The American Quarter Horse was the first breed that was developed in the U.S. The breed originated from Arabian, Turk and Barb breeds and was named for it’s ability to run a quarter of a mile faster than any other breed. An extremely versatile breed, they are known especially for their “cow sense”, their athleticism and their even temperament.
So what happened? While some Quarter Horses still embody this ideal, there is a seemingly mutant strain that’s called the “Halter Horse.” These horses are so heavily muscled that they look inflated. They probably couldn’t run a quarter of a mile faster than I can, and they have a host of conformational and health problems.
These horses are obese, tend toward having very straight (post) legs and fetlocks, and often carry the gene for Hyperkalemic periodic paralysis (HYPP), an inherited disease of the muscle which is caused by a genetic defect.
The stallion Impressive, foaled in 1969 is credited with starting the trend toward very heavily muscled Quarter Horses. Many of the Halter lines of QH today trace back to him. Unfortunately, he also was the foundation sire for HYPP. It was a genetic mutation started by Impressive that causes the disease.
According to the UC Davis Veterinary Medicine Website:
HYPP is characterized by sporadic attacks of muscle tremors (shaking or trembling), weakness and/or collapse. Attacks can also be accompanied by loud breathing noises resulting from paralysis of the muscles of the upper airway. Occasionally, sudden death can occur following a severe paralytic attack, presumably from heart failure or respiratory muscle paralysis.
You’ll see that horses are advertised as N/H (heterozygous), H/H (homozygous) or N/N (normal). Once again, according the the UC Davis site:
Breeding an affected heterozygous horse (N/H) to an affected heterozygous horse (N/H) will result in approximately 50% carrying the defective gene (N/H), approximately 25% will be normal (N/N) and approximately 25% will be homozygous carriers (H/H). Breeding an affected heterozygous horse (N/H) to a normal horse (N/N) will result in approximately 50% normal offspring and approximately 50% carrying the defective gene (N/H).
It is a crime that the AQHA has not wiped out this debilitating disease which could be eradicated by NOT breeding horses that carry the gene. I understand that some people use the halter style horse to add some bulk to performance horses. Certainly I understand that when you have a calf at the end of your rope it’s helpful to have a horse with some substance. But can’t this be accomplished without turning this classic American breed into a muscle bound, poorly conformed freak?