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White Line Disease in Horses

White Line Disease is an annoying and often painful hoof disease, which is not yet known to every horse owner. What is it exactly, how does the disease develop, how is it treated, and what can you do to prevent White Line Disease as much as possible?

White Line Disease (WLD) is a separation process in which the inner hoof wall detaches between the middle layer (stratum medium) and inner layer (stratum internum) of the hoof. The pushing apart of the hoof wall and the subsequent softening of the hoof tissue occur right next to the white line in the hoof. Hence the name White Line Disease.

WLD can start at the toe, side, or at the heel. The infection is sometimes in a specific spot, but can also spread over a large part of the hoof. Often, it affects the toe part (front) of the hoof. With WLD, the softening creeps up from the bottom of the hoof to the top, approaching the coronary band if left untreated. White Line Disease will not affect the coronary band.

Causes of White Line Disease

The cause of WLD is unknown, there is not a single source. Wet conditions, mud, and dirty stables are thought to contribute to the condition, although they are probably not the (only) cause. Infections likely play a role, with bacteria, fungi, or a combination of both commonly found. However, it is not clear if they actually initiate the softening or simply take advantage to further degrade and infect the hoof. Some sources state that the softening only occurs once the hoof wall starts to separate. WLD also tends to occur in extreme dryness, when hooves become brittle and sometimes even crack, allowing dirt to penetrate more easily.

Often, the anatomical features of the hoof also play a role. If the shape of the hoof is not ideal, additional forces can be exerted on the hoof wall. Long toes and low heels put extra pressure on the inner hoof wall and reduce blood flow in the foot. This makes it more susceptible to infections. Two studies found that low zinc levels in the feed may contribute to the development of WLD. A lack of copper can also play a role.

White Line Disease occurs in all breeds and in horses with or without shoes. Sometimes only one hoof is affected, sometimes multiple hooves. Horses that have had laminitis are more susceptible. The connection in the hoof wall is already weaker after laminitis. Also, if your horse has had a hoof abscess or if rocks regularly get stuck in the hoof wall, these could be entry points for WLD. Occasionally, the condition is caused by stepping on a nail.

Diagnosis of White Line Disease in Horses

White Line Disease can be identified with the naked eye. Sometimes X-rays are taken to support the diagnosis. The veterinarian can then better see how deep the hoof wall is affected.

In the initial phase of WLD, a horse is usually not lame, but as White Line Disease progresses, lameness may develop. The connection between the middle and inner hoof wall may detach to the point where rotation of the coffin bone occurs. This is very painful. Fortunately, WLD is often found in its early stages by the farrier. You may notice a wider 'seam' between the hoof wall and the sole, with some crumbly material visible. Sensitive and thin soles can also be signs of WLD, and the horse may react sensitively to a pair of tongs test.

In advanced stages, a flattening (dish) may occur on one side of the hoof. On the other side, a bump may form under the coronary band. The bump will be just above the affected part of the hoof wall. When the hoof wall is affected, the coffin bone will move towards the side with the least resistance, causing the bump and the flattening on the opposite side. This is very painful, and the horse may become lame.

Treatment of White Line Disease

The most important treatment provided by the veterinarian is the excision of the hoof wall. Beforehand, it must be determined, possibly with an X-ray, how far this is necessary. The excision can sometimes be performed by a specialized farrier. All infected hoof tissue must be removed to eliminate the infection. When WLD occurs on its own, it is usually treatable. However, if it occurs in a horse that has had laminitis or if the horse has a rotated coffin bone, recovery can be more difficult. The further the hoof is affected, the longer the recovery period will be.

In general, it is not necessary or even beneficial to constantly disinfect the excised hoof after treatment. This can hinder the growth of healthy hoof tissue if too aggressive agents are used. However, it is necessary for the veterinarian to return every few weeks to re-excise any new affected areas. This process continues until no new softening occurs. Since the detached horn wall cannot reattach itself and needs to be entirely rebuilt from the coronary band, healing will always take a considerable amount of time.

For severely affected hooves, sometimes special shoeing is required. It is important that the forces on the hoof are optimized through adjustments of the stance so that no 'splitting' forces are exerted on the hoof wall. This way, healing can proceed optimally.

Prevention of White Line Disease

Since the exact cause of WLD is not known, it is difficult to provide a definitive solution to prevent your horse from developing this condition. However, it is important to properly care for the hooves. Additionally, there are various supplements available on the market that promote hoof health and enhance your horse's resistance.

Tips to prevent White Line Disease:

Ensure the farrier visits on time to maintain the hooves;
Remove all stones from the hoof and hoof wall every day;
Prevent hooves from drying out by wetting them regularly and applying a layer of grease afterward (to retain moisture);
Keep the stable floor clean and dry;
Don't let your horse stand in a muddy paddock for 24 hours a day, ensure there is a dry area available;
Provide a supplement that promotes hoof growth and quality, such as liquid silicon
Ensure your horse's resistance is optimal, for example, by using cannabinoids from clove.

Conclusion: Early Intervention is Essential for White Line Disease

White Line Disease (WLD) is a separation process in which the inner hoof wall detaches. Often, there is crumbly hoof material visible, and the hoof wall separates. When the detachment and softening extend far upwards in the hoof, the coffin bone may rotate, causing severe pain and lameness. The exact cause of WLD is not entirely clear, but good stable hygiene and a dry place to stand are important. Regular hoof care and the right supplements also contribute to preventing WLD. Treatment involves excising the affected hoof tissue by a veterinarian. Recovery can take a long time. Early intervention is crucial to prevent worsening. Therefore, check the hooves daily and consult your farrier if in doubt.