1. GBED: Glycogen Branching Enzyme Deficiency
By: Kaylea Foust and Alison Billas

2. Classification of GBED
Autosomal (non-sex) recessive
Foal must receive abnormal alleles from dam and sire

3. History and Background
First research at University of Minnesota
Funded by American Quarter Horse Association
GBED first identified in foal in 2001
Two years later the gene responsible for the production of glycogen branching enzyme was found
Located on equine chromosome 26

4. Cause of GBED Abnormal glycogen production
Foals are unable to fully utilize glucose, the body’s primary source of energy
Glycogen structures are not properly branched
GBE protein is absent
Only Cross Resulting in GBED G g GG Gg gg

5. Animals Affected
Affects about 10% of Quarter horses and related bloodlines
All identified GBED horses have been Quarter or American Paint horses
Breeders have 25% chance for a GBED foal

6. Signs/Symptoms of GBED
Late term abortion and still births are common
Average life span: Four months
Always lethal

7. Signs and Symptoms of GBED
If the foal is alive:
Weakness and low birth body temperatures
Low white blood cell count
Sudden death due to heart failure or seizures
High respiratory rate and weak muscles
Contracted tendons in all legs
Overall weakness and inability to stand up

8. Prevention and Treatment
Bottle feeding the foal and assistance to stand up helps the foal to grow stronger
Minnesota researchers discovered the genetic defect
Developed a test using DNA samples to determine carriers
Pull out 10 mane or tail hairs from dam or sire
To determine foal status, liver or muscle necropsies are preferred

9. Bibliography