Glycogen Branching Enzyme Deficiency (GBED)

Glycogen Branching Enzyme Deficiency or GBED is a fatal genetic mutation that affects Quarter Horse foals. The mutation prevents foals from properly utilizing glucose, causing damage to the muscles and vital organs. Affected foals often die at birth or shortly thereafter.

This genetic mutation, identified by Dr. Stephanie Valberg of the University of Minnesota in 2004, appears to have developed from one specific horse but now unfortunately affects the horses’ multiple descendants – some say as many as 10% of Quarter Horses have the GBED mutation. To develop the defect, a foal’s parents must both be carriers of GBED.

There is no cure available for GBED at this time, but there is a DNA test to identify whether or not a horse is carrying the mutation. To perform a genetic test for GBED, 20-30 strands of hair from the horse’s main or tail need to be collected and sent to Animal Genetics for evaluation. The hair must be pulled, not cut, so that the root material will remain intact because the hair root provides the DNA material for the test.

Identifying the gene can help equine breeders avoid combining affected parents. Ultimately, the genetic disorder should be eliminated by careful breeding, but in the mean time, you can contact Animal Genetics to have your horse tested for the presence of GBED.  For more information about submitting a sample for GBED testing, please visit the Animal Genetics equine sample collection page

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