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→ Energy deficiency in muscles and organs


  • Spontaneous abortions
  • Weakness
  • Low body temperature
  • Accelerated breathing
  • Tremors

General Information:

  • Foals may die shortly after birth due to organ failure (liver or heart).
  • Glucose cannot be stored as Glycogen → lack of nourishment in muscles and organs.
  • Affected foals usually die within the first 8 weeks.

Inheritance: autosomal recessive

→ Only animals with two copies of the genetic variant (gbed/gbed) are affected. Animals with only one copy (N/gbed) are clinically normal carriers.

Possible Genotypes:

Genotype The horse is:
N/N normal. The horse has no copies of the genetic variant causative for GBED/GSD IV and therefore cannot pass it on to its offspring.
N/gbed a carrier. The horse is clinically healthy. The genetic variant causative for GBED/GSD IV will be passed on to its offspring with a probability of 50%.
gbed/gbed affected. The horse is affected and will not live long enough to reproduce.



  • Carriers may be bred to normal animals (N/gbed x N/N) without any risk of producing affected offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
  • Breeding two carriers (N/gbed x N/gbed) is not recommended due to the possibility of 25% of the offspring being affected.

Testinformation: This test detects a single basepair change in exon 1 of the GBE1 gene.

Ward TL, Valberg SJ, Adelson DL, Abbey CA, Binns MM, and Mickelson JR. (2004). Glycogen branching enzyme (GBE1) mutation causing equine glycogen storage disease IV. Mamm Genome 15, 570-577.

Further information is available at Online Mendelian Inheritance in Animals.

Breeds affected:

Test #: H103

Samples: Blood, Hair

Price: 35 € (net)

Time required: 10-14 days

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