Recent research suggests that at least 3% of abortions in Quarter horses are due to glycogen branching enzyme deficiency. Some foals are born alive but are often weak and require warming and assistance to nurse after birth. These foals may appear healthy for a time but eventually the may develop seizures, become too weak to stand, or in some cases, they die suddenly.
Recognizing genetic defects in foals
Foals affected by GBED that survive birth generally die or are euthanized within 8 weeks of age, and although a few foals have survived to the age of 4 months, GBED is always fatal.
© 2013 by April Raine
Owners may note that GBED foals are less active than other foals. In spite of aggressive treatment, all known cases of GBED have been euthanized or died by 18 weeks of age.
Glycogen branching enzyme deficiency (GBED) is a disorder first recognized by clinicians at the University of Minnesota that causes muscle weakness in Quarter Horses and related breeds. The clinical presentation of this disease is variable. Late term abortion or stillbirth is described for GBED.
Dr. Stephanie Valberg’s laboratory recognized that foals with these symptoms have a unique muscle disease and that all these foals are related to one another. The discovery of an abnormal sugar within the skeletal muscle of these foals led the researchers to identify a genetic defect responsible for forming the sugar (glycogen) that provides energy for numerous tissues in the body.
Approximately 8-10 percent of American Quarter Horses are affected; Paints can be carriers. Appaloosas and other breeds that descend from the American Quarter Horse may be carriers. An estimated 3 or more percent of second- and third-term abortions are caused by GBED.
GBED results in second- and third-term abortions and stillborn foals. Researchers think many aborted and stillborn foals whose cause of death was not previously identified might have had GBED. Foals that survive birth generally die or are euthanized within 8 weeks of age. Although a few foals have survived to the age of 4 months, GBED is always fatal.
Now owners are able to test their horses to see if they carry this defect and this can prevent this disease from occurring. Testing can be done to determine of horses carry this genetic defect and are likely to pass it on to their offspring.
The Veterinary Genetics Laboratory at UC Davis offers a Test for GBED