Fissures and Horn Cracks
Fissures and horn cracks are caused by shearing forces (1) when horses place unequal load on their hooves. They are separations along the horn tubules that commence when the horn starts to crack due to tension in the hoof. These separations develop in the toe or side wall of the hoof or in the rear area of the bar according to the specific asymmetrical shape of the extremities. The cracks generally open up between the steeper and the more slanted parts of the hoof wall. Cracks in these areas are caused by the different forces exerted by lifting up and putting down the foot. While the steeper parts of the hoof wall are subject to an upward force due to the pressure from the ground, the more slanted parts of the hoof wall are leveraged outwards (and inwards with superslanted walls). Even if the hoof is very long so that abrasion is not a problem, it is in danger of developing fatigue cracks that could turn into horn cracks lateron. In general, it can be stated that the greater the asymmetry of the extremities and the longer the tubular horn of the bearing wall, the greater the leverage forces and therefore the danger of fissures and horn cracks developing in the horn capsule.
The only way to prevent or treat this phenomenon is to eliminate the uneven load. Grating those parts of the wall that are less subject to strain in order to control horn abrasion ensures that they are run off just as quickly as those under great strain. Slanted side, bearing and toe walls bent outwards are corrected from the outside to reduce the bending forces on them. The hoof wall is grated as high as possible in the area of the horn cracks to shorten the especially long and stable exterior tubules since it exerts the greatest spreading on the horn cracks. Lying bars are cut back while bulged sole horn that forces the horn of the heel wall outwards is removed.
As soon as this strain is equalised, the horn cracks will start to disappear. However, regardless of the amount of horn and quality of the hooves, all therapy should be geared towards treating the causes of horn cracks. If they are not the result of an injury, fissures and horn cracks in the hoof horn should alarm the owner to the fact that the horse's extremities are suffering from an extremely detrimental strain situation. Using the conventional aids such as special horseshoes, horn substitutes, tapes or the ever-popular transverse grating will have no effect whatsoever on the causes. Even if they temporarily stabilise the situation, they cannot solve the orthopaedic problem that causes this major problem. The damage to the horse is not eliminated, but exacerbated due to the fact that it continues to exist.
(1) with the exception of defects of the horn wall resulting from injuries (for example, injuries in the coronet)