Impressive (April 15, 1969 – March 20, 1995) was born an Appendix American Quarter Horse, who earned his full AQHA registration in 1971. He was the 1974 World Champion Open Aged

halter A halter or headcollar is headgear that is used to lead or tie up livestock and, occasionally, other animals; it fits behind the ears (behind the poll), and around the muzzle. To handle the animal, usually a lead rope is attached. On smalle ...

stallion, the first such World Champion in his breed, despite carrying only 48 halter points in total. He sired 2,250 foals, of which thirty went on to be World Champions themselves. In his showing days, Impressive changed hands a number of times. One of his owners was Dean Landers, who also owned the halter stallions Two Eyed Jack, Coy's Bonanza, and Sonny Dee Bar. Although Impressive was sent to race training, he never raced. He was sent home and the next year he was excluded from any performance discipline due to

pedal osteitis Laminitis is a disease that affects the feet of ungulates and is found mostly in horses and cattle. Clinical signs include foot tenderness progressing to inability to walk, increased digital pulses, and increased temperature in the hooves. Sever ...

, leaving halter as his only choice. His groundbreaking 1974 World Championship soon cemented his role in that discipline. Each time Impressive was resold, his price rose quickly; at one point, an offer of $300,000 for him was refused by Brown, who said "ain't nobody in this world got enough money to buy this horse." Impressive was highly sought after for breeding, despite at one time carrying a

stud fee A stud animal is a registered animal retained for breeding. The terms for the male of a given animal species (stallion, bull, rooster, etc.) usually imply that the animal is intact—that is, not castrated—and therefore capable of siring offsp ...

of $25,000. He sired a total of 2,250 foals, and as of 2003, was estimated to have in excess of 55,000 living descendants. He was bred for his muscular and refined form, which was passed on to his get often enough to make him at least the #5 all-time leading Quarter Horse sire when ranked by AQHA points earned by all progeny combined. Over time, it became evident that many horses descended from Impressive were afflicted with the genetic disease

hyperkalemic periodic paralysis Hyperkalemic periodic paralysis (HYPP, HyperKPP) is an inherited autosomal dominant disorder that affects sodium channels in muscle cells and the ability to regulate potassium levels in the blood. It is characterized by muscle hyperexcitability ...

(HYPP). While it is unclear if Impressive himself ever manifested clinical signs of HYPP in his lifetime, he is considered the

index case The index case or patient zero is the first documented patient in a disease epidemic within a population, or the first documented patient included in an epidemiological study. It can also refer to the first case of a condition or syndrome (not n ...

, as the disease has never been observed in horses which are not descendants of his line. HYPP is a

dominant gene In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...

, and as such, all animals with even one copy of the gene, identified as "N/H", will exhibit some symptoms of the disease. Horses with two copies, identified as "H/H." will always pass on the condition, and research suggests that H/H horses may have more severe symptoms than N/H horses. After a number of years of debate, effective since January 1, 2007, the AQHA amended rule 205(c)(3) and rule Rule 227(e) to require all descendants of Impressive to be tested prior to being registered, and ban from registration all horses born after January 1, 2007 with HYPP genetics confirmed by

DNA test Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, o ...

ing to be

homozygous Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mo ...

for the condition (H/H). Other breed registries that accept animals with Quarter Horse bloodlines, including the

American Paint Horse Association The American Paint Horse Association (APHA) is a breed registry for the American Paint Horse. It is currently headquartered in Fort Worth, Texas.

and the

Appaloosa Horse Club The Appaloosa Horse Club, located in Moscow, Idaho, is dedicated to preserving and promoting the Appaloosa breed. The state of Idaho adopted the Appaloosa as its state horse in 1975. More than 630,000 Appaloosas have been registered with the Appal ...

, have instituted testing requirements but have yet to bar animals with the condition. There is currently a widespread effort among many breeders to eliminate the disease by

selective breeding Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant m ...

, but there are those who continue to breed without regard for it, or even deliberately seeking the muscular enhancement correlated with it, and in doing so perpetuate the disease's existence.

Pedigree

External links

HYPP: getting to grips with Hyperkalemic Periodic Paralysis - Horsetalk.co.nz

Impressive data sheet and pedigree

UC Davis VGL: Hyperkalemic Periodic Paralysis
{{DEFAULTSORT:Impressive (Horse) American Quarter Horse show horses American Quarter Horse sires 1968 animal births 1995 animal deaths