As breeding season is right around the corner for those of us in the northern hemisphere, I think it is good to take into consideration genetic testing. The 5 panel test is a group of five diseases commonly found in quarter horses and related breeds. Knowing if your mare or stallion carries the genetic defects that can cause these diseases can help steer you to a breeding match that will prevent experiencing these debilitating diseases in the offspring.

HYPP
HYPP (Hyperkalemic Periodic Paralysis) is a disease that results in uncontrolled muscle spasms and/or paralysis. They can be as severe as to cause death. The defect results in too much potassium being leaked into the blood stream. It can be managed by a low potassium diet and also the use of potassium wasting diuretics. If a horse has 2 copies of the gene, they are most likely to manifest signs. If one copy of the gene, less likely.

MH
MH (Malignant Hypothermia) is a disease where the horse’s body temperature gets too high, heart rate is elevated, has excessive sweating and tying up. The genetic defect causes an excessive amount of calcium build up in the muscle cells. The effects are usually seen after exercise, stress or anesthesia. If the horse has to be anesthetized, there are drugs to help prevent an attack. MH is a disease where with just 1 copy of the mutated gene, you can get signs of the disease.

HERDA
HERDA (Hereditary Equine Regional Dermal Asthenia ) is a disease where there is a defect in the production of collagen in the body. The common manifestation is excessively elastic skin with slow healing wounds, most commonly on the top line. There is no treatment and most horses are euthanized. HERDA requires 2 copies of the defective gene to show clinical signs and is commonly found along with PSSM(Polysaccharide Storage Myopathy) in some horses.

GBED
GBED (Glycogen Branching Enzyme Deficiency) is a disease where the body cannot make proper glycogen. Glycogen is to animal cells what starch is to plant cells. It is a storage form of sugar to use in cells when needed. GBED is fatal and most animals die or are euthanized by about 8 weeks of age. The brain and the muscles cannot function properly and this leads to death. There is not treatment for this disease. It can also cause abortions or stillborn foals. It requires both copies of the gene to be mutated in order for the disease to manifest.

PSSM
PSSM(Polysaccharide Storage Myopathy) is kind of the opposite of GBED. The body stores too much glycogen in the muscle cells. This leads tying up, muscle stiffness and sweating. There are two types of PSSM. PSSM 1 is able to be found on the 5 panel test via genetic testing. PSSM 2 is found by a muscle biopsy. This disease can be managed by a low carbohydrate diet, regular exercise and proper warm up and cooling down with exercise.

This quick over view of these diseases hopefully has convinced you of the importance of being good stewards of our horses and doing our best to not perpetuate these genetic defects that can have devastating consequences. Speak to your veterinarian about whether or not a 5 panel test is recommended in your situation. Happy New Year!