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Dwarfism in the Friesian breed with associated health problems


  • Short legs in comparison to a normal sized head and torso
  • Inward protruded rib cage
  • Hyperextension of fetlock joints
  • Tendon laxity
  • Abnormal gait with outward rotation

General Information:

  • Abnormal development of legs and rib cage.
  • Affected horses have a normal sized head and torso but unproportional short legs.
  • Rib cage shows inward protrusion of ribs which may lead to breathing issues.
  • Tendon laxity leads to instable joints and hence to abnormal gait.

Inheritance: autosomal recessive

→ Only animals with two copies of this variant (fd/fd) are affected. Animals with only one copy of the variant (N/fd) are clinically healthy carriers.

Possible Genotypes:

Genotype: The horse is: Effects:
N/N normal. The horse has no copies of the genetic variant causitive for dwarfism and therefore cannot pass it on to its offspring.
N/fd a carrier.
The horse is clinically healthy.  It has one copy of the genetic variant causitive for dwarfism, which will be passed on to its offspring with a probability of 50%.
fd/fd affected. The horse is affected and has two copies of the genetic variant causitive for dwarfism.  The variant will be passed on to its offspring with a probability of 100%. All offspring will be carriers.



  • Carriers may be bred to normal animals (N/fd x N/N) without any risk of producing affected offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
  • Breeding two carriers (N/fd x N/fd) is not recommended due to the possibility of 25% of the offspring being affected.
  • Affected animals (fd/fd) should not be used for breeding.

Tes tinformation: This test detects the change of a single basepair in the B4GALT7 gene.

Leegwater, P.A., Vos-Loohuis, M., Ducro, B.J., Boegheim, I.J., van Steenbeek, F.G., Nijman, I.J., Monroe, G.R., Bastiaansen, J.W., Dibbits, B.W., van de Goor, L.H., Hellinga, I., Back, W., Schurink, A. : Dwarfism with joint laxity in Friesian horses is associated with a splice site mutation in B4GALT7. BMC Genomics 17:839, 2016. Pubmed reference: 27793082. DOI: 10.1186/s12864-016-3186-0.

Further information is available Online Mendelian Inheritance in Animals.

Breeds affected:

Test #: H119

Samples: Blood, Hair

Special Price: 30 € (net)

Time required: 10-14 days

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