In response to recent requests for information about white line disease, American Farrier Journal editors have assembled a few facts from the magazine’s archives.

  1. White line is a keratolytic process involving the deeper nonpigmented zone of the stratum medium. It involves a separation of the layers of the hoof wall (between the stratum medium and the stratum internum). It starts at the bottom of the separation and works its way up into the hoof.
  2. Farriers often are the first to see it, usually as a separation of the hoof wall.
  3. Many veterinarians and researchers now believe that the bacterial or fungal infection that many horse owners and farriers focus on is actually a secondary problem. The bacteria or fungi that cause the infection gain access to the interior of the hoof due to a compromised hoof wall. This can be caused by trauma, laminitis, stress due to imbalance, or improper nutrition among other causes.
  4. To get rid of white line disease, you have to identify the cause of the compromised hoof wall and correct it.  Something as simple as a poorly balanced hoof can place stress of the hoof wall, causing a separation of the white line and creating a pathway for infection.
  5. Other treatment consists of opening the damaged area and trimming away the diseased horn tissue. Hoof wall resection may be necessary in extreme cases. Topical agents may be helpful in fighting the bacterial or fungal infection (AFJ, July/August 2009, Pages 31-38).
  6. While some believe that white line is caused by excessive moisture or unsanitary conditions, it also occurs in horses in dry climates and those kept in well-cleaned stalls.
  7. Scottish researcher Susan Kempson has studied the role of nutrition in helping to prevent White Line Disease (AFJ, April 2006, Pages 35-40). She concludes that the lack or excess of a particular nutrient causes a breakdown in the permeable layer of the hoof wall, allowing bacteria to get into the hoof. To help prevent this, she recommends:
    • A diet that is well balanced in calcium and phosphorus. You need a ratio of 1.6 parts calcium to 1-part phosphorus.
    • Alfalfa as a good source of calcium for horses that have trouble absorbing it.
    • Avoiding excess vitamins A and D — particularly A.
    • Avoid excess selenium. One part per million is adequate. Once you get over 5 parts per million, you’re getting into toxic levels.
    • Copper, which can provide some protection against too much selenium.
    • Avoiding excess carbohydrates, particularly the molasses-based mixes.
    • High-fiber diets, to reduce the production of trans-fatty acids in the intestines.
    • An appropriate supplement that will stimulate good horn growth.

Dr. Stephen O’Grady, veterinarian and farrier from Marshall, Va., reports that in 58 cases of white line disease he treated over 7 years, 40 were successfully resolved with debridement alone and the rest with resection, debridement and a dye marker (AFJ, July/August 2007, Pages 81-82). To review a paper on managing white line disease that O’Grady presented to the American Association of Equine Practitioners, visit his website at:

http://www.equipodiatry.com/article_white_line.htm