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Hydropower

Hydropower (from Ancient Greek ὑδρο-, "water"), also known as water power, is the use of falling or fast-running water to produce electricity or to power machines. This is achieved by converting the gravitational potential or kinetic energy of a water source to produce power. Hydropower is a method of sustainable energy production. Hydropower is now used principally for hydroelectric power generation, and is also applied as one half of an energy storage system known as pumped-storage hydroelectricity.

Hydropower is an attractive alternative to fossil fuels as it does not directly produce carbon dioxide or other atmospheric pollutants and it provides a relatively consistent source of power. Nonetheless, it has economic, sociological, and environmental downsides and requires a sufficiently energetic source of water, such as a river or elevated lake. International institutions such as the World Bank view hydropower as a low-carbon means for economic development.

Since ancient times, hydropower from watermills has been used as a renewable energy source for irrigation and the operation of mechanical devices, such as gristmills, sawmills, textile mills, trip hammers, dock cranes, domestic lifts, and ore mills. A trompe, which produces compressed air from falling water, is sometimes used to power other machinery at a distance.

Calculating the amount of available power
A hydropower resource can be evaluated by its available power. Power is a function of the hydraulic head and volumetric flow rate. The head is the energy per unit weight (or unit mass) of water. The static head is proportional to the difference in height through which the water falls. Dynamic head is related to the velocity of moving water. Each unit of water can do an amount of work equal to its weight times the head.

The power available from falling water can be calculated from the flow rate and density of water, the height of fall, and the local acceleration due to gravity:

 * $$\dot{W}_\text{out} =-\eta \ \dot{m} g \ \Delta h =-\eta \ \rho \dot{V} \ g \ \Delta h$$

 * where
 * $$\dot{W}_\text{out}$$ (work flow rate out) is the useful power output (SI unit: watts)
 * $$\eta$$ ("eta") is the efficiency of the turbine (dimensionless)
 * $$\dot{m}$$ is the mass flow rate (SI unit: kilograms per second)
 * $$\rho$$ ("rho") is the density of water (SI unit: kilograms per cubic metre)
 * $$\dot{V}$$ is the volumetric flow rate (SI unit: cubic metres per second)
 * $$g$$ is the acceleration due to gravity (SI unit: metres per second per second)
 * $$\Delta h$$ ("Delta h") is the difference in height between the outlet and inlet (SI unit: metres)

To illustrate, the power output of a turbine that is 85% efficient, with a flow rate of 80 cubic metres per second (2800 cubic feet per second) and a head of 145 m, is 97 megawatts:
 * $$\dot{W}_\text{out} = 0.85\times 1000 \ (\text{kg}/\text{m}^3) \times 80 \ (\text{m}^3/\text{s}) \times 9.81 \ (\text{m}/\text{s}^2) \times 145 \ \text{m} = 97 \times 10^6 \ (\text{kg}\ \text{m}^2/\text{s}^3) = 97 \ \text{MW}$$

Operators of hydroelectric stations compare the total electrical energy produced with the theoretical potential energy of the water passing through the turbine to calculate efficiency. Procedures and definitions for calculation of efficiency are given in test codes such as ASME PTC 18 and IEC 60041. Field testing of turbines is used to validate the manufacturer's efficiency guarantee. Detailed calculation of the efficiency of a hydropower turbine accounts for the head lost due to flow friction in the power canal or penstock, rise in tailwater level due to flow, the location of the station and effect of varying gravity, the air temperature and barometric pressure, the density of the water at ambient temperature, and the relative altitudes of the forebay and tailbay. For precise calculations, errors due to rounding and the number of significant digits of constants must be considered.

Some hydropower systems such as water wheels can draw power from the flow of a body of water without necessarily changing its height. In this case, the available power is the kinetic energy of the flowing water. Over-shot water wheels can efficiently capture both types of energy. The flow in a stream can vary widely from season to season. The development of a hydropower site requires analysis of flow records, sometimes spanning decades, to assess the reliable annual energy supply. Dams and reservoirs provide a more dependable source of power by smoothing seasonal changes in water flow. However, reservoirs have a significant environmental impact, as does alteration of naturally occurring streamflow. Dam design must account for the worst-case, "probable maximum flood" that can be expected at the site; a spillway is often included to route flood flows around the dam. A computer model of the hydraulic basin and rainfall and snowfall records are used to predict the maximum flood.

Disadvantages and limitations
Some disadvantages of hydropower have been identified. Dam failures can have catastrophic effects, including loss of life, property and pollution of land.

Dams and reservoirs can have major negative impacts on river ecosystems such as preventing some animals traveling upstream, cooling and de-oxygenating of water released downstream, and loss of nutrients due to settling of particulates. River sediment builds river deltas and dams prevent them from restoring what is lost from erosion. Furthermore, studies found that the construction of dams and reservoirs can result in habitat loss for some aquatic species. Large and deep dam and reservoir plants cover large areas of land which causes greenhouse gas emissions from underwater rotting vegetation. Furthermore, although at lower levels than other renewable energy sources, it was found that hydropower produces methane equivalent to almost a billion tonnes of CO2 greenhouse gas a year. This occurs when organic matters accumulate at the bottom of the reservoir because of the deoxygenation of water which triggers anaerobic digestion.

People who live near a hydro plant site are displaced during construction or when reservoir banks become unstable. Another potential disadvantage is cultural or religious sites may block construction.

Compressed air
A plentiful head of water can be made to generate compressed air directly without moving parts. In these designs, a falling column of water is deliberately mixed with air bubbles generated through turbulence or a venturi pressure reducer at the high-level intake. This allows it to fall down a shaft into a subterranean, high-roofed chamber where the now-compressed air separates from the water and becomes trapped. The height of the falling water column maintains compression of the air in the top of the chamber, while an outlet, submerged below the water level in the chamber allows water to flow back to the surface at a lower level than the intake. A separate outlet in the roof of the chamber supplies the compressed air. A facility on this principle was built on the Montreal River at Ragged Shutes near Cobalt, Ontario, in 1910 and supplied 5,000 horsepower to nearby mines.

Electricity
Hydroelectricity is the biggest hydropower application. Hydroelectricity generates about 15% of global electricity and provides at least 50% of the total electricity supply for more than 35 countries. In 2021, global installed hydropower electrical capacity reached almost 1400 GW, the highest among all renewable energy technologies.

Hydroelectricity generation starts with converting either the potential energy of water that is present due to the site's elevation or the kinetic energy of moving water into electrical energy.

Hydroelectric power plants vary in terms of the way they harvest energy. One type involves a dam and a reservoir. The water in the reservoir is available on demand to be used to generate electricity by passing through channels that connect the dam to the reservoir. The water spins a turbine, which is connected to the generator that produces electricity.

The other type is called a run-of-river plant. In this case, a barrage is built to control the flow of water, absent a reservoir. The run-of river power plant needs continuous water flow and therefore has less ability to provide power on demand. The kinetic energy of flowing water is the main source of energy.

Both designs have limitations. For example, dam construction can result in discomfort to nearby residents. The dam and reservoirs occupy a relatively large amount of space that may be opposed by nearby communities. Moreover, reservoirs can potentially have major environmental consequences such as harming downstream habitats. On the other hand, the limitation of the run-of-river project is the decreased efficiency of electricity generation because the process depends on the speed of the seasonal river flow. This means that the rainy season increases electricity generation compared to the dry season.

The size of hydroelectric plants can vary from small plants called micro hydro, to large plants that supply power to a whole country. As of 2019, the five largest power stations in the world are conventional hydroelectric power stations with dams.

Hydroelectricity can also be used to store energy in the form of potential energy between two reservoirs at different heights with pumped-storage. Water is pumped uphill into reservoirs during periods of low demand to be released for generation when demand is high or system generation is low.

Other forms of electricity generation with hydropower include tidal stream generators using energy from tidal power generated from oceans, rivers, and human-made canal systems to generating electricity.

Rain power
Rain has been referred to as "one of the last unexploited energy sources in nature. When it rains, billions of litres of water can fall, which have enormous electric potential if used in the right way." Research is being done into the different methods of generating power from rain, such as by using the energy in the impact of raindrops. This is in its very early stages with new and emerging technologies being tested, prototyped and created. Such power has been called rain power. One method in which this has been attempted is by using hybrid solar panels called "all-weather solar panels" that can generate electricity from both the sun and the rain.

According to zoologist and science and technology educator, Luis Villazon, "A 2008 French study estimated that you could use piezoelectric devices, which generate power when they move, to extract 12 milliwatts from a raindrop. Over a year, this would amount to less than 0.001kWh per square metre – enough to power a remote sensor." Villazon suggested a better application would be to collect the water from fallen rain and use it to drive a turbine, with an estimated energy generation of 3 kWh of energy per year for a 185 m2 roof. A microturbine-based system created by three students from the Technological University of Mexico has been used to generate electricity. The Pluvia system "uses the stream of rainwater runoff from houses' rooftop rain gutters to spin a microturbine in a cylindrical housing. Electricity generated by that turbine is used to charge 12-volt batteries."

The term rain power has also been applied to hydropower systems which include the process of capturing the rain.

Ancient history
Evidence suggests that the fundamentals of hydropower date to ancient Greek civilization. Other evidence indicates that the waterwheel independently emerged in China around the same period. Evidence of water wheels and watermills date to the ancient Near East in the 4th century BC. Moreover, evidence indicates the use of hydropower using irrigation machines to ancient civilizations such as Sumer and Babylonia. Studies suggest that the water wheel was the initial form of water power and it was driven by either humans or animals.

In the Roman Empire, water-powered mills were described by Vitruvius by the first century BC. The Barbegal mill, located in modern-day France, had 16 water wheels processing up to 28 tons of grain per day. Roman waterwheels were also used for sawing marble such as the Hierapolis sawmill of the late 3rd century AD. Such sawmills had a waterwheel that drove two crank-and-connecting rods to power two saws. It also appears in two 6th century Eastern Roman sawmills excavated at Ephesus and Gerasa respectively. The crank and connecting rod mechanism of these Roman watermills converted the rotary motion of the waterwheel into the linear movement of the saw blades.

Water-powered trip hammers and bellows in China, during the Han dynasty (202 BC – 220 AD), were initially thought to be powered by water scoops. However, some historians suggested that they were powered by waterwheels. This is since it was theorized that water scoops would not have had the motive force to operate their blast furnace bellows. Many texts describe the Hun waterwheel; some of the earliest ones are the Jijiupian dictionary of 40 BC, Yang Xiong's text known as the Fangyan of 15 BC, as well as Xin Lun, written by Huan Tan about 20 AD. It was also during this time that the engineer Du Shi (c. AD 31) applied the power of waterwheels to piston-bellows in forging cast iron.

Ancient Indian texts dating back to the 4th century BC refer to the term cakkavattaka (turning wheel), which commentaries explain as arahatta-ghati-yanta (machine with wheel-pots attached), however whether this is water or hand powered is disputed by scholars India received Roman water mills and baths in the early 4th century AD when a certain according to Greek sources. Dams, spillways, reservoirs, channels, and water balance would develop in India during the Mauryan, Gupta and Chola empires.

Another example of the early use of hydropower is seen in hushing, a historic method of mining that uses flood or torrent of water to reveal mineral veins. The method was first used at the Dolaucothi Gold Mines in Wales from 75 AD onwards. This method was further developed in Spain in mines such as Las Médulas. Hushing was also widely used in Britain in the Medieval and later periods to extract lead and tin ores. It later evolved into hydraulic mining when used during the California Gold Rush in the 19th century.

The Islamic Empire spanned a large region, mainly in Asia and Africa, along with other surrounding areas. During the Islamic Golden Age and the Arab Agricultural Revolution (8th–13th centuries), hydropower was widely used and developed. Early uses of tidal power emerged along with large hydraulic factory complexes. A wide range of water-powered industrial mills were used in the region including fulling mills, gristmills, paper mills, hullers, sawmills, ship mills, stamp mills, steel mills, sugar mills, and tide mills. By the 11th century, every province throughout the Islamic Empire had these industrial mills in operation, from Al-Andalus and North Africa to the Middle East and Central Asia. Muslim engineers also used water turbines while employing gears in watermills and water-raising machines. They also pioneered the use of dams as a source of water power, used to provide additional power to watermills and water-raising machines. Islamic irriguation techniques including Persian Wheels would be introduced to India, and would be combined with local methods, during the Delhi Sultanate and the Mughal Empire.

Furthermore, in his book, The Book of Knowledge of Ingenious Mechanical Devices, the Muslim mechanical engineer, Al-Jazari (1136–1206) described designs for 50 devices. Many of these devices were water-powered, including clocks, a device to serve wine, and five devices to lift water from rivers or pools, where three of them are animal-powered and one can be powered by animal or water. Moreover, they included an endless belt with jugs attached, a cow-powered shadoof (a crane-like irrigation tool), and a reciprocating device with hinged valves.

19th century
In the 19th century, French engineer Benoît Fourneyron developed the first hydropower turbine. This device was implemented in the commercial plant of Niagara Falls in 1895 and it is still operating. In the early 20th century, English engineer William Armstrong built and operated the first private electrical power station which was located in his house in Cragside in Northumberland, England. In 1753, the French engineer Bernard Forest de Bélidor published his book, Architecture Hydraulique, which described vertical-axis and horizontal-axis hydraulic machines.

The growing demand for the Industrial Revolution would drive development as well. At the beginning of the Industrial Revolution in Britain, water was the main power source for new inventions such as Richard Arkwright's water frame. Although water power gave way to steam power in many of the larger mills and factories, it was still used during the 18th and 19th centuries for many smaller operations, such as driving the bellows in small blast furnaces (e.g. the Dyfi Furnace) and gristmills, such as those built at Saint Anthony Falls, which uses the 50 ft drop in the Mississippi River.

Technological advances moved the open water wheel into an enclosed turbine or water motor. In 1848, the British-American engineer James B. Francis, head engineer of Lowell's Locks and Canals company, improved on these designs to create a turbine with 90% efficiency. He applied scientific principles and testing methods to the problem of turbine design. His mathematical and graphical calculation methods allowed the confident design of high-efficiency turbines to exactly match a site's specific flow conditions. The Francis reaction turbine is still in use. In the 1870s, deriving from uses in the California mining industry, Lester Allan Pelton developed the high-efficiency Pelton wheel impulse turbine, which used hydropower from the high head streams characteristic of the Sierra Nevada.

20th century
The modern history of hydropower begins in the 1900s, with large dams built not simply to power neighboring mills or factories but provide extensive electricity for increasingly distant groups of people. Competition drove much of the global hydroelectric craze: Europe competed amongst itself to electrify first, and the United States' hydroelectric plants in Niagara Falls and the Sierra Nevada inspired bigger and bolder creations across the globe. American and USSR financers and hydropower experts also spread the gospel of dams and hydroelectricity across the globe during the Cold War, contributing to projects such as the Three Gorges Dam and the Aswan High Dam. Feeding desire for large scale electrification with water inherently required large dams across powerful rivers, which impacted public and private interests downstream and in flood zones. Inevitably smaller communities and marginalized groups suffered. They were unable to successfully resist companies flooding them out of their homes or blocking traditional salmon passages. The stagnant water created by hydroelectric dams provides breeding ground for pests and pathogens, leading to local epidemics. However, in some cases, a mutual need for hydropower could lead to cooperation between otherwise adversarial nations. Hydropower technology and attitude began to shift in the second half of the 20th century. While countries had largely abandoned their small hydropower systems by the 1930s, the smaller hydropower plants began to make a comeback in the 1970s, boosted by government subsidies and a push for more independent energy producers. Some politicians who once advocated for large hydropower projects in the first half of the 20th century began to speak out against them, and citizen groups organizing against dam projects increased.

In the 1980s and 90s the international anti-dam movement had made finding government or private investors for new large hydropower projects incredibly difficult, and given rise to NGOs devoted to fighting dams. Additionally, while the cost of other energy sources fell, the cost of building new hydroelectric dams increased 4% annually between 1965 and 1990, due both to the increasing costs of construction and to the decrease in high quality building sites. In the 1990s, only 18% of the world's electricity came from hydropower. Tidal power production also emerged in the 1960s as a burgeoning alternative hydropower system, though still has not taken hold as a strong energy contender.

United States
Especially at the start of the American hydropower experiment, engineers and politicians began major hydroelectricity projects to solve a problem of 'wasted potential' rather than to power a population that needed the electricity. When the Niagara Falls Power Company began looking into damming Niagara, the first major hydroelectric project in the United States, in the 1890s they struggled to transport electricity from the falls far enough away to actually reach enough people and justify installation. The project succeeded in large part due to Nikola Tesla's invention of the alternating current motor. On the other side of the country, San Francisco engineers, the Sierra Club, and the federal government fought over acceptable use of the Hetch Hetchy Valley. Despite ostensible protection within a national park, city engineers successfully won the rights to both water and power in the Hetch Hetchy Valley in 1913. After their victory they delivered Hetch Hetchy hydropower and water to San Francisco a decade later and at twice the promised cost, selling power to PG&E which resold to San Francisco residents at a profit.

The American West, with its mountain rivers and lack of coal, turned to hydropower early and often, especially along the Columbia River and its tributaries. The Bureau of Reclamation built the Hoover Dam in 1931, symbolically linking the job creation and economic growth priorities of the New Deal. The federal government quickly followed Hoover with the Shasta Dam and Grand Coulee Dam. Power demand in Oregon did not justify damming the Columbia until WWI revealed the weaknesses of a coal-based energy economy. The federal government then began prioritizing interconnected power—and lots of it. Electricity from all three dams poured into war production during WWII.

After the war, the Grand Coulee Dam and accompanying hydroelectric projects electrified almost all of the rural Columbia Basin, but failed to improve the lives of those living and farming there the way its boosters had promised and also damaged the river ecosystem and migrating salmon populations. In the 1940s as well, the federal government took advantage of the sheer amount of unused power and flowing water from the Grand Coulee to build a nuclear site placed on the banks of the Columbia. The nuclear site leaked radioactive matter into the river, contaminating the entire area.

Post-WWII Americans, especially engineers from the Tennessee Valley Authority, refocused from simply building domestic dams to promoting hydropower abroad. While domestic dam building continued well into the 1970s, with the Reclamation Bureau and Army Corps of Engineers building more than 150 new dams across the American West, organized opposition to hydroelectric dams sparked up in the 1950s and 60s based on environmental concerns. Environmental movements successfully shut down proposed hydropower dams in Dinosaur National Monument and the Grand Canyon, and gained more hydropower-fighting tools with 1970s environmental legislation. As nuclear and fossil fuels grew in the 70s and 80s and environmental activists push for river restoration, hydropower gradually faded in American importance.

Africa
Foreign powers and IGOs have frequently used hydropower projects in Africa as a tool to interfere in the economic development of African countries, such as the World Bank with the Kariba and Akosombo Dams, and the Soviet Union with the Aswan Dam. The Nile River especially has borne the consequences of countries both along the Nile and distant foreign actors using the river to expand their economic power or national force. After the British occupation of Egypt in 1882, the British worked with Egypt to construct the first Aswan Dam, which they heightened in 1912 and 1934 to try to hold back the Nile floods. Egyptian engineer Adriano Daninos developed a plan for the Aswan High Dam, inspired by the Tennessee Valley Authority's multipurpose dam.

When Gamal Abdel Nasser took power in the 1950s, his government decided to undertake the High Dam project, publicizing it as an economic development project. After American refusal to help fund the dam, and anti-British sentiment in Egypt and British interests in neighboring Sudan combined to make the United Kingdom pull out as well, the Soviet Union funded the Aswan High Dam. Between 1977 and 1990 the dam's turbines generated one third of Egypt's electricity. The building of the Aswan Dam triggered a dispute between Sudan and Egypt over the sharing of the Nile, especially since the dam flooded part of Sudan and decreased the volume of water available to them. Ethiopia, also located on the Nile, took advantage of the Cold War tensions to request assistance from the United States for their own irrigation and hydropower investments in the 1960s. While progress stalled due to the coup d'état of 1974 and following 17-year-long Ethiopian Civil War Ethiopia began construction on the Grand Ethiopian Renaissance Dam in 2011.

Beyond the Nile, hydroelectric projects cover the rivers and lakes of Africa. The Inga powerplant on the Congo River had been discussed since Belgian colonization in the late 19th century, and was successfully built after independence. Mobutu's government failed to regularly maintain the plants and their capacity declined until the 1995 formation of the Southern African Power Pool created a multi-national power grid and plant maintenance program. States with an abundance of hydropower, such as the Democratic Republic of the Congo and Ghana, frequently sell excess power to neighboring countries. Foreign actors such as Chinese hydropower companies have proposed a significant amount of new hydropower projects in Africa, and already funded and consulted on many others in countries like Mozambique and Ghana.

Small hydropower also played an important role in early 20th century electrification across Africa. In South Africa, small turbines powered gold mines and the first electric railway in the 1890s, and Zimbabwean farmers installed small hydropower stations in the 1930s. While interest faded as national grids improved in the second half of the century, 21st century national governments in countries including South Africa and Mozambique, as well as NGOs serving countries like Zimbabwe, have begun re-exploring small-scale hydropower to diversify power sources and improve rural electrification.

Europe
In the early 20th century, two major factors motivated the expansion of hydropower in Europe: in the northern countries of Norway and Sweden high rainfall and mountains proved exceptional resources for abundant hydropower, and in the south coal shortages pushed governments and utility companies to seek alternative power sources.

Early on, Switzerland dammed the Alpine rivers and the Swiss Rhine, creating, along with Italy and Scandinavia, a Southern Europe hydropower race. In Italy's Po Valley, the main 20th century transition was not the creation of hydropower but the transition from mechanical to electrical hydropower. 12,000 watermills churned in the Po watershed in the 1890s, but the first commercial hydroelectric plant, completed in 1898, signaled the end of the mechanical reign. These new large plants moved power away from rural mountainous areas to urban centers in the lower plain. Italy prioritized early near-nationwide electrification, almost entirely from hydropower, which powered their rise as a dominant European and imperial force. However, they failed to reach any conclusive standard for determining water rights before WWI.

Modern German hydropower dam construction built off a history of small dams powering mines and mills going back to the 15th century. Some parts of Germany industry even relied more on waterwheels than steam until the 1870s. The German government did not set out building large dams such as the prewar Urft, Mohne, and Eder dams to expand hydropower: they mostly wanted to reduce flooding and improve navigation. However, hydropower quickly emerged as an added bonus for all these dams, especially in the coal-poor south. Bavaria even achieved a statewide power grid by damming the Walchensee in 1924, inspired in part by loss of coal reserves after WWI.

Hydropower became a symbol of regional pride and distaste for northern 'coal barons', although the north also held strong enthusiasm for hydropower. Dam building rapidly increased after WWII, this time with the express purpose of increasing hydropower. However, conflict accompanied the dam building and spread of hydropower: agrarian interests suffered from decreased irrigation, small mills lost water flow, and different interest groups fought over where dams should be located, controlling who benefited and whose homes they drowned.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Hydropower


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Horse breed

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 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 the Morgan horse, originated from a single sire from which all current breed members descend. More than 300 horse breeds exist in the world today.

Origin of breeds
Modern horse breeds developed in response to a need for "form to function", the necessity to develop certain physical characteristics to perform a certain type of work. 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, 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. 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. Other horse breeds developed specifically for light agricultural work, heavy and light carriage and road work, various equestrian disciplines, or simply as pets.

Purebreds and registries

Horses have been selectively bred since their domestication. 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.

An early example of people who practiced selective horse breeding were the Bedouin, who had a reputation for careful breeding practices, keeping extensive pedigrees of their Arabian horses and placing great value upon pure bloodlines. Though these pedigrees were originally transmitted by an oral tradition, written pedigrees of Arabian horses can be found that date to the 14th century. In the same period of the early Renaissance, the Carthusian monks of southern Spain bred horses and kept meticulous pedigrees of the best bloodstock; the lineage survives to this day in the Andalusian horse. One of the earliest formal registries was General Stud Book for Thoroughbreds, which began in 1791 and traced back to the Arabian stallions imported to England from the Middle East that became the foundation stallions for the breed.

Some breed registries have a closed stud book, where registration is based on pedigree, and no outside animals can gain admittance. For example, a registered Thoroughbred or Arabian must have two registered parents of the same breed.

Other breeds have a partially closed stud book, but still allow certain infusions from other breeds. For example, the modern Appaloosa must have at least one Appaloosa parent, but may also have a Quarter Horse, Thoroughbred, or Arabian parent, so long as the offspring exhibits appropriate color characteristics. The Quarter Horse normally requires both parents to be registered Quarter Horses, but allows "Appendix" registration of horses with one Thoroughbred parent, and the horse may earn its way to full registration by completing certain performance requirements.

Open stud books exist for horse breeds that either have not yet developed a rigorously defined standard phenotype, or for breeds that register animals that conform to an ideal via the process of passing a studbook selection process. Most of the warmblood breeds used in sport horse disciplines have open stud books to varying degrees. While pedigree is considered, outside bloodlines are admitted to the registry if the horses meet the set standard for the registry. These registries usually require a selection process involving judging of an individual animal's quality, performance, and conformation before registration is finalized. A few "registries," particularly some color breed registries, are very open and will allow membership of all horses that meet limited criteria, such as coat color and species, regardless of pedigree or conformation.

Breed registries also differ as to their acceptance or rejection of breeding technology. For example, all Jockey Club Thoroughbred registries require that a registered Thoroughbred be a product of a natural mating, so-called "live cover". A foal born of two Thoroughbred parents, but by means of artificial insemination or embryo transfer, cannot be registered in the Thoroughbred studbook. However, since the advent of DNA testing to verify parentage, most breed registries now allow artificial insemination, embryo transfer, or both. The high value of stallions has helped with the acceptance of these techniques because they allow a stallion to breed more mares with each "collection" and greatly reduce the risk of injury during mating. Cloning of horses is highly controversial, and at the present time most mainstream breed registries will not accept cloned horses, though several cloned horses and mules have been produced. Such restrictions have led to legal challenges in the United States, sometime based on state law and sometimes based on antitrust laws.

Hybrids
Horses can crossbreed with other equine species to produce hybrids. These hybrid types are not breeds, but they resemble breeds in that crosses between certain horse breeds and other equine species produce characteristic offspring. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, the hinny, is a cross between a stallion and a jenny (female donkey). Most other hybrids involve the zebra (see Zebroid). With rare exceptions, most equine hybrids are sterile and cannot reproduce. A notable exception is hybrid crosses between horses and Equus ferus przewalskii, commonly known as Przewalski's horse.

title: Horse breed


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Horse breeding

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.

Terminology
The male parent of a horse, a stallion, is commonly known as the sire and the female parent, the mare, is called the dam. Both are genetically important, as each parent genes can be existent with a 50% probability in the foal. Contrary to popular misuse, "colt" refers to a young male horse only; "filly" is a young female. Though many horse owners may simply breed a family mare to a local stallion in order to produce a companion animal, most professional breeders use selective breeding to produce individuals of a given phenotype, or breed. Alternatively, a breeder could, using individuals of differing phenotypes, create a new breed with specific characteristics.

A horse is "bred" where it is foaled (born). Thus a colt conceived in England but foaled in the United States is regarded as being bred in the US. In some cases, most notably in the Thoroughbred breeding industry, American- and Canadian-bred horses may also be described by the state or province in which they are foaled. Some breeds denote the country, or state, where conception took place as the origin of the foal.

Similarly, the "breeder", is the person who owned or leased the mare at the time of foaling. That individual may not have had anything to do with the mating of the mare. It is important to review each breed registry's rules to determine which applies to any specific foal.

In the horse breeding industry, the term "half-brother" or "half-sister" only describes horses which have the same dam, but different sires. Horses with the same sire but different dams are simply said to be "by the same sire", and no sibling relationship is implied. "Full" (or "own") siblings have both the same dam and the same sire. The terms paternal half-sibling, and maternal half-sibling are also often used. Three-quarter siblings are horses out of the same dam, and are by sires that are either half-brothers (i.e. same dam) or who are by the same sire.

Thoroughbreds and Arabians are also classified through the "distaff" or direct female line, known as their "family" or "tail female" line, tracing back to their taproot foundation bloodstock or the beginning of their respective stud books. The female line of descent always appears at the bottom of a tabulated pedigree and is therefore often known as the bottom line. In addition, the maternal grandfather of a horse has a special term: damsire.

"Linebreeding" technically is the duplication of fourth-generation or more distant ancestors. However, the term is often used more loosely, describing horses with duplication of ancestors closer than the fourth generation. It also is sometimes used as a euphemism for the practice of inbreeding, a practice that is generally frowned upon by horse breeders, though used by some in an attempt to fix certain traits.

Estrous cycle of the mare

The estrous cycle (also spelled oestrous) controls when a mare is sexually receptive toward a stallion, and helps to physically prepare the mare for conception. It generally occurs during the spring and summer months, although some mares may be sexually receptive into the late fall, and is controlled by the photoperiod (length of the day), the cycle first triggered when the days begin to lengthen. The estrous cycle lasts about 19–22 days, with the average being 21 days. As the days shorten, the mare returns to a period when she is not sexually receptive, known as anestrus. Anestrus – occurring in the majority of, but not all, mares – prevents the mare from conceiving in the winter months, as that would result in her foaling during the harshest part of the year, a time when it would be most difficult for the foal to survive.

This cycle contains 2 phases:
 * Estrus, or Follicular, phase: 5–7 days in length, when the mare is sexually receptive to a stallion. Estrogen is secreted by the follicle. Ovulation occurs in the final 24–48 hours of estrus.
 * Diestrus, or Luteal, phase: 14–15 days in length, the mare is not sexually receptive to the stallion. The corpus luteum secretes progesterone.

Depending on breed, on average, 16% of mares have double ovulations, allowing them to twin, though this does not affect the length of time of estrus or diestrus.

Effects on the reproductive system during the estrous cycle
Changes in hormone levels can have great effects on the physical characteristics of the reproductive organs of the mare, thereby preparing, or preventing, her from conceiving.
 * Uterus: increased levels of estrogen during estrus cause edema within the uterus, making it feel heavier, and the uterus loses its tone. This edema decreases following ovulation, and the muscular tone increases. High levels of progesterone do not cause edema within the uterus. The uterus becomes flaccid during anestrus.
 * Cervix: the cervix starts to relax right before estrus occurs, with maximal relaxation around the time of ovulation. The secretions of the cervix increase. High progesterone levels (during diestrus) cause the cervix to close and become toned.
 * Vagina: the portion of the vagina near the cervix becomes engorged with blood right before estrus. The vagina becomes relaxed and secretions increase.
 * Vulva: relaxes right before estrus begins. Becomes dry, and closes more tightly, during diestrus.

Hormones involved in the estrous cycle, during foaling, and after birth
The cycle is controlled by several hormones which regulate the estrous cycle, the mare's behavior, and the reproductive system of the mare. The cycle begins when the increased day length causes the pineal gland to reduce the levels of melatonin, thereby allowing the hypothalamus to secrete GnRH.
 * GnRH (Gonadotropin releasing hormone): secreted by the hypothalamus, causes the pituitary to release two gonadotrophins: LH and FSH.
 * LH (Luteinizing hormone): levels are highest 2 days following ovulation, then slowly decrease over 4–5 days, dipping to their lowest levels 5–16 days after ovulation. Stimulates maturation of the follicle, which then in turn secretes estrogen. Unlike most mammals, the mare does not have an increase of LH right before ovulation.
 * FSH (Follicle-stimulating hormone): secreted by the pituitary, causes the ovarian follicle to develop. Levels of FSH rise slightly at the end of estrus, but have their highest peak about 10 days before the next ovulation. FSH is inhibited by inhibin (see below), at the same time LH and estrogen levels rise, which prevents immature follicles from continuing their growth. Mares may however have multiple FSH waves during a single estrous cycle, and diestrus follicles resulting from a diestrus FSH wave are not uncommon, particularly in the height of the natural breeding season.
 * Estrogen: secreted by the developing follicle, it causes the pituitary gland to secrete more LH (therefore, these 2 hormones are in a positive feedback loop). Additionally, it causes behavioral changes in the mare, making her more receptive toward the stallion, and causes physical changes in the cervix, uterus, and vagina to prepare the mare for conception (see above). Estrogen peaks 1–2 days before ovulation, and decreases within 2 days following ovulation.
 * Inhibin: secreted by the developed follicle right before ovulation, "turns off" FSH, which is no longer needed now that the follicle is larger.
 * Progesterone: prevents conception and decreases sexual receptibility of the mare to the stallion. Progesterone is therefore lowest during the estrus phase, and increases during diestrus. It decreases 12–15 days after ovulation, when the corpus luteum begins to decrease in size.
 * Prostaglandin: secreted by the endrometrium 13–15 days following ovulation, causes luteolysis and prevents the corpus luteum from secreting progesterone
 * eCG – equine chorionic gonadotropin – also called PMSG (pregnant mare serum gonadotropin): chorionic gonadotropins secreted if the mare conceives. First secreted by the endometrial cups around the 36th day of gestation, peaking around day 60, and decreasing after about 120 days of gestation. Also help to stimulate the growth of the fetal gonads.
 * Prolactin: stimulates lactation
 * Oxytocin: stimulates the uterus to contract

Breeding and gestation
While horses in the wild mate and foal in mid to late spring, in the case of horses domestically bred for competitive purposes, especially horse racing, it is desirable that they be born as close to January 1 in the northern hemisphere or August 1 in the southern hemisphere as possible, so as to be at an advantage in size and maturity when competing against other horses in the same age group. When an early foal is desired, barn managers will put the mare "under lights" by keeping the barn lights on in the winter to simulate a longer day, thus bringing the mare into estrus sooner than she would in nature. Mares signal estrus and ovulation by urination in the presence of a stallion, raising the tail and revealing the vulva. A stallion, approaching with a high head, will usually nicker, nip and nudge the mare, as well as sniff her urine to determine her readiness for mating.

Once fertilized, the oocyte (egg) remains in the oviduct for approximately 5.5 more days, and then descends into the uterus. The initial single cell combination is already dividing and by the time of entry into the uterus, the egg might have already reached the blastocyst stage.

The gestation period lasts for about eleven months, or about 340 days (normal average range 320–370 days). During the early days of pregnancy, the conceptus is mobile, moving about in the uterus until about day 16 when "fixation" occurs. Shortly after fixation, the embryo proper (so called up to about 35 days) will become visible on trans-rectal ultrasound (about day 21) and a heartbeat should be visible by about day 23. After the formation of the endometrial cups and early placentation is initiated (35–40 days of gestation) the terminology changes, and the embryo is referred to as a fetus. True implantation – invasion into the endometrium of any sort – does not occur until about day 35 of pregnancy with the formation of the endometrial cups, and true placentation (formation of the placenta) is not initiated until about day 40-45 and not completed until about 140 days of pregnancy. The fetus's sex can be determined by day 70 of the gestation using ultrasound. Halfway through gestation the fetus is the size of between a rabbit and a beagle. The most dramatic fetal development occurs in the last 3 months of pregnancy when 60% of fetal growth occurs.

Colts are carried on average about 4 days longer than fillies.

Care of the pregnant mare
Domestic mares receive specific care and nutrition to ensure that they and their foals are healthy. Mares are given vaccinations against diseases such as the Rhinopneumonitis (EHV-1) virus (which can cause miscarriage) as well as vaccines for other conditions that may occur in a given region of the world. Pre-foaling vaccines are recommended 4–6 weeks prior to foaling to maximize the immunoglobulin content of the colostrum in the first milk. Mares are dewormed a few weeks prior to foaling, as the mare is the primary source of parasites for the foal.

Mares can be used for riding or driving during most of their pregnancy. Exercise is healthy, though should be moderated when a mare is heavily in foal. Exercise in excessively high temperatures has been suggested as being detrimental to pregnancy maintenance during the embryonic period; however ambient temperatures encountered during the research were in the region of 100 degrees F and the same results may not be encountered in regions with lower ambient temperatures.

During the first several months of pregnancy, the nutritional requirements do not increase significantly since the rate of growth of the fetus is very slow. However, during this time, the mare may be provided supplemental vitamins and minerals, particularly if forage quality is questionable. During the last 3–4 months of gestation, rapid growth of the fetus increases the mare's nutritional requirements. Energy requirements during these last few months, and during the first few months of lactation are similar to those of a horse in full training. Trace minerals such as copper are extremely important, particularly during the tenth month of pregnancy, for proper skeletal formation. Many feeds designed for pregnant and lactating mares provide the careful balance required of increased protein, increased calories through extra fat as well as vitamins and minerals. Overfeeding the pregnant mare, particularly during early gestation, should be avoided, as excess weight may contribute to difficulties foaling or fetal/foal related problems.

Foaling

Mares due to foal are usually separated from other horses, both for the benefit of the mare and the safety of the soon-to-be-delivered foal. In addition, separation allows the mare to be monitored more closely by humans for any problems that may occur while giving birth. In the northern hemisphere, a special foaling stall that is large and clutter free is frequently used, particularly by major breeding farms. Originally, this was due in part to a need for protection from the harsh winter climate present when mares foal early in the year, but even in moderate climates, such as Florida, foaling stalls are still common because they allow closer monitoring of mares. Smaller breeders often use a small pen with a large shed for foaling, or they may remove a wall between two box stalls in a small barn to make a large stall. In the milder climates seen in much of the southern hemisphere, most mares foal outside, often in a paddock built specifically for foaling, especially on the larger stud farms. Many stud farms worldwide employ technology to alert human managers when the mare is about to foal, including webcams, closed-circuit television, or assorted types of devices that alert a handler via a remote alarm when a mare lies down in a position to foal.

On the other hand, some breeders, particularly those in remote areas or with extremely large numbers of horses, may allow mares to foal out in a field amongst a herd, but may also see higher rates of foal and mare mortality in doing so.

Most mares foal at night or early in the morning, and prefer to give birth alone when possible. Labor is rapid, often no more than 30 minutes, and from the time the feet of the foal appear to full delivery is often only about 15 to 20 minutes. Once the foal is born, the mare will lick the newborn foal to clean it and help blood circulation. In a very short time, the foal will attempt to stand and get milk from its mother. A foal should stand and nurse within the first hour of life.

To create a bond with her foal, the mare licks and nuzzles the foal, enabling her to distinguish the foal from others. Some mares are aggressive when protecting their foals, and may attack other horses or unfamiliar humans that come near their newborns.

After birth, a foal's navel is dipped in antiseptic to prevent infection. The foal is sometimes given an enema to help clear the meconium from its digestive tract. The newborn is monitored to ensure that it stands and nurses without difficulty. While most horse births happen without complications, many owners have first aid supplies prepared and a veterinarian on call in case of a birthing emergency. People who supervise foaling should also watch the mare to be sure that she passes the placenta in a timely fashion, and that it is complete with no fragments remaining in the uterus. Retained fetal membranes can cause a serious inflammatory condition (endometritis) and/or infection. If the placenta is not removed from the stall after it is passed, a mare will often eat it, an instinct from the wild, where blood would attract predators.

Foal care
Foals develop rapidly, and within a few hours a wild foal can travel with the herd. In domestic breeding, the foal and dam are usually separated from the herd for a while, but within a few weeks are typically pastured with the other horses. A foal will begin to eat hay, grass and grain alongside the mare at about 4 weeks old; by 10–12 weeks the foal requires more nutrition than the mare's milk can supply. Foals are typically weaned at 4–8 months of age, although in the wild a foal may nurse for a year.

How breeds develop
Beyond the appearance and conformation of a specific type of horse, breeders aspire to improve physical performance abilities. This concept, known as matching "form to function," has led to the development of not only different breeds, but also families or bloodlines within breeds that are specialists for excelling at specific tasks.

For example, the Arabian horse of the desert naturally developed speed and endurance to travel long distances and survive in a harsh environment, and domestication by humans added a trainable disposition to the animal's natural abilities. In the meantime, in northern Europe, the locally adapted heavy horse with a thick, warm coat was domesticated and put to work as a farm animal that could pull a plow or wagon. This animal was later adapted through selective breeding to create a strong but rideable animal suitable for the heavily armored knight in warfare.

Then, centuries later, when people in Europe wanted faster horses than could be produced from local horses through simple selective breeding, they imported Arabians and other oriental horses to breed as an outcross to the heavier, local animals. This led to the development of breeds such as the Thoroughbred, a horse taller than the Arabian and faster over the distances of a few miles required of a European race horse or light cavalry horse. Another cross between oriental and European horses produced the Andalusian, a horse developed in Spain that was powerfully built, but extremely nimble and capable of the quick bursts of speed over short distances necessary for certain types of combat as well as for tasks such as bullfighting.

Later, the people who settled America needed a hardy horse that was capable of working with cattle. Thus, Arabians and Thoroughbreds were crossed on Spanish horses, both domesticated animals descended from those brought over by the Conquistadors, and feral horses such as the Mustangs, descended from the Spanish horse, but adapted by natural selection to the ecology and climate of the west. These crosses ultimately produced new breeds such as the American Quarter Horse and the Criollo of Argentina. In Canada, the Canadian Horse descended from the French stock Louis XIV sent to Canada in the late 17th century.[6] The initial shipment, in 1665, consisted of two stallions and twenty mares from the Royal Stables in Normandy and Brittany, the centre of French horse breeding.[7] Only 12 of the 20 mares survived the trip. Two more shipments followed, one in 1667 of 14 horses (mostly mares, but with at least one stallion), and one in 1670 of 11 mares and a stallion. The shipments included a mix of draft horses and light horses, the latter of which included both pacing and trotting horses.[1] The exact origins of all the horses are unknown, although the shipments probably included Bretons, Normans, Arabians, Andalusians and Barbs.

In modern times, these breeds themselves have since been selectively bred to further specialize at certain tasks. One example of this is the American Quarter Horse. Once a general-purpose working ranch horse, different bloodlines now specialize in different events. For example, larger, heavier animals with a very steady attitude are bred to give competitors an advantage in events such as team roping, where a horse has to start and stop quickly, but also must calmly hold a full-grown steer at the end of a rope. On the other hand, for an event known as cutting, where the horse must separate a cow from a herd and prevent it from rejoining the group, the best horses are smaller, quick, alert, athletic and highly trainable. They must learn quickly, have conformation that allows quick stops and fast, low turns, and the best competitors have a certain amount of independent mental ability to anticipate and counter the movement of a cow, popularly known as "cow sense."

Another example is the Thoroughbred. While most representatives of this breed are bred for horse racing, there are also specialized bloodlines suitable as show hunters or show jumpers. The hunter must have a tall, smooth build that allows it to trot and canter smoothly and efficiently. Instead of speed, value is placed on appearance and upon giving the equestrian a comfortable ride, with natural jumping ability that shows bascule and good form.

A show jumper, however, is bred less for overall form and more for power over tall fences, along with speed, scope, and agility. This favors a horse with a good galloping stride, powerful hindquarters that can change speed or direction easily, plus a good shoulder angle and length of neck. A jumper has a more powerful build than either the hunter or the racehorse.

History of horse breeding
The history of horse breeding goes back millennia. Though the precise date is in dispute, humans could have domesticated the horse as far back as approximately 4500 BCE. However, evidence of planned breeding has a more blurry history. It is well known, for example, that the Romans did breed horses and valued them in their armies, but little is known regarding their breeding and husbandry practices: all that remains are statues and artwork. Mankind has plenty of equestrian statues of Roman emperors, horses are mentioned in the Odyssey by Homer, and hieroglyphics and paintings left behind by Egyptians tell stories of pharaohs hunting elephants from chariots. Nearly nothing is known of what became of the horses they bred for hippodromes, for warfare, or even for farming.

One of the earliest people known to document the breedings of their horses were the Bedouin of the Middle East, the breeders of the Arabian horse. While it is difficult to determine how far back the Bedouin passed on pedigree information via an oral tradition, there were written pedigrees of Arabian horses by CE 1330. The Akhal-Teke of West-Central Asia is another breed with roots in ancient times that was also bred specifically for war and racing. The nomads of the Mongolian steppes bred horses for several thousand years as well, and the Caspian horse is believed to be a very close relative of Ottoman horses from the earliest origins of the Turks in Central Asia.

The types of horse bred varied with culture and with the times. The uses to which a horse was put also determined its qualities, including smooth amblers for riding, fast horses for carrying messengers, heavy horses for plowing and pulling heavy wagons, ponies for hauling cars of ore from mines, packhorses, carriage horses and many others.

Medieval Europe bred large horses specifically for war, called destriers. These horses were the ancestors of the great heavy horses of today, and their size was preferred not simply because of the weight of the armor, but also because a large horse provided more power for the knight's lance. Weighing almost twice as much as a normal riding horse, the destrier was a powerful weapon in battle meant to act like a giant battering ram that could quite literally run down men on an enemy line.

On the other hand, during this same time, lighter horses were bred in northern Africa and the Middle East, where a faster, more agile horse was preferred. The lighter horse suited the raids and battles of desert people, allowing them to outmaneuver rather than overpower the enemy. When Middle Eastern warriors and European knights collided in warfare, the heavy knights were frequently outmaneuvered. The Europeans, however, responded by crossing their native breeds with "oriental" type horses such as the Arabian, Barb, and Turkoman horse This cross-breeding led both to a nimbler war horse, such as today's Andalusian horse, but also created a type of horse known as a Courser, a predecessor to the Thoroughbred, which was used as a message horse.

During the Renaissance, horses were bred not only for war, but for haute ecole riding, derived from the most athletic movements required of a war horse, and popular among the elite nobility of the time. Breeds such as the Lipizzan and the now extinct Neapolitan horse were developed from Spanish-bred horses for this purpose, and also became the preferred mounts of cavalry officers, who were derived mostly from the ranks of the nobility. It was during this time that firearms were developed, and so the light cavalry horse, a faster and quicker war horse, was bred for "shoot and run" tactics rather than the shock action as in the Middle Ages. Fine horses usually had a well muscled, curved neck, slender body, and sweeping mane, as the nobility liked to show off their wealth and breeding in paintings of the era.

After Charles II retook the British throne in 1660, horse racing, which had been banned by Cromwell, was revived. The Thoroughbred was developed 40 years later, bred to be the ultimate racehorse, through the lines of three foundation Arabian stallions and one Turkish horse.

In the 18th century, James Burnett, Lord Monboddo noted the importance of selecting appropriate parentage to achieve desired outcomes of successive generations. Monboddo worked more broadly in the abstract thought of species relationships and evolution of species. The Thoroughbred breeding hub in Lexington, Kentucky was developed in the late 18th century, and became a mainstay in American racehorse breeding.

The 17th and 18th centuries saw more of a need for fine carriage horses in Europe, bringing in the dawn of the warmblood. The warmblood breeds have been exceptionally good at adapting to changing times, and from their carriage horse beginnings they easily transitioned during the 20th century into a sport horse type. Today's warmblood breeds, although still used for competitive driving, are more often seen competing in show jumping or dressage.

The Thoroughbred continues to dominate the horse racing world, although its lines have been more recently used to improve warmblood breeds and to develop sport horses. The French saddle horse is an excellent example as is the Irish Sport Horse, the latter being an unusual combination between a Thoroughbred and a draft breed.

The American Quarter Horse was developed early in the 18th century, mainly for quarter racing (racing ¼ of a mile). Colonists did not have racetracks or any of the trappings of Europe that the earliest Thoroughbreds had at their disposal, so instead the owners of Quarter Horses would run their horses on roads that lead through town as a form of local entertainment. As the USA expanded West, the breed went with settlers as a farm and ranch animal, and "cow sense" was particularly valued: their use for herding cattle increased on rough, dry terrain that often involved sitting in the saddle for long hours.

However, this did not mean that the original ¼-mile races that colonists held ever went out of fashion, so today there are three types: the stock horse type, the racer, and the more recently evolving sport type. The racing type most resembles the finer-boned ancestors of the first racing Quarter Horses, and the type is still used for ¼-mile races. The stock horse type, used in western events and as a farm and patrol animal is bred for a shorter stride, an ability to stop and turn quickly, and an unflappable attitude that remains calm and focused even in the face of an angry charging steer. The first two are still to this day bred to have a combination of explosive speed that exceeds the Thoroughbred on short distances clocked as high as 55 mph, but they still retain the gentle, calm, and kindly temperament of their ancestors that makes them easily handled.

The Canadian horse's origin corresponds to shipments of French horses, some of which came from Louis XIV's own stable and most likely were Baroque horses meant to be gentlemen's mounts. These were ill-suited to farm work and to the hardscrabble life of the New World, so like the Americans, early Canadians crossed their horses with natives escapees. In time they evolved along similar lines as the Quarter Horse to the South as both the US and Canada spread westward and needed a calm and tractable horse versatile enough to carry the farmer's son to school but still capable of running fast and running hard as a cavalry horse, a stockhorse, or a horse to pull a conestoga wagon.

Other horses from North America retained a hint of their mustang origins by being either derived from stock that Native Americans bred that came in a rainbow of color, like the Appaloosa and American Paint Horse,  with those East of the Mississippi River increasingly bred to impress and mimic the trends of the upper classes of Europe: The Tennessee Walking Horse and Saddlebred were originally plantation horses bred for their gait and comfortable ride in the saddle as a plantation master would survey his vast lands like an English lord.

Horses were needed for heavy draft and carriage work until replaced by the automobile, truck, and tractor. After this time, draft and carriage horse numbers dropped significantly, though light riding horses remained popular for recreational pursuits. Draft horses today are used on a few small farms, but today are seen mainly for pulling and plowing competitions rather than farm work. Heavy harness horses are now used as an outcross with lighter breeds, such as the Thoroughbred, to produce the modern warmblood breeds popular in sport horse disciplines, particularly at the Olympic level.

Deciding to breed a horse
Breeding a horse is an endeavor where the owner, particularly of the mare, will usually need to invest considerable time and money. For this reason, a horse owner needs to consider several factors, including:
 * Does the proposed breeding animal have valuable genetic qualities to pass on?
 * Is the proposed breeding animal in good physical health, fertile, and able to withstand the rigors of reproduction?
 * For what purpose will the foal be used?
 * Is there a market for the foal if the owner does not wish to keep the foal for its entire life?
 * What is the anticipated economic benefit, if any, to the owner of the ensuing foal?
 * What is the anticipated economic benefit, if any, to the owner(s) of the sire and dam or the foal?
 * Does the owner of the mare have the expertise to properly manage the mare through gestation and parturition?
 * Does the owner of the potential foal have the expertise to properly manage and train a young animal once it is born?

There are value judgements involved in considering whether an animal is suitable breeding stock, hotly debated by breeders. Additional personal beliefs may come into play when considering a suitable level of care for the mare and ensuing foal, the potential market or use for the foal, and other tangible and intangible benefits to the owner.

If the breeding endeavor is intended to make a profit, there are additional market factors to consider, which may vary considerably from year to year, from breed to breed, and by region of the world. In many cases, the low end of the market is saturated with horses, and the law of supply and demand thus allows little or no profit to be made from breeding unregistered animals or animals of poor quality, even if registered.

The minimum cost of breeding for a mare owner includes the stud fee, and the cost of proper nutrition, management and veterinary care of the mare throughout gestation, parturition, and care of both mare and foal up to the time of weaning. Veterinary expenses may be higher if specialized reproductive technologies are used or health complications occur.

Making a profit in horse breeding is often difficult. While some owners of only a few horses may keep a foal for purely personal enjoyment, many individuals breed horses in hopes of making some money in the process.

A rule of thumb is that a foal intended for sale should be worth three times the cost of the stud fee if it were sold at the moment of birth. From birth forward, the costs of care and training are added to the value of the foal, with a sale price going up accordingly. If the foal wins awards in some form of competition, that may also enhance the price.

On the other hand, without careful thought, foals bred without a potential market for them may wind up being sold at a loss, and in a worst-case scenario, sold for "salvage" value—a euphemism for sale to slaughter as horsemeat.

Therefore, a mare owner must consider their reasons for breeding, asking hard questions of themselves as to whether their motivations are based on either emotion or profit and how realistic those motivations may be.

Choosing breeding stock
The stallion should be chosen to complement the mare, with the goal of producing a foal that has the best qualities of both animals, yet avoids having the weaker qualities of either parent. Generally, the stallion should have proven himself in the discipline or sport the mare owner wishes for the "career" of the ensuing foal. Mares should also have a competition record showing that they also have suitable traits, though this does not happen as often.

Some breeders consider the quality of the sire to be more important than the quality of the dam. However, other breeders maintain that the mare is the most important parent. Because stallions can produce far more offspring than mares, a single stallion can have a greater overall impact on a breed. Research from Nagoya University supports the belief that the most important factor affecting a thoroughbred's race performance is the quality of its sire, whereas the effect of the age of its broodmare is negligible. However, the mare may have a greater influence on an individual foal because its physical characteristics influence the developing foal in the womb and the foal also learns habits from its dam when young. Foals may also learn the "language of intimidation and submission" from their dam, and this imprinting may affect the foal's status and rank within the herd. Many times, a mature horse will achieve status in a herd similar to that of its dam; the offspring of dominant mares become dominant themselves.

A purebred horse is usually worth more than a horse of mixed breeding, though this matters more in some disciplines than others. The breed of the horse is sometimes secondary when breeding for a sport horse, but some disciplines may prefer a certain breed or a specific phenotype of horse. Sometimes, purebred bloodlines are an absolute requirement: For example, most racehorses in the world must be recorded with a breed registry in order to race.

Bloodlines are often considered, as some bloodlines are known to cross well with others. If the parents have not yet proven themselves by competition or by producing quality offspring, the bloodlines of the horse are often a good indicator of quality and possible strengths and weaknesses. Some bloodlines are known not only for their athletic ability, but could also carry a conformational or genetic defect, poor temperament, or for a medical problem. Some bloodlines are also fashionable or otherwise marketable, which is an important consideration should the mare owner wish to sell the foal.

Horse breeders also consider conformation, size and temperament. All of these traits are heritable, and will determine if the foal will be a success in its chosen discipline. The offspring, or "get", of a stallion are often excellent indicators of his ability to pass on his characteristics, and the particular traits he actually passes on. Some stallions are fantastic performers but never produce offspring of comparable quality. Others sire fillies of great abilities but not colts. At times, a horse of mediocre ability sires foals of outstanding quality.

Mare owners also look into the question of if the stallion is fertile and has successfully "settled" (i.e. impregnated) mares. A stallion may not be able to breed naturally, or old age may decrease his performance. Mare care boarding fees and semen collection fees can be a major cost.

Costs related to breeding
Breeding a horse can be an expensive endeavor, whether breeding a backyard competition horse or the next Olympic medalist. Costs may include:
 * The stud and booking fee
 * Fees for collecting, handling, and transporting semen (if AI is used and semen is shipped)
 * Mare exams: to determine if she is healthy enough to breed, to determine when she ovulates, and (if AI is used) to inseminate her
 * Mare transport, care, and board if the mare is bred live cover at the stallion's residence
 * Veterinary bills to keep the pregnant mare healthy while in foal
 * Possible veterinary bills during pregnancy or foaling should something go wrong
 * Veterinary bills for the foal for its first exam a few days following foaling

Stud fees are determined by the quality of the stallion, his performance record, the performance record of his get (offspring), as well as the sport and general market that the animal is standing for.

The highest stud fees are generally for racing Thoroughbreds, which may charge from two to three thousand dollars for a breeding to a new or unproven stallion, to several hundred thousand dollars for a breeding to a proven producer of stakes winners. Stallions in other disciplines often have stud fees that begin in the range of $1,000 to $3,000, with top contenders who produce champions in certain disciplines able to command as much as $20,000 for one breeding. The lowest stud fees to breed to a grade horse or an animal of low-quality pedigree may only be $100–$200, but there are trade-offs: the horse will probably be unproven, and likely to produce lower-quality offspring than a horse with a stud fee that is in the typical range for quality breeding stock.

As a stallion's career, either performance or breeding, improves, his stud fee tends to increase in proportion. If one or two offspring are especially successful, winning several stakes races or an Olympic medal, the stud fee will generally greatly increase. Younger, unproven stallions will generally have a lower stud fee earlier on in their careers.

To help decrease the risk of financial loss should the mare die or abort the foal while pregnant, many studs have a live foal guarantee (LFG) – also known as "no foal, free return" or "NFFR" - allowing the owner to have a free breeding to their stallion the next year. However, this is not offered for every breeding.

Covering the mare
There are two general ways to "cover" or breed the mare:
 * Live cover: the mare is brought to the stallion's residence and is covered "live" in the breeding shed. She may also be turned out in a pasture with the stallion for several days to breed naturally ('pasture bred'). The former situation is often preferred, as it provides a more controlled environment, allowing the breeder to ensure that the mare was covered, and places the handlers in a position to remove the horses from one another should one attempt to kick or bite the other. However, this causes more stress for the mare as she feels like she is being forced to undergo this procedure.
 * Artificial Insemination (AI): the mare is inseminated by a veterinarian or an equine reproduction manager, using either fresh, cooled or frozen semen.

After the mare is bred or artificially inseminated, she is checked using ultrasound 14–16 days later to see if she "took", and is pregnant. A second check is usually performed at 28 days. If the mare is not pregnant, she may be bred again during her next cycle.

It is considered safe to breed a mare to a stallion of much larger size. Because of the mare's type of placenta and its attachment and blood supply, the foal will be limited in its growth within the uterus to the size of the mare's uterus, but will grow to its genetic potential after it is born. Test breedings have been done with draft horse stallions bred to small mares with no increase in the number of difficult births.

Live cover
When breeding live cover, the mare is usually boarded at the stud. She may be "teased" several times with a stallion that will not breed to her, usually with the stallion being presented to the mare over a barrier. Her reaction to the teaser, whether hostile or passive, is noted. A mare that is in heat will generally tolerate a teaser (although this is not always the case), and may present herself to him, holding her tail to the side. A veterinarian may also determine if the mare is ready to be bred, by ultrasound or palpating daily to determine if ovulation has occurred. Live cover can also be done in liberty on a paddock or on pasture, although due to safety and efficacy concerns, it is not common at professional breeding farms.

When it has been determined that the mare is ready, both the mare and intended stud will be cleaned. The mare will then be presented to the stallion, usually with one handler controlling the mare and one or more handlers in charge of the stallion. Multiple handlers are preferred, as the mare and stallion can be easily separated should there be any trouble.

The Jockey Club, the organization that oversees the Thoroughbred industry in the United States, requires all registered foals to be bred through live cover. Artificial insemination, listed below, is not permitted. Similar rules apply in other countries, such as Australia.

By contrast, the U.S. standardbred industry allows registered foals to be bred by live cover, or by artificial insemination (AI) with fresh or frozen (not dried) semen. No other artificial fertility treatment is allowed. In addition, foals bred via AI of frozen semen may only be registered if the stallion's sperm was collected during his lifetime, and used no later than the calendar year of his death or castration.

Artificial insemination
Whereas the various national Thoroughbred associations typically require live cover, by 2009 most horse breeds allowed for the artificial insemination of mares with cooled, frozen or even fresh semen.

Artificial insemination (AI) has several advantages over live cover, and has a very similar conception rate:
 * The mare and stallion never have to come in contact with each other, which therefore reduces breeding accidents, such as the mare kicking the stallion.
 * AI opens up the world to international breeding, as semen may be shipped across continents to mares that would otherwise be unable to breed to a particular stallion.
 * A mare also does not have to travel to the stallion, so the process is less stressful on her, and if she already has a foal, the foal does not have to travel.
 * AI allows more mares to be bred from one stallion, as the ejaculate may be split between mares.
 * AI reduces the chance of spreading sexually transmitted diseases between mare and stallion.
 * AI allows mares or stallions with health issues, such as sore hocks which may prevent a stallion from mounting, to continue to breed.
 * Frozen semen may be stored and used to breed mares even after the stallion is dead, allowing his lines to continue. However, the semen of some stallions does not freeze well. Some breed registries may not permit the registration of foals resulting from the use of frozen semen after the stallion's death, although other large registries accept such usage and provide registrations. The overall trend is toward permitting use of frozen semen after the death of the stallion.

A stallion is usually trained to mount a phantom (or dummy) mare, although a live mare may be used, and he is most commonly collected using an artificial vagina (AV) which is heated to simulate the vagina of the mare. The AV has a filter and collection area at one end to capture the semen, which can then be processed in a lab. The semen may be chilled or frozen and shipped to the mare owner or used to breed mares "on-farm". When the mare is in heat, the person inseminating introduces the semen directly into her uterus using a syringe and pipette.

Advanced reproductive techniques

Often an owner does not want to take a valuable competition mare out of training to carry a foal. This presents a problem, as the mare will usually be quite old by the time she is retired from her competitive career, at which time it is more difficult to impregnate her. Other times, a mare may have physical problems that prevent or discourage breeding. However, there are now several options for breeding these mares. These options also allow a mare to produce multiple foals each breeding season, instead of the usual one. Therefore, mares may have an even greater value for breeding.
 * Embryo transfer: This relatively new method involves flushing out the mare's fertilized embryo a few days following insemination, and transferring to a surrogate mare, which has been synchronized to be in the same phase of the estrous cycle as the donor mare.
 * Gamete intrafallopian transfer (GIFT): The mare's ovum and the stallion's sperm are deposited in the oviduct of a surrogate dam. This technique is very useful for subfertile stallions, as fewer sperm are needed, so a stallion with a low sperm count can still successfully breed.
 * Egg transfer: An oocyte is removed from the mare's follicle and transferred into the oviduct of the recipient mare, who is then bred. This is best for mares with physical problems, such as an obstructed oviduct, that prevent breeding.
 * Intracytoplasmic sperm injection (ICSI): Used in horses due to lack of successful co-incubation of female and male gametes in simple IVF. A plug of the zona pellucida is removed and a single sperm cell is injected into the ooplasm of the mature oocyte. An advantage of ICSI over IVF is that lower quality sperm can be used since the sperm does not have to penetrate the zona pellucida. The success rate of ICSI is 23-44% blastocyst development.

The world's first cloned horse, Prometea, was born in 2003. Other notable instances of horse cloning are:
 * In 2006, Scamper, an extremely successful barrel racing horse, a gelding, was cloned. The resulting stallion, Clayton, became the first cloned horse to stand at stud in the U.S.
 * In 2007, a renowned show jumper and Thoroughbred, Gem Twist, was cloned by Frank Chapot and his family. In September 2008, Gemini was born. Other clones followed, leading to the development of a breeding line from Gem Twist.
 * In 2010, the first lived equine cloned of a Criollo horse was born in Argentina, and was the first horse clone produced in Latin America. In the same year a cloned polo horse was sold for $800,000 - the highest known price ever paid for a polo horse.
 * In 2013, the world-famous polo star Adolfo Cambiaso helped his high-handicap team La Dolfina win the Argentine National Open, scoring nine goals in the 16-11 match. Two of those he scored atop a horse named Show Me, a clone, and the first to ride onto the Argentine pitch.

title: Horse breeding


text:
Talk:Human sexuality

Wikipedia Ambassador Program assignment
This article is the subject of an educational assignment at Lewis University supported by WikiProject Psychology and the Wikipedia Ambassador Program during the 2011 Q3 term. Further details are available on the course page.

Above message substituted from on 14:24, 7 January 2023 (UTC)

Abstience versus abstinence-only
The text currently reads In the United States, some sex education programs encourage abstinence, the choice to restrain oneself from sexual activity.. However, it is a matter of WP:BLUESKY that abstinence-only is the teaching Sexual abstinence and no other form of birth control. I would not question the text were the link to abstinence or to sexual abstinence, or if the pipe and descriptive phrase were removed, e.g., In the United States, some sex education programs encourage abstinence-only sex education. See this edit and this edit for context. --Shmuel (Seymour J.) Metz Username:Chatul (talk) 10:59, 16 May 2022 (UTC)

 * your last edit was too biased. And yes I agree that it should say only. Honestly that's what I thought it said and I consider it a type on my part. Thank you for bringing this up. It is obviously a big distinction Tjpolega (talk) 11:15, 16 May 2022 (UTC)

Dichotomous thinking
Early on in this article, this is present re nature vs nurture and extent of homosexuality. Njsm11 (talk) 02:19, 2 July 2022 (UTC)

Noting the GLM and scales. Njsm11 (talk) 02:24, 2 July 2022 (UTC)

Also MANCOVA and the Sell. Njsm11 (talk) 00:56, 3 July 2022 (UTC)

"Cisgender sexuality" listed at Redirects for discussion
An editor has identified a potential problem with the redirect Cisgender sexuality and has thus listed it for discussion. This discussion will occur at Redirects for discussion/Log/2022 July 8 until a consensus is reached, and readers of this page are welcome to contribute to the discussion. TraderCharlotte (talk) 03:39, 8 July 2022 (UTC)

Oxytocin release during orgasm
The following passage is overly specific: "Oxytocin, sometimes referred to as the 'love hormone,' is released in both sexes during sexual intercourse when an orgasm is achieved." In particular, the phrase "during sexual intercourse" is not a necessary part of every situation "when an orgasm is achieved" i.e. during orgasm. Orgasm doesn't require sexual intercourse. No matter whether the quoted source includes that phrase, the facts need to be stated as simply as possible. yoyo (talk) 06:12, 12 October 2022 (UTC)

Recent edits by CactiStaccingCrane and SchreiberBike
A recent edit (https://en.wikipedia.org/w/index.php?title=Human_sexuality&diff=prev&oldid=1121873947) removed the word proximity from "Flirting, the use of indirect behavior to convey romantic or sexual interest. It can involve verbal or non-verbal cues, such as sexual comments, body language, gazing, or close proximity to another," via WP;JWB, I reverted that edit and SchreiberBike reinstated the change with the comment "close proximity" is redundant in that context. "Close" inherently deals with proximity.. However, close is an adjective, not a noun, so the sentence is now grammatically incorrect. Either or close proximity to another or or proximity to another would be grammatically correct. Shmuel (Seymour J.) Metz Username:Chatul (talk) 16:02, 15 November 2022 (UTC)

 * I agree with you. I'm just trying around with my new JWB power and accidentally make a crater on the ground. CactiStaccingCrane (talk) 16:06, 15 November 2022 (UTC)
 * You are right. I didn't read the full context. Please consider me whacked with a wet trout. Rainbow trout transparent.png SchreiberBike | ⌨ 16:22, 15 November 2022 (UTC)

Social causes for sexuality
" Hypothesized social causes are supported by only weak evidence, distorted by numerous confounding factors."

This sentence is not clear enough. The data shows that the specificity of which social causes are involved is murky, but "the evidence for environmental influence is unequivocal, given that MZ twin concordances tend to be far less than 100%" - source

Change the sentence to clarify that the prevalence of these social causes is unequivocal, but the exact nature of what these causes are is undeveloped and only established by weak evidence.

Even if the sentence is true, readers may read it in a different way. Lainlain987 (talk) 19:02, 28 January 2023 (UTC)
 * The text is supported by the source (which you linked): However, there is considerably more evidence supporting nonsocial causes of sexual orientation than social causes. This evidence includes the cross-culturally robust finding that adult homosexuality is strongly related to childhood gender nonconformity; moderate genetic influences demonstrated in well-sampled twin studies; the cross-culturally robust fraternal-birth-order effect on male sexual orientation; and the finding that when infant boys are surgically and socially “changed” into girls, their eventual sexual orientation is unchanged (i.e., they remain sexually attracted to females). In contrast, evidence for the most commonly hypothesized social causes of homosexuality—sexual recruitment by homosexual adults, patterns of disordered parenting, or the influence of homosexual parents—is generally weak in magnitude and distorted by numerous confounding factors.
 * "Environmental" (i.e. non-genetic) and "social" are not the same thing. For example, the fraternal birth order effect (mentioned in the source) is a non-social environmental effect. Crossroads -talk- 23:22, 29 January 2023 (UTC)
 * Hii where 41.116.66.156 (talk) 11:04, 21 March 2023 (UTC)

Not even so much as a mention of fetishism/kinks/paraphilias?
It feels like a disappointing oversight that there is not even so much as a mention of atypical sexual interests, fetishism, kinks, paraphilia, etc., despite the fact that they are a unique and interesting part of human sexuality. Sexual fetishes are not so uncommon as to be an invalid or non-noteworthy part of human sexuality, and so I hope that we can figure out a reasonable way to work them into this article. FuwaFuwaDL (talk) 08:56, 9 May 2023 (UTC)

 * What sexual fetishes are you referring to? Justanotherguy54 (talk) 06:27, 26 May 2023 (UTC)
 * I'm talking about in a general sense, there is no mention of paraphilic (fetish) interests or behavior in this page on human sexuality. FuwaFuwaDL (talk) 15:53, 26 May 2023 (UTC)

Thanks for the idea. I’ll incorporate some things in future. Zenomonoz (talk) 22:05, 26 May 2023 (UTC)

Undefined ref
please fill in a source for the ref you named "rodriguez". -- Fyrael (talk) 19:29, 25 September 2023 (UTC)

 * I deleted the empty citation as the other citation appeared to support the claim. Zenomonoz (talk) 20:26, 25 September 2023 (UTC)

title: Talk:Human sexuality