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Can Proper Nutrition Help Prevent or Control Thrush?


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There has been a vast amount of information published in the scientific horse industry literature concerning the causes, prevention and treatment of thrush. Although often overlooked, proper nutrition can promote the development of hoof tissue with better characteristics to help prevent or control thrush.

Causes of Thrush

Thrush develops in the equine foot when bacterial organisms begin populating the dark and moist crevices, or sulci, of the frog. These organisms thrive and divide in oxygen poor anerobic environments that are often contaminated with moist organic material. The organisms causing thrush are opportunistic and common in the soil and environment. All horses are exposed. High humidity or wet environments predispose horses to thrush. Once the organisms begin dividing in the frog sulci, the stage is set for a progressive invasion and subsequent infection of the frog tissue.

Other Predisposing Factors to Thrush

The blocking of oxygen to the tissue of the frog and surrounding areas will predispose a horse to developing thrush. Oxygen can be blocked to the foot tissue from foot pads, boots, or the application of grease and oils to the foot. Strong astringents such as formaldehyde, copper sulfate, and chlorine are caustic to live tissue. These chemicals denature the proteins in the external layer of the tissues and thereby reduce the ability of oxygen to penetrate.

Symptoms of Thrush

The material associated with thrush is usually black in color and characteristically has a highly unpleasant odor. Infection of the frog and surrounding tissues often leads to lameness.

Nutritional Factors Related to Thrush

In white line disease the first line of defense from environmental microbes invading the hoof capsule is a ‘sound’ hoof wall structure. Dr. Susan Kempson, a noted equine nutrition researcher in the Dept of Preclinical Veterinary Sciences, Royal School of Veterinary Studies, at the University of Edinburgh in Scotland, found that many of the same organisms that are linked with white line disease are organisms associated with thrush. The same nutrients necessary for a sound hoof wall are also necessary for dense frog and sole tissue. For example, calcium is required for the proper bonding of cells to each other. Zinc is important for healthy keratin, the tough pigmented material found in the outer layers of the frog and sole. Methionine is necessary to form the healthy “cross links” of collagen that add strength and elasticity to tissue. Phospholipids are needed to form healthy cell membranes that give the cells the ability to maintain proper moisture and oxygen balance, and to repel excess environmental moisture. Copper and ascorbic acid are also necessary, serving as catalysts in the formation of strong and healthy tissue. Many other nutrients also have a role in forming and maintaining healthy hoof tissues and serve to help prevent thrush.

The Role of the Immune System in the Resistance to Thrush

The body has two basic biochemical mechanisms to resist thrush. The first are enzymes that directly attack the invaders at the tissue level, including peroxides peroxidases which chemically release oxygen to kill the bacteria. The second biochemical protecting factor is antibodies that circulate and attack the offending organisms. Proper dietary protein and dietary zinc are important for good immune system function.


Nutrient Excesses may Decrease the Bodies Resistance to Thrush

With today’s equine feeding methods the excesses and imbalances of nutrients are probably more detrimental to the horse than deficiencies of individual nutrients.  Some examples include:
1. Creating a calcium deficiency by feeding bran. Whether from wheat, rice or other grains, bran contains phytate, which is high in phosphorus. Phosphorus excess leads to calcium deficiency by blocking the absorption of calcium from the small intestinal tract. Low calcium levels weaken the connective tissues of the frog, sole, and hoof capsule.
2. Excessive dietary starches and carbohydrates have been implicated in creating high tissue carbohydrate and sugar levels resulting in a nutrient rich environment for the bacteria associated with thrush. Excess carbohydrate diets are also linked to metabolic syndromes such as insulin resistance.
3. Excessive dietary sulfur often results from MSM supplementation, supplementation with the sulfur containing amino acids methionine and cystine, or a combination of both MSM and methionine/cystine supplementation. Excess sulfur interferes with copper.  An adequate tissue level of copper is necessary for strong and dense connective tissue growth.
4. Selenium supplementation or feeding diets fortified with selenium often leads to selenium excess. The horse’s daily requirement for selenium is close to levels that create excesses, resulting in weak connective tissue by replacing the sulfur that is important for strong collagen cross linking.

Prevention of Thrush

Effective thrush prevention involves a combination of maintaining a clean, dry (but not too dry) environment, cleaning the feet on a routine basis, adequate exercise, and proper preventative nutrition. Proper nutrition involves supplying nutrients in the correct amounts and ratios to each other without over supplementing.

Treatment of Thrush

If the horse develops 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. Do not utilize a thrush remedy that contains caustic chemicals such as turpentine, formaldehyde, copper sulfate, or chlorine. Hoof disinfectants containing tame iodine are ideal. “Sugardine” treatments utilizing sugar-betadine solutions packed into the frog sulci have been found to be effective in many cases. Surgical debridement of affected frog tissue may be necessary.
The most important resources for the horse owner regarding proper advice and treatment for thrush are the informed farrier and veterinarian.

With special thanks to -
J. Frank Gravlee, DVM, MS, CNS
Founder of Life Data Labs, Inc.
Developer of Farrier’s Formula®
Co-authored by H. Scott Gravlee, DVM
Equine Nutrition Consultant