The story of Tami is that of terror and sadly the truth for up to 25% of the Quarter Horse owner population. Right now you are asking, "What was the cause of death?" Well the answer would be Hyperkalaemic Periodic Paralysis, or HYPP a genetic mutation with in the cell membrane of muscle fibers. HYPP usually first appears within the first 10 years of life with attacks of muscle weakness caused by cold, rest after exercise, fasting, or ingestion of potassium (Fontaine, 1000). This muscle disease is that of genetic defect, more specifically a point mutation, in the DNA of the Sodium Channel Gene. The mutation is an Autosomal Dominant Trait, which means only one copy of the gene is needed to express HYPP, and it is also equally occurring in males and females.
Here is a Handy Glossary to Help Understand HYPP
|Pedigree of HYPP Breeding|
According to AAEP (American Association of Equine Practitioners), the mutation is a point mutation. A point mutation is a mutation where one letter, or point, in the DNA is changed and in this case changes the coding of the gene. The new mutated gene codes for an abnormal channel to be expressed in the skeletal muscles. Sodium channels are "pores" in the muscle cell membranes, which control concentrations of potassium and sodium ions in the muscle fibers. When the defective gene is present, it causes that channel to become "leaky". This allows the potassium ions to leak, which then, overexcites the muscles causing them to contract involuntarily.
|Horse During HYPP Attack|
A suggested diet to manage a horse with HYPP would be a diet low in potassium, along with feeding multiple times a day, and frequent exercise and/or allowing the horse access to a large field.. Low potassium feeds include a late boom Timothy or low potassium grass hay, beet pulp with no molasses, and small amounts of oats. This high glucose, high carbohydrate diet allows the pancreas to be stimulated to secrete insulin which lowers glucose levels and potassium levels. There are also medications that can be prescribed by a veterinarian that help stabilize blood levels and that increase renal potassium ATPase activity. The medications will help rid the body of potassium and help with fluctuations of the potassium ion levels in the blood which can trigger an attack.
The problem then becomes, people do not want to know if their horse has HYPP and people do not want to tell potential buyers the horse has the possibility of being HYPP positive. However, legally, a person has the right to know! The Sale of Goods Act of 1979 Sections 13 & 14 cover the sale of horses. Both sections deal with the private and public sale of a horse. Under both sections, claims can be filed for the "misrepresentation" of the horse. This would include a false claim that the horse is negative for HYPP.
A Pre-Purchase Exam performed by your vet, is always suggested when purchasing a horse. The exam should allow you to gain a general understanding of the horse's health. From the health of the horse's teeth to x-rays to a complete lameness exam and as far as drug testing can be included in this exam. Of course, if there were the question that the horse could be an "Impressive" descendant a test for HYPP would not be out of the question for this exam either. In any event, that the horse comes back positive for HYPP or any other sort of alarming results appear upon the pre-purchase exam, one would be advised not to pursue any further testing on horse by the vet.
The story of Hyperkalaemic Periodic Paralysis is rather Impressive. This gene mutation causes an unbelievable and majestic musculature in the descendants of Impressive, the mutation also formed a devastating disease. People are breeding to Impressive descendants for this glorious musculature to win halter classes, but ignoring the severe disease that has no cure. Impressive's offspring have naturally fit bodies. While ideally we could keep breeding Impressive descendants because, who would not want a perfectly muscled dream horse? However, these dream-like genes also carry a nightmare of episodes of weakness, collapse, or even death from the mutation forming HYPP. Working horses regularly will provide a beautifully toned horse and can lead to the winning of a halter class. Along with the win of the halter class, the hard work put in by the horse and handler will create a bond worth more than a blue ribbon.