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Glycogen branching enzyme deficiency

Contracted tendons is a common symptom of foals with GBED

Glycogen Branching Enzyme Deficiency (GBED) is a genetic disease affecting horses, especially American Quarter Horses and related breeds.


Diagnosis, Symptoms, and Prognosis

Lacking an enzyme necessary for storing glycogen, the horse's brain, heart muscle, and skeletal muscles cannot function, leading to rapid death. This condition may be diagnosed with a muscle biopsy. Most foals with GBED are aborted or stillborn, and those that survive live only for a few months. Symptoms include general weakness, contracted tendons, seizures, cardiac arrest, and sudden death. There is no known treatment.


The disease occurs in foals who are homozygous for the lethal GBED allele, meaning both parents must be heterozygous for the allele. A blood test for this allele was developed by the University of Minnesota College of Veterinary Medicine and as of 2005 is licensed to the UC Davis Veterinary Genetics Laboratory. Using this, breeders can avoid crosses that could produce GBED foals, and eventually selectively breed it out. Initial samples suggest that about 10% of Quarter Horses are carriers.

This genetic disease has been linked to the foundation sire King.

See also

Glycogen storage disease type IV

External links


"Testing for Genetic Diseases." Equus 353. pp 40-41.


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