves and is not limited to the heels alone. It can be seen as side wall flares or dorsal (front) hoof wall thickening. All forms of hoof wall distortion has a negative effect on the horn tubules and therefore the ability of the hoof the deal with forces placed against it. Minimizing that distortion is one important key to maintaining a strong hoof capsule. Keeping the horn tubules in their original form will help maintain a house of straws that even the big bad wolf couldn’t blow down.
1. The Principles of Horseshoeing (P3) By Dr. Doug Butler and Jacob Butler Page 611