White Line Disease (WLD) has a variety of other names such as stall rot, hollow foot, wall thrush, and seedy toe. The white line referenced in its name is where the outside hoof wall meets the sole. The condition occurs when bacteria or fungus infect the layers of the hoof wall. This causes a deterioration of the hoof wall and leads to lameness.
The symptoms include the horn wall looking chalky or white and gradual separation of the hoof wall as referenced above. For more on it please see:
If you are concerned that White Line Disease may be an issue for your horse please visit your vet. There are a variety of treatments for white line disease that are available. They include: