Spring weather and thrush

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Here’s what you need to know about thrush prevention this season, and how to treat it before it gets worse.

During the winter months, hoof condition often deteriorates. One or more contributing factors may include diminished forage nutritional quality, relative inactivity and nutrient under- or over-supplementation. To add insult to injury, spring weather translates to wet ground conditions. These factors increase the susceptibility of the hoof to thrush. Although often overlooked, proper nutrition can promote denser hoof tissue that is more resilient to microbial invasions.

The microbes associated with thrush thrive and divide in oxygen-poor anaerobic environments that are often contaminated with moist organic material. Once the organisms begin dividing in the deep moist recesses of frog sulci, the stage is set for a progressive invasion and subsequent infection of the frog and sole tissue.

The blocking of oxygen to the tissue of the frog can predispose a horse to developing thrush. Oxygen can be blocked to the hoof tissue from foot pads, boots, or the application of grease and oils to the hoof. 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.

Nutritional factors related to thrush

The same nutrients necessary for a sound hoof wall are also necessary for dense frog and sole tissue. 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. Copper and ascorbic acid are also necessary, serving as catalysts in the formation of strong and healthy tissue.

Considering 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:

  • A calcium deficiency can be created 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.
  • Excessive dietary starches and carbohydrates have been implicated in creating a nutrient-rich environment for the bacteria associated with thrush.
  • Excessive dietary sulfur often results from giving MSM, feeding the sulfur containing amino acids methionine and cystine, or a combination of supplementing both MSM and methionine/cystine. Excess sulfur interferes with copper. An adequate tissue level of copper is necessary for strong and dense connective tissue growth.
  • The horse’s daily requirement for selenium is close to levels that create excesses. Selenium over-supplementation results in weak connective tissue due to the replacement of the sulfur cross-links with selenium. Sulfur is important for strong collagen cross linking.

Prevention of thrush

Effective thrush prevention involves a combination of maintaining a clean and dry environment, cleaning the feet on a routine basis, adequate exercise, and proper preventative nutrition. A good hoof supplement will provide the proper nutrients in the correct amounts and ratios to each other without leading to over supplementing.

Treatment of thrush

If the thrush develops, provide the horse with a clean and dry environment. Clean the bottom of the foot and frog area daily 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. A hoof clay containing iodine packed into the frog sulci has been found to be effective. Surgical debridement of affected frog tissue may be necessary in many cases.

Last but not least, keep in mind that the most important resources for horse owners regarding proper advice and treatment for thrush are the informed farrier and veterinarian.