Posted by Dr. Cory Reng on June 15 2004 15:38
Equine Newsletter 1st Quarter 2004
These (H/H) horses will pass the trait on to 100% of their offspring. While the genetic test does a good job determining whether or not your horse will pass HYPP on to offspring, it does not predict how severe symptoms may be. For example, a (N/H) horse may die of an HYPP attack while a (H/H) horse may never have severe symptoms, especially if managed correctly.
Managing HYPP horses has become something of an art form, especially since many of the top horsemen showing halter horses have some of the most severely affected horses. Because symptoms are related to potassium metabolism, feeding a diet low in potassium is a paramount. This means avoid feeding alfalfa to HYPP horses. Feeding a diet of grass, hay, and grain usually minimizes symptoms. If a horse is starting a minor attack, feeding grain will often cause an insulin release that will direct potassium back into the cells. Severe attacks will need to be treated with IV fluids by your veterinarian. These attacks are an emergency.
The controversy is based around whether or not HYPP horses will be able to continue to qualify for registry in AQHA. There is a great deal of pressure to consider HYPP a genetic defect that would disallow registration. The other side is that many of the top winning halter horses are homozygous or heterozygous HYPP. Does AQHA want to disqualify for registration the bloodlines that have produced most of the World Champion quarter horses for the last ten years?
Those who argue that HYPP is a genetic defect that should be eliminated will cite other times that a show ring fad have almost ruined a breed. The example most often cited is "Snorter Dwarfs" in Hereford Cattle. This genetic defect became common when very short blocky cattle were winning in the show ring. Heavy selection on short blocky bloodlines made the genetic defect of tiny cattle with deformed nasal passages common. Because genetic testing was not possible at that time, all cattle in bloodlines that had produced "Snorter Dwarfs" were eliminated from the breed.
The other side of the argument is that many of AQHA's top producing and most desirable bloodlines carry the HYPP gene. Many argue that by eliminating these bloodlines, they may put the industry back 25 or more years.
Whichever side of the argument you are on, or even if you choose to stay out of it completely, testing will become more and more important. Though there is a blood test available, most breeders are now using the tail hair DNA test. This test only requires a few tail hairs from your horse. Horses that are related to "Impressive" will need to be tested for registry. There is a discount available for AQHA members.