Animal production industries have seen substantial changes over the past several decades, the result of domestic/export market forces and technological changes. The number of large operations has increased, and animal and feed production are increasingly separated in terms of both management and geography. Concern that these changes are harming the environment has prompted local, State, and Federal policies and programs to control pollution from animal production facilities.
Trends in Animal Production and Manure Nutrients
Changes in the structure of livestock and poultry production are behind many of the current concerns about animals and the environment. Structural changes have been driven by both innovation and economies of scale. Organizational innovations, such as production contract arrangements, enable growers to access the capital necessary to adopt innovative technologies and garner economies of size in their efforts to increase profits. The significant economic benefits from vertical coordination, particularly for poultry and swine operations, have led to both larger operations and greater geographic concentration of animals.
For example, the number of hog farms fell more than 70 percent between 1992 and 2004 while the hog inventory remained stable. Larger farms account for an increasing share of total output. The average size of U.S. hog farms grew from 945 head in 1992 to 2,589 head in 1998 and to 4,646 head in 2004. The share of hogs produced on farms with more than 2,000 head increased from less than 30 percent to nearly 80 percent. Similar trends occurred in the dairy, poultry, and cattle sectors.
The innovations and economies of size that underlie changes in the livestock and poultry sectors also served to separate animal production from crop production. Large, specialized facilities today focus on producing animals and purchase most of their feed from off the farm. This means there is generally less land on the animal farm on which to spread manure. The amount of land per animal unit declined nearly 40 percent across all animal types between 1982 and 1997, from 3.6 to 2.2 acres per AU (AU defined as 1,000 pounds of live weight).
Environmental Impacts of Animal Production
The major source of environmental degradation from confined animal production is the wastes (manure, urine, bedding material) that are produced. Animal waste can be transmitted through runoff of nutrients, organic matter, and pathogens to surface water; leaching of nitrogen and pathogens to ground water; and volatilization of gases and odors to the atmosphere. Pollutants may originate at production houses/lots where animals are kept; manure storage structures such as tanks, ponds, and lagoons; or land where manure collects or is applied.
http://www.ers.usda.gov/Briefing/AgAndEnvironment/animalagriculture.htm
