In the late 1980s, a mysterious disease ROCKED the Quarter Horse world, as well as breeds crossed with Quarter Horses. Horses suffering muscle tremors, weakness, collapse, and even death made headlines when the cause was traced to a genetic disease attributed to a prominent Quarter Horse bloodline. When researchers announced that HYPP (hyperkalemic periodic paralysis) linked to one very famous stallion named Impressive, there was an uproar in breeding barns across the country.
A decade later breeders began to accept the importance of reducing the spread of this deadly disease. In 1998, the American Quarter Horse Association adopted a rule requiring all foals descending from Impressive to be tested for HYPP, with results listed on their registration papers. In 2007, horses carrying two genes for this disease were no longer…
