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Section C: Animals in the agro-ecosystem
Projected
outcomes:
1. Students will learn how to apply ecological
analysis to animal production systems.
Background
/ Lessons:
Introduction
“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?
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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.
Activity
1: Water and Numbers
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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 http://ipcm.wisc.edu/pubs/pdf/mnr_facs.pdf
for a brief overview of manure management guidelines.
Many more in-depth publications about manure
management are available at http://ipcm.wisc.edu/pubs/nutrient_ref.htm
and http://extension.agron.iastate.edu/immag/pubs.html.
- 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.
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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, in 1998 the
Iowa DNR estimated 465,000 fish were killed due
to manure spills from confinement facilities (http://www.earthweshare.org/n/iaspillskills.htm).
In addition to harming aquatic life, microorganisms
from livestock manure can threaten human health
if they get into the water supply. (See http://www.ers.usda.gov/publications/aib771/aib771ap.pdf
and http://www.dnr.state.wi.us/org/water/wm/nps/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. http://ipcm.wisc.edu/pubs/pdf/manu_gui.pdf,
http://www.exnet.iastate.edu/Publications/PM1518K.pdf,
http://www.cias.wisc.edu/pdf/artofcompost.pdf.
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Ecological
question 3: How do the living organisms in the
system interact?
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 http://cecommerce.uwex.edu/pdfs/A3715.PDF).
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:
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Ecological
question 4: What are the energy flows?
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/),
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.wisc.edu/cias/wicst/pubs/energy.htm,
http://www.wisc.edu/cias/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://cecommerce.uwex.edu/showcat.asp?id=7).
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).
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Conclusion
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.
Activity
2. Ecological Pawprint Analysis
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