The Connemara pony, a breed developed in Ireland, is close to the perfect mount for many riders. These equines are not too big and are sturdy and strong without being coarse. Good jumpers with a pleasant temperament, Connemara ponies are ideal for many children and small adults.

In the past few years, evidence of a genetic problem has been seen in the Connemara breed. A number of ponies have shown a condition in which the outer hoof wall splits away from the inner hoof structure. Affected ponies end up bearing weight on the soles of their hooves rather than the hoof wall, a development that can be intensely painful and prevents the ponies from moving easily or performing any work. Given the designation of hoof wall separation syndrome (HWSS), this defect can't be cured through nutrition, farrier care, or dietary supplementation. Severely affected animals must be euthanized.

HWSS is commonly noticed in foals as young as a few weeks or months old, and is expressed more severely in some ponies than in others. Testing of hoof samples from affected animals has indicated a defect in lipid metabolism within the tubular structures of the hoof tissue. Without this normal binding function, the hoof wall is not connected to underlying tissues and is easily broken away from the hoof.

The gene responsible for HWSS is apparently recessive, and carrier ponies used for breeding can appear completely normal but can pass the defect to their offspring. If two carrier ponies are mated, each offspring has a one in four chance of being genetically normal and the same chance of being affected. An average of one in every two offspring will be a carrier, not displaying the syndrome but capable of passing the defect on. Because carrier ponies show no signs, there is no outward way to identify them and exclude them from the breeding program.

Studies at the University of California, Davis are being carried out to identify the defective gene and design ways to carry out genetic testing on Connemara stallions and broodmares. Owners of Connemara ponies who would like to submit DNA samples from their animals are asked to contact researchers Carly Stevens (cstevens@ucdavis.edu) or Miriam Aguilar (miraguilar@ucdavis.edu) for more information.