Genetic Diseases in Horses

Many people wonder what to look for when buying a horse. Often, new buyers look for a nice temperament and solid training on the ground and in the saddle. They may overlook illnesses, and genetic disease. 

Genetic defects usually only show up from line-breeding or inbreeding. The two that have shown up from line-breeding were hidden from the public for years to protect big breeders. HYPP and HERDA.

HYPP-Hyperkalemic Periodic Paralysis Disease is a disease of the muscles, not the nerves, but the symptoms look like a nerve problem. It is a defect in the cells that cause them to allow too much sodium to enter the cell.  This creates too much “voltage” in the cell which causes twitching or muscle weakness. Some horses have been found dead in their stalls from tremor attacks. It mostly affects horses with “Impressive” in their bloodlines. Impressive’s DNA shows that he goes back to Three Bars several times. as he is line bred. Since then, the AQHA will not let you register an Impressive bred horse unless it is a double negative.  If you end up with a horse that has HYPP, feed only grass hay and oats and keep the potassium levels. They do better on pasture with free access to salt. 

Another genetic disease HERDA (hereditary equine regional dermal asthenia, or Hyperelastosis cutis), is one of the biggest cover ups in the cutting horse world. This is a genetic disease that causes a defect in the skin on the horses back. It appears that the muscle doesn’t attach the skin to the horse, so when you put a saddle on the horse the skin is horribly destroyed. Some top blood lines in the cutting industry may be carriers. It was stated that carriers come from the Poco Bueno line. However, It is a recessive gene, meaning that you have to cross a sire and a dam that are both carriers, and then one out of four foals will have the disease. Poco Tivio mares were the most successfully bred with Doc Bar. Smart Little Lena is a very popular cutting sire and the most expensive. If these horses are carriers there will be a huge shock to the cutting community. Remember again, that it is a recessive gene.

GBED (Glycogen Branching enzyme deficiency) is a disease of foals with Quarterhorse bloodlines that results in death within a few months of birth. This is newly recognized, as the deaths were previously chalked up to other causes. Signs can include abortion, still birth, low body temperature and weakness at birth, sudden death from seizures or heart stopping, and inability to get up from the weakness.