The intense selection for equine performance traits over many generations has resulted in horses with enhanced muscle mass and improved physical performance; however, reported muscle disorders have also become common.

The surprisingly large number of known heritable muscle diseases in horses currently include polysaccharide storage myopathy type 1 (PSSM1), hyperkalemic periodic paralysis (HYPP), malignant hyperthermia (MH) and immune-mediated myositis (IMM), among many others. Disease-causing gene mutations (mutant alleles) have been identified for PSSM1, HYPP, MH and IMM in all horse breeds. These breakthroughs mean that researchers can genetically test for these alleles, decipher whether a particular one is causing disease in an individual horse, and determine how often a mutant allele occurs in different breeds.

The Equine Genetics and Genomics Laboratory at the University of Minnesota (UMN) is conducting a study to determine the genetic mechanisms associated with equine muscle disorders and how diet and exercise affect them. The primary goal of this study is to build a database of more than 3,000 horses that will help veterinarians, researchers and horse owners develop comprehensive treatment strategies for muscle diseases in individual horses.

How You Can Help

UMN requesting the help of horse owners to assist in building our database by doing the following:

  • Provide information in the Muscle Disease in Horses survey for a horse on your property with suspected or diagnosed muscle disease.
  • Provide the same information in the same survey for another horse of similar age and breed on your property without suspected or diagnosed muscle disease.
  • Upload photos, videos and medical files (e.g., blood tests, muscle biopsy results, or genetic testing if available) for each horse to our secure file-receiving folder on Dropbox.
  • Mail-in hay, grain, supplement and hair roots samples to our laboratory.

All horse breeds are welcome to participate. For more detailed instructions on how to participate, information about the study and questions, please visit the UMN website. You can also follow UMN on Facebook and email us at This research is funded in part by a grant from Morris Animal Foundation, as well as support from private donors.

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