Glycogen Branching Enzyme Deficiency (GBED) is a fatal condition caused by the bodies inability to properly store sugar.
In a normal horse, the body stores sugar as energy by converting glucose to glycogen. This inherited disorder prevents the body from producing the enzyme needed to branch the glycogen structure, preventing the horse from being able to adequately store the sugars. This means that the horse will not be able to store enough energy to fuel important organs, such as the muscles and brain.
Foals born affected by GBED suffer from a range of symptoms associated with this lack of fuel, such as low energy, weakness, and difficulty rising. Other symptoms include low body temperature, contracted muscles, seizures, and sudden death. Unfortunately, GBED is always fatal; most affected foals will die before the age of 8 weeks. GBED often causes fetuses to be aborted in utero. Research suggests that as many as 3% of aborted Quarter Horse foals were homozygous for the GBED mutation.
Studies show that the mutation responsible for GBED is carried by as many as 10% of Quarter Horse, Paint Horse breeds and related breeds. GBED is an autosomal recessive trait, meaning a foal can only by affected if the foal inherits the disease from both parents. Horses that are carriers of the GBED have 1 copy of the mutation, but do not have any symptoms associated with the disorder. This makes DNA testing important to screen for carriers and prevent this fatal condition.
The mutation, which causes this disease, has been identified by Dr. Stephanie Valberg and Dr. James Mickelson of the University of Minnesota, and licensed for diagnostic use by Animal Genetics Inc.
Animal Genetics license GBED test is now available -
please download submission form to submit a sample..
US per sample.
Collect sample by pulling (not cutting) 20-30
mane or tail hairs with roots attached. It is important that you
pull the hairs and confirm that the actual root of the hair is being
collected. The root contains the genetic material of your horse
that is needed for DNA testing. Therefore, cut hairs do not provide
an adequate sample of your horse. Place the collected hairs of each
horse in a separate zip-lock bag labeling the bags accordingly with
the horses name or identification number. Download and complete
a submission form for each sample and send along with
payment to Animal Genetics for testing.
Results are given using the following symbolic
horse carries two copies of the GBED mutation and is homozygous
for GBED. The horse is affected with the GBED genetic disorder.
the normal and GBED alleles were detected. Horse tested heterozygous
for GBED and is a carrier of GBED. There is a 50% chance this horse will pass a GBED allele to its offspring.
tested negative for GBED.