Animal Agriculture In the U.S. – Trends in Production and Manure Management

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Where Are Animal Agriculture Farms Most Common?

The animal agriculture industry is widespread across the U.S. with some areas having more of certain types of farms than others. The sectors highlighted in this module include dairy, beef cattle, layer chickens (eggs), meat chickens (broilers), and pigs.

The images below shows where each of the five highlighted sectors are located in the U.S. The darker colors on each map indicate more animals in that area. These maps are based on the most recent (2012) Census of Agriculture, which is conducted every five years by the USDA National Agriculture Statistics Service.

map showing where dairy cattle are located in the US

map showing where beef cattle are located in the US

map showing where layer chickens are located in the US

map showing where broiler chickens are located in the US

map showing where pigs are located in the US

Trends In Animal Agriculture

The graphs below show data from the USDA Census of Agriculture from 1987 until the most recent one (2012).

For dairy and beef cattle, you can see clear trends showing that the number of animals is declining slightly but the number of farms is declining drastically. This means that the average farm with cattle in 2012 had many more animals than the average cattle farm in 1987. In each graph, the orange line represents the number of animals and the blue line represents the number of farms.

For pigs, the number of animals has increased slightly and the number of farms has decreased a lot. Like with cattle, this means that the average pig farm in 2012 had many more animals than the average farm in 1987. Chickens show a different trend in that the number of birds in the U.S. has increased but the number of farms has also increased.

How Much Manure Do Animals Produce?

The amount of manure animals produce varies greatly based on species; a dairy cow will produce much more manure than a chicken, for example. Two cows can excrete very different amounts of manure based on the feed they eat, their size, and age. The same is true of chickens and pigs.

The U.S. Department of Agriculture Natural Resources Conservation Service (NRCS) estimates that for every 1000 pounds of body weight, most common farm animals will excrete between 60 and 80 pounds of manure per day (source). Based on those numbers a 1400 pound dairy cow will excrete 112 pounds of manure and a layer hen will excrete around 1/3 of a pound of manure per day.

The American Society of Agricultural and Biological Engineers (ASABE) released standard D384.2 “Manure Production and Characteristics” in 2005. Table 1 and Table 2 of that standard provide numbers that are similar to the NRCS manure production estimates. The ASABE standard estimates that a layer hen will excrete 0.19 pounds of manure per day and a dairy cow (weight not specified) will excrete 150 pounds per day.

The amount of manure an animal excretes is not necessarily the same amount that farms collect or store. For animals housed in open lots, manure dries considerably as it lays on the surface of the pen. For example, a feedlot steer may excrete 80 or 90 pounds of manure per day, but after that manure has dried on the pen surface, the farm may only end up with 8 or 9 pounds of manure to collect. The same goes for layer hen manure on manure belts or in storage structures.

For animals housed in barns with flush systems, the total volume will include animal manure, wasted feed and water, and water used for the flush system.

How Has Manure Management Changed?

In decades past, most farms handled manure as a solid* material, often mixed with bedding, and hauled the manure and bedding out to a field regularly, referred to as “daily haul”. Photos 1 and 2 (below) show what a daily haul system looks like.

small farm tractor and manure spreader

Photo 1. (Above) A spreader being loaded with manure directly from the barn.

small farm tractor and manure spreader in field

Photo 2. (Above) Spreading manure in a recently harvested field. Photos 1 and 2 are courtesy of Anne Cumbie Randle.

As farms have grown larger, and technologies improve, more manure is being handled as a slurry or liquid* — especially on dairy and pig farms. Beef cattle feedlots, and layer chicken and broiler farms mostly handle manure as a solid.

The volume of manure generated on many modern animal feeding operations necessitates storing manure in engineered structures. Manure storage has become a more visible feature on farms compared to past decades.

The primary purpose of storage systems is to provide a place to contain manure so that farmers can apply manure to fields at times when nutrients can best be utilized by crops and thereby avoid applying it to fields at inappropriate times such as when soils are frozen, snow-covered or saturated. Avoiding these times reduces the risk of runoff to water and soil compaction. Also, while not yet common, manure treatment systems that generate renewable energy or process manure for other value-added products start with storage.

* Solid manure is generally at least 20% solids and 80% or less moisture but can be stacked and piled. Liquid manure is usually 5% solids and 95% or more moisture. Slurry manure is in between. Both slurry and liquid manure are moved via pumps. (See Figure 1 on page 11 of LPES Lesson 20).

The Basics of Manure Management

The components of a manure management system include:

Collection. How much manure is produced by the animals on the farm? How will the farm gather manure for storage?

Storage. How will the manure be contained until it can be used or treated? Photos 1-3 below show some examples of manure storage.

Treatment. Not all systems are designed to include manure treatment. Treatment systems tend to be very expensive, but they can lead to new uses for manure or new revenue streams for the farm. Anaerobic or aerobic lagoons, composting, anaerobic digestion, vermicomposting, and thermal technologies are examples of manure treatment.

Transport. How will the manure be moved from the storage structure to the field or to its intended use?

Utilization. Manure has many beneficial uses. The most common use (by far) is land application as a plant fertilizer.

Recommended Resource: University of Minnesota videos on the “Basics of Manure Management

a liquid manure storage structure

Photo 1. (Above) An earthen liquid manure storage structure. Ideally, this type of manure storage would have a marker installed that indicates when the liquid level reaches the maximum design limit (a depth that provides enough capacity to store the expected volume of wastewater plus a margin of safety in case of a large rainfall or prolonged period of bad weather that prevents pumping out to a field). Photo courtesy of Tetra Tech.

solid manure storage area at a layer farm

Photo 2. (Above) A storage area for solid manure.  It is important that any runoff from this area is captured and contained. Photo courtesy of Saqib Mukhtar, University of Florida.

A cement slurry manure storage structure on a dairy farm.

Photo 3. (Above) A concrete storage structure for slurry manure on a dairy farm. The ramp in the foreground allows access to remove accumulated solids.

A Look at Five Different Types of Animal Agriculture

Click on a photo to start a short virtual tour showing the outside, inside, and basic manure handling and storage practices on layer, beef, pig, dairy, and broiler farms. These tours discuss typical manure collection intervals and practices along with typical storage facilities and management. Links to additional resources are provided throughout the text and at the end of each tour.

looking down a row of cages in a layer chicken barn

Layer hens

beef cattle in a feedlot

Beef feedlots

pigs in a confinement building


dairy cattle eating

Dairy Cattle

broiler chicks in a barn

Broiler (meat) chickens

Recommended Resources

For the fun activity below, use the scroll bar at the right of the frame to move down and show the “continue” or “submit” buttons if they do not appear.

Next: What Does Manure Collection and Storage Look Like?


These materials were developed by the Livestock and Poultry Environmental Learning Center (LPELC) with funding from the U.S. Environmental Protection Agency and with input from the Natural Resources Conservation Service, National Cattlemen’s Beef Association, National Milk Producers Federation, National Pork Board, United Egg Producers, and U.S. Poultry and Egg Association.

For questions on these materials, contact Jill Heemstra, All images in this module, unless indicated otherwise, were provided by Jill.

Reviewers: Tetra Tech, Inc.; Mark Risse, University of Georgia; Leslie Johnson, University of Nebraska; Bill Couser, Couser Cattle; Tom Hebert, Bayard Ridge Group; Glenn Carpenter, USDA NRCS; Joe Harrison, Washington State University; and Jace Thornton, National Cattlemen’s Beef Association

Nutrient Planning on Swine Farms


LESSONS LEARNED – See links below for more detail.
Mouse over the bottom of the slide to slow or pause slides.

Thirteen swine producers from Corn Belt states participated in a project with faculty from University of Nebraska and Purdue University to understand the movement of nutrients (nitrogen and phohsphorus) on commercial swine facilities. These farms ranged in size from 2,000 to 16,000 head finishing capacity with most farms being wean to finish or feeder pig to finish operations. The project team developed a whole farm nutrient balance for each farm for both 2006 and 2007 based upon farm specific data.

Primary project outcomes include an understanding of the primary sources of nutrients arriving on these farms, the magnitude of imbalances experience by these farms, and the value of specific nutrient management practices to minimizing the nutrient imbalances experienced by swine production.

To learn more about the concept of Whole Farm Nutrient Balance (WFNB), the lessons learned from this on-farm research, and the tools developed for use by producers, the following introduction is suggested:

WFNB for Pork Production – An Introduction

Lessons Learned


Archived Workshop on WFNB

  • Introduction to WFNB
  • Lessons Learned from 13 Commercial Swine Facilities
  • Introduction to WFNB Tools


This project was funded by The National Pork Board. The authors wish to extend their appreciation for the financial support provided for completing this on-farm research project.

Managing Manure on Horse Farms

Why Is It Important to Manage Horse Manure?

When managed properly, nutrients from manure should be seen as part of a larger cycle occurring on the farm. Nutrients enter the farm as feed or fertilizer, are excreted as manure, and are subsequently spread on the soil, taken up by plants, or transported off the farm as waste. Related: Horse Manure Composting: Facilities and Methods

The soil can store nutrients, provided the amount of manure applied to the soil is not excessive. When land has excess manure, more nutrients than crops can take up, these nutrients will build up in the soil and pose a hazard to ground or surface water. Excess nutrients can be carried by water through runoff or leaching to surface or ground water.

To minimize environmental risk, all horse farms should develop management plans that provide for proper storage, use, and disposal of horse manure.

What Is Nutrient Management?

The purpose of nutrient management is to implement practices that permit the efficient use of manure for crop production while preventing environmental damage that may be caused by nutrients. Nutrient management planning is a site specific exercise and, if the recommendations are followed, nutrient losses should be minimal. In general nutrient management considers how many nutrients are accumulating on a farm, their potential impacts on the environment, and how to best utilize them. Usually considered in nutrient management planning are:

  • goals of the farm as well as any constraints,
  • available farm resources (land, equipment, financial resources),
  • potential critical areas on the farm (sensitive water bodies, neighbors concerns, erosion, manure storage etc),
  • and nutrient balance (shown in the figure below).
Recycling Diagram

Importance of Nutrient Balance

Farm nutrient inputs consist of feed and fertilizer, but also animals, legume nitrogen, and bedding. Farms may export nutrients through outputs such as grain, animals, milk, meat, eggs, manure, and hay. Some nutrients are recycled on the farm, from feed to livestock to soil to plant and back to feed again. The optimal situation is for the farm to remain in balance between inputs and outputs without losses either as runoff to surface water or as leachate to groundwater. For more information, see Whole Farm Nutrient Balance.

Additional Articles On Horse Manure Management

The challenges of managing manure nutrients are different on a horse farms than on many larger farms. Horse farms often have fewer animals and sometimes several animal species on the same farm, but may have limited acreage for spreading manure. Some horse farms also face a challenge because they do not export nutrients from their system the way that many other farms do–by marketing outputs such as milk or selling animals that are produced.

The following articles are available on this website and include links to additional resources for each topic.

You may also want to see Nutrient Planning on Small Farms. It provides information about how to feed animals and manage their diets; calculate how much manure is produced. There is also information on basic soil science and soil fertility; and nutrient (manure) management – manure use on and off the farm and nutrient management planning.

Author: Michael Westendorf, Rutgers, The State University of New Jersey

USDA Small Farm Definitions

Farm Classification System

The USDA Economic Research Service (USDA-ERS) has developed a farm classification system to divide U.S. farms into eight mutually exclusive and more homogeneous groups. The farm typology focuses on “family farms,” or farms organized as proprietorships, partnerships, and family corporations that are not operated by a hired manager. To be complete, however, it also includes nonfamily farms. A collapsed farm typology combines the eight groups into three categories.

Small Family Farms (gross sales less than $250,000)

Rural-residence family farms:

  • Retirement farms. Small farms whose operators report they are retired.
  • Residential/lifestyle farms. Small farms whose operators report a major occupation other than farming.

Intermediate family farms: 

Farming-occupation farms. Family farms whose operators report farming as their major occupation.  

  •  Low-sales farms. Gross sales less than $100,000.
  • High-sales farms. Gross sales between $100,000 and $249,999.

Commercial Family Farms: (gross sales more than $250,000) 

  • Large family farms. Gross sales between $250,000 and $499,999.
  • Very large family farms. Gross sales of $500,000 or more.

Nonfamily farms:

  • Any farm not classified as a family farm, that is, any farm for which the majority of the farm business is not owned by individuals related by blood, marriage, or adoption.  

The National Commission on Small Farms selected $250,000 in gross sales as the cutoff between small and large-scale farms.

Collapsed Farm Typology

The collapsed farm typology combines the seven farm typology groups into three categories:

  • Rural residence farms. Includes limited-resource, retirement, and residential lifestyle farms.
  • Intermediate farms. Includes farming occupation/lower-sales and farming occupation/higher-sales farms.
  • Commercial farms. Includes large, very large, and nonfamily farms.

Pathogens and Potential Risks Related to Livestock or Poultry Manure

Links to PEDv (Porcine Epidemic Diarrhea Virus).


Microorganisms (e.g. virus, bacteria, protozoa, and fungi) surround us, on us, and in us; they are ubiquitous and everything in the world is governed by them.  They are part of our everyday lives.  They influence the the quality of our soil, food grown on that soil, and how our body reacts to that food. They are diverse, ranging from a simple mix of protein and DNA to complex multi-cellular  small “animals”.  Most environmental microorganisms spend their entire lives as quiet members of their ecological society, but some reach a level of infamy.  Pathogens may only represent a very small portion of all microorganisms, but they are often the most visible, thanks to readily reported outbreaks, food recalls, and proliferation of internet news blogs and sites.

What is a Pathogen?

A pathogen is a biological agent that causes disease or illness; this disease can occur in humans, animals, or crops. Zoonotic pathogens refers to pathogens naturally transmitted from animals to humans and are often heard about on news sites or involved in food recalls.

All animals including pets, livestock, wildlife and humans, are possible hosts of potential human pathogens. We will focus on pathogens originating from livestock and poultry that might be transported to humans via air, water, soil, crop, and fomites (inanimate objects) contacted directly or indirectly by manure.

Zoonotic Pathogens

There are four general classes of zoonotic pathogens:

  1. viruses
  2. bacteria
  3. protozoan parasites
  4. helminth parasites

Zoonotic viruses are those found mainly in animals that cause disease in people who come into contact with the animal or share a vector (transmitter of disease) like a mosquito (West Nile Virus is a virus of birds which mosquitoes carry and can transmit to people). Viruses can only multiply when they are inside a host cell.

  • Until very recently, it was considered that most fecal or urine transmitted viruses of livestock were not zoonotic, but things have changed somewhat in recent years, and we are now in a steep learning curve as to how important ruminants and poultry are as reservoirs of these zoonotic viral agents.

Zoonotic bacterial pathogens are, like all bacteria, single celled microorganisms that can survive and, under favorable conditions, reproduce in terrestrial and aquatic environments. The zoonotic bacteria are those that typically cycle in domestic animals without causing disease in their typical hosts. However, when they get transmitted into people, the disease that is produced can be severe.

  • Examples of zoonotic bacteria are Salmonella spp., strains of Escherichia coli such as E. coli 0157:H7, Listeria monocytogenes, and Campylobacter spp.

Zoonotic protozoan parasites, are protozoa that are found in other animals and which can infect people. There are basically two roles that humans can play in this scenario. They can be accidental hosts in the life cycle of the protozoan, where the protozoan undergoes the same development in the human as it does in its normal reservoir host. Or, the human may be an intermediate host in the life cycle of the parasites, just like any other vertebrate; in this case, the reservoir host shed many stages into the environment with the goal of infecting as many intermediate hosts as possible.

  • In the case of zoonotic protozoa relative to domestic farm animals, only a few have proven to be of significant concern relative to the infection of people.
    • Species of Cryptosporidium found in horses, cattle, pigs, and sheep can accidentally infect people, with C. parvum of young ruminants being the most common offender.
    • Giardia of livestock typically does not seem to occur in people, but it does seem that they might be infected with the human form and could then serve as a source of stages that might be passed to humans.

Zoonotic helminth parasites are worms, nematodes (roundworms), cestodes (tapeworms), or trematodes (flukes), that have cycles similar to protozoa. Again, people can be infected accidentally by the worm in the same manner as a reservoir host or they can be serving as just another vertebrate intermediate host in the life cycle of the parasite.

  • Fortunately, in the case of domestic farm animals, the helminth parasites are for the most part not zoonotic with respect to people. The only forms with stages that might be infectious to people from manure would be the egg of the pig roundworm, Ascaris suum.

Photo source: Jeanette Thurston-Enriquez webcast presentation.

Detailed discussion of protozoan parasites, bacteria, and viruses can be found on pages 5, 12, and 18, respectively, of the USDA NRCS technical note

Waterborne Pathogens in Agricultural Watersheds

Several outbreaks of human illness and death have been attributed to drinking water contaminated with livestock manure. Of 66 drinking water outbreaks in affluent nations, the probable cause of 12 of the outbreaks was livestock manure (see Hrudey and Hrudey, 2004 in Research Summaries. These included:

  • An outbreak at the 1999 Washington County Fair, New York (E. coli O157:H7; of 781 confirmed cases, 71 people were hospitalized, and 2 died);
  • An outbreak in Walkerton, Ontario, Canada in 2000 (E. coli O157:H7 and Campylobacter jejuni; 2,300 people were ill, 65 were hospitalized and 7 died).

These outbreaks were indicative of the capability of the pathogens to survive and be leached through soil to groundwater sources of drinking water.

2008 distribution of confirmed zoonotic diseases. Data source:[ Centers for Disease Control MMWR Surveillance Summaries].

Not all illness outbreaks are livestock related. For example, animal manure was initially suggested as the source of the largest drinking water outbreak in U.S. history – the Cryptosporidium outbreak in Milwaukee, WI in 1993. Several years later following advances in microbiology and genetics, human sewage was identified as the likely contributor.

Antibiotic Resistant Bacteria in Agricultural Manures

An antibiotic-resistant bacterial population is one in which resistance is either intrinsic or has been acquired from exposure either to antibiotics or to other antibiotic resistant bacterial populations. The increased frequency of antibiotic resistant pathogens has become a serious public health concern as demonstrated with outbreaks of methicillin-resistant Staphylococcus aureus (MRSA) and antibiotic resistant Salmonella such as Salmonella DT104. Little research and information is available on the presence of antibiotic resistant bacteria originating in manure and manure land applied environments, and, thus, little is known about their fate and transport in soil, water, crops, and agronomic systems.

A listing of possible zoonotic pathogens can be found on pages 6 – 10 of an EPA literature review.

Authored by: Michael Jenkins and John Brooks, USDA ARS, Dwight Bowman and Janice Liotta, Cornell University.

Question or concerns, contact John Brooks (

Feed Management Planning as a Tool to Reduce Nutrient Excretion

Why is Feed Management Important to Nutrient Planning?

Feed represents the largest import of nutrients to the farm, followed by commercial fertilizer. Feed management practices impact the amount of nutrients that are imported to the farm and excreted in manure. The excreted nutrients are subsequently available for volatile loss (nitrogen) to the atmosphere and potentially lost via surface runoff (nitrogen and phosphorus) or leached to ground water (nitrogen and phosphorus).

Nutrient management planning addresses the proper distribution of manure nutrients, but typically only focuses on the nutrients after they have been excreted by the animal. It may seem obvious, but the amount of N and P consumed by an animal is directly related to the amount it excretes. Formulating an inexpensive ration with excess N or P, will increase the amount of these nutrients excreted in the manure. Depending on the requirements of the farm nutrient management plan, this may mean that the manure must be spread over a larger number of acres compared to manure that contains lower N or P levels.

Feed management opportunities currently exist to reduce imports of nutrients (particularly N and P) to most animal livestock and poultry operations. Since consulting nutritionists play such a key role with regard to importation of nutrients to the farm, a systematic approach to evaluate the role that Feed Management has on whole farm nutrient management is warranted.

Resources Available for Managing Feed Nutrients

The National Feed Management Education Project (NFMEP) has developed a systematic approach to feed management and whole farm nutrient management. The team has developed a series of fact sheets and resources for the four major species. In addition, the LPE Learning Center Small Farms team has developed resources for small acreage livestock and poultry owners.



Authors: Joe Harrison, Washington State University and Jill Heemstra, University of Nebraska

Manure Management on Small Farms

What Does “Small Farm” Mean?

Small farms are typically smaller in size, with fewer animal numbers, less acreage and have a lighter regulatory burden than larger farms, which may often be designated as Concentrated Animal Feeding Operations or CAFO’s. Small farms are often able to implement lower cost solutions to animal waste concerns than are larger farms.

The USDA and EPA give broad definitions of what constitutes a small farm. A small farm could have 150 dairy cows in the midwestern or western dairy belt or it could be a 30–head flock of sheep raised for an organic market. It could be a 100 head sow herd or 10 head of beef cows and their calves on a retirement farm. Small farms may include both commercial and hobby farms.

Small farms are often quite diverse (University of Rhode Island Small Acreage Livestock Program). A horse-boarding farm in the northeast that exports all manure off-site is very different from a 150-head dairy farm that spreads all manure on owned acreage. Both could be called small farms but the management challenges would be very different for each. A majority of residential/lifestyle farms may also experience high stocking rates (or animal units per acre). Farms with limited land resources must rely on exporting manure to manage the animal waste.

What is an Animal Feeding Operation (AFO)?

Animal feeding operations (AFOs) are agricultural enterprises where animals are kept and raised in confined situations. As defined by the Environmental Protection Agency (EPA), and your state regulatory agency, an AFO is a lot or facility where animals have been, are, or will be stabled or confined and fed, or maintained for a total of 45 days or more in any 12-month period. Feed is brought to the animals rather than the animals grazing or otherwise seeking feed in pastures or fields or on rangeland. Animals are not considered to be stabled or confined when they are in areas such as pastures or rangeland that sustain crops or forage growth during the entire time that animals are present.

Small Farm Livestock Collage

Small farms must first determine if they meet the definition of an AFO. If not, they are considered a “pasture based operation.” If the operation meets the definition of an AFO, then they must determine if they meet the definition of a CAFO (small or medium). This determination is a function of size and connection to surface water resources. There are times when a pasture based operation may be subject to regulation. Any Animal Feeding Operation (AFO) that discharges manure or wastewater into a natural or man-made ditch, stream or other waterway can also be defined as a CAFO, regardless of size. See What if My Operation is an AFO but not a CAFO?.

USDA Definition of Small Farm

The United States Department of Agriculture defines a small farm as having less than $250,000 in annual gross sales (USDA Small Farm Definitions). According to the National Commission on Small Farms these farms constitute 90 percent of U.S. farms, contain 67 percent of farm land, and hold 77 percent of farm sector net worth. In 2004, small farms accounted for 26 percent of all agricultural receipts from crops and livestock. The Small Business Administration (SBA) generally classifies farms as small if they have sales less than $500,000. By SBA standards, about 97 percent of U.S. family farms are small (USDA-Economic Research Service).

All farms with livestock, regardless of size, can be environmental risks. It doesn’t matter if there is one animal or many, if animal housing, pastures and manure is not properly managed, there is a potential to harm the environment or cause problems for neighbors.


Environmental Stewardship for Small Farms

All small farms should strive to achieve good land and animal stewardship: Small-Scale Farmers and the Environment: How to be a Good Steward ( Spanish Language Version). Well managed farms will:

  1. Minimize barnyard and manure runoff into streams or wetlands
  2. Properly account for manure spread on crop or pastureland
  3. Properly store manure to utilize this resource during the growing season
  4. Manage animals and manure on pastures to maintain pasture quality, control field erosion, and control animal traffic near streams
  5. Keep records about their operation.

Small farm manure management poses different kinds of challenges than does manure management on larger farms. This section will connect you with some of the best resources about managing manure on small farms. Follow the links below for helpful information:

Authors: Michael Westendorf, Rutgers, The State University of New Jersey and Mark Rice, North Carolina State University; Updated November 25, 2008