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Horses and Manure
Michael Westendorf, Extension Specialist in Animal
Sciences & Uta Krogmann, Extension Specialist in Solid Waste Management
Published 2/16/2004
Fact Sheet # 036
Horses
are important for companionship, sport, work, pleasure, education, and
therapy. In New Jersey, in addition to playing an important role in the
state’s economy, horses help to maintain open, green spaces that add to
the scenic beauty of the state. Horses and the farms on which they live
are often very valuable. To be good stewards of the land, however, horse
farmers should manage their farms in a way to minimize the potential for
negatively impacting the environment with horse manure.
This fact sheet gives an overview about the influence of equine
physiology on horse manure excretion, horse manure quantity and
composition; environmental benefits and impacts of horse manure;
nutrient balance of horse farms, horse manure management and regulatory
compliance assistance.
Equine Physiology
Some basic knowledge about horses and how they digest and metabolize
food and produce manure (feces and urine) can help to more effectively
control potential pollution.
Depending on size, age, and productive status (work, sport, pleasure,
breeding, pregnancy, lactation, retirement), a horse will digest about
60% of most feedstuffs. Feed that is 60% digestible indicates that if a
horse is fed 25 pounds of dry feed, 15 will be digested and 10 pounds
will be excreted as manure (feces). This will vary by feed. Feeds that
are higher in fiber such as hays and grasses have a lower
digestibility. Conversely, concentrate feeds that contain grains such
as corn, oats, and/or barley, usually have a higher efficiency of
digestion and less fecal excretion.
Nitrogen (N) is a major component of protein. Horses need protein for
maintenance, growth, reproduction, lactation, and work. Phosphorus (P)
is a macromineral needed for maintenance, growth, and other physiologic
functions. Water is also essential for bodily functions. Water is lost
from the body primarily in the excretion of feces and urine, sweat,
evaporation from the lungs and skin, and in the case of lactation, from
milk. It also affects the consistency of manure.
All nutrients that are digested (absorbed) are metabolized in the
horse’s body. Some of these, especially nitrogen in proteins, are
excreted in the urine. After being digested and metabolized in the body,
waste nitrogen is converted to urea in the liver and excreted in the
urine. Additional undigested nitrogen is excreted in the feces.
Overfeeding protein will increase the excretion of
nitrogen.
Overfeeding phosphorus will increase the excretion of phosphorous, most
of which is excreted in the feces. Horses should be fed a diet that is
digestible and formulated to meet nutritional requirements, while
avoiding excesses. Overfeeding can result in higher levels of nitrogen
and phosphorus in the manure. Horse farmers should feed horses according
to their nutritional needs. Specific recommendations for nitrogen
(protein) and phosphorus (intakes) are given in the National Resource
Council publication, Nutrient Requirements of Horses.
Manure Quantity and
Composition
A 1000-pound horse will defecate from 4 to 13 times
each day and produce 35 to 50 pounds of wet manure (feces plus urine)
daily, or approximately 9.1 tons per year. Typically a ton of horse
manure will contain 11 pounds of N, 2 pounds of P, and 8 pounds of
potassium (K). To obtain more accurate numbers, manure should be tested
for nutrient content. Check Rutgers Cooperative Extension fact sheet,
FS935, Feed and Forage Testing Labs for more information.
A horse kept in a stall will require about 10 to 20 pounds of bedding
per day. This bedding should be replaced on a regular basis. Because of
many types of bedding materials, wood byproduct (shavings, chips,
sawdust), straw, or paper, the composition of the mix of manure and
bedding will vary from farm to farm. In general, manure plus bedding
will have a volume of between 2 and 3 cubic feet per horse per day.
Environmental Impacts
and Benefits
Environmental Benefits:
When managed properly, manure can be a valuable resource on a farm.
Manure can be a source of nutrients for crop production and can improve
soil quality. The organic matter present in manure can improve both
tilth and water holding capacity of the soil. Manure can also be used as
a fertilizer (N and P) for crops. However, most horse owners do not have
enough land to use the amount of manure that is produced. Monitoring
horse manure so that it does not cause environmental impacts is the goal
of manure management.
Nutrients:
When not
managed properly, horse manure (feces and urine) can pollute the
environment, mainly as ground or surface water pollution due to the
nutrients nitrogen, phosphorus, and carbon (organic matter). These
nutrients can reach waterways as surface runoff or leachate from the
manure pile.
Nitrogen excreted from horses is usually present either as urea in
urine, which is quickly converted to ammonia (NH3),
or it remains in association with organic matter in the feces. Ammonia
(NH3)
can be volatilized into the atmosphere. If NH3 from
horse manure comes into contact with surface waters, it can cause
nutrient enrichment and excessive algae growth. This process is referred
to as eutrophication. Eutrophication is the process of nutrient
enrichment in a lake or slow-moving stream occurring when excess
nutrients from manure, fertilization, sewage, etc. are deposited. This
can result in waters rich in mineral and organic nutrients that promote
a proliferation of plant life, especially algae, which reduces the
dissolved oxygen content and often causes the extinction of other
organisms. (Adapted from Concise Columbia Electronic Encyclopedia, 1999
& American Heritage Dic. of the English Language, 4th ed.) In the case
of nitrogen, the excessive algae and conversion of ammonia to nitrate
(NO3)
causes a reduction in dissolved oxygen in the water, which can
contribute to fish kills through oxygen depletion.
Nitrogen present in organic matter in the feces will be converted in the
soil to ammonia and then nitrate, which can be taken up by plants. If
plants do not take up nitrate it will easily move through the soil and
can eventually leach into the groundwater where it can be a human health
concern. Nitrate can also undergo the process of denitrification in the
soil and be lost into the atmosphere as gaseous nitrogen (NO, N2O,
or N2).
Phosphorus is also present in manure. When spread on the land it will
not leach like nitrogen, unless the soil matrix where phosphorus binds
becomes overly saturated with phosphorus. However, phosphorus will run
off if applied at the wrong time of the year and/or when soil erosion
occurs. This can lead to contamination of surface waters where it may
cause eutrophication.
When
manure is not properly incorporated into the soil, organic matter
present in manure (contains carbon, nitrogen and phosphorus) can be a
concern when it runs off into surface waters. Eutrophication and
additional oxygen depletion may occur due to the decomposition of the
organic matter.
Pathogens and Vermin:
In addition to the above concerns,
pathogens may be present in manure. Some of these are, E. Coli,
Salmonella, and Cryptosporidium parvum, however the frequency of
Salmonella and Cryptosporidium parvum are low in horse feces and there
have been no known outbreaks of E. coli infections in humans attributed
to horses. Internal parasite infestations in horses may also result from
horse manure. Flies, dust, rodents, and odors may also be manure related
concerns on horse farms. These problems can be minimized by proper
design of housing and manure storage areas and care when turning or
moving manure piles.
Nutrient Balance of Horse Farms
When
managed properly, nutrients from manure should be viewed as part of an
overall cycle occurring on the farm. Nutrients enter the farm as feed or
fertilizer, are excreted as manure, and are subsequently spread on the
soil for uptake by plants. The plants are then used as feed or sold from
the farm. See diagram below.
Nutrient
inputs consist of feed, animals, fertilizer, legumes, and bedding.
Outputs are animals, milk, meat, manure, and crops. Recycling also
occurs on the farm, from feed to horse to soil to plant and back to feed
again. The optimal goal is for the farm to remain in balance between
inputs and outputs without losses either as runoff from manure and soil
to surface water or as leachate to groundwater.
Soil can store nutrients assuming that the amount of manure applied to
the soil is not excessive. When the land application of manure is not
managed properly, heavy rains can cause nutrient runoff to surface water
or leachate to groundwater. When land is over-manured and the ability of
crops to take up nutrients is exceeded, these nutrients build up in the
soil and pose a hazard in ground or surface water.
Ideally, farms will be able
to maintain a balanced nutrient cycle and prevent wasteful loss of
nutrients as pollution. According to the 1996 Equine Industry Survey,
49,000 horses are housed on 7,600 operations on 81,000 acres in the
State of New Jersey. This is an average 1.65 acres per horse and
represents an acceptable stocking density. When managed properly there
should be adequate acreage for spreading manure on a farm with this
stocking density and maintaining a balance of nutrients. Farms that
stable or board horses on smaller acreages may have significantly less
available land for spreading. These farms will have to find ways of
disposing manure off the farm.
Horse
Manure Management
Manure
should be removed from stalls or exercise lots on a regular basis. There
should be a plan for manure removal. Manure disposal options include
removal from the farm by haulers, direct land application, or composting
with on-farm or off-farm use of compost.
Location and size of manure storage sites are important. Manure storage
piles should be kept in a dry area not affected by flooding or storm
runoff from other structures or pastures. Do not store manure on a
stream bank, near a wetland, or in an area that is close to the water
table. Store on level ground if possible. Long-term storage structures,
such as composting or stack storage, should have adequate space. The
storage structure should have a firm base and be covered to prevent
runoff or leaching (tarp or roof). Appropriate conservation practices
(buffers, filter strips, etc.) should be implemented to reduce surface
loss of manure nutrients if the storage area is not covered.
When spreading, manure should be harrowed or otherwise incorporated into
the soil. Since nutrient losses from spreading manure should be avoided,
manure should be applied based on a soil test and crop or pasture grass
nutrient needs. It is important to remember that not all nutrients in
manure are immediately available to the present crop. Therefore,
previous manure applications must also be considered when applying
manure to crops.
Spread only when the crops need nutrients. Avoid spreading on frozen
ground or near waterways. Remember that horse manure may contain
internal parasites. It is important not to spread horse manure on
pastures where horses could become re-exposed to parasites, unless there
is a good de-worming program.
Composting of horse manure, when done properly, will result in the
destruction of internal parasites. The composted product can then be
spread on pastures. Composting is managed, accelerated decomposition of
organic materials. Microorganisms, including bacteria, actinomycetes,
and fungi, break down the organic materials at elevated temperatures. It
requires proper levels of moisture and air and the appropriate feedstock
mixture to ensure proper decomposition. Turning the composting material
helps to ensure that all parts of the manure are at elevated
temperatures for certain time periods. The final product will be freer
of odors than horse manure and may have value as a soil amendment or
fertilizer. The composting process will also reduce the total volume of
manure for disposal. Siting issues need to be addressed and are similar
as discussed under manure storage.
Regulatory Compliance Assistance
Horse farms that pollute or discharge waste into New Jersey waters
(regardless of the size of farm) are regulated as Concentrated Animal
Feeding Operations by the New Jersey Department of Environmental
Proection (NJDEP). To assist New Jersey horse farmers, the state
Department of Agriculture is developing an assessment process to help
farmers manage their own manure without polluting. Rutgers Cooperative
Extension and the USDA Natural Resources Conservation Service are
available to help develop plans for managing horse manure.
Conclusion
Horse owners need to be aware of how their horses' manure is managed.
Nutrient inputs, outputs, cycles, and losses all occur on a farm.
Recycling of nutrients should be encouraged, and losses that contaminate
surface or ground water should be eliminated. Horse owners should
remember that nutrients have value not only for feeding horses, but also
as manure that can have value for the whole farm. It is the horse
farmer’s responsibility as a land steward to keep that cycle in balance.
Additional information
For more information about horse manure management, please contact
Rutgers Cooperative Extension. More fact sheets about the management of
horse manure are in production. These will address the regulatory
control of horse manure management, the composition of manure,
composting, horse manure management, and nutrient management. The
publication by Wheeler and Zajaczkowski (2002) is an excellent overview
of horse manure management.
Please
contact your local county Rutgers Cooperative Extension office, listed in
the blue pages, under County Government, or visit the CE, Cook College Web
site, www.rce.rutgers.edu for information.
References
Agricultural Waste
Management Field Handbook.
1992. National Engineering Handbook. USDA Natural Resources Conservation
Service.
Livestock Poultry Environmental Stewardship Curriculum.
2001. MidWest Plan Service. Iowa State University. Ames, IA.
NJDA. 1996.
New Jersey
Equine Industry Survey.
New Jersey Department of Agriculture, New Jersey Agricultural Statistics
Service, and New Jersey Equine Advisory Board. Trenton, NJ.
NRC. 1989. Nutrient Requirements of Horses (5th Rev. Ed). National
Academy Press, Washington, DC.
Wheeler, E. and J. S. Zajaczkowski. 2002. Horse Facilities 3: Horse
Manure Stable Management. Pennsylvania State University. State College,
PA.
www.pubs.cas.psu.edu/freepubs/ub035.
© 2004 by Rutgers Cooperative Extension, New Jersey
Agricultural Experiment Station, Rutgers, The State University of New
Jersey. This material may be copied for educational purposes only by
not-for-profit accredited educational institutions.
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