Section C: Animals in the agro-ecosystem
- Projected Outcomes
- Background / Lessons
- Ecological question 1: What are the nutrient flows in the system?
- Ecological question 2: What are the sources and sinks of pollutants in the system?
- Ecological question 3: What are the interactions of living organisms in the system?
- Ecological question 4: What are the energy flows in the system?
- Career Pathway content standards
- Students will learn how to apply ecological analysis to animal production systems.
“Mother earth never attempts to farm without live stock…”
Sir Albert Howard, An Agricultural Testament, Oxford University Press, 1940, p. 4.
Animal agriculture can have very negative ecosystem impacts, or it can bring ecosystem benefits. In general, when animals are raised in large confinement systems and fed grain, their production uses more energy and causes more pollution than the production of field crops. When animals are raised in small groups primarily on pasture, their production uses less energy and tends to cause less pollution than field crop production. However, good management is the key in all cases. Well-managed confinement systems can minimize environmental damage, and poorly managed grazing can cause serious environmental problems.
In sustainable agriculture the goal is to take advantage of ecosystem processes by designing an agricultural system that works with them.
As we look at the agroecology of animal production, we should keep four questions in mind:
- Where do key nutrients come from?
- What are the sources and sinks of pollutants in this system?
- How do the living organisms in the system interact?
- What are the energy flows?
Ecological question 1: What are the nutrient flows in the system?
In a sustainable system they will be recycled on-site or generated in a renewable fashion.
When livestock feed is obtained from off the farm, it is extremely difficult to close nutrient cycles, especially for phosphorus, potassium, and carbon. These nutrients are being exported from the farms producing the feed, and they accumulate on the livestock farms in the form of manure, creating nutrient imbalances in both locations.
When the livestock feed comes from the same farm or from farms within a few miles, the nutrient cycles for these major nutrients can be nearly closed, because it is cost-effective to return the nutrients in the manure to the fields where the feed is grown. Nutrient losses from export of the nutrients contained in the animals are minor compared to the nutrient value of the manure. Moreover, good manure management can minimize leaching and runoff of nutrients in manure.
Water is not typically thought of as a nutrient, but when livestock feed is grown using irrigation, that disrupts the natural hydrological cycle, which can have far-ranging ecological impacts. Much of the forage and grain fed to beef produced in the west is grown using irrigation. Some of this irrigation water is pumped from aquifers at unsustainable rates. Some is diverted from river systems, altering aquatic communities and reducing the water available for other uses. For example about 85% of the water taken from the Colorado River in California, Arizona, and Nevada is used for agricultural purposes. Long before the Colorado River reaches its historic outlet to the ocean in Mexico, it has completely dried up. Some of the water withdrawn goes to fruit and vegetable production, but livestock production is also a major water user (see http://www.cpluhna.nau.edu/Change/waterdevelopment6.htm).
In Iowa and Wisconsin production of livestock feed and forage generally does not require irrigation. In both these states, the withdrawal of irrigation water from streams and rivers is regulated to protect aquatic life. However, even in this area the potential exists for local conflicts over agricultural water use.
Sustainable nutrient management practices:
- Managed grazing allows animals to consume plant nutrients right where they are produced, and return most of those nutrients to the pasture soil in the form of manure (without additional capital, labor, and energy costs for storage and spreading).
- Mixed species pastures contain legumes that support nitrogen-fixing bacteria, reducing or eliminating the need for N inputs from off-site.
- Year-round ground cover on well-managed pastures tends to retain soil nutrients on-site.
- Many high-quality forage crops are legumes that support nitrogen-fixing bacteria.
- Proper manure management minimizes nutrient runoff, leaching, and volatilization as well as unpleasant odors. It also returns nutrients to the fields where they are needed for optimum plant growth. See Nutrient Management Fast Facts for a brief overview of plant nutrients in different types of manure. Many more in-depth publications about manure management are available at at http://ipcm.wisc.edu/downloads/nutrient-managment/, including When and Where to Apply Manure.
- Composting is a form of manure management that stabilizes nutrients and can also reduce weed seed viability and disease pressure.
- Deep bedded systems absorb nutrient-rich urine as well as manure solids and lend themselves to composting.
Ecological question 2: What are the sources and sinks of pollutants in the system?
A sustainable system will minimize the amount of pollutants.
In livestock production systems, animal waste or manure is usually the largest potential source of pollution. Other pollution sources from livestock production can include erosion from poorly managed grazing, improper disposal of dead animals, improper disposal of milkroom waste, and dust and odors from CAFOs (Confined Animal Feeding Operations).
Since most field crops in Wisconsin and Iowa are used for animal feed, the pollution that may result from field crop production, including erosion and runoff and leaching of fertilizers and pesticides, can be viewed as an indirect result of livestock production.
Manure is a valuable farm resource if it is properly managed. All too often, though, manure is a major agricultural pollutant. For example, the Iowa Department of Natural Resources attributes more than a quarter of the fish kills in the state to animal waste (http://www.igsb.uiowa.edu/gsbpubs/pdf/WFS-2008-05.pdf and http://programs.iowadnr.gov/fishkill/default.aspx). In addition to harming aquatic life, microorganisms from livestock manure can threaten human health if they get into the water supply. (See http://www.dnr.state.wi.us/runoff/ag/waterquality.htm) As discussed above, when livestock is raised or finished far from where their feed is grown, it is usually not economical for the farmer to apply the manure only as needed for optimum crop growth.
Sustainable practices to minimize pollution
- Livestock production should be sited close enough to the area of feed production for the return of manure to those fields to be profitable.
- Grazing should be managed to prevent soil erosion and degradation of stream and river banks. Both rotational grazing and traditional extensive grazing can minimize pollution, if well-managed.
- Manure must be stored, handled, and applied in such a way that it will not leach or run off and contaminate surface or ground water. Deep bedding and composting are manure management practices used by many sustainable livestock producers. Manure Storage, The Art and Science of Composting.
Ecological question 3: What are the interactions of living organisms in the system?
Typically, sustainable agro-ecosystems will try to work with species interactions and will favor species diversity.
Grazing systems are based on direct species interactions. When livestock is raised in confinement, natural ecological interactions are interrupted. Feed crops are raised in a monoculture, then harvested, transported, stored, and fed to livestock held in areas where all other living species except human workers are excluded as much as possible. The species interactions on pastures can bring additional challenges such as loss to predators and exposure to parasites. However, they also bring ecosystem services, such as nutrient cycling, pest management, and efficient capture and storage of solar energy.
Rotationally managed pastures can provide habitat for wildlife and native prairie plants (see Grassland birds: Fostering habitats using rotational grazing).
Another issue to consider is the genetic diversity of the farm animals themselves. For thousands of years, localized selection of traits in farm animals led to a proliferation of regional breeds. For example, in England, a country smaller than the state of Wisconsin, there are more than 25 breeds of sheep, most developed in and named for an area no bigger than a US county. These breeds varied widely in their adaptations and the characteristics of their meat and wool. (For a listing of recognized sheep breeds worldwide, see the left panel at http://www.ansi.okstate.edu/breeds/sheep/). Modern commodity livestock production and processing emphasizes uniformity and a few traits such as leanness and efficiency of growth. This emphasis has led to having one or two breeds dominate production agriculture for our entire country and beyond. Perhaps the most extreme example is the domestic turkey. All turkey meat raised by large commercial growers in the US is from one breed, the Broad-breasted White. This turkey has been bred to put on weight fast, to have white feathers that leave the skin a uniform creamy color, and to grow a large amount of breast meat. In fact the breasts of mature birds are so large that these animals cannot mate naturally. Recently, some specialty producers have begun to grow and market some of the more than 20 other American breeds with different size and flavor characteristics and better abilities to fend for themselves. See http://www.feathersite.com/Poultry/Turkeys/BRKTurkey.html, http://www.newholland.com/na/News/nhn/NovDec01/V47No8_1.htm. For all our farm animals, older and uncommon breeds offer an important reservoir of genetic traits, from disease resistance and adaptation to a variety of climates to variations in flavor and other traits of interest to the consumer or farmer. Organizations such as the American Livestock Breeds Conservancy are now working to preserve rare breeds of farm animals in our country. (See http://www.albc-usa.org/).
Manure management can have a significant effect on soil organisms. Raw manure contains pathogens that can threaten human health until they are broken down or consumed by benign organisms. The nutrients and organic matter in manure can benefit soil life. Compost contains a variety of generally beneficial soil organisms, though the predominant organisms will vary, depending on the materials and process used.
What are the impacts on other organisms of feed production? For example, in aquaculture systems high-value carnivorous fish such as trout and salmon are often fed fish meal. Production of this fish meal may damage marine ecosystems. At the other end of the process, pollution from livestock production, such as sedimentation and nutrient runoff, can damage aquatic ecosystems.
In some cases the livestock may transmit disease or may escape and displace native species. For example, farm animals such as pigs, goats, dogs, and cats have contributed to the extinction of many flightless birds on islands in the Pacific Ocean. In Wisconsin there is debate about whether deer farms may have introduced Chronic Wasting Disease to the state.
Sustainable practices include:
- Grazing on multi-species pasture (http://clean-water.uwex.edu/pubs/pasture/pasturereport.pdf).
- Managing grazing and haying to encourage nesting success for grassland birds such as meadowlarks, grasshopper sparrows, and bobolinks (see Grassland birds: Fostering habitats using rotational grazing).
- Grazing different livestock species together or in sequence.
- Use of traditional breeds adapted to the climate and to outdoor conditions.
- Providing shade and/or shelterbelts.
- Management of water access to protect streams and prevent erosion (see Grazing streamside pastures).
Ecological question 4: What are the energy flows in the system?
Sustainable agro-ecosystems rely more on solar energy than on fossil fuels. Sustainable systems minimize energy waste.
In general, grazing systems maximize use of solar energy and minimize use of fossil fuels. Unlike in confinement animal production systems, no fossil fuels are used to harvest, dry, or transport the feed to the grazing animals when forage growth is good. Also, energy use for extracting, transporting, and applying fertilizer to well-managed pastures is minimal. Confinement systems such as hoophouses that rely on natural ventilation and on deep bedding for manure management require less energy for both construction and operation than fully confined systems with mechanical ventilation and liquid manure management systems. On the other hand, manure from confinement systems can be used to generate electricity (see http://www.mnproject.org/e-biogas.html), though it is not clear whether the energy recovered compensates for the extra energy required for the confinement system. According to the Wisconsin Integrated Cropping Systems Trial, the energy efficiency of rotational grazing systems is about twice that of forage-based cropping systems and about four times that for row crop production. (See http://www.cias.wisc.edu/wicst/pubs/energy.htm, http://www.cias.wisc.edu/wicst/pubs/images/energy/table3.html.)
Sustainable energy management practices:
- Rotational grazing
- Grazing of standing crops
- Stockpiling of winter forage on pastures minimizes energy used for manure spreading
- Design buildings to eliminate or minimize reliance on mechanical ventilation, heating, and cooling
- If animals are in confinement, consider generating electricity from manure
- Install and maintain energy efficient systems for major energy users such as refrigeration of milk (see http://learningstore.uwex.edu/Energy-Conservation-C29.aspx).
More than half of the energy in our food system is used not on the farm, but in transportation, processing, storage and packaging, and home cooking.
Sustainable practices for the consumer:
- Buy local foods, when possible
- Avoid excess packaging
- Use energy-efficient appliances and techniques when possible
- Use renewable energy sources, if possible (solar and wind power)
- Consider eating lower on the food chain or sticking to grass-fed meat and dairy products (most of the food energy contained in grain is used by livestock to sustain their own life and only a small amount is stored as meat. Thus it takes 4 lbs of corn to produce 1 lb of pork and 7 to 10 lbs of corn to produce 1 lb of beef).
Poorly managed animal agriculture can have extremely negative impacts on the environment and can be very wasteful of natural resources. However, animals play critical roles in natural eco-systems, and animal agriculture that mimics and builds on natural systems can be far less damaging to the environment than even well-managed cropping systems that try to function without animals.
In the last twenty years or so, ideas about grazing have changed considerably, as the use of lightweight electric fencing allowed much more flexible and detailed management of livestock on pasture. There is still much to be learned about managed or rotational grazing, but it is the foundation of livestock management on many sustainable farms.
Career Pathway content standards
|Projected Outcome||National Agricultural Education Standards
Performance Element or
(in this section)
|1. Identify sources and sinks for pollutants in livestock production systems and practices to minimize this pollution.||AS.08 Analyze environmental factors associated with animal production.
ESS.03.03 Apply hydrology principles to environmental service systems.
AS.07.02 Comply with government regulations and safety standards for facilities used in animal production.
|2. Describe how livestock production interacts with the surrounding environmental and genetic diversity.||ESS.03.02 Apply soil science principles to environmental service systems.||C-1|
|3. List ways in which sustainable livestock production minimizes energy waste.||NRS.02.04 Demonstrate natural resource enhancement techniques.
ESS.04.02 Manage safe disposal of all categories of solid waste.
ESS.05.01 Compare and contrast the impact of conventional and alternative energy sources on the environment.
|4. Describe how sustainable practices can affect farm profitablity.||CS.03.03 Flexibility/Adaptability: describe traits that enable one to be capable and willing to accept change.
AS.08 Analyze environmental factors associated with animal production.