Horse
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Equus ferus caballus (see text)
Equus laurentius
The horse (Equus caballus) is a hoofed (ungulate) mammal, one of eight living species of the family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today. Humans began to domesticate horses around 4500 BC, and their domestication is believed to have been widespread by 3000 BC; by 2000 BC the use of domesticated horses had spread throughout the Eurasian continent. Although most horses today are domesticated, there are still endangered populations of the Przewalski's Horse, the only remaining true wild horse, as well as more common feral horses which live in the wild but are descended from domesticated ancestors.
There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from anatomy to life stages, size, colors, markings, breeds, locomotion, and behavior. Horses are anatomically designed to use speed to escape predators, and have a well-developed sense of balance and a strong fight-or-flight instinct. Related to this need to flee from predators in the wild is an unusual trait: horses are able to sleep both standing up and laying down. Female horses, called mares, carry their young for approximately 11 months, and a young horse, called a foal, can stand and run shortly following birth. Most horses begin training under saddle or in harness between the ages of two and four. They reach full adult development by age five, and have an average lifespan of between 25 and 30 years.
Horse breeds are loosely divided into three categories based on general temperament: spirited "hot bloods" with speed and endurance; "cold bloods," such as draft horses and some ponies, suitable for slow, heavy work; and "warmbloods," developed from crosses between hot bloods and cold bloods, often focusing on creating breeds for specific riding purposes, particularly in Europe. There are over 300 breeds of horses in the world today, developed for many different uses.
Horses and humans interact in many ways, not only in a wide variety of sport competitions and non-competitive recreational pursuits, but also in working activities including police work, agriculture, entertainment, assisted learning and therapy. Horses were historically used in warfare. A wide variety of riding and driving techniques have been developed, using many different styles of equipment and methods of control. Many products are derived from horses, including meat, milk, hide, hair, bone, and pharmaceuticals extracted from the urine of pregnant mares. Humans provide domesticated horses with food, water and shelter, as well as attention from specialists such as veterinarians and farriers.
Contents
Biology
Horse anatomy is described by a large number of specific terms, as illustrated by the chart to the right. Specific terms also describe various ages, colors and breeds.
Age
Depending on breed, management and environment, the domestic horse today has a life expectancy of 25 to 30 years. It is uncommon, but a few animals live into their 40s and, occasionally, beyond. The oldest verifiable record was "Old Billy," a 19th-century horse that lived to the age of 62.[2] In modern times, Sugar Puff, who had been listed in the Guinness Book of World Records as the world's oldest living pony, died in 2007, aged 56.[3]
Regardless of a horse's actual birthdate, for most competition purposes an animal is considered a year older on January 1 of each year in the northern hemisphere[4][5] and August 1 in the southern hemisphere.[6] The exception is in endurance riding, where the minimum age to compete is based on the animal's calendar age.[7] A very rough estimate of a horse's age can be made from looking at its teeth.[5]
The following terminology is used to describe horses of various ages:
In horse racing, the definitions of colt, filly, mare, and stallion may differ from those given above. In the UK, Thoroughbred horse racing defines a colt as a male less than five years old, and a filly as a female less than five years old.[17] In the USA, both Thoroughbred racing and harness racing defines colts and fillies as four years old and younger.[18]
Size
The English-speaking world measures the height of horses in hands, abbreviated "h" or "hh," for "hands high," measured at the highest point of an animal's withers, where the neck meets the back, chosen as a stable point of the anatomy, unlike the head or neck, which move up and down; one hand is 4 inches (10 cm). Intermediate heights are defined by hands and inches, rounding to the lower measurement in hands, followed by a decimal point and the number of additional inches between 1 and 3. Thus a horse described as "15.2 h," is 15 hands, 2 inches (62 in/160 cm) in height.[19] The size of horses varies by breed, but can also be influenced by nutrition.
The general rule for cutoff in height between what is considered a horse and a pony at maturity is 14.2 hands (58 in/150 cm). An animal 14.2 h or over is usually considered to be a horse and one less than 14.2 h as a pony.[20] However, there are exceptions to the general rule. Some breeds which typically produce individuals both under and over 14.2 h are considered horses regardless of their height.[21] Conversely, some pony breeds may have features in common with horses, and individual animals may occasionally mature at over 14.2 h, but are still considered to be ponies.[22]
The distinction between a horse and pony is not simply a difference in height, but takes account of other aspects of phenotype or appearance, such as conformation and temperament. Ponies often exhibit thicker manes, tails and overall coat. They also have proportionally shorter legs, wider barrels, heavier bone, shorter and thicker necks, and short heads with broad foreheads. They often have calmer temperaments than horses and also a high level of equine intelligence that may or may not be used to cooperate with human handlers.[20] In fact, small size, by itself, is sometimes not a factor at all. While the Shetland pony stands on average 10 hands high (40 in/100 cm),[23] the Falabella and other miniature horses, which can be no taller than 30 inches (76 cm), the size of a medium-sized dog, are classified by their respective registries as very small horses rather than as ponies.[24]
Light riding horses such as Arabians, Morgans, or Quarter Horses usually range in height from 14 to 16 hands (56 to 64 in/140 to 160 cm) and can weigh from 850 to 1,200 pounds (390 to 540 kg). Larger riding horses such as Thoroughbreds, American Saddlebreds or Warmbloods usually start at about 15.2 hands (62 in/160 cm) and often are as tall as 17 hands (68 in/170 cm), weighing from 1,100 to 1,500 pounds (500 to 680 kg). Heavy or draft horses such as the Clydesdale, Belgian, Percheron, and Shire are usually at least 16 to 18 hands (64 to 72 in/160 to 180 cm) high and can weigh from about 1,500 to 2,000 pounds (680 to 910 kg).
The largest horse in recorded history was probably a Shire horse named Sampson[25] The current record holder for the world's smallest horse is Thumbelina, a fully mature miniature horse affected by dwarfism. She is 17 inches (43 cm) tall and weighs 60 pounds (27 kg).[26], who lived during the late 1800s. He stood 21.2½ hands high (86.5 in/220 cm), and his peak weight was estimated at 3,360 pounds (1,520 kg).
Colors and markings
Horses exhibit a diverse array of coat colors and distinctive markings, described with a specialized vocabulary. Often, a horse is classified first by its coat color, before breed or sex.[27] Flashy or unusual colors are sometimes very popular, as are horses with particularly attractive markings. Horses of the same color may be distinguished from one another by their markings.[28]
The genetics that create many horse coat colors have been identified, although research continues on specific genes and mutations that result in specific color traits.[29] Essentially, all horse colors begin with a genetic base of "red" (chestnut) or "black," with the addition of alleles for spotting, graying, suppression or dilution of color, or other effects acting upon the base colors to create the dozens of possible coat colors found in horses.[30]
Horses which are light in color are often misnamed as being "white" horses. A horse that looks pure white is, in most cases, actually a middle-aged or older gray. Grays have black skin underneath their white hair coat (with the exception of small amounts of pink skin under white markings). The only horses properly called white are those with pink skin under a white hair coat, a fairly rare occurrence.[31] There are no truly albino horses, with pink skin and red eyes, as albinism is a lethal condition in horses.[32]
Reproduction and development
Pregnancy lasts for approximately 335–340 days[33] and usually results in one foal. Twins are very rare.[34] Colts are carried on average about 4 days longer than fillies.[35] Horses are a precocial species, and foals are capable of standing and running within a short time following birth.[36]
Horses, particularly colts, may sometimes be physically capable of reproduction at about 18 months. In practice, individuals are rarely allowed to breed before the age of three, especially females.[33] Horses four years old are considered mature, although the skeleton normally continues to develop until the age of six; the precise time of completion of development also depends on the horse's size, breed, gender, and the quality of care provided by its owner. Also, if the horse is larger, its bones are larger; therefore, not only do the bones take longer to actually form bone tissue, but the epiphyseal plates are also larger and take longer to convert from cartilage to bone. These plates convert after the other parts of the bones, but are crucial to development.[37]
Depending on maturity, breed, and the tasks expected, young horses are usually put under saddle and trained to be ridden between the ages of two and four.[38] Although Thoroughbred race horses are put on the track at as young as two years old in some countries,[39] horses specifically bred for sports such as dressage are generally not entered into top-level competition until they are a minimum of four years old, because their bones and muscles are not solidly developed, nor is their advanced training complete.[40] For endurance riding competition, horses are not deemed mature enough to compete until they are a full 60 calendar months (5 years) old.[7]
Anatomy
- See also: Muscular system of the horse, Respiratory system of the horse, and Circulatory system of the horse
Skeletal system
Horses have a skeleton that averages 205 bones.[41] A significant difference between the horse skeleton, compared to that of a human, is the lack of a collarbone—the horse's front limb system is attached to the spinal column by a powerful set of muscles, tendons and ligaments that attach the shoulder blade to the torso. The horse's legs and hooves are also unique structures. Their leg bones are proportioned differently from those of a human. For example, the body part that is called a horse's "knee" is actually made up of the carpal bones that correspond to the human wrist. Similarly, the hock, contains the bones equivalent to those in the human ankle and heel. The lower leg bones of a horse correspond to the bones of the human hand or foot, and the fetlock (incorrectly called the "ankle") is actually the proximal sesamoid bones between the cannon bones (a single equivalent to the human metacarpal or metatarsal bones) and the proximal phalanges, located where one finds the "knuckles" of a human. A horse also has no muscles in its legs below the knees and hocks, only skin, hair, bone, tendons, ligaments, cartilage, and the assorted specialized tissues that make up the hoof.[42]
Hooves
The critical importance of the feet and legs is summed up by the traditional adage, "no foot, no horse".[43] The horse hoof begins with the distal phalanges, the equivalent of the human fingertip or tip of the toe, surrounded by cartilage and other specialized, blood-rich soft tissues such as the laminae. The exterior hoof wall and horn of the sole is made of essentially the same material as a human fingernail.[44] The end result is that a horse, weighing on average 1,100 pounds (500 kg),[45] travels on the same bones as a human on tiptoe.[46] For the protection of the hoof under certain conditions, some horses have horseshoes placed on their feet by a professional farrier. The hoof continually grows, and needs to be trimmed (and horseshoes reset, if used) every five to eight weeks.[47]
Teeth
Horses are adapted to grazing. In an adult horse, there are 12 incisors, adapted to biting off the grass or other vegetation, at the front of the mouth. There are 24 teeth adapted for chewing, the premolars and molars, at the back of the mouth. Stallions and geldings have four additional teeth just behind the incisors, a type of canine teeth that are called "tushes." Some horses, both male and female, will also develop one to four very small vestigial teeth in front of the molars, known as "wolf" teeth, which are generally removed because they can interfere with the bit. There is an empty interdental space between the incisors and the molars where the bit rests directly on the bars (gums) of the horse's mouth when the horse is bridled.[48]
The incisors show a distinct wear and growth pattern as the horse ages, as well as change in the angle at which the chewing surfaces meet. The teeth continue to erupt throughout life as they are worn down by grazing, so a very rough estimate of a horse's age can be made by an examination of its teeth, although diet and veterinary care can affect the rate of tooth wear.[5]
Digestion
Horses are herbivores with a digestive system adapted to a forage diet of grasses and other plant material, consumed steadily throughout the day. Therefore, compared to humans, they have a relatively small stomach but very long intestines to facilitate a steady flow of nutrients. A 1,000 pounds (450 kg) horse will eat 15 to 25 pounds (6.8 to 11 kg) of food per day and, under normal use, drink 10 US gallons (38 L) to 12 US gallons (45 L) of water. Horses are not ruminants, so they have only one stomach, like humans, but unlike humans, they can also digest cellulose from grasses due to the presence of a "hind gut" called the cecum, or "water gut," which food goes through before reaching the large intestine. Unlike humans, horses cannot vomit, so digestion problems can quickly cause colic, a leading cause of death.[49]
Senses
- See also: Equine vision
The horse's senses are generally superior to those of a human. As prey animals, they must be aware of their surroundings at all times.[50] They have the largest eyes of any land mammal, and because their eyes are positioned on the sides of their heads, horses have a range of vision of more than 350°, with approximately 65° of this being binocular (seen with both eyes) and the remaining 285° monocular (seen with only one eye).[51] Horses have excellent day and night vision, but studies indicate that they have two-color, or dichromatic vision; their color vision is somewhat like red-green color blindness in humans. This means that certain colors, especially red and related colors, appear more green.[52]
Their hearing is good,[50] and the pinna of each ear can rotate up to 180°, giving the potential for 360° hearing without having to move the head.[53] Their sense of smell, while much better than that of humans, is not their strongest asset; they rely to a greater extent on vision.[50]
Horses have a great sense of balance, due partly to their ability to feel their footing and partly to highly developed proprioceptive abilities (the unconscious sense of where the body and limbs are at all times).[54] A horse's sense of touch is well developed. The most sensitive areas are around the eyes, ears and nose. Via touch, horses perceive and respond immediately to changes in their environment,[55] sensing contact as subtle as an insect landing anywhere on the body.[56]
Horses have an advanced sense of taste that allows them to sort through grains and grasses to choose what they would most like to eat,[57] and their prehensile lips can easily sort even the smallest grains. Horses generally will not eat poisonous plants. However, there are exceptions and horses will occasionally eat toxic amounts of poisonous plants even when there is adequate healthy food.[58]
Movement
All horses move naturally with four basic gaits: the four-beat walk, which averages four miles per hour; the two-beat trot or jog, which averages 8 to 12 miles (13 to 19 km) per hour (faster for harness racing horses); and the leaping gaits known as the canter or lope (a three-beat gait that is 12 to 15 miles (19 to 24 km) per hour), and the gallop.[59] The gallop averages 25 to 30 miles (40 to 48 km) per hour.[60] The world record for a horse galloping over a short, sprint distance is 55 miles (89 km) per hour.[61] Besides these basic gaits, some horses perform a two-beat pace, instead of the trot.[62] In addition, there are several four-beat "ambling" gaits that are approximately the speed of a trot or pace, though smoother to ride. These include the lateral slow gait, rack, running walk, and tölt as well as the diagonal fox trot.[63] Ambling gaits are often genetic traits in specific breeds, known collectively as gaited horses.[64] In most cases, gaited horses replace the standard trot with one of the ambling gaits.[65]
Behavior
Horses are prey animals with a well-developed fight-or-flight instinct. Their first response to threat is to startle and usually flee, although they are known to stand their ground and defend themselves or their offspring in cases where flight is not possible, or when their young are threatened. They also tend to be curious; when startled, they will often hesitate an instant to ascertain the cause of their fright, and may not always flee from something that they perceive as non-threatening. Through selective breeding, some breeds of horses are quite docile, particularly certain large draft horses. Most light horse riding breeds were developed for speed, agility, alertness and endurance; natural qualities that extend from their wild ancestors.[66] Horses are herd animals, with a clear hierarchy of rank, led by a dominant animal (usually a mare). They are also social creatures who are able to form companionship attachments to their own species and to other animals, including humans. They communicate in various ways, including vocalizations such as nickering or whinnying, mutual grooming, and body language. Many horses will become difficult to manage if they are isolated. Through proper training, it is possible to teach any horse to accept a human as a type of companion, and thus be comfortable away from other horses.[67] When confined with insufficient companionship, exercise or stimulation, individuals may develop stable vices, an assortment of bad habits, mostly psychological in origin, that include wood chewing, wall kicking, "weaving" (rocking back and forth) and other problems.[68]
Intelligence and learning
In the past, horses were considered unintelligent, with no abstract thinking ability, unable to generalize, and driven primarily by a herd mentality. However, recent studies show that they perform a number of cognitive tasks on a daily basis, and frequently engage in mental challenges that include food procurement and social system identification. They have also been shown to have good spatial discrimination abilities.[69]
Studies have assessed equine intelligence in the realms of problem solving, learning speed, and knowledge retention. Results show that horses excel at simple learning, but also are able to solve advanced cognitive challenges that involve categorization and concept learning. They have been shown to learn from habituation, desensitization, Pavlovian conditioning, and operant conditioning. They respond to and learn from both positive and negative reinforcement.[69]
Domesticated horses tend to face greater mental challenges than wild horses, due to living in artificial environments that stifle instinctual behavior while learning tasks that are not natural.[69] Horses are creatures of habit that respond and adapt well to regimentation, and respond best when the same routines and techniques are used consistently. Some trainers believe that "intelligent" horses are reflections of intelligent trainers who effectively use response conditioning techniques and positive reinforcement to train in the style that fits best with an individual animal's natural inclinations. Others who handle horses regularly note that personality also may play a role separate from intelligence in determining how a given animal responds to various experiences.[70]
Temperament
Horses are mammals, and as such are all "warm-blooded" creatures, as opposed to reptiles, which are cold-blooded. However, these words have developed a separate meaning in the context of equine terminology, used to describe temperament, not body temperature. For example, the "hot-bloods," such as many race horses, exhibit more sensitivity and energy, while the "cold-bloods," such as most draft breeds, are quieter and calmer.[71]
"Hot blooded" breeds include "oriental horses" such as the Akhal-Teke, Barb, Arabian horse and now-extinct Turkoman horse, as well as the Thoroughbred, a breed developed in England from the older oriental breeds. Hot bloods tend to be spirited, bold, and learn quickly. They are bred for agility and speed.[72] They tend to be physically refined—thin-skinned, slim, and long-legged.[73] The original oriental breeds were brought to Europe from the Middle East and North Africa when European breeders wished to infuse these traits into racing and light cavalry horses.[72]
Muscular, heavy draft horses are known as "cold bloods," as they are bred not only for strength, but also to have the calm, patient temperament needed to pull a plow or a heavy carriage full of people. They are sometimes nicknamed "gentle giants."[74] Well-known draft breeds include the Belgian and the Clydesdale. Some, like the Percheron are lighter and livelier, developed to pull carriages or to plow large fields in drier climates. Others, such as the Shire, are slower and more powerful, bred to plow fields with heavy, clay-based soils.[75] The cold-blooded group also includes some pony breeds.[76]
"Warmblood" breeds, such as the Trakehner or Hanoverian, developed when European carriage and war horses were crossed with Arabians or Thoroughbreds, producing a riding horse with more refinement than a draft horse, but greater size and more phlegmatic temperament than a lighter breed.[77] Certain pony breeds with warmblood characteristics have been developed for smaller riders.[78]
Today, the term "Warmblood" refers to a specific subset of sport horse breeds that have dominated the Olympic Games and international FEI competition in dressage and show jumping since the 1970s. Prior to that time, the term "warm blood" often referred to any cross between cold-blooded and hot-blooded breeds. Examples included breeds such as the Irish Draught or the Cleveland Bay. Less often, the term was even used to refer to breeds of light riding horse other than Thoroughbreds or Arabians, such as the Morgan horse.[79]
Sleep patterns
- See also: Horse sleep patterns and Sleep in non-humans
Horses are able to sleep both standing up and lying down. In an adaptation from life in the wild, horses are able to enter light sleep by using a "stay apparatus" in their legs, allowing them to doze without collapsing. [80] Horses sleep better when in groups because some animals will sleep while others stand guard to watch for predators. A horse kept alone will not sleep well because its instincts are to keep a constant eye out for danger.[81]
Unlike humans, horses do not sleep in a solid, unbroken period of time, but take many short periods of rest. Horses may spend anywhere from four to fifteen hours a day in standing rest, and from a few minutes to several hours lying down. Total sleep time in a day may range from several minutes to a couple of hours,[81] mostly in short intervals of about 15 minutes each.[82]
Horses must lie down to reach REM sleep. They only have to lie down for an hour or two every few days to meet their minimum REM sleep requirements.[81] However, if a horse is never allowed to lie down, after several days it will become sleep-deprived, and in rare cases may suddenly collapse as it involuntarily slips into REM sleep while still standing.[83] This condition differs from narcolepsy, although horses may also suffer from that disorder.[84]
Taxonomy and evolution
The horse as it is known today adapted by evolution to survive in areas of wide-open terrain with sparse vegetation, surviving in an ecosystem where other large grazing animals, especially ruminants, could not.[85] Horses and other equids are odd-toed ungulates of the order Perissodactyla, a group of mammals that was dominant during the Tertiary period. In the past, this order contained 14 families and many species, but only three families—Equidae (the horse and related species), the tapir and the rhinoceros—containing 18 known species have survived to the present day.[86] The earliest known member of the Equidae family was the Hyracotherium, which lived between 45 and 55 million years ago, during the Eocene period and had 4 toes on each front foot, and 3 toes on each back foot.[87] The extra toe on the front feet soon disappeared with the Mesohippus, which lived 32 to 37 million years ago,[88] and by about 5 million years ago, the modern Equus had developed.[89] The extra side toes shrank in size until they have vanished in modern horses. All that remains is a set of small vestigial bones on the leg above the hoof,[90] known informally as ergots, chestnuts, or splint bones.[91] Their legs also lengthened as their toes disappeared and until they were a hoofed animal capable of running at great speed.[90]
Over millions of years, equid teeth also evolved from browsing on soft, tropical plants to adapt to browsing of drier plant material, and grazing of tougher plains grasses. Thus the proto-horses changed from leaf-eating forest-dwellers to grass-eating inhabitants of semi-arid regions worldwide, including the steppes of Eurasia and the Great Plains of North America. For reasons not fully understood, Equus caballus disappeared from North America around 10,000 years ago, at the end of the last ice age.[92]
The "Four Foundations" theory
Modern DNA evidence suggests that domesticated horses evolved from multiple wild populations.[93] Specifically, the "Four Foundations" theory suggests that the modern horse evolved from multiple ancient wild prototypes, each adapted to a given habitat.[94] However, an older theory holds that there was only one type of wild horse, the Tarpan subtype, and all other types diverged in form after domestication to meet human needs.[95]
Under the four foundations theory, all types and breeds of horses are thought to have developed from the following base prototypes:[96]
Domestication and surviving wild species
Competing theories exist as to the time and place of initial domestication. The earliest evidence for the domestication of the horse comes from Ukraine and dates to approximately 4,000 BC.[97] It is thought that the horse was completely domesticated by 3000 BC, and by 2000 BC there was a sharp increase in the number of horse bones found in human settlements in northwestern Europe, indicating the spread of domesticated horses throughout the continent.[98]
Wild species surviving into modern times
A truly wild horse is a species or subspecies which has no ancestors that were ever domesticated. Therefore, most "wild" horses today are actually feral horses, animals that escaped or were turned loose from domestic herds and the descendants of those animals.[99]
Only two types of truly wild horses survived into recorded history. One, the Tarpan (Equus ferus ferus) survived into the historical era, but became extinct in 1887. Its pure genetic line was lost, but three attempts have been made to re-create the Tarpan. In the early 1930s, Berlin Zoo Director Lutz Heck and Heinz Heck of the Munich Zoo began a program that by the 1960s produced the Heck horse. In 1936, Polish university professor Tadeusz Vetulani began a program using Konik horses, and in the mid-1960s Harry Hegard started a program in the United States using feral mustangs and local working ranch horses that has resulted in the Hegardt or Stroebel's Horse. None of the breeding programs were completely successful, although all three resulted in horses with many similarities to the Tarpan.[100]
There is only one true wild horse species alive today, the Przewalski's Horse (Equus ferus przewalskii). It is rare Asian animal, also known as the Mongolian Wild Horse, Mongolian people know it as the taki, and the Kyrgyz people call it a kirtag. Small wild breeding populations of this animal, named after the Russian explorer Nikolai Przhevalsky, exist in Mongolia.[101] There are also small populations maintained at zoos throughout the world. The species was considered extinct in the wild between 1969 and 1992, but a small breeding population was reestablished in the wild due to the conservations efforts by numerous zoos.[102]
Feral populations
Feral horses are born and live in the wild, but are descended from domesticated animals.[99] Many populations of feral horses exist throughout the world.[103][104] Studies of feral herds have provided useful insights into the behavior of prehistoric horses,[105] as well as greater understanding of the instincts and behaviors that drive horses that live in domesticated conditions.[106]
Other modern equids
Besides the horse, there are seven other species of genus equus in the equidae family. These are the ass or donkey, Equus asinus; the Mountain Zebra, Equus zebra; Plains Zebra, Equus burchelli; Grévy's Zebra, Equus grevyi; the Kiang, Equus kiang; and the Kulan, Equus hemionus, including its subspecies, the Onager, Equus hemionus onager.[107]
Horses can crossbreed with other members of the equus genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey).[108] Other hybrids include the zorse, a cross between a zebra and a horse that is bred in Africa and used for trekking on Mount Kenya.[109] With rare exceptions, most hybrids are sterile and cannot reproduce.[110]
Breeds
Horse breeds are groups of horses with distinctive characteristics that are transmitted consistently to their offspring, such as conformation, color, performance ability, or disposition. These inherited traits are usually the result of a combination of natural crosses and artificial selection methods aimed at producing horses for specific tasks. Certain breeds are known for certain talents. For example, Standardbreds are known for their speed in harness racing. Some breeds have been developed through centuries of crossings with other breeds, while others, such as Tennessee Walking Horses and Morgans, developed from a single sire from which all current breed members descend. There are more than 300 horse breeds in the world today.[111]
Origin of breeds
- See also: Domestication of the horse
Modern horse breeds developed in response to a need for "form to function", the necessity to develop certain physical characteristics in order to perform a certain type of work.[112] Thus, powerful but refined breeds such as the Andalusian or the Lusitano developed in the Iberian peninsula as riding horses that also had a great aptitude for dressage,[113] while heavy draft horses such as the Clydesdale and the Shire developed out of a need to perform demanding farm work and pull heavy wagons.[114] Ponies of all breeds originally developed mainly from the need for a working animal that could fulfill specific local draft and transportation needs while surviving in harsh environments. However, by the 20th century, many pony breeds had Arabian and other blood added to make a more refined pony suitable for riding.[115] Other horse breeds developed specifically for light agricultural work, heavy and light carriage and road work, various equestrian disciplines, or simply as pets.[112]
Purebreds and registries
Horses have been selectively bred since their domestication. Today, there are over 300 breeds of horses in the world. However, the concept of purebred bloodstock and a controlled, written breed registry only became of significant importance in modern times. Today, the standards for defining and registration of different breeds vary. Sometimes purebred horses are called Thoroughbreds, which is incorrect; "Thoroughbred" is a specific breed of horse, while a "purebred" is a horse (or any other animal) with a defined pedigree recognized by a breed registry.