Glycogen-branching enzyme deficiency

It is important for providing energy for skeletal and cardiac muscle contraction, and for maintaining glucose hemostasis in the blood.

These branches are important, as they provide additional "free ends" for linear chains of α-1,4-glycosidic bonds, which can then be broken down by amylase.

GBED is caused by an autosomal recessive mutation to the GBE1 gene, which leads glycogen branching enzyme activity that is reduced to absent.

Symptoms include general weakness, contracted tendons, hypoglycemic seizures, cardiac arrest, and sudden death.

Using this, breeders can avoid crosses that could produce GBED foals, and eventually selectively breed it out.