Thrush and white line disease develop in the equine hoof when anaerobic microorganisms populate “oxygen poor” environments. The bacterial and fungal organisms causing thrush thrive and rapidly divide in these environments that have little available oxygen. These microbes are opportunistic and common in the soil and the horse’s surroundings.All horses are exposed. Both barefoot and shod horses can develop these “hoof eating” microbial invasions.

High moisture environments tend to soften the foot allowing the bacteria and fungal organisms an easier entrance. Hooves with the correct moisture balance have a denser hoof wall and sole, reducing the ability of microbes to invade the tissue.

In cases of thrush, a substance collects in the sulci of the frog that is usually black in color and characteristically has a highly unpleasant odor. Infection of the frog and surrounding tissues often leads to lameness. To help prevent or treat thrush, provide the horse with a clean and dry environment to stand. Clean the bottom of the foot and frog area by removing any debris and wash the area thoroughly. Apply a non-caustic topical disinfectant or antimicrobial clay to the frog area at least twice per week.

Regarding white line disease, the medial (middle) hoof wall is the structure first affected. The initial stages are non-painful. Often the farrier is the first to detect white line disease during a routine trimming or shoeing procedure. Irregularity or thickening of the “white line” on the solar surface of the hoof is usually detectable, often with a dry, chalky material accumulating at the white line on the solar surface. The farrier may notice abnormal percussion in areas of the hoof wall. The hoof wall may be dished inward (concave) opposite of the affected areas and the hoof wall may bulge above the affected areas. As the hoof wall becomes increasingly hollow the outer hoof wall begins to break away. If the horse is shod, nail holes can appear darkened from previous shoeing, and the hoof wall develops less “nail holding” ability. Lameness develops in the advanced stages. It is interesting to note that white line disease often occurs in clean, well-managed stables. Properly balanced nutrition strengthens the sole and hoof wall, thereby reducing the likelihood or severity of thrush or white line disease.

The treatment of white line disease or thrush is most effective when a quality hoof supplement, such as Farrier’s Formula^® Double Strength, is utilized in combination with safe and effective topical hoof disinfectants:

Farrier’s Finish^® is a liquid topical disinfectant that is ideal for the small cracks and crevices that initially occur in the hoof wall with white line disease. In shod horses, Farrier’s Finish^® can also be applied along the edges of shoes so that capillary action will pull the product into the white line area.

Life Data^® Hoof Clay^® is an antimicrobial hoof clay used for filling the larger defects that result from pieces of the hoof wall breaking away due to white line disease. If barefoot, the Hoof Clay should also be applied along the white line area where the sole meets the hoof wall. Life Data^® Hoof Clay^® is effective for thrush when applied into the sulci around the frog.

Do not use topical products that prevent oxygen from passing through the hoof wall. Avoid remedies containing caustic chemicals such as bleach, copper sulfate, grease, motor oil, pine tar, formaldehyde, acetone, and turpentine. A good rule of thumb would be to avoid preparations that you would not want in contact with your own skin.

The most important resources for the horse owner regarding proper advice and treatment for white line disease and thrush are the farrier and veterinarian.

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Frank Gravlee, DVM, MS, CNS

Scott Gravlee, DVM, CNS

Life Data Labs, Inc.