Friesian dwarfism (B4GALT7-related) - Friesian horse

Friesian dwarfism in Friesian horses

This genetic test detects the B4GALT7 variant c.50G>A that causes Friesian dwarfism, also described as B4GALT7-related dwarfism, in Friesian horses. Affected horses show characteristic disproportionate growth: the limbs, ribs and often the neck are shortened, while head size and back length can appear relatively normal.

The variant disrupts normal B4GALT7 function, a gene involved in extracellular matrix formation and normal bone development. This leads to abnormal growth and joint support, including lax flexor tendons and hyperextension of the fetlock joints.

Practical value of this test

• GG: the horse does not carry the tested variant.
• GA: the horse is a carrier and can pass the variant on without having dwarfism caused by this variant.
• AA: this genotype causes Friesian dwarfism.

Because Friesian dwarfism is inherited as an autosomal recessive disorder, this DNA test helps breeders identify carriers reliably and avoid carrier-to-carrier matings. This supports the prevention of affected foals while allowing valuable bloodlines to be used responsibly.