How does the change in hoof shape between shoeings affect the internal structures of the horse’s foot? Scientists at the Derona Equine Performance Laboratory, part of the Utrecht University Vet School, have been investigating.
In earlier work*, Dr Meike van Heel and colleagues demonstrated that the hoof shape gradually changes as the hoof grows after being shod. They found that the hoof angle changed by an average of 3.3 degrees in front and 3.2 degrees in hind feet between two shoeing sessions. The shoe tends to protect the hoof horn at the toe, while friction between the shoe and the wall tends to wear down the horn at the heels.
In the current study, they used a combination of force plate measurements and radiography to assess how hoof growth between shoeing sessions affects the forces on the joints of the lower limb.
They recorded the pressure exerted by the foot. This was done by standing the horse on a force plate . Computer software produced a map of the pressures underneath the foot. It also calculated the centre of pressure. The researchers then took measurements from the radiographs and assessed the position of the distal interphalangeal (DIP or coffin) joint and proximal interphalangeal (PIP or pastern) joint in relation to the centre of pressure.
Initial measurements were taken two days after the horses had been shod. They were then repeated just before the horses were shod again eight weeks later.
How did the horses adapt to the change in foot shape between shoeings? The scientists found that the horses compensated by altering the angle of the DIP joint. In other words, the hoof pastern axis tended to be broken backwards. On the other hand, there was no change in loading of the PIP joint.
This has implications for the deep flexor tendon and navicular bone. The pressure on them is increased by the increased extension of the distal interphalangeal joint.
The researchers also noticed a difference between feet. On average the hoof angle of the front feet differs by 2.9 degrees. They noted that the foot with the lower hoof angle is subject to greater changes between shoeings.
They suggest that horses with feet of significantly different shape may be prone to overloading problems in the low-heeled foot.
Leaving the horses for eight weeks between shoeings exaggerates the changes that occur within the feet. Had the horses been shod more frequently, the changes in angle and force on the structures within the foot would have been less marked.
Dr van Heel suggests that to minimise the risk of damage to the deep flexor tendon and navicular bone, the shoeing interval should be kept short. Ideally the shoeing interval should be selected individually for each horse - taking into account the shape, characteristics of each horses. As the changes are more severe in the foot with the lower hoof angle, they suggest that this foot gives the best indication of when the horse should be reshod.
*MC van Heel, M Moleman, A Barneveld, PR van Weeren, W Back.
Changes in location of centre of pressure and hoof un-rollment pattern in relation to an 8-week shoeing interval in the horse.
Equine Vet J. (2005) 37, 536 - 540.
For more details see:
Hoof growth between two shoeing sessions leads to a substantial increase of the moment about the distal, but not the proximal, interphalangeal joint.
M Moleman, MC van Heel, PR van Weeren, W.Back.
Equine Vet J (2006) 38, 170 - 174.