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A feedlot or feed yard is a type of animal feeding operation (AFO) which is used in factory farming for finishing livestock, notably beef cattle, but also swine, horses, sheep, turkeys, chickens or ducks, prior to slaughter. Large beef feedlots are called concentrated animal feeding operations (CAFOs) in the United States and intensive livestock operations (ILOs) or confined feeding operations (CFOs)  in Canada. They may contain thousands of animals in an array of pens. Most feedlots require some type of governmental permit and must have plans in place to deal with the large amount of waste that is generated. The Environmental Protection Agency has authority under the Clean Water Act to regulate all animal feeding operations in the United States. This authority is delegated to individual states in some cases. In Canada, regulation of feedlots is shared between all levels of government.
Prior to entering a feedlot, cattle spend most of their life grazing on rangeland or on immature fields of grain such as green wheat pasture. Once cattle obtain an entry-level weight, about 650 pounds (300 kg), they are transferred to a feedlot to be fed a specialized animal feed which consists of corn byproducts (derived from ethanol production), barley, and other grains as well as alfalfa, cottonseed meal, and premixes composed of microingredients such as vitamins, minerals, chemical preservatives, antibiotics, fermentation products, and other essential ingredients that are purchased from premix companies, usually in sacked form, for blending into commercial rations. Because of the availability of these products, a farmer who uses his own grain can formulate his own rations and be assured his animals are getting the recommended levels of minerals and vitamins. In the American northwest and Canada, barley, low grade durum wheat, chick peas (garbanzo beans), oats and occasionally potatoes are used as feed.
In a typical feedlot, a cow's diet is roughly 95% grain. High-grain diets lower the pH in the animals' rumen. Due to the stressors of these conditions, it becomes necessary to give the animals antibiotics to prevent them from getting diseases. 
Feedlot diets are usually very dense in food energy, to encourage the deposition of fat (known as marbling in butchered meat) in the animal's muscles. This fat is desirable to consumers, as it contributes to flavor and tenderness. The animal may gain an additional 400 pounds (180 kg) during its 3–4 months in the feedlot. Once cattle are fattened up to their finished weight, the fed cattle are transported to a slaughterhouse.
Increasing numbers of cattle feedlots are utilizing out-wintering pads made of timber residue bedding in their operations. Nutrients are retained in the waste timber and livestock effluent and can be recycled within the farm system after use.
The beef industry today is highly dependent upon technology, but this has not always been true. In the early 20th century, feeder operations were separate from all other related operations and feedlots were non-existent. They appeared in the 1950s and 1960s as a result of hybrid grains and irrigation techniques; the ensuing larger grain crops led to abundant grain harvests. However, the first known feedlot was designed and built by Gustavus Swift in 1876 on the south side of Chicago.  It was suddenly possible to feed large numbers of cattle in one location and so, to cut transportation costs, grain farm and feedlot locations merged. Cattle were no longer sent from all across the southern states to places like California, where large slaughter houses were located. In the 1980s, meat packers followed the path of feedlots and are now located close by them as well.
There are many methods used to sell cattle to meat packers. Spot, or cash, marketing is the traditional and most commonly used method. Prices are influenced by current demand and are determined by live weight or per head. Similar to this is forward contracting, in which prices are determined the same way but are not directly influenced by market demand fluctuations. Forward contracts determine the selling price between the two parties negotiating for a set amount of time. However, this method is the least used because it requires some knowledge of production costs and the willingness of both sides to take a risk in the futures market. Another method, formula pricing, is becoming the most popular process, as it more accurately represents the value of meat received by the packer. This requires trust between the packers and feedlots though, and is under criticism from the feedlots because the amount paid to the feedlots is determined by the packers’ assessment of the meat received. Finally, live- or carcass-weight based formula pricing is most common. Other types include grid pricing and boxed beef pricing. The most controversial marketing method stems from the vertical integration of packer-owned feedlots, which still represents less than 10% of all methods, but has been growing over the years.