Farming is a complex, multicomponent, interactive process that is dependent on land, animal, human and water resources as well as capital investment. Throughout the world it is practiced in many different ways and environments and with differing degrees of intensity and biological efficiency. Animal production systems vary from mainly capital intensive in the western world to mainly capital extensive systems in the developing world.
The FAO (Sere and Steinfeld, 1996) has defined 3 main livestock production systems; Industrial, Mixed and Grazing systems.
Industrial livestock systems are those in which the animals are detached from the land base of feed supply and waste disposal. They depend on external supplies of feed, energy and other inputs. Industrial systems provide >50 percent of global pork and poultry meat production and 10 percent of beef and mutton production. Excess nitrogen and phosphorus nutrients due to large quantities of feed imports, can lead to problems with manure disposal and pose a potential pollution risk.
In mixed farming systems, crops and livestock production are integrated on the same farm. Globally mixed farming systems produce the largest share of total meat (54 percent), and milk (90 percent). Mixed farming is the main system for smallholder farmers in many developing countries.
Grazing systems are defined as livestock systems in which more than 90 percent of dry matter fed to animals comes from rangelands, pastures, annual forages and purchased feeds and less than 10 percent of the total value of production comes from non-livestock farming activities. In terms of total production, grazing systems supply only 9 percent of global meat production yet provide the sole source of income for 20 million pastoral families.