Skip to content
Search Library
thumbnail

Understanding the slight differences among muscle problems in horses can be uphill work for even the most astute student of equine health. Great advances in equine myopathies have occurred over the last 20 years, but with these advances come some ambiguity, especially for those suddenly confronted with a problem. Polysaccharide storage myopathy (PSSM) is one muscle disease that sometimes puzzles caretakers.

Diagnosis of PSSM depends on microscopic examination of a muscle biopsy or genetic testing. Muscle from affected horses contains an abnormal polysaccharide, which makes horses more sensitive to the effects of insulin. In turn, these horses take up glucose into their muscle more efficiently than unaffected horses.

Two forms of PSSM are recognized, type 1 and type 2, though both forms share a common set of clinical signs: painful muscles, skin twitching, sweating, weakness, reluctance to move with light exercise, gait abnormalities, mild colic, muscle wasting, and abnormal bloodwork such as elevated serum creatine kinase (CK) and aspartate aminotransferase (AST). Clinical signs usually appear by the time horses are two or three years old but might be noticeable earlier, as young as weanlings.

Type 1 affects horses of many breeds, with at least 20 different ones documented. While members of light-horse breeds are commonly diagnosed, draft breeds seem particularly prone to the disorder. Though rare in Clydesdales and Shires, many Belgians and Percherons are affected. Some estimates put the rate of diagnosis at 36-50% in these two draft breeds.

Type 2 is diagnosed primarily in light horses, such as stock-type breeds, Arabians, and Thoroughbreds.

Nutritional management of horses with PSSM generally leads to fewer clinical signs. Therefore, taking a hard look at a horse’s diet is the first step. Action items for dietary management include:

  • Revise the diet so much of the horse’s energy is derived from fat and fermentable fiber rather than from starch. Common fat-rich feedstuffs are vegetable oil and stabilized rice bran. Useful sources of fermentable fiber include beet pulp and soybean hulls. Re•Leve Concentrate is ideal for horses with low energy requirements, such as easy keepers, while Re•Leve Original is appropriate for horses with normal energy needs. Both forms of Re•Leve contain high-quality fortification so all protein, vitamin, and mineral requirements are met. Although Re•Leve is not available in Australia, a KER nutrition advisor can recommend a similar customized ration. Please call 1800 772 198 or e-mail advice@ker.com to learn more.
  • Choose hays low in nonstructural carbohydrates (NSC). Though all hay should be tested for NSC content, grass hays are the best place to start for easy keepers. Alfalfa is generally low in NSC, so this legume might be appropriate for horses with elevated energy needs. Soaking hay just prior to feeding is one way to remove some starch.
  • Double-check the vitamin E and selenium content of the diet. If one of the Re•Leve feeds is chosen, sufficient quantities of these essential antioxidants will be consumed, assuming feeding recommendations are adhered to. If another feed is chosen and vitamin E levels are suspect, supplement with a natural source of vitamin E such as water-soluble Nano•E or Preserve PS (or Preserve in Australia).

In addition to these nutritional tips, the importance of regular exercise cannot be overstated. The combination of diet modification to reduce starch and near-daily physical activity are critical to the success of treatment.

Unsure how to proceed with feeding a horse with PSSM? Start a discussion with a Kentucky Equine Research nutrition advisor today.

X

Subscribe to Equinews and get the latest equine nutrition and health news delivered to your inbox. Sign up for free now!