White Line Disease in Horses: Causes, Symptoms, Support

As the saying goes, “No Hoof, No Horse.” This still holds true to today, as maintaining a horse’s hoof health is critical for any horse of any age, breed, sex, or discipline. Every horse needs careful attention paid to their hooves. In some cases, with either poor hoof care or at no fault to the owner, a horse may develop White Line Disease (WLD).

WLD can lead to permanent lameness in some horses, or even death, as a horse must be euthanized due to a poor quality of life. It is a serious enough disease that affects many horses worldwide. Thus, every horse owner needs to be aware of its dangers and how to take precautions.

How Does a Horse Get White Line Disease?

White Line Disease is a fungal and/or bacterial infection within the hoof of the horse. Yet, how WLD manifests itself in the horse still frustrates many scientists and veterinarians today. This is because the exact causes of WLD are still not fully understood. Yet, we do know some predisposing factors and how best to manage them.

First, to understand WLD, it is important to understand some general anatomy of the horse’s hoof. The outer hoof is made up of the:

  • Hoof wall: outer hard layer pigmented that grows down from the coronary band (located at top of the hoof).
  • Sole: underside of the hoof that covers from the wall to the bars and frog.
  • Frog: the V-shaped structure on the underside of the hoof.

The white line forms at the junction of the outer hoof wall and the sole and is usually visible on the underside of the horse’s hoof. The “white line” is usually yellowish in color, and it serves a critical purpose in horse hoof integrity. It joins the sole to the inner hoof wall and protects the interior of the hoof, particularly the coffin bone.

Before a horse suffers from WLD, there must first be some separation in the hoof wall. Surprisingly, separation in the hoof wall is more common than we think in horses. Usually, mechanical forces, nutritional deficiencies or other outside stressors can lead to this phenomenon. However, not all hoof wall separations lead to WLD.

In certain cases, the separation of the hoof wall gives certain “hoof eating” bacteria or fungi the opportunity to enter the hoof and start proliferating. This leads to WLD. These microorganisms are also referred to as keratinopathogenic, meaning they degrade the keratin in the hoof, leading to multiple problems, including:

  • Accelerated hoof wall separation.
  • Reduced hoof structural integrity, formation of pockets of air, bulging or concaving of the hoof wall, and other distortions.
  • Solid hoof wall becomes grey/white powdery with breakdown, usually seen around white line.
  • Formation of deep cracks within the hoof wall.
  • Rotation of distal phalanx (coffin bone).

How Can I Prevent White Line Disease?

Horses of any age, breed, sex, and discipline can be affected by WLD. It also does not matter if a horse is barefoot or wearing shoes. WLD can strike anytime. However, prevention should always be a focus in keeping your horses safe and happy. 

One of the most important tips in WLD prevention, or early diagnosis, is for frequent inspection and care by a farrier. They are best in early detection of any hoof wall separations and how best to care for the problem. They can help with maintaining a strong sole/hoof wall connection.

Other tips include keeping your horses in dry and clean areas as often as possible. WLD is more common in horses kept in dirty, wet, and poorly ventilated areas. Yet, WLD has also been seen in horses kept on dry surfaces, frustrating both scientists and veterinarians. This has led to the belief that other factors are in play, to include mechanical forces (i.e., horses walking on hard surfaces like roads) and genetics (horses with poor hoof conformation).

How Can My Horse’s Diet Help with White Line Disease?

Interestingly, nutrition is also a critical factor in preventing and managing horses afflicted with WLD. Not only is a balanced diet important in maintaining optimal health, it also limits any deficiencies that can increase the risk of poor hoof integrity and infection.

There are some key nutrients that are critically important for maintaining hoof health, which include:

  • Biotin. As a B-vitamin, biotin is essential for healthy hoof growth. It is involved in the synthesis of keratin. Research has shown that horses deficient in biotin can be at risk of poor hoof quality and WLD.
  • Vitamin A plays an important role in maintaining healthy skin and mucous membranes, including the sensitive tissues in the hoof. It can also help boost an immune response to fungal and bacterial infections.
  • Vitamin C has multiple roles in the horse, including collagen synthesis, which is a key component of hoof structure. It’s also seen as a powerful antioxidant in helping to battling infections.
  • Zinc is an essential mineral with multiple roles in the horse, which includes the formation of keratin. Zinc deficiencies have been linked to poor hoof quality and increased susceptibility to WLD.
  • Copper is another essential mineral for hoof health. It helps with synthesis of collagen. Copper deficiencies can lead to brittle hooves and susceptibility to WLD.
  • Iodine is a powerful antifungal nutrient that can help fight hoof infections and WLD.
  • Other minerals: Iron, calcium, and even selenium all have key roles in maintaining hoof health and integrity.
  • Amino acids, of which the most important are the sulphur containing ones, like methionine. They help build strong and healthy hooves.
  • Omega-3 fatty acids are known for their strong anti-inflammatory properties. They can help reduce pain or swelling in the hoof. They also play a role in maintaining hoof wall integrity and reduce the risk of infection.

Despite the robust list of nutrients that all contribute to healthy hooves, thankfully, most of the daily needs of your horses can be met with high-quality forage and a quality horse feed. It is important to remember that forage alone will not meet the dietary needs of your horses. Thus, a well-balanced horse feed is always recommended for any horse. All Tribute® feeds are fortified in all the above listed nutrients to support hoof health.

For example, if given enough high-quality forage each day, a horse’s hindgut produces enough biotin to meet their daily needs. However, most forages are lacking in some nutrients, like key amino acids and/or may be lower in some essential or trace minerals. This is why a well formulated horse feed is always recommended. Then, in situations where the forage quality is moderate to low quality, a horse will undoubtedly need extra nutrition to meet its biotin needs.

In some circumstances, some horses may need extra nutritional support on top of their high-quality forage and horse feed. Hoof supplements, like Tough As Nails®, would be a good choice. This would be especially true of any horses experiencing WLD or having other hoof quality issues.

Take Home Message

The most important tip is to ensure your horse’s hooves are cared for and inspected by a qualified farrier often. They will be able to help recognize and treat any hoof wall separation and/or recognize early signs of WLD. It is also worthwhile to discuss your horse’s hoof health with your veterinarian.

Remember that proper nutrition is an essential component of preventing and managing WLD in horses. Providing a diet of high-quality forage and a high-quality horse feed will help in maintaining your horse’s hooves and reduce the risk of infection and WLD. A hoof supplement may be warranted if your horse is recovering from WLD or experiencing other hoof-related issues. If you have any questions or concerns about your horse’s diet, please feel free to contact us for any advice and a free consultation.


O’ Grady, S. (2019). White line disease: A review (1998-2018). Equine Veterinary Education. 33”102-112.

O’Grady, S. (2006). How to manage white line disease. AAEP Proceedings, 52:520-525.

Article By: Chris Mortensen, Ph.D.
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