The American Quarter Horse, or Quarter Horse, is an American
breed of
horse
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...
that excels at sprinting short distances. Its name is derived from its ability to outrun other horse breeds in races of a quarter mile or less; some have been clocked at speeds up to 44 mph (70.8 km/h). The development of the Quarter Horse traces to the 1600s.
The American Quarter Horse is the most popular breed in the United States today, and the
American Quarter Horse Association is the largest breed registry in the world, with almost three million living American Quarter Horses registered in 2014. The American Quarter Horse is well known both as a race horse and for its performance in
rodeos,
horse show
A horse show is a judged exhibition of horses and ponies. Many different horse breeds and equestrian disciplines hold competitions worldwide, from local to the international levels. Most horse shows run from one to three days, sometimes longer ...
s, and as a working
ranch
A ranch (from es, rancho/Mexican Spanish) is an area of land, including various structures, given primarily to ranching, the practice of raising grazing livestock such as cattle and sheep. It is a subtype of a farm. These terms are most ofte ...
horse.
The compact body of the American Quarter Horse is well suited for the intricate and quick maneuvers required in
reining,
cutting
Cutting is the separation or opening of a physical object, into two or more portions, through the application of an acutely directed force.
Implements commonly used for wikt:cut, cutting are the knife and saw, or in medicine and science the scal ...
, working cow horse,
barrel racing
Barrel racing is a rodeo event in which a horse and rider attempt to run a cloverleaf pattern around preset barrels in the fastest time. In collegiate and professional ranks, it is usually a women's event, though both sexes compete at amateur and ...
,
calf roping, and other
western riding
Western riding is considered a style of horse riding which has evolved from the ranching and welfare traditions which were brought to the Americas by the Spanish Conquistadors, as well as both equipment and riding style which evolved to meet th ...
events, especially those involving live cattle. The American Quarter Horse is also used in
English
English usually refers to:
* English language
* English people
English may also refer to:
Peoples, culture, and language
* ''English'', an adjective for something of, from, or related to England
** English national ide ...
disciplines,
driving
Driving is the controlled operation and movement of a vehicle, including cars, motorcycles, trucks, buses, and bicycles. Permission to drive on public highways is granted based on a set of conditions being met and drivers are required to f ...
, show jumping, dressage, hunting, and many other
equestrian
The word equestrian is a reference to equestrianism, or horseback riding, derived from Latin ' and ', "horse".
Horseback riding (or Riding in British English)
Examples of this are:
* Equestrian sports
*Equestrian order, one of the upper classes i ...
activities.
Breed history
Colonial era
In the 1600s on the Eastern seaboard of what today is the United States, imported English Thoroughbred horses were first bred with assorted native horses.
[Denhardt ''Quarter Running Horse'' pp. 4–8]
One of the most famous of these early imports was
Janus, a Thoroughbred who was the grandson of the
Godolphin Arabian. He was foaled in 1746, and imported to colonial Virginia in 1756.
[Denhardt ''Quarter Running Horse'' pp. 20–32] The influence of Thoroughbreds like Janus contributed genes crucial to the development of the colonial "Quarter Horse".
[Mackay-Smith ''Colonial Quarter Race Horse'' p. 106][Mackay-Smith ''Colonial Quarter Race Horse'' p. 138] The resulting horse was small, hardy, quick, and was used as a work horse during the week and a race horse on the weekends.
As
flat racing
Horse racing is an equestrian performance sport, typically involving two or more horses ridden by jockeys (or sometimes driven without riders) over a set distance for competition. It is one of the most ancient of all sports, as its basic pr ...
became popular with the colonists, the Quarter Horse gained even more popularity as a sprinter over courses that, by necessity, were shorter than the classic racecourses of England. These courses were often no more than a straight stretch of road or flat piece of open land. When competing against a Thoroughbred, local sprinters often won. As the Thoroughbred breed became established in America, many colonial Quarter Horses were included in the original American stud books.
[Mackay-Smith ''Colonial Quarter Race Horse'' p. xxxi] This began a long association between the Thoroughbred breed and what would later become officially known as the "Quarter Horse", named after the race distance at which it excelled. Some Quarter Horses have been clocked at up to 44 mph.
Westward expansion
In the 19th century, pioneers heading West needed a hardy, willing horse. On the
Great Plains, settlers encountered horses that descended from the Spanish stock
Hernán Cortés and other Conquistadors had introduced into the viceroyalty of
New Spain, which today includes the Southwestern United States and Mexico.
The horses of the West included herds of
feral
A feral () animal or plant is one that lives in the wild but is descended from domesticated individuals. As with an introduced species, the introduction of feral animals or plants to non-native regions may disrupt ecosystems and has, in some ...
animals known as
Mustangs
The mustang is a free-roaming horse of the Western United States, descended from horses brought to the Americas by the Spanish. Mustangs are often referred to as wild horses, but because they are descended from once-domesticated animals, they ...
, as well as horses domesticated by
Native Americans, including the
Comanche,
Shoshoni
The Shoshone or Shoshoni ( or ) are a Native American tribe with four large cultural/linguistic divisions:
* Eastern Shoshone: Wyoming
* Northern Shoshone: southern Idaho
* Western Shoshone: Nevada, northern Utah
* Goshute: western Utah, east ...
and
Nez Perce
The Nez Percé (; autonym in Nez Perce language: , meaning "we, the people") are an Indigenous people of the Plateau who are presumed to have lived on the Columbia River Plateau in the Pacific Northwest region for at least 11,500 years.Ames, K ...
tribes. As the colonial Quarter Horse was crossed with these western horses, the pioneers found that the new crossbred had innate "cow sense", a natural instinct for working with cattle, making it popular with cattlemen on
ranch
A ranch (from es, rancho/Mexican Spanish) is an area of land, including various structures, given primarily to ranching, the practice of raising grazing livestock such as cattle and sheep. It is a subtype of a farm. These terms are most ofte ...
es.
[Mackay-Smith ''Colonial Quarter Race Horse'' p. 193]
Development as a distinct breed
![Petermccuewithcaudell](https://upload.wikimedia.org/wikipedia/commons/5/59/Petermccuewithcaudell.jpg)
Early
foundation sires of Quarter horse type included
Steel Dust, foaled 1843;
Shiloh (or Old Shiloh), foaled 1844; Old Cold Deck (1862); Lock's Rondo, one of many "Rondo" horses, foaled in 1880; Old Billy—again, one of many "Billy" horses—foaled circa 1880;
Traveler, a stallion of unknown breeding, known to have been in Texas by 1889;
[Close, ''Legends 2: Outstanding Quarter Horse Stallions and Mares.''] and
Peter McCue
Peter McCue (1895–1923) was a racehorse and sire influential in the American Quarter Horse Association (or AQHA), although he died before the AQHA was formed.
Life
Peter McCue (foaled 1895) was registered in the '' American Stud Book'' as a T ...
, foaled 1895, registered as a
Thoroughbred
The Thoroughbred is a horse breed best known for its use in horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed. Thoroughbreds are ...
but of disputed pedigree.
Another early foundation sire for the breed was
Copperbottom, foaled in 1828, who tracks his lineage through the
Byerley Turk
The Byerley Turk (c. 1680 – c. 1703), also spelled Byerly Turk, was the earliest of three stallions that were the founders of the modern Thoroughbred horse racing bloodstock (the other two are the Godolphin Arabian and the Darley Arabian).Ahnert ...
, a foundation sire of the
Thoroughbred
The Thoroughbred is a horse breed best known for its use in horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed. Thoroughbreds are ...
horse breed.
[Sir Archy](_blank)
/ref>[History of the Quarter Horse](_blank)
/ref>
The main duty of the ranch horse in the American West was working cattle. Even after the invention of the automobile, horses were still irreplaceable for handling livestock on the range. Thus, major Texas cattle ranch
A ranch (from es, rancho/Mexican Spanish) is an area of land, including various structures, given primarily to ranching, the practice of raising grazing livestock such as cattle and sheep. It is a subtype of a farm. These terms are most ofte ...
es, such as the King Ranch
King Ranch is the largest ranch in the United States. At some it is larger than the state of Rhode Island and country of Luxembourg. It is mainly a cattle ranch, but also produced the Triple Crown winning racehorse Assault.
The ranch is lo ...
, the 6666 (Four Sixes) Ranch, and the Waggoner Ranch
The Waggoner Ranch is a historic north Texas ranch located 13 miles south of Vernon, Texas. The land was used primarily to raise crops, beef cattle and horses as well as for oil production. It was notable for being the largest ranch within one fen ...
played a significant role in the development of the modern Quarter Horse. The skills required by cowboys and their horses became the foundation of the rodeo, a contest which began with informal competition between cowboys and expanded to become a major competitive event throughout the west. To this day, the Quarter Horse dominates in events that require speed as well as the ability to handle cattle.
Sprint races were also popular weekend entertainment and racing became a source of economic gain for breeders. As a result, more Thoroughbred blood was added into the developing American Quarter Horse breed. The American Quarter Horse also benefitted from the addition of Arabian, Morgan, and even Standardbred
The Standardbred is an American horse breed best known for its ability in harness racing, where members of the breed compete at either a trot or pace. Developed in North America, the Standardbred is recognized worldwide, and the breed can trace i ...
bloodlines.
In 1940, the American Quarter Horse Association (AQHA) was formed by a group of horsemen and ranchers from the Southwestern United States dedicated to preserving the pedigrees of their ranch horses.[Denhardt ''Quarter Horse'' pp. 143–167] After winning the 1941 Fort Worth Exposition and Fat Stock Show grand champion stallion, the horse honored with the first registration number, P-1, was Wimpy, a descendant of the King Ranch
King Ranch is the largest ranch in the United States. At some it is larger than the state of Rhode Island and country of Luxembourg. It is mainly a cattle ranch, but also produced the Triple Crown winning racehorse Assault.
The ranch is lo ...
foundation sire Old Sorrel. Other sires alive at the founding of the AQHA were given the earliest registration numbers Joe Reed P-3, Chief P-5, Oklahoma Star P-6, Cowboy P-12, and Waggoner's Rainy Day P-13.[American Quarter Horse Association ''Combined Stud Book 1-2-3-4-5'' p. 1] The Thoroughbred
The Thoroughbred is a horse breed best known for its use in horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed. Thoroughbreds are ...
race horse Three Bars
3 is a number, numeral, and glyph.
3, three, or III may also refer to:
* AD 3, the third year of the AD era
* 3 BC, the third year before the AD era
* March, the third month
Books
* '' Three of Them'' (Russian: ', literally, "three"), a 1901 ...
, alive in the early years of the AQHA, is recognized by the American Quarter Horse Hall of Fame as one of the significant foundation sires for the Quarter Horse breed. Other significant Thoroughbred sires seen in early AQHA pedigrees include Rocket Bar, Top Deck and Depth Charge.[Wiggins ''Great American Speedhorse'' p. 166]
"Appendix" and "Foundation" horses
Since the American Quarter Horse was formally established as a breed, the AQHA stud book has remained open to additional Thoroughbred
The Thoroughbred is a horse breed best known for its use in horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed. Thoroughbreds are ...
blood via a performance standard. An "Appendix" American Quarter Horse is a first generation cross between a registered Thoroughbred and an American Quarter Horse or a cross between a "numbered" American Quarter Horse and an "appendix" American Quarter Horse. The resulting offspring is registered in the "appendix" of the American Quarter Horse Association's studbook, hence the nickname. Horses listed in the appendix may be entered in competition, but offspring are not initially eligible for full AQHA registration. If the Appendix horse meets certain conformational criteria and is shown or raced successfully in sanctioned AQHA events, the horse can earn its way from the appendix into the permanent studbook, making its offspring eligible for AQHA registration.
Since Quarter Horse/Thoroughbred crosses continue to enter the official registry of the American Quarter Horse breed, this creates a continual gene flow from the Thoroughbred breed into the American Quarter Horse breed, which has altered many of the characteristics that typified the breed in the early years of its formation. Some breeders argue that the continued addition of Thoroughbred bloodlines are beginning to compromise the integrity of the breed standard. Some favor the earlier style of horse and have created several separate organizations to promote and register "Foundation" Quarter Horses.
American Quarter Horses today
The American Quarter Horse is best known today as a show horse, race horse
Horse racing is an equestrian performance sport, typically involving two or more horses ridden by jockeys (or sometimes driven without riders) over a set distance for competition. It is one of the most ancient of all sports, as its basic pr ...
, reining and cutting
Cutting is the separation or opening of a physical object, into two or more portions, through the application of an acutely directed force.
Implements commonly used for wikt:cut, cutting are the knife and saw, or in medicine and science the scal ...
horse, rodeo competitor, ranch
A ranch (from es, rancho/Mexican Spanish) is an area of land, including various structures, given primarily to ranching, the practice of raising grazing livestock such as cattle and sheep. It is a subtype of a farm. These terms are most ofte ...
horse, and all-around family horse. Quarter Horses are commonly used in rodeo events such as barrel racing
Barrel racing is a rodeo event in which a horse and rider attempt to run a cloverleaf pattern around preset barrels in the fastest time. In collegiate and professional ranks, it is usually a women's event, though both sexes compete at amateur and ...
, calf roping and team roping
Team roping also known as heading and heeling is a rodeo event that features a steer (typically a Corriente) and two mounted riders. The first roper is referred to as the "header", the person who ropes the front of the steer, usually around ...
; and gymkhana
Gymkhana () ( ur, جِمخانہ, sd, جمخانه, hi, जिमख़ाना, as, জিমখানা, bn, জিমখানা) is a British Raj term which originally referred to a place of assembly. The meaning then altered to den ...
or O-Mok-See. Other stock horse events such as cutting
Cutting is the separation or opening of a physical object, into two or more portions, through the application of an acutely directed force.
Implements commonly used for wikt:cut, cutting are the knife and saw, or in medicine and science the scal ...
and reining are open to all breeds but are dominated by American Quarter Horse.
The breed is not only well-suited for western riding
Western riding is considered a style of horse riding which has evolved from the ranching and welfare traditions which were brought to the Americas by the Spanish Conquistadors, as well as both equipment and riding style which evolved to meet th ...
and cattle
Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult ma ...
work. Many race tracks offer Quarter Horses a wide assortment of pari-mutuel horse racing with earnings in the millions. Quarter Horses have also been trained to compete in dressage and show jumping. They are also used for recreational trail riding
Trail riding is riding outdoors on trails, bridle paths, and forest roads, but not on roads regularly used by motorised traffic. A trail ride can be of any length, including a long distance, multi-day trip. It originated with horse riding, and ...
and in mounted police
Mounted police are police who patrol on horseback or camelback. Their day-to-day function is typically picturesque or ceremonial, but they are also employed in crowd control because of their mobile mass and height advantage and increasingly in t ...
units.[
The American Quarter Horse has also been exported worldwide. European nations such as Germany and Italy have imported large numbers of Quarter Horses. Next to the American Quarter Horse Association (which also encompasses Quarter Horses from Canada), the second largest registry of Quarter Horses is in Brazil, followed by Australia. In the UK the breed is also becoming very popular, especially with the two Western riding Associations, the Western Horse Association and The Western Equestrian Society. The British American Quarter Horse breed society is the AQHA-UK. With the internationalization of the discipline of reining and its acceptance as one of the official seven events of the World Equestrian Games, there is a growing international interest in Quarter Horses. The American Quarter Horse is the most popular breed in the United States today, and the American Quarter Horse Association is the largest breed registry in the world, with nearly 3 million American Quarter Horses registered worldwide in 2014. The ]Texas Legislature
The Texas Legislature is the state legislature of the US state of Texas. It is a bicameral body composed of a 31-member Senate and a 150-member House of Representatives. The state legislature meets at the Capitol in Austin. It is a powerful ar ...
designated the American Quarter Horse as the official "State Horse of Texas" in 2009.
Breed characteristics
The Quarter Horse has a small, short, refined head with a straight profile, and a strong, well-muscled body, featuring a broad chest and powerful, rounded hindquarters. They usually stand between high, although some Halter-type and English hunter-type horses may grow as tall as .
There are two main body types: the stock type and the hunter or racing type. The stock horse type is shorter, more compact, stocky and well-muscled, yet agile. The racing and hunter type Quarter Horses are somewhat taller and smoother muscled than the stock type, more closely resembling the Thoroughbred
The Thoroughbred is a horse breed best known for its use in horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed. Thoroughbreds are ...
.
Quarter Horses come in nearly all colors
Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associa ...
. The most common color is sorrel
Sorrel (''Rumex acetosa''), also called common sorrel or garden sorrel, is a perennial herbaceous plant in the family Polygonaceae. Other names for sorrel include spinach dock and narrow-leaved dock ('dock' being a common name for the genus '' ...
, a brownish red, part of the color group called chestnut by most other breed registries. Other recognized colors include bay, black
Black is a color which results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white ...
, brown
Brown is a color. It can be considered a composite color, but it is mainly a darker shade of orange. In the CMYK color model used in printing or painting, brown is usually made by combining the colors orange and black. In the RGB color model us ...
, buckskin, palomino, gray
Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...
, dun
A dun is an ancient or medieval fort. In Ireland and Britain it is mainly a kind of hillfort and also a kind of Atlantic roundhouse.
Etymology
The term comes from Irish ''dún'' or Scottish Gaelic ''dùn'' (meaning "fort"), and is cognat ...
, red dun, grullo
Grulla or grullo, also called blue dun, gray dun or mouse dun, is a color of horses in the dun family, characterized by tan-gray or mouse-colored hairs on the body, often with shoulder and dorsal stripes and black barring on the lower legs. In t ...
(also occasionally referred to as blue dun), red roan, blue roan, bay roan, perlino
The cream gene is responsible for a number of horse coat colors. Horses that have the cream gene in addition to a base coat color that is chestnut will become palomino if they are heterozygous, having one copy of the cream gene, or cremello, ...
, cremello
The cream gene is responsible for a number of horse coat colors. Horses that have the cream gene in addition to a base coat color that is chestnut will become palomino if they are heterozygous, having one copy of the cream gene, or cremello, ...
, and white
White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White o ...
. In the past, spotted color patterns were excluded, but now with the advent of DNA testing to verify parentage, the registry accepts all colors as long as both parents are registered.
Stock type
A stock horse is a horse of a type that is well suited for working with livestock, particularly cattle. Reining and cutting
Cutting is the separation or opening of a physical object, into two or more portions, through the application of an acutely directed force.
Implements commonly used for wikt:cut, cutting are the knife and saw, or in medicine and science the scal ...
horses are smaller in stature, with quick, agile movements and very powerful hindquarters. Western pleasure
Western pleasure is a western style competition at horse shows that evaluates horses on manners and suitability of the horse for a relaxed and slow but collected gait cadence, along with calm and responsive disposition. The horse is to appear to ...
show horses are often slightly taller, with slower movements, smoother gaits, and a somewhat more level topline – though still featuring the powerful hindquarters characteristic of the Quarter Horse.
Halter type
Horses shown in-hand in 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 ...
competition are larger yet, with a very heavily muscled appearance, while retaining small heads with wide jowls and refined muzzles. There is controversy amongst owners, breeder and veterinarians regarding the health effects of the extreme muscle mass that is currently fashionable in the specialized halter horse, which typically is and weighs in at over when fitted for halter competition. Not only are there concerns about the weight to frame ratio on the horse's skeletal system
A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...
, but the massive build is also linked to 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) in descendants of the stallion Impressive (see Genetic diseases
A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...
below).
Racing and hunter type
Quarter Horse race horses are bred to sprint short distances ranging from 220 to 870 yards. Thus, they have long legs and are leaner than their stock type counterparts, but are still characterized by muscular hindquarters and powerful legs. Quarter Horses race primarily against other Quarter Horses, and their sprinting ability has earned them the nickname, "the world's fastest athlete." The show hunter
The Hunter division is a branch of horse show competition that is judged on the horse's performance, soundness and when indicated, conformation, suitability or manners. A "show hunter" is a horse that competes in this division.
Show hunters, i ...
type is slimmer, even more closely resembling a Thoroughbred
The Thoroughbred is a horse breed best known for its use in horse racing. Although the word ''thoroughbred'' is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed. Thoroughbreds are ...
, usually reflecting a higher percentage of appendix breeding. They are shown in hunter/jumper classes at both breed shows and in open USEF-rated horse show
A horse show is a judged exhibition of horses and ponies. Many different horse breeds and equestrian disciplines hold competitions worldwide, from local to the international levels. Most horse shows run from one to three days, sometimes longer ...
competition.
Genetic diseases
There are several genetic diseases of concern to Quarter Horse breeders:
*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), which is caused by an autosomal
An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosom ...
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 ...
linked to the stallion Impressive. It is characterized by uncontrollable muscle twitching and substantial muscle weakness or paralysis among affected horses. Because it is a dominant gene, only one parent has to have the gene for it to be transmitted to offspring. There is a DNA test for HYPP, which is required by the AQHA. Since 2007, the AQHA bars registration of horses who possess the homozygous form (H/H) of the gene, and though heterozygous
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 ...
(H/N) horses are still eligible for registration, altering that status is currently being discussed. Additionally all Quarter Horses born 2007 or later that are confirmed to be descendants of Impressive must carry a note about the risks of HYPP on their registration papers. Due to HYPP, the halter classes are undergoing significant changes. 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 ...
classes are dominated by the Impressive bloodline. Impressive, a very prolific halter horse, brought to the stock breeds the muscle mass that is popular in halter competition today. This muscle mass is linked to HYPP, and as the condition is reduced within the breed, the style of horse in halter classes is also likely to change. Already there have been rule changes, including the creation of a "Performance Halter class" in which a horse must possess a Register of Merit in performance or racing before it can compete.
*Malignant hyperthermia
Malignant hyperthermia (MH) is a type of severe reaction that occurs in response to particular medications used during general anesthesia, among those who are susceptible. Symptoms include muscle rigidity, fever, and a fast heart rate. Complica ...
. A causative mutated allele
An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution.
::"The chro ...
, ryanodine receptor 1 gene (RyR1) at nucleotide C7360G, generating a R2454G amino acid substitution. has been identified in the American Quarter Horse and breeds with Quarter Horse ancestry, inherited as an autosomal dominant It can be caused by overwork, anesthesia, or stress.
*Hereditary Equine Regional Dermal Asthenia
Hereditary equine regional dermal asthenia (HERDA), also known as hyperelastosis cutis (HC), is an inherited autosomal recessive connective tissue disorder. It develops from a homozygous recessive mutation that weakens collagen fibers that allow th ...
(HERDA), also known as hyperelastosis cutis (HC). This is caused by an autosomal
An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosom ...
recessive gene, and thus, unlike HYPP, HERDA can only be transmitted if both parents carry the gene. When a horse has this disease, there is a collagen defect that results in the layers of skin not being held firmly together. Thus, when the horse is ridden under saddle or suffers trauma to the skin, the outer layer often splits or separates from the deeper layer, or it can tear off completely. It rarely heals without disfiguring scars. Sunburn can also be a concern. In dramatic cases, the skin can split along the back and even roll down the sides, with the horse literally being skinned alive. Most horses with HERDA are euthanized for humane reasons between the age of two and four years. The very hotly debated and controversial theory, put forth by researchers at Cornell University
Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...
and Mississippi State University is that the sire line of the great foundation stallion Poco Bueno is implicated as the origin of the disease. As of May 9, 2007, Researchers working independently at Cornell University and at the University of California, Davis
The University of California, Davis (UC Davis, UCD, or Davis) is a public land-grant research university near Davis, California. Named a Public Ivy, it is the northernmost of the ten campuses of the University of California system. The inst ...
announced that a DNA test for HERDA has been developed. Over 1,500 horses were tested during the development phase of the test, which is now available to the general public through both institutions.
* Glycogen Branching Enzyme Deficiency (GBED) is a genetic disease where the horse is lacking an enzyme necessary for storing glycogen, the horse's heart muscle and skeletal muscles cannot function, leading to rapid death. The disease occurs in foals who are 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 lethal GBED allele, meaning both parents carry one copy of the gene. The stallion King P-234
King (1932–1958), often known as King P-234, was an outstanding early Quarter Horse stallion who influenced the breed throughout the early years of the American Quarter Horse Association (or AQHA).
Life
King was born June 25, 1932, the offsp ...
has been linked to this disease. There is a DNA blood test for this gene.
*Equine polysaccharide storage myopathy
Equine polysaccharide storage myopathy (EPSM, PSSM, EPSSM) is a hereditary glycogen storage disease of horses that causes exertional rhabdomyolysis. It is currently known to affect the following breeds American Quarter Horses, American Paint Horse ...
, also called EPSM or PSSM, is a metabolic muscular condition in horses that causes tying up, and is also related to a glycogen storage disorder. While also seen in some draft horse
A draft horse (US), draught horse (UK) or dray horse (from the Old English ''dragan'' meaning "to draw or haul"; compare Dutch ''dragen'' and German ''tragen'' meaning "to carry" and Danish ''drage'' meaning "to draw" or "to fare"), less oft ...
breeds, PSSM has been traced to three specific but undisclosed bloodlines in Quarter Horses, with an autosomal
An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosom ...
recessive
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 ...
inheritance pattern. 48% of Quarter Horses with symptoms of neuromuscular disease have PSSM. To some extent it can be diet controlled with specialized low-starch diets, but genetic testing is advised before breeding, as the condition exists at a subclinical level in approximately 6% of the general Quarter Horse population.
*Lethal White Syndrome
Lethal white syndrome (LWS), also called overo lethal white syndrome (OLWS), lethal white overo (LWO), and overo lethal white foal syndrome (OLWFS), is an autosomal genetic disorder most prevalent in the American Paint Horse. Affected foals are bo ...
. Although "cropout
A cropout, crop-out or crop out is a horse with body spots, including pinto or leopard complex spotting, or "high white" horse markings, with a sire and dam who both appeared to have been solid-colored. There are several variations in the defini ...
" Quarter Horses with Paint markings were not allowed to be registered for many years, the gene for such markings is a recessive and continued to periodically appear in Quarter Horse foals. Thus, it is believed that some Quarter Horses may carry the gene for Lethal White Syndrome. There is a DNA test for this condition.
*Cleft Palate Birth defect, this is not just a genetic disorder. There is not just one thing that will cause this issue. It can be caused from genetics, hormones, mineral deficiency, tranquilizers, or steroids. Cleft palates are extremely uncommon. The surgery to repair the cleft palate does not have a high success rate. Only about a 20% success rate is seen from the surgery. Quarter horses seem to have the most research done with them, and this defect occurs more in quarter horses based on the research. Some observations of a horse with a cleft palate and no surgery are: lifting head high when eating, dropping head low to drink, coughing when beginning of exercise, and placing wormers or other oral medications in the side of the jaw and taking about hour to administer full dose.
See also
*Quarab
The Quarab is a horse breed from the United States, developed from a part-Arabian cross of Arabian horses, American Quarter Horses and Paint horses. Members of the breed are found that resemble all three of the foundation breeds, leading to thr ...
* Quarter pony
References
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Further reading
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External links
American Quarter Horse Association
Information about Quarter Horses in Europe
{{short description, American horse breed
Horse breeds
Horse breeds originating in the United States