Members of the Friesian Horse Association of North America should contact FHANA regarding testing procedures and submission of samples.

Hydrocephalus in the Friesian horse is a developmental defect of the foal characterized by an accumulation of cerebrospinal fluid in the ventricular system of the brain. Foals are born with grossly enlarged foreheads and are often stillborn or require euthanasia soon after birth. A hydrocephalic foal also presents a potential dystocia (difficult birth) for the mare. While hydrocephaly may have other causes such as infection or trauma, a mutation associated with this  condition has been identified in the Friesian horse in the B3GALNT2 gene. Friesians or Friesian crossbreds should be tested prior to breeding to avoid production of an affected foal. The mutation is recessive and the genetic test allows breeders to avoid breeding two carriers together. Should two carriers be bred, the probability is that one out of four foals will be hydrocephalic.

The cost is $35 for each test (or $60 for the Friesian Dwarfism and Hydrocephaly tests).