The white line lies between the hard side wall of the hoof and the more pliable sole. It allows some elasticity and mobility within the hoof and the line is part of the lamellae which lock the hoof onto the pedal bone. Reduced horn quality and hardness leaves the structure more susceptible to damage and vascular disturbances. It is known that when the white line is weakened foreign material (grit) may be caught in it and gradually work its way into the foot with the pressure and shearing forces as the cow moves along especially on hard surfaces. If foreign material ascends the white line and penetrates the sensitive tissue of corium, infection will most likely occur, which leads to lameness and further damage to the white line at the point of origin.
A regular hoof trimming program and attention to the hoof quality with regular foot bathing of the herd will assist in spotting potential white line disease. The elimination of standing water and maintenance of high quality walkways will help to ensure healthy hoof horn structure. Old damaged concrete surfaces are a source of hard grit and this often causes white line disease.