Animal Feeding Operations

What are Animal Feeding Operations (AFOs)?

Photo of cows within a large stock pen

According to the United States Environmental Protection Agency (EPA), there are currently 450,000 Animal Feeding Operations (AFOs) in the United States. AFOs are confined spaces where animals are raised. If an animal operation keeps animals confined for at least 45 days in a 12 month period and there is no grass or other vegetation in the area during the normal growing period, then it is considered an AFO. These operations are an efficient way for farmers and ranchers to maintain livestock. AFOs contain animals, feed, manure and urine, dead animals, and production operations in one combined land space. According to EPA, AFOs create more than 500 million tons of waste every year. Depending on water sources, AFOs can pose a potential risk for contaminating agricultural crops. It is important to ensure that AFOs are positioned correctly so that runoff does not impact nearby waterways, wells or other water sources.

For more information, visit EPA’s Animal Feeding OperationsExternal website.

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AFOs and Pollutants

Pollutants from AFOs can be harmful to human and animal life. They can result in reduced biodiversity and death of fish populations. Nitrogen and phosphorus pollution can contribute to algal blooms which can potentially result in negative health effects in animals and humans. Nitrates, which are transformed from nitrogen in manure or from fertilizers, are the most commonly found contaminant in drinking water wells. Nearly 4.5 million people in the United States are exposed to high levels of nitrates from well sources (1). Microbes that affect animals, such as Cryptosporidium, can also affect humans and cause illness.

The following pollutants can potentially affect the water quality located near an AFO:

Includes nitrogen, ammonia, and phosphorus which can reduce oxygen in surface waters, encourage the growth of harmful algal blooms, and contaminate drinking water.

Organic Matter
Animal waste, vegetable matter, etc.

Include parasites, bacteria, and viruses which cause disease in humans.

Solid matter such as feed and feathers, which can limit the growth of desirable aquatic plants in surface waters and protect disease-causing microorganisms.

Pesticides & Hormones
Researchers have associated pesticides and hormones with hormone-related changes in fish.

The presence of antibiotics may contribute to the development of antibiotic-resistant pathogens.

Trace elements
Includes arsenic and copper, which can contaminate surface waters and possibly harm human health.


Heavy metals (2)

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EPA Inspection of Concentrated Animal Feeding Operations (CAFOs)

EPA inspects livestock facilities to ensure that they are operating according to U.S. federal laws. While visiting an AFO an EPA inspector will gather information to help EPA determine whether the livestock facility qualifies as a Concentrated Animal Feeding Operation (CAFO). There are a variety of factors that are taken into consideration to determine whether a facility is a CAFO. Some of these factors include size of the facility, number of animals, and types of manure handling systems used. Regardless of the size of the facility, EPA may classify a facility as a CAFO if it determines that the operation is the source of a significant amount of pollution. If an EPA inspector determines that the operation qualifies as a CAFO, the facility operator is required to apply for a permit and follow certain guidelines (3).

In addition to federal requirements, some states have their own requirements for CAFOs. Contact your EPA regional contact to find out who to contact on the state level.

For additional information about the inspection process, the EPA provides a brochure entitled “What to Expect when EPA Inspects Your Livestock Operation”Cdc-pdfExternal [PDF – 330 kb].

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  1. Pew Commission on Industrial Farm Animal Production. Environment: What AFO Pollution Can Do. Available at
  2. Centers for Disease Control and Prevention. Concentrated Animal Feeding Operations (CAFOs). Available at
  3. U.S. Environmental Protection Agency. Animal Agriculture: Concentrated Animal Feeding Operations-Livestock Operation Inspection. Office of Enforcement & Compliance Assurance, Washington, DC. May 2003.
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