Oat
The oat (Avena sativa) is a species of cereal grain, and the seeds of this plant. They are used for food for people and as fodder for animals, especially poultry and horses. Oat straw is used as animal bedding and sometimes as animal feed.
Since oats are unsuitable for making bread on their own, due to their lack of gluten, they are often served as a porridge made from crushed or rolled oats (see oatmeal), and are also baked into cookies (oatcakes), which can have added wheat flour. As oat flour or oatmeal, they are also used in a variety of other baked goods (e.g. bread made from a mixture of oatmeal and wheat flour) and cold cereals, and as an ingredient in muesli and granola. Oats may also be consumed raw, and cookies with raw oats are becoming popular. Oats are also occasionally used in Britain for brewing beer. Oatmeal stout is one variety brewed using a percentage of oats for the wort. The more rarely used Oat Malt is produced by the Thomas Fawcett & Sons Maltings and was used in the Maclay Oat Malt Stout before Maclay ceased independent brewing operations.
Oats also have non-food uses. Oat straw is also used in corn dolly making, and it is the favourite filling for home made lace pillows. Oat extract can be used to soothe the skin conditions, e.g. in baths, skin products, etc.
A now obsolete Middle English name for the plant was haver (still used in most other Germanic languages), surviving in the name of the livestock feeding bag haversack. In contrast with the names of the other grains, "oat" is usually used in the plural.

# Origin
The wild ancestor of Avena sativa and the closely-related minor crop, A. byzantina, is the hexaploid wild oat A. sterilis. Genetic evidence shows that the ancestral forms of A. sterilis grow in the Fertile Crescent of the Near East. Domesticated oats appear relatively late, and far from the Near East, in Bronze Age Europe. Oats, like rye, are usually considered a secondary crop, i.e. derived from a weed of the primary cereal domesticates wheat and barley. As these cereals spread westwards into cooler, wetter areas, this may have favoured the oat weed component, leading to its eventual domestication. 

# Cultivation
Oats are grown throughout the temperate zones. They have a lower summer heat requirement and greater tolerance of rain than other cereals like wheat, rye or barley, so are particularly important in areas with cool, wet summers such as Northwest Europe, even being grown successfully in Iceland. Oats are an annual plant, and can be planted either in autumn (for late summer harvest) or in the spring (for early autumn harvest).
Historical attitudes towards oats vary. Oat bread was first manufactured in England, where the first oat bread factory was established in 1899. In Scotland they were, and still are, held in high esteem, as a mainstay of the national diet. A traditional saying in England is that "oats are only fit to be fed to horses and Scotsmen", to which the Scottish riposte is "and England has the finest horses, and Scotland the finest men". Samuel Johnson notoriously defined oats in his Dictionary as "a grain, which in England is generally given to horses, but in Scotland supports the people". While frequently seen as derogatory, this is no less than the literal truth. Oats are so central to traditional Scottish cuisine that the Scottish English word "corn" refers to oats instead of wheat, as in England, and maize in North America and Australia. Oats grown in Scotland command a premium price throughout the United Kingdom as a result of these traditions.

# Health
Oats are generally considered "healthy", or a health food, being touted commercially as nutritious. The discovery of the healthy cholesterol-lowering properties has led to wider appreciation of oats as human food.

## Soluble fiber
Oat bran is the outer casing of the oat. Its consumption is believed to lower LDL ("bad") cholesterol, and possibly to reduce the risk of heart disease.
After reports found that oats can help lower cholesterol, an "oat bran craze" swept the U.S. in the late 1980s, peaking in 1989, when potato chips with added oat bran were marketed. The food fad was short-lived and faded by the early 1990s. The popularity of oatmeal and other oat products again increased after the January 1998 decision by the Food and Drug Administration (FDA) when it issued its final rule allowing a health claim to be made on the labels of foods containing soluble fiber from whole oats (oat bran, oat flour and rolled oats), noting that 3 grams of soluble fiber daily from these foods, in conjunction with a diet low in saturated fat, cholesterol, and fat may reduce the risk of heart disease.  In order to qualify for the health claim, the whole oat-containing food must provide at least 0.75 grams of soluble fiber per serving. The soluble fiber in whole oats comprise a class of polysaccharides known as Beta-D-glucan.
Beta-D-glucans, usually referred to as beta-glucans, comprise a class of non-digestible polysaccharides widely found in nature in sources such as grains, barley, yeast, bacteria, algae and mushrooms. In oats, barley and other cereal grains, they are located primarily in the endosperm cell wall.
Oat beta-glucan is a soluble fiber. It is a viscous polysaccharide made up of units of the sugar D-glucose. Oat beta-glucan is comprised of mixed-linkage polysaccharides. This means that the bonds between the D-glucose or D-glucopyranosyl units are either beta-1, 3 linkages or beta-1, 4 linkages. This type of beta-glucan is also referred to as a mixed-linkage (13), (14)-beta-D-glucan. The (13)-linkages break up the uniform structure of the beta-D-glucan molecule and make it soluble and flexible. In comparison, the non-digestible polysaccharide cellulose is also a beta-glucan but is non-soluble. The reason  that it is non-soluble is that cellulose consists only of (14)-beta-D-linkages. The percentages of beta-glucan in the various whole oat products are: oat bran, greater than 5.5% and up to 23.0%; rolled oats, about 4%; whole oat flour about 4%.
Oats after corn (maize) has the highest lipid content of any cereal, e.g., greater than 10 percent for oats and as high as 17 percent for some maize cultivars compared to about 23 percent for wheat and most other cereals. The polar lipid content of oats (about 817% glycolipid and 1020% phospholipid or a total of about 33% ) is greater than that of other cereals since much of the lipid fraction is contained within the endosperm.

## Protein
Oat is the only cereal containing a  globulin or legume-like protein, avenalin, as the major (80%) storage protein. Globulins are characterized by water solubility; because of this property, oats may be turned into  milk but not into bread. The more typical cereal proteins such as gluten and zein are prolamines(prolamins). The minor protein of oat is a prolamine: avenin.
Oat protein is nearly equivalent in quality to soy protein, which has been shown by the World Health Organization to be the equal to meat, milk, and egg protein. The protein content of the hull-less oat kernel (groat) ranges from 1224%, the highest among cereals. 

## Celiac Disease
Coeliac disease, or celiac disease, from Greek "koiliakos", meaning "suffering in the bowels", is a disease often associated with ingestion of wheat, or more specifically a group of proteins labelled prolamines, or more commonly, gluten.
Oats lack many of the prolamines found in wheat; however, oats do contain avenin. Avenin is a prolamine that is toxic to the intestinal submucosa and can trigger a reaction in some celiacs.
Although oats do contain avenin, there are several studies suggesting that oats can be a part of a gluten free diet if it is pure. The first such study was published in 1995. A follow-up study indicated that it is safe to use oats even in a longer period
Additionally, oats are frequently processed near wheat, barley and other grains such that they become contaminated with other glutens.  Because of this, the FAO's Codex Alimentarius Commission officially lists them as a crop containing gluten. Oats from Ireland and Scotland, where less wheat is grown, are less likely to be contaminated in this way.
Oats are part of a gluten free diet in, for example, Finland and Sweden. In both of these countries there are "pure oat" products on the market.

# Agronomy
Oats are sown in the spring, as soon as the soil can be worked. An early start is crucial to good yields as oats will go dormant during the summer heat. Oats are cold-tolerant and will be unaffected by late frosts or snow. Typically about 100 kg/hectare (about 2 bushels per acre) are sown, either broadcast or drilled in 150 mm (6 inch) rows. Lower rates are used when underseeding with a legume. Somewhat higher rates can be used on the best soils. Excessive sowing rates will lead to problems with lodging and may reduce yields.
Winter oats may be grown as an off-season groundcover and plowed under in the spring as a green fertilizer.
Oats remove substantial amounts of nitrogen from the soil. They also remove phosphorus in the form of P2O5 at the rate of .25 pounds per bushel per acre (1 bushel = 32 pounds at 14% moisture). Oats remove potash (K2O) at a rate of .19 pounds per bushel per acre.  If the straw is removed from the soil rather than being ploughed back, the removal rate of phosphorus is 8 pounds per ton per acre and the rate of potash removal is 40 pounds per ton per acre. Usually 50100 kg/hectare (50100 pounds per acre) of nitrogen in the form of urea or ammonium sulphate is sufficient. A sufficient amount of nitrogen is particularly important for plant height and hence straw quality and yield. When the prior-year crop was a legume, or where ample manure is applied, nitrogen rates can be reduced somewhat.
The vigorous growth habit of oats will tend to choke out most weeds. A few tall broadleaf weeds, such as ragweed, goosegrass and buttonweed (velvetleaf), can occasionally be a problem as they complicate harvest. These can be controlled with a modest application of a broadleaf herbicide such as 2,4-D while the weeds are still small.
Modern harvest technique is a matter of available equipment, local tradition, and priorities. Best yields are attained by swathing, cutting the plants at about 10 cm (4 inches) above ground and putting them into windrows with the grain all oriented the same way, just before the grain is completely ripe. The windrows are left to dry in the sun for several days before being combined using a dummy head. Then the straw is baled.
Oats can also be left standing until completely ripe and then combined with a grain head. This will lead to greater field losses as the grain falls from the heads and to harvesting losses as the grain is threshed out by the reel. Without a draper head, there will also be somewhat more damage to the straw since it will not be properly oriented as it enters the throat of the combine. Overall yield loss is 1015% compared to proper swathing.
Historical harvest methods involved cutting with a scythe or sickle, and threshing under the feet of cattle. Late 19th and early 20th century harvesting was performed using a binder. Oats were gathered into shocks and then collected and run through a stationary threshing machine.
A good yield is typically about 3,000 kg/hectare (100 bushels/acre) of grain and two tonnes of straw.

# Trivia
- The eruption of Mount Tambora caused a change in world climate resulting in a volcanic winter and the "year without a summer" in 1816, during which time the price of oats rose dramatically, for example in the USA from 12 to 92 cents per bushel. This led to the starvation of many horses, which in turn led to transportation problems, which Baron Karl von Drais attempted to solve by inventing the dandy horse, the direct precursor to the bicycle.
- Oats are sometimes marketed, while in seed-form, as 'Cat Grass'. This is then grown and fed to the cat as a treat, or as aid to digestion.