Hooves are a very adaptable system to external influences. Unfortunately, in many domestic situations, those external influences are not necessarily helping the hoof development, and ultimately the horse. When more negative influences/stimuli are present than positive ones, the hooves regress. Unfortunately, this may also include how the hoof is trimmed.
On the flip side, given the right stimuli, and enough of it, hooves can change for the better, even at a later stage in life. The limiting factor, however, are the state of the pedal bone, cartilage distortion, and just how much pathology is present and how long it has been present for.
Above the hind hoof of a 19-yo that has been “barefoot-trimmed” for years. The left image is taken at the start when I took on the horse, the image on the right, one year late. Both images were taken four weeks post the previous trim.
The contour of the hoof on the left is a common sight. Looking at its coronet, we notice how curved and how steep it is. The steepness indicates a negative plantar angle, which has a negative effect on ligament and tendon strain, as well as timing of break-over.
The curved coronet is the result of excessive wall loading and longitudinal contraction. If a hoof bears too much weight on the outer rim, aka hoof wall, rather than distributing it across the whole bottom structure (at full load), then the coronet usually ends up with this upward distortion in the mid-section of the hoof. While some argue this is merely cosmetic, a cross-section of such hoof reveals that the underlying coronary corium is actually compressed.
This is similar to a human’s cuticle being pushed upwards. The other response to the upwards distortion of the coronet is the longitudinal contraction of the hoof. When you look at the blue line marking the wall horn tubule at the toe and then compare that to the horn tubules of the side, you can see how the converge towards each other. This means that the back of the hoof has rotated forward in relation to its toe. The result of this is that there is less space in side the hoof capsule, especially in the back half of the hoof, where we find the digital cushion in the navicular region. Typically, this leads to compromised comfort and the horse tends to compensate for that.
On the right, the hoof is in a much more “relaxed” state. The coronet has straightened out and the wall horn tubules are running nearly parallel to each other. A little bit more to do here to achieve a parallel alignment. The hoof has lengthened in the back half and can happily load the heels without the need to compensate.
The horse is now happily striding out and willing to go forward.