A horse breed is a selectively bred population of domesticated horses, often with pedigrees recorded in a breed registry. However, the term is sometimes used in a broader sense to define landrace animals of a common phenotype located within a limited geographic region, or even feral "breeds" that are naturally selected. Depending on definition, hundreds of "breeds" exist today, developed for many different uses. 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.
Horse breeding is reproduction in horses, and particularly the human-directed process of selective breeding of animals, particularly purebred horses of a given breed. Planned matings can be used to produce specifically desired characteristics in domesticated horses. Furthermore, modern breeding management and technologies can increase the rate of conception, a healthy pregnancy, and successful foaling.
Genomic imprinting is an epigenetic phenomenon that causes genes to be expressed or not, depending on whether they are inherited from the female or male parent. Genes can also be partially imprinted. Partial imprinting occurs when alleles from both parents are differently expressed rather than complete expression and complete suppression of one parent's allele. Forms of genomic imprinting have been demonstrated in fungi, plants and animals. In 2014, there were about 150 imprinted genes known in mice and about half that in humans. As of 2019, 260 imprinted genes have been reported in mice and 228 in humans.
Zebras are African equines with distinctive black-and-white striped coats. There are three living species: Grévy's zebra, the plains zebra, and the mountain zebra. Zebras share the genus Equus with horses and asses, the three groups being the only living members of the family Equidae. Zebra stripes come in different patterns, unique to each individual. Several theories have been proposed for the function of these stripes, with most evidence supporting them as a deterrent for biting flies. Zebras inhabit eastern and southern Africa and can be found in a variety of habitats such as savannahs, grasslands, woodlands, shrublands, and mountainous areas.
In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different varieties, species or genera through sexual reproduction. Generally, it means that each cell has genetic material from two different organisms, whereas an individual where some cells are derived from a different organism is called a chimera. Hybrids are not always intermediates between their parents, but can show hybrid vigor, sometimes growing larger or taller than either parent. The concept of a hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics, attention is focused on the numbers of chromosomes. In taxonomy, a key question is how closely related the parent species are.
The mule is a domestic equine hybrid between a donkey and a horse. It is the offspring of a male donkey and a female horse. The horse and the donkey are different species, with different numbers of chromosomes; of the two possible first-generation hybrids between them, the mule is easier to obtain and more common than the hinny, which is the offspring of a male horse and a female donkey.
The donkey is a domesticated equine. It derives from the African wild ass, Equus africanus, and may be classified either as a subspecies thereof, Equus africanus asinus, or as a separate species, Equus asinus. It was domesticated in Africa some 5000–7000 years ago, and has been used mainly as a working animal since that time.
A zebroid is the offspring of any cross between a zebra and any other equine to create a hybrid. In most cases, the sire is a zebra stallion. The offspring of a donkey sire and zebra dam, called a donkra, and the offspring of a horse sire and a zebra dam, called a hebra, do exist, but are rare and are usually sterile. Zebroids have been bred since the 19th century. Charles Darwin noted several zebra hybrids in his works.
Equus is a genus of mammals in the family Equidae, which includes horses, asses, and zebras. Within the Equidae, Equus is the only recognized extant genus, comprising seven living species. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. The genus most likely originated in North America and spread quickly to the Old World. Equines are odd-toed ungulates with slender legs, long heads, relatively long necks, manes, and long tails. All species are herbivorous, and mostly grazers, with simpler digestive systems than ruminants but able to subsist on lower-quality vegetation.
The humanzee is a hypothetical hybrid of chimpanzee and human, thus a form of human–animal hybrid. Serious attempts to create such a hybrid were made by Soviet biologist Ilya Ivanovich Ivanov in the 1920s, and possibly by researchers in China in the 1960s, though neither succeeded.
Grévy's zebra, also known as the imperial zebra, is the largest living wild equid and the most threatened of the three species of zebra, the other two being the plains zebra and the mountain zebra. Named after Jules Grévy, it is found in parts of Kenya and Ethiopia. Superficially, Grévy's zebras' physical features can help to identify it from the other zebra species; their overall appearance is slightly closer to that of a mule, compared to the more "equine" (horse) appearance of the plains and mountain zebras. Compared to other zebra species, Grévy's are the tallest; they have mule-like, larger ears, and have the tightest stripes of all zebras. They have distinctively erect manes, and more slender snouts.
A mare is an adult female horse or other equine. In most cases, a mare is a female horse over the age of three, and a filly is a female horse three and younger. In Thoroughbred horse racing, a mare is defined as a female horse more than four years old. The word can also be used for other female equine animals, particularly mules and zebras, but a female donkey is usually called a "jenny". A broodmare is a mare used for breeding.
The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offspring are sterile. These barriers maintain the integrity of a species by reducing gene flow between related species.
The Baudet du Poitou, also called the Poitevin or Poitou donkey, is a French breed of donkey. It is one of the largest breeds, and jacks were bred to mares of the Poitevin horse breed to produce Poitevin mules, which were formerly in worldwide demand for agricultural and other work. The Baudet has a distinctive coat, which hangs in long, ungroomed locks or cadenettes.
Sterility is the physiological inability to effect sexual reproduction in a living thing, members of whose kind have been produced sexually. Sterility has a wide range of causes. It may be an inherited trait, as in the mule; or it may be acquired from the environment, for example through physical injury or disease, or by exposure to radiation.
Ann Trommershausen Bowling was an American scientist who was one of the world's leading geneticists in the study of horses, conducting research in the areas of molecular genetics and cytogenetics. She was a major figure in the development of testing to determine animal parentage, first with blood typing in the 1980s and then DNA testing in the 1990s. She later became known for her studies of hereditary diseases in horses and equine coat color genetics, as well as research on horse evolution and the development of horse breeds. She studied the population genetics of feral horses, did considerable work to help preserve the Przewalski's horse, and was one of the founding members of the international project to map the horse genome. She was an adjunct professor at the University of California, Davis (UCD), and at the time of her death in 2000 was the executive associate director of the Veterinary Genetics Laboratory (VGL) there. Her unexpected death on December 8, 2000, at age 57 was attributed to a massive stroke.
Equid hybrids, also called hybrid equines, are created from the crossing of members from the horse family such as a horse, donkey and zebra.
Caenorhabditis nigoni is a male-female species in the Elegans group of the genus Caenorhabditis, first identified and described as "Caenorhabditis species 9" or "C. sp. 9" before being renamed as "C. nigoni". The specific epithet is a tribute to Victor Nigon who first studied Caenorhabditis elegans in the laboratory with Ellsworth Dougherty in the 1940s. Isolates come from the Democratic Republic of the Congo and Kerala, India.
The kunga was a hybrid equid that was used as a draft animal in ancient Syria and Mesopotamia, where it also served as an economic and political status symbol. Cuneiform writings from as early as the mid-third millennium BCE describe the animal as a hybrid but do not provide the precise taxonomical nature of the breeding that produced it. Modern paleogenomics has revealed it to have been the offspring of a female domesticated donkey and a wild male Syrian wild ass. They fell out of favor after the introduction of domesticated horses and mules into the region at the end of the 3rd millennium BCE.
