Under modern systems of livestock production, traditional husbandry has been superseded by advances in technology and associated values of productivity and efficiency. Animals are no longer raised under free-range or extensive conditions. They are being confined and raised as if they were mindless and emotionless cogs in the complex machinery of factory farming. Often this is done at the expense and compromise of their needs and rights to humane consideration and treatment

Animals may be given insufficient space, light, ventilation and comfort, causing stress, malformation, loss of productivity and infertility. Under such conditions stress and malformation occur, as well as loss of productivity. Inadequate housing may also occur through negligence or through ignorance of the optimum conditions required and of animal psychology and behaviour. With breeding animals it may lead to infertility, rather than the desirable peak condition

Extensive, free-range conditions were first replaced by semi-intensive conditions of raising livestock in enclosed pastures or fields. Next, with increasing land costs dictating a more frugal use of arable land, animals were removed from the land to intensive confinement systems

Factory farming is a very attractive commercial proposition for industrial investors and with a greater demand for meat and egg products and a comparatively higher standards of living in these countries, the trend towards intensive farming methods is likely to increase. The competition for land space also contributes to the trend. Factory farming is characterized by the widespread use of antibiotics in animal feeds, which could lead to drug resistance in bacteria pathogenic to both humans and animals. Hormones, which may cause cancer in humans, are used as implants to stimulate growth in beef cattle. Pesticides, nitrate fertilizers, herbicides and moulds (aflatoxins), contaminate grains and other crops used in the animals' feed. Some of these substances, which are hazardous to humans if ingested in sufficient amounts, may be stored in the animal's fat, muscles and internal organs, or be concentrated and excreted in milk, which is ingested by humans. Although some of these substances are identified animal carcinogens, their use is often justified on the grounds that they help reduce production costs

Factory farming exists mainly in the developed Western countries. The highest incidence of factory farming is to be found in the USA; in Europe the highest incidence is found in the UK. Most cattle and sheep are still raised for part of their lives under extensive conditions ranging from feedlot corrals to half-open barns which afford varying degrees of freedom and protection from the elements. However, the free-range and semi-intensive operations require the most labour. Thus, there is a growing trend to raise cattle and sheep in total confinement buildings, especially in northern climates. Almost all broiler chickens and laying hens and some sixty to seventy percent of all hogs are now housed intensively in total confinement. The relatively high cost of installing factory farming units is a restricting factor on their incidence in developing countries. Intensive farming units rarely give animals sufficient space, light or comfort, and in certain cases, such as with 'sweat houses' for pig fattening, ventilation is also restricted. In both developed and developing countries, poultry markets feature live chickens and sometimes pigeons and other birds. Most poultry is kept in confined, unclean quarters and suffer from hunger and thirst. Markets may also house live rabbits, turtles, lambs, or kids, and inhumane slaughter as well as maltreatment may occur

Factory farming is an inadequate means of producing protein, leading to the spread of animal diseases and drug resistant animal and human diseases, animal stress and malformation; a threat to the farming community from industrial investors; maintenance of high food prices because of the cost of installation; and export of high protein grain crops from protein-deficient countries to developed countries

It has been repeatedly demonstrated that animals will continue to function and produce even when suffering injury and stress: battery hens will continue to lay their one egg every 17 hours even when their backs are de-feathered and scratched to open sores; dairy cows will continue to produce even when their feet are painfully inflamed from laminitis; crated veal calves will still gain weight even when suffering from anaemia and diarrhoea from an iron-deficient liquid diet; pigs will still reach market weight, even if crowded to the point of cannibalism; and beef cattle can still be used even if in severe distress from ulcers prior to slaughter