Confinement at high stocking density is one part of a systematic effort to produce the highest output at the lowest cost by relying on economies of scale, modern machinery, biotechnology, and global trade. Confinement at high stocking density requires antibiotics and pesticides to mitigate the spread of disease and pestilence exacerbated by these crowded living conditions. There are differences in the way factory farming techniques are practiced around the world.
There is a continuing debate over the benefits and risks of factory farming. The issues include the efficiency of food production; animal welfare; whether it is essential to feed the growing global human population; the environmental impact and the health risks.
The UN and OIE estimate that in coming decades there will be billions of additional consumers in developing countries eating meat factory farmed in developing countries, but currently only about 40 out of the around 200 countries in the world have the capacity to adequately respond to a health crisis originating from animal disease (such as avian flu, West Nile virus, bluetongue, and foot and mouth disease). Widespread use of antibiotics increases the chance of a pandemic resistant to known measures, which is exacerbated by a globally distributed food system. Decreased genetic diversity increases the chance of a food crisis.
Innovations in agriculture beginning in the late 19th century paralleled developments in mass production in other industries. The identification of nitrogen and phosphorus as critical factors in plant growth led to the manufacture of synthetic fertilizers, making possible more intensive types of agriculture. The discovery of vitamins and their role in animal nutrition, in the first two decades of the 20th century, led to vitamin supplements, which in the 1920s allowed certain livestock to be raised indoors. The discovery of antibiotics and vaccines facilitated raising livestock in larger numbers by reducing disease. Chemicals developed for use in World War II gave rise to synthetic pesticides. Developments in shipping networks and technology have made long-distance distribution of agricultural produce feasible.
According to the BBC, factory farming in Britain began in 1947 when a new Agriculture Act granted subsidies to farmers to encourage greater output by introducing new technology, in order to reduce Britain's reliance on imported meat. The United Nations writes that intensification of animal production was seen as a way of providing food security. The agriculture correspondent of The Guardian wrote in 1964:
During the same period, the number of people involved in farming dropped as the process became more automated. In the 1930s, 24 percent of the American population worked in agriculture compared to 1.5 percent in 2002; in 1940, each farm worker supplied 11 consumers, whereas in 2002, each worker supplied 90 consumers.
The number of farms has also decreased, and their ownership is more concentrated. In the U.S., four companies produce 81 percent of cows, 73 percent of sheep, 57 percent of pigs and 50 percent of chickens. In 1967, there were one million pig farms in America; as of 2002, there were 114,000, with 80 million pigs (out of 95 million) killed each year on factory farms as of 2002, according to the U.S. National Pork Producers Council. According to the Worldwatch Institute, 74 percent of the world's poultry, 43 percent of beef, and 68 percent of eggs are produced this way.
Although Europe has become increasingly skeptical of factory farming, after a series of diseases such as BSE (mad cow) and foot and mouth disease affected its agricultural industries, globally there are indications that the industrialized production of farm animals is set to increase. According to Denis Avery of the Hudson Institute, Asia increased its consumption of pork by 18 million tons in the 1990s. As of 1997, the world had a stock of 900 million pigs, which Avery predicts will rise to 2.5 billion pigs by 2050. He told the College of Natural Resources at the University of California, Berkeley that three billion pigs will thereafter be needed annually to meet demand.
Factory farms hold large numbers of animals, typically cows, pigs, turkeys, or chickens, often indoors, typically at high densities. The aim of the operation is to produce as much meat, eggs, or milk at the lowest possible cost. Food is supplied in place, and a wide variety of artificial methods are employed to maintain animal health and improve production, such as the use of antimicrobial agents, vitamin supplements, and growth hormones. Physical restraints are used to control movement or actions regarded as undesirable. Breeding programs are used to produce animals more suited to the confined conditions and able to provide a consistent "product".
The distinctive characteristic of factory farms is the intense concentration of livestock. At one farm (Farm 2105) run by Carrolls Foods of North Carolina, the second-largest pig producer in the U.S., twenty pigs are kept per pen and each confinement building or "hog parlor" holds 25 pens. The company's chief executive officer, F.J. "Sonny" Faison, has said: "It's all a supply-and-demand price question … The meat business in this country is just about perfect, uncontrolled supply-and-demand free enterprise. And it continues to get more and more sophisticated, based on science. Only the least-cost producer survives in agriculture." The animals are better off in total confinement, according to Faison:
The designation "confined animal feeding operation" in the U.S. resulted from that country's 1972 Federal Clean Water Act, which was enacted to protect and restore lakes and rivers to a "fishable, swimmable" quality. The United States Environmental Protection Agency (EPA) identified certain animal feeding operations, along with many other types of industry, as point source polluters of groundwater. These operations were designated as CAFOs and subject to special anti-pollution regulation.
In 24 states in the U.S., isolated cases of groundwater contamination have been linked to CAFOs. For example, the ten million hogs in North Carolina generate 19 million tons of waste per year. The U.S. federal government acknowledges the waste disposal issue and requires that animal waste be stored in lagoons. These lagoons can be as large as . Lagoons must be protected with an impermeable liner, but can nonetheless leak waste into groundwater under some conditions, and run-off from manure spread back onto fields as fertilizer can leak into surface water in the case of an unforeseen heavy rainfall. A lagoon that burst in 1995 released 25 million gallons of nitrous sludge in North Carolina's New River. The spill allegedly killed eight to ten million fish.
Dennis Avery of the Hudson Institute's agricultural think-tank, the Center for Global Food Issues, has called modern farming a "conservation triumph," because it involves getting higher yields of crops and livestock from land. He predicts that, after 2050, three billion pigs will be needed annually to meet demand: "For the sake of the environment," he writes, "we had better hope those hogs are raised in big, efficient confinement systems."
The use of controlled indoor environments means that animals unsuited to the local climate can be farmed. As an example, the UK has one of the few climates well suited to the outdoor farming of pigs.
A 2006 FAO report says that the livestock sector of the world's economy that provides "one-third of humanity's protein intake" is one of the top three contributor's to the world's most serious environmental problems and that major reductions in impact could be achieved at reasonable cost through decentralization and intensification regulatory measures that reduce greenhouse gas emissions, improve livestock diets, improve animal waste management, and decrease land degradation.
The large concentration of animals, animal waste, and the potential for dead animals in a small space poses ethical issues. It is recognised that some techniques used to sustain intensive agriculture can be cruel to animals. As awareness of the problems of intensive techniques has grown, there have been some efforts by governments and industry to remove inappropriate techniques.
In the UK, the Farm Animal Welfare Council was set up by the government to act as an independent advisor on animal welfare in 1979. and expresses its policy as five freedoms: from hunger & thirst; from discomfort; from pain, injury or disease; to express normal behaviour; from fear and distress.
There are differences around the world as to which practices are accepted and there continue to be changes in regulations with animal welfare being a strong driver for increased regulation. For example, the EU is bringing in further regulation to set maximum stocking densities for meat chickens by 2010, where the UK Animal Welfare Minister commented, "The welfare of meat chickens is a major concern to people throughout the European Union. This agreement sends a strong message to the rest of the world that we care about animal welfare.”
However, given the assumption that intensive farming techniques are a necessity, it is recognized that some apparently cruel techniques are better than the alternative. For example, in the UK, de-beaking of chickens is deprecated, but it is recognized that it is a method of last resort, seen as better than allowing vicious fighting and ultimately cannibalism. Between 60 and 70 percent of six million breeding sows in the U.S. are confined during pregnancy, and for most of their adult lives, in by gestation crates. According to pork producers and many veterinarians, sows will fight if housed in pens. The largest pork producer in the U.S. said in January 2007 that it will phase out gestation crates by 2017. They are being phased out in the European Union, with a ban effective in 2013 after the fourth week of pregnancy. With the evolution of factory farming, there has been a growing awareness of the issues amongst the wider public, not least due to the efforts of animal rights and welfare campaigners. As a result gestation crates, one of the more contentious practices, are the subject of laws in the U.S., Europe and around the world to phase out their use as a result of pressure to adopt less confined practices.
Pesticides are used to control organisms which are considered harmful and they save farmers money by preventing product losses to pests. In the US, about a quarter of pesticides used are used in houses, yards, parks, golf courses, and swimming pools and about 70% are used in agriculture. However, pesticides can make their way into consumers' bodies which can cause health problems. One source of this is bioaccumulation in animals raised on factory farms.
The CDC writes that chemical, bacterial, and viral compounds from animal waste may travel in the soil and water. Residents near such farms report nuisances such as unpleasant smell, flies and adverse health effects.
The CDC has identified a number of pollutants associated with the discharge of animal waste into rivers and lakes, and into the air. The use of antibiotics may create antibiotic-resistant pathogens; parasites, bacteria, and viruses may be spread; ammonia, nitrogen, and phosphorus can reduce oxygen in surface waters and contaminate drinking water; pesticides and hormones may cause hormone-related changes in fish; animal feed and feathers may stunt the growth of desirable plants in surface waters and provide nutrients to disease-causing micro-organisms; trace elements such as arsenic and copper, which are harmful to human health, may contaminate surface waters.
In the European Union, growth hormones are banned on the basis that there is no way of determining a safe level. The UK has stated that in the event of the EU raising the ban at some future date, to comply with a precautionary approach, it would only consider the introduction of specific hormones, proven on a case by case basis. The various techniques of factory farming have been associated with a number of European incidents where public health has been threatened or large numbers of animals have had to be slaughtered to deal with disease. Where disease breaks out, it may spread more quickly, not only due to the concentrations of animals, but because modern approaches tend to distribute animals more widely.. The international trade in animal products increases the risk of global transmission of virulent diseases such as swine fever, BSE, foot and mouth and bird flu.