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Icelandic Horse Connection

EPSM

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A compilation of information about EPSM (equine polysaccharide storage myopathy), including information by Beth A. Valentine, DVM, PhD.

EPSM is a muscle condition that results in a buildup of glycogen in the muscle. An EPSM horse is unable to process the buildup, which results in an excess of stored glycogen. The horse becomes weak and has muscle cramps.

EPSM has been found in Icelandic Horses in North America and in Iceland.

The following are some signs that have been observed in affected horses from different breeds.
  • Lack of muscle mass or conditioning, especially in the shoulder or hind quarters
  • "Stringhalt", "shivers", or fibrotic myopathy-type gait, especially when backing or turning
  • Trembling, especially after exercise

  • Difficulty rising, backing, or reluctance to back

  • Lack of energy

  • Poor performance

  • Reluctance to pick up feet for shoeing, etc.

  • Lifting or "stomping" of hind limb or limbs, especially while standing

  • Episodes of "colic", especially after exercise

  • Slightly stiff or awkward hind limb gait

  • Slightly short strided hind limb gait

Glycogen comes from grains, and Dr. Valentine recommends a special diet for EPSM horses.

The diet can be found at: http://www.draftresource.com/EPSM/Draft_EPSM_DIets2.html
and http://www.buckeyenutrition.com/equinetechnical/EPSM.html

A study of 250 horses diagnosed with EPSM offered the following results:
  • Gait abnormality (including stiff gait, difficulty cantering, odd hind limb action, stifle problems, but not including shivers): 129 horses—91 were Quarterhorse, draft, or warmblood related, 38 were other breeds. Of these horses, 118, or 92%, responded to diet change.

  • Tying up: 90 horses—48 were Quarterhorse, draft, or warmblood related, 42 were other breeds; 84, or 93%, responded to diet change.

  • Lack of energy and/or poor performance: 73 horses—54 were Quarterhorse, draft, or warmblood related, 19 were other breeds; 68, or 93%, responded to diet change.

  • Muscle loss or poor muscling: 64 horses—51 were Quarterhorse, draft, or warmblood related, 13 were other breeds; 56, or 88%, responded to diet change.

  • Severe generalized weakness (these horses had difficulty standing up after lying down): 22 horses—19 were Quarterhorse, draft, or warmblood related (mostly drafts), 3 were other breeds; 12, or 54%, responded to diet change.

  • Shivers: 21 horses—17 were Quarterhorse, draft, or warmblood related (mostly drafts and warmbloods), 18, or 86%, responded to diet change.

  • Behavior problems in harness or under saddle: 18 horses—9 were Quarterhorse, draft, or warmblood related, 9 were other breeds; 16, or 89%, responded to diet change.

  • Back pain or total body pain: 15 horses—10 were Quarterhorse, draft, or warmblood related, 5 were other breeds; 14, or 93%, responded to diet change.

  • Difficulty with trimming hooves or shoeing: 12 horses—11 were Quarterhorse, draft, or warmblood related, 1 was another breed; 11, or 92%, responded to diet change.

  • Weakness in the hind limbs: 11 horses—10 were Quarterhorse, draft, or warmblood related, 1 was another breed; 10, or 91%, responded to diet change.

  • Episodic colic: 6 horses—5 were Quarterhorse, draft or warmblood related, 1 was another breed; 6, or 100%, responded to diet change.


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