EQUUS ‘Farm Calls’ episode 20: White line disease in horses

EQUUS “Farm Calls” is brought to you in 2022 by Farnam—Your Partner in Horse Care.

“There is a lot of confusion about white line disease,” said Dr. Steve O’Grady, who worked as a professional farrier for a decade before becoming an equine veterinarian. “White line disease can occur in the hoof wall of any horse of any breed or discipline. It can happen to the best horse in the world or one in unhygienic conditions. One that is well-shod or barefoot.”

White line disease starts at the ground surface and progresses upward in the hoof wall.

O’Grady said that you can’t transfer white line disease from one horse to another, and they have tried through experiments!

However, veterinarians and farriers still don’t know why some horses get white line disease and others in the same barn don’t. “The horse has to have the propensity,” he said.

O’Grady noted that white line disease is not a fungal disease. You can find bacteria and yeast early in the disease process, then separation occurs in the hoof wall. “Fungi then take over,” he stated.

White line disease actually takes place in front of the white line at the sole/wall junction, he explained. He reminded horse owners that as you get closer to the circulation in the inner hoof that the hoof tubules become more diffuse and softer.

O’Grady explained that when the hoof splits or offers an entry point, bacteria invades. “They become horn-digesting organisms and cause separation up the hoof wall,” he said.

White line disease is often found by the farrier trimming a horse’s foot and finding separation. It can be—or become—a deep “trough” in the hoof wall.

“Put the foot on the ground and slowly tap on the hoof with a rock or something hard,” suggested O’Grady. “Start at the heel and slowly go around the hoof from the ground. You can hear the hollow that corresponds with a separation in the wall.”

O’Grady said you often see a defect or distortion in the hoof capsule when you have white line disease.

He warned that long toe/low heel trimming of the hoof could predispose the horse to stresses that allow white line disease to get a foothold. He also said horses with club feet and that had hooves with sheared heels seem to be more prone to white line disease


That separation needs to be cleaned out “to get to the bottom of the space,” said O’Grady. “Trim the foot and put something like Keratex in there with cotton or pine tar to keep debris from pushing into the hoof wall separation. If it is extensive, a veterinarian or farrier needs to clean it out with a brush or hoof knife until you have a solid perimeter…you resect part of the hoof wall. Then you use a wire brush to keep it clean until it grows out.”

O’Grady said white line disease can cause a serious separation of the epidermal lamellae that causes a loss of connection between the hoof wall and bone. “Then you can get rotation,” he warned. “That’s mechanical laminitis.”

He said you might need the veterinarian to X-ray the foot.

“Appropriate farriery and resection will resolve white line disease,” he said.

About Dr. O’Grady

Dr. Steve O’Grady worked as a professional farrier for a decade prior to obtaining his degree in veterinary medicine. Dr. O’Grady worked in Virginia with Dr. Dan Flynn at Georgetown Equine Hospital for 10 years, then in 2003 he opened Northern Virginia Equine in Marshall, Virginia, which was devoted to foot disease and equine therapeutic farriery.

Dr. O’Grady’s current practice is called Virginia Therapeutic Farriery in Keswick, which is a referral practice that provides advanced services in equine podiatry. O’Grady also sees referral patients at Georgetown Equine Hospital in Virginia and Palm Beach Equine Clinic in Wellington, Florida.


  • What is white line disease?
  • What causes it?
  • How is it diagnosed?
  • How is it treated?
  • How can you prevent it?
  • What other issues can look like white line disease?




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