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Beef cattle production is a strong animal industry within the United States and throughout the world. Since beef cattle can graze forages in the open range and pasturelands, they serve a unique role in providing high quality protein for human consumption from byproducts and forage sources that humans and non-ruminant animals do not consume. Considerable land in the U.S. and the world that will not support intensive crop production, can often times sustain grasses and forages that provide conservation of the land, and produce feeds that cattle can utilize. Beef cattle production is dispersed throughout the U.S., but a significant amount of beef is produced on the rangelands of the Western U.S. About 830,000 farms had beef cows in 2000 and almost 12 million cattle on feed annually.
Beef cattle production ranges from the beef cow herd that typically graze on pastureland or graze the remaining residue on the land after grain harvest to growing and finishing young cattle in feedlots. The feedlot-housing systems used in beef cattle production typically varies by climate and can range from open earthen lots with very little shelter to open shed and lot or an enclosed confinement building. Manure handling and storage ranges from solid manure with bedding included, and runoff water from open lots to liquid slurry and treatment lagoon systems. Due to the increasing size of beef operations, the large volume of manure production, collection, storage and application to the land has presented challenges.
This module will look at beef cattle production from a historical perspective, economic impact of the beef industry in the U.S., typical production practices and manure management systems used today.
- Background of Beef Production in U.S.
- Products from Beef
- Production Phases
- Manure Management
- Potential Environmental Impacts
- Study Questions
Background of Beef Production in U.S.
Beef cattle production is an important industry in the United States and throughout the world. Since beef cattle can graze forages in the open range and pasturelands, they serve a unique role in providing high quality protein for human consumption from byproducts and forage sources that humans do not consume. Considerable land in the U.S. and the world that will not support intensive crop production, can often times sustain grasses and forages that conserve the land, and produce feeds that cattle can utilize. Beef cattle production is dispersed throughout the U.S., but a significant amount of beef is produced on the rangelands of the Western U.S.
The cattle used for beef production in the U.S. historically originated from two areas of the world. These include the Bos taurus cattle from Europe and the Bos indicus from tropical countries. Bos taurus were native to the temperate countries of the UK (Scotland, England and Wales), France, Belgium, Spain, Italy, Germany, Austria and Switzerland. These cattle were used primarily for meat and milk production with other byproducts such as hides tanned for leather. Bos indicus were native cattle in the tropical countries of SE Asia, and Africa. They have the characteristic "humped back" appearance, the capability to tolerate high temperature and humidity environments, disease resistance to ticks, mosquitoes and other tropical insects, and often were used for work, meat and milk production.
According to "The Science of Animal Husbandry" by Blakely and Bade, Second edition (1979) and "Animal Science" by Gillespie (1998), when Columbus came to America, there were no domestic type animals. Cattle etc., were brought on Columbus' second voyage in 1493. Small importations continued periodically with Vera Cruz bringing the Spanish type longhorn cattle from Spain into Mexico in 1521. These cattle later spread throughout the western U.S. as they were brought to Christian missions built by the Spanish. Herds of 424,000 cattle at two missions have been recorded. More cattle were brought to the New World by Portuguese traders in 1553. The English were the first to bring large numbers of cattle to the United States when they founded the Jamestown colony in 1611. Following the American Revolution, livestock moved westward, and by the early 1800s were distributed over most of the East, the South and the far West.
The animals imported from Europe were used mainly for milk, butter, hides and draft. With wild game plentiful, meat was not the citizen's main concern. These animals under the guiding hands of notables like George Washington and Thomas Jefferson multiplied and purebred herds developed in the East.
Cattle production today has become more specialized in the U.S. with concentrations of feedlot cattle in Texas, Colorado, Nebraska, Kansas, Iowa, California and Oklahoma and cow-calf operations in Missouri, South Dakota, North Dakota, Nebraska, Kansas, Kentucky, Montana, Tennessee, and Oklahoma. Today, the U.S. ranks fourth in the world in total cattle numbers.
As the standard of living has increased throughout the world, protein consumption has increased and the overall quality of human diets has improved. Beef has become a significant protein source in the U.S. diet with nearly 70 lbs of beef consumed per person each year in the U.S. Beef is offered on the menus of most restaurants and consumption of beef is considered a status of wealth in many countries because it is usually a relatively expensive protein food source.
The size of the beef industry in the U.S. has declined gradually over the last 15 years. There were 1.0 million beef cow operations in 1986, which had declined to 0.83 million operations in 2000. The numbers of beef cows, however, have remained stable at about 33 million head. The number of cattle produced for meat consumption has also remained steady with 11.9 million on feed in 1992 compared to 11.8 million in 2001. The current annual gross sale of feedlot cattle is $36.8 billion while the total value of our beef animal inventory is estimated at $70.6 billion. The beef industry provides more than one million jobs in the U.S., creating a ripple effect in the economy. For every dollar of cattle sales, there is approximately five dollars in additional business activity generated. During the 1990s, U.S. Beef production generated more than $30 billion annually in direct economic output, plus about five times that amount per year in related economic output.
There are many beef cattle operations in the U.S., but most are small in the numbers of animals that they produce. A similar trend is shown with beef cow operations.
Products from Beef Production
Typically, we think of beef cattle being produced only for meat production for human consumption. Obviously, the meat is processed into many nutritious products, including, steaks, roasts, hamburger, sausages, etc. However, there are several valuable byproducts from the beef animal that also serve mankind. These include leather goods, fertilizers, cosmetics, drugs, hair products, perfumes, gelatin products, glues and animal feed byproducts, to name a few.
Byproducts from each 1,000 lbs steer are worth $96 ($3.4 billion annually for the U.S.) and benefits the consumer with health, clothing and nutritional products.
Segments of the Beef Industry
The beef industry encompasses all segments from conception of the animal to the delivery of food to the consumer's table. The cow-calf production sector involves breeding of cows with bulls or artificial insemination, conception, gestation, birth of the calf and lactation periods until weaning of the calf from the cow. The calf is weaned at approximately 500 to 600 lbs. live weight or about 6 to 8 months of age. From this age, the calves are usually fed on grassland until they weigh approximately 750 to 800 lbs. live weight when they are called stocker cattle. Stocker calves are placed in a confinement feedlot for approximately 90 to 120 days until they reach a live weight of 1100 to 1250 lbs. On some farms, depending on the availability of feed, weaned calves may be placed directly into a confinement feedlot for growing and finishing, skipping the grassland phase.
In today's specialized beef industry, one producer may operate a cow-calf business producing weaned calves, another producer may background the calves on forage or pastureland, and still another may finish the stocker cattle in the feedlot. Some cattle businesses manage all three sectors of beef production; however, these are typically relatively small production units. Often, several large producers from the various phases form alliances to enhance the flow of cattle through the process. Also, there are specialized heifer replacement operations with the objective of producing genetically superior females to be placed into breeding herds to supply better calves for beef production.
Life cycle of beef cattle
After a calf is weaned from the cow at about 6 to 8 months of age, bull calves are typically castrated and ultimately, fed until market weight. Genetically superior bull calves are separated out for use in breeding programs. Heifers that will be kept in the herd reach sexual maturity by 15-months of age and are bred to deliver their first calf when they are 24-months of age. The gestation period for beef cattle is 9 months. Following the first calf, the female, now a cow, is rebred after a two to three month period and another calf delivered 9 months later. The goal is a 12-month calving interval. The average cow will stay productive in a breeding herd for 7 to 9 years if no disease or physical problems develop.
Feeding beef cattle
Beef cattle, like other ruminants, possess a digestive system that includes a multi-compartment stomach that can digest fibrous materials such as grass, corn stalks, cottonseeds, alfalfa and grass hays, etc. Bacteria and protozoa that reside in cattle's stomach make it possible to release nutrients from fibrous feeds that can be utilized by the animal. Unlike most other animals, cattle can consume byproduct feeds like corn gluten, distiller's grains, brewer's grains, potato chips, soybean hulls, citrus pulp and other products that are considered waste products. Cattle are also fed protein sources, such as soybean meal, canola meal, alfalfa and urea, and cereal grains such as corn, sorghum, barley, wheat, and oats. Generally, feedlot cattle are fed predominantly high quality fibrous diets early in their growth periods and high-energy cereal grain diets during the finishing periods. The breeding herd commonly grazes fibrous forages from pastureland, rangeland and from field residues, such as corn stalks. A mature cow consumes about 5 tons of fibrous feed (forages) per year.
Beef cattle consume feeds that range from high quality cereal grains such as corn, soybeans, wheat, barley, sorghum, etc. called concentrates to high and low quality fibrous feeds such as legume hays, i.e., alfalfa, clover, birdsfoot trefoil, soybeans, etc.; grass hays, i.e., brome, timothy, fescue, blue grass, coastal bermuda, etc.; mixtures of legumes and grasses; corn stalk residue, soybean residue, winter wheat, and other forages. The quality of forages can vary greatly depending upon the maturity and time of harvest, fertilization practices, method of harvest and preservation. Formulating a diet to meet specific animal needs requires knowing the nutrient content of the forage and balancing the diet with appropriate grains, minerals and vitamins. Forages can be preserved dry as hay in the form of large round bales or small rectangular bales, or fermented in the absence of oxygen by chopping the forage into smaller particle size and placed in storage structures called a silo. Silos can be upright above ground containers, horizontal concrete structures or horizontal plastic containers. All of these structures must be sealed for the anaerobic fermentation process to succeed in preserving the forage. Fermenting preserves the nutrient value of the feed so that it can be stored for a long time without spoilage. As mentioned before, beef cattle can consume fibrous feed sources and byproducts (waste products from other industries) that humans and non-ruminant animals (pigs and chickens) cannot consume. Thus, beef cattle provide a high quality, value-added protein source for humans from lower quality feed resources.
Feedlot cattle are commonly fed in open fence-line bunk feeders with the producer delivering the feed daily using a tractor and feed wagon, or by mechanical feed delivery systems to a stationary feed bunk. The cowherd normally obtains the majority of their diet from grazing, however, salt-mineral blocks (sometime fortified with protein and vitamins) and possibly a concentrate mix (predominantly cereal grains and protein) are fed during the winter or drought seasons when the quality of the pasture is poor. Generally, crop residues, such as corn stalks, require supplemental grains or protein and minerals at certain times of the life cycle (especially late in pregnancy and during early lactation) of the breeding herd.
Housing systems for beef cattle in confinement feedlots vary, depending on the climate in the area and topography of the site. They include total confinement buildings, open sheds and lots or open lots with windbreaks and/or shades. The lots are usually paved if located in humid climates to minimize mud problems. Beef cattle are hearty animals that tolerate a wide range of climatic conditions. Most buildings have open sidewalls and are naturally ventilated. Open sheds and lots are typically positioned to allow for protection from prevailing winds and maximize sun exposure during winter. In summer, shades and open areas allow for cooling and air movement. In arid climates, sprinkler systems are used in hot weather for cooling as well as for dust control.
In most confinement buildings or in a loafing sheds, with the shed and lot system, bedding on a solid floor is used to keep cattle dry. Some cattle are housed in a confinement building with total slotted floors where the manure drops into a storage container beneath the floor. However, this system in not commonly used today because of cost and potential feet and leg problems. In humid regions of the U.S. (Midwestern, Northeastern and Southeastern U.S.) cattle are often housed in a paved, or partially paved, feedlot with a loafing shed containing bedding for comfort of the cattle and a large fenced area for the cattle to use as an exercise area. In more arid areas (Western and Southwestern U.S.), cattle are reared in earthen lots with only windbreak fences and/or shades to protect the cattle during inclement weather.
The cowherd may also be housed in feedlots during the winter season or during calving season to facilitate closer observation of any calving problems. More typically, however, the breeding herd grazes pastures, rangeland or cornstalks and other crop residues after harvest. In most cases, the breeding herd is on the open range or pasture for 9 to 12 months of the year.
Manure Management System
Beef cattle manure can be handled as a solid, semi-solid or a liquid. The bedding used in loafing sheds will form a manure pack with the manure incorporated into the bedding material. Common bedding materials include, straw, sand, wood shaving, sawdust, recycled newspaper print, and chopped corn stalks. Generally, the manure pack is removed once or twice a year and spread onto cropland or pastureland for use as a fertilizer resource. Solid manure scraped from open lots is usually applied to cropland after removal, or stockpiled in a solid manure storage facility near the feedlot. Solid manure storage is generally in a structure with a paved floor and walls on three sides to allow the material to be stacked. In humid areas, manure storages may need to be covered to keep the manure drier. Solid manure is surface applied to cropland with a box-type manure spreader or a flail-type manure spreader. Clean up-slope runoff water and roof water should be diverted around the manure storage to minimize the amount of storage needed.
Manure in a liquid or semi-solid form (slurry) is generally stored for at least 180 days before removal and application to cropland or pastureland. Depending on the site, pumps, transfer pipes or channels may be required to move the manure from the animal housing areas to storage. Semi-solid manure is stored in either above ground concrete or steel tanks or below ground earthen or concrete tanks. Liquid manure may be stored in formed tanks, earthen storages, or in earthen lagoons that can consist of one cell or more cells. Lagoons provide treatment of the manure (by anaerobic, aerobic or a combination of aerobic and anaerobic processes) as well as storage. Composting is another option for solid manure management.
Runoff from open cattle lots must be controlled, especially during heavy rainfall events. Runoff control systems include settling basins (to remove manure solids) in combination with earthen detention ponds; transfer of runoff into a lagoon system; or for small feedlots, a settling basin in combination with grass infiltration areas.Equipment to transfer and apply manure to cropland includes tanker wagons and trucks that can spread manure on the surface or inject it directly beneath the soil surface or irrigation systems with stationary or moving delivery systems. Very dilute liquids can often be applied with irrigation systems.
More Manure Images
(Adapted in part from Livestock and Poultry Environmental Stewardship Curriculum, MidWest Plan Service; and Proposed US EPA Confined Feeding Rule.)
USEPA's 1998 National Water Quality Inventory indicates that agricultural operations, including animal feeding operations (AFOs), are a significant source of water pollution in the U.S. States estimate that agriculture contributes in part to the impairment of at least 170,750 river miles, 2,417,801 lake acres, and 1,827 estuary square miles (Table 1). Agriculture was reported to be the most common pollutant of rivers and streams.
However, one should not overlook the many positive environmental benefits of agriculture. For example, agricultural practices that conserve soil and increase productivity while improving soil quality also increase the amount of carbon-rich organic matter in soils, thereby providing a global depository for carbon dioxide drawn from the atmosphere by growing plants. The same farming practices that promote soil conservation also decrease the amount of carbon dioxide accumulating in the atmosphere and threatening global warming.
Other benefits compared to urban or industrial land use include greatly reduced storm runoff, groundwater recharge and water purification as infiltrating surface water filters through plant residue, roots and several feet of soil to reach groundwater.
In many watersheds, animal manures represent a significant portion of the total fertilizer nutrients added. In a few counties, with heavy concentrations of livestock and poultry, nutrients from confined animals exceed the uptake potential of non-legume harvested cropland and hayland. USDA estimates that recoverable manure nitrogen exceeds crop system needs in 266 of 3,141 counties in the U.S. (8%) and that recoverable manure phosphorus exceeds crop system needs in 485 counties (15%). It should be pointed out that while legumes are able to produce their own nitrogen, they will use applied nitrogen instead if it is available. The USDA analysis does not consider actual manure management practices used or transport of applied nutrients outside the county; however, it is a useful indicator of excess nutrients on a broad scale. Whole-farm nutrient balance is a very useful tool to identify potential areas of excess.
Air emissions from Animal Feeding Operations (AFO) can be odorous. Furthermore, volatilized ammonia can be redeposited on the earth and contribute to eutrophication of surface waters.
Animal manures are a valuable fertilizer and soil conditioner, if applied under proper conditions at crop nutrient requirements. Potential sources of manure pollution include open feedlots, pastures, treatment lagoons, manure stockpiles or storage, and land application fields. Oxygen-demanding substances, ammonia, nutrients (particularly nitrogen and phosphorus), solids, pathogens, and odorous compounds are the pollutants most commonly associated with manure. Manure is also a potential source of salts and trace metals, and to a lesser extent, antibiotics, pesticides and hormones. This problem has been magnified as poultry and livestock production has become more concentrated. AFO pollutants can impact surface water, groundwater, air, and soil. In surface water, manure's oxygen demand and ammonia content can result in fish kills and reduced biodiversity. Solids can increase turbidity and smother benthic organisms. Nitrogen and phosphorus can contribute to eutrophication and associated algae blooms which can produce negative aesthetic impacts and increase drinking water treatment costs. Turbidity from the blooms can reduce penetration of sunlight in the water column and thereby limit growth of seagrass beds and other submerged aquatic vegetation, which serve as critical habitat for fish, crabs, and other aquatic organisms. Decay of the algae (as well as night-time algal respiration) can lead to depressed oxygen levels, which can result in fish kills and reduced biodiversity. Eutrophication is also a factor in blooms of toxic algae and other toxic estuarine microorganisms, such as Pfiesteria piscicida. These organisms can impact human health as well as animal health. Human and animal health can also be impacted by pathogens and nitrogen in animal manure. Nitrogen is easily transformed into the nitrate form and if transported to drinking water sources can result in potentially fatal health risks to infants. Trace elements in manure may also present human and ecological risks. Salts can contribute to salinization and disruption of the ecosystem. Antibiotics, pesticides, and hormones may have low-level, long-term ecosystem effects.
In ground water, pathogens and nitrates from manure can impact human health via drinking water. Nitrate contamination is more prevalent in ground waters than surface waters. According to the U.S. EPA, nitrate is the most widespread agricultural contaminant in drinking water wells, and nearly 2% of our population (1.5 million people) is exposed to elevated nitrate levels from drinking water wells.
|Total Quantity in US||Amount of Waters Surveyed||Quantity Impaired by All Sources||Quantity Impaired by Agriculture|
|23% of total
|36% of surveyed
|59% of impaired
|Lakes, Ponds, and Reservoirs
|42% of total
|39% of surveyed
|31% of impaired
90,500 square miles
|32% of total
28,889 square miles
|38% of surveyed
11,025 square miles
|15% of impaired
1,827 square miles
Table 2 lists the leading pollutants impairing surface water quality in the U.S. Agricultural production is a potential source of most of these.
Table 2. Five Leading Pollutants Causing Water Quality Impairment in the U.S.
(Percent of incidence of each pollutant is shown in parentheses. For example, siltation is listed as a cause of impairment in 38% of impaired river miles.)
|1||Siltation (38%)||Nutrients (44%)||Pathogens (47%)|
|2||Pathogens (36%)||Metals (27%)||Oxygen-Depleting Substances (42%)|
|3||Nutrients (29%)||Siltation (15%)||Metals (23%)|
|4||Oxygen-Depleting Substances (23%)||Oxygen-Depleting Substances (14%)||Nutrients (23%)|
|5||Metals (21%)||Suspended Solids (10%)||Thermal Modifications (18%)|
List of Contaminants in Animal Manure:
- Oxygen-Demanding Substances
- Antibiotics, Pesticides, and Hormones
- Airborne Emissions from Animal Production Systems
- Comprehensive Nutrient Management Planning
- Study Questions
When discharged to surface water, biodegradable material is decomposed by aquatic bacteria and other microorganisms. During this process, dissolved oxygen is consumed, reducing the amount available for aquatic animals. Severe depressions in dissolved oxygen levels can result in fish kills. There are numerous examples nationwide of fish kills resulting from manure discharges and runoff from various types of AFOs.
Manure may be deposited directly into surface waters by grazing animals. Manually-collected manure may also be introduced into surface waters. This is typically via storage structure failure, overflow, operator error, etc.
Manure can also enter surface waters via runoff if it is over-applied or misapplied to land. For example, manure application to saturated or frozen soils may result in a discharge to surface waters. Factors that promote runoff to surface waters are steep land slope, high rainfall, low soil porosity, and proximity to surface waters. Incorporation of the manure into the soil decreases runoff.
Nitrogen (N) is an essential nutrient required by all living organisms. It is ubiquitous in the environment, accounting for 78 percent of the atmosphere as elemental nitrogen (N2). This form of nitrogen is inert and does not impact environmental quality since it is not bioavailable to most organisms and therefore has no fertilizer value. Nitrogen can form other compounds, however, which are bioavailable, mobile, and potentially harmful to the environment. The nitrogen cycle shows the various forms of nitrogen and the processes by which they are transformed and lost to the environment.
Nitrogen in manure is primarily in the form of organic nitrogen and ammonia nitrogen compounds. In its organic form, nitrogen is unavailable to plants. However, organic nitrogen can be transformed into ammonium (NH4+) and nitrate (NO3-) forms, via microbial processes which are bioavailable and have fertilizer value. These forms can also produce negative environmental impacts when they are transported in the environment.
"Ammonia-nitrogen" includes the ionized form (ammonium, NH4+) and the un-ionized form (ammonia, NH3). Ammonium is produced when microorganisms break down organic nitrogen products such as urea and proteins in manure. This decomposition occurs in both aerobic and anaerobic environments. In solution, ammonium is in chemical equilibrium with ammonia.
Ammonia exerts a direct biochemical oxygen demand (BOD) on the receiving water since dissolved oxygen is consumed as ammonia is oxidized. Moderate depressions of dissolved oxygen are associated with reduced species diversity, while more severe depressions can produce fish kills.
Additionally, ammonia can lead to eutrophication, or nutrient over-enrichment, of surface waters. While nutrients are necessary for a healthy ecosystem, the overabundance of nutrients (particularly nitrogen and phosphorus) can lead to nuisance algae blooms.
Pfiesteria often lives as a nontoxic predatory animal, becoming toxic in response to fish excretions or secretions (NCSU, 1998). While nutrient-enriched conditions are not required for toxic outbreaks to occur, excessive nutrient loadings can help create an environment rich in microbial prey and organic matter that Pfiesteria uses as a food supply. By increasing the concentration of Pfiesteria, nutrient loads increase the likelihood of a toxic outbreak (Citizens Pfiesteria Action Commission, 1997).
The degree of ammonia volatilization is dependent on the manure management system. For example, losses are greater when manure remains on the land surface rather than being incorporated into the soil, and are particularly high when the manure is spray irrigated onto land. Environmental conditions also affect the extent of volatilization. For example, losses are greater at higher pH levels, warmer temperatures and drier conditions, and in soils with low cation exchange capacity, such as sands. Losses are decreased by the presence of growing plants. (Follett, 1995)
Nitrifying bacteria can oxidize ammonium to nitrite (NO2-) and then to nitrate (NO3-). Nitrite is toxic to most fish and other aquatic species, but it typically does not accumulate in the environment because it is rapidly transformed to nitrate in an aerobic environment. Alternatively, nitrite (and nitrate) can undergo bacterial denitrification in an anoxic environment. In denitrification, nitrate is converted to nitrite, and then further converted to gaseous forms of nitrogen - elemental nitrogen (N2), nitrous oxide (N2O), nitric oxide (NO), and/or other nitrogen oxide (NOx) compounds. Nitrification occurs readily in the aerobic environments of receiving streams and dry soils while denitrification can be significant in anoxic bottom waters and saturated soils.
Nitrate is a useful form of nitrogen because it is biologically available to plants and is therefore a valuable fertilizer. However, excessive levels of nitrate in drinking water can produce negative health impacts on infant humans and animals. Nitrate poisoning affects infants by reducing the oxygen-carrying capacity of the blood. The resulting oxygen starvation can be fatal. Nitrate poisoning, or methemoglobinemia, is commonly referred to as "blue baby syndrome" because the lack of oxygen can cause the skin to appear bluish in color. To protect human health, EPA has set a drinking water Maximum Contaminant Level (MCL) of 10 mg/l for nitrate-nitrogen. Once a water source is contaminated, the costs of protecting consumers from nitrate exposure can be significant. Nitrate is not removed by conventional drinking water treatment processes; its removal requires additional, relatively expensive treatment units.
Nitrogen in livestock manure is almost always in the organic, ammonia or ammonium form but may become oxidized to nitrate after being diluted. It can reach surface waters via direct discharge of animal wastes. Lagoon leachate and land-applied manure can also contribute nitrogen to surface and ground waters. Nitrate is water soluble and moves freely through most soils. Nitrate contributions to surface water from agriculture are primarily from groundwater connections and other subsurface flows rather than overland runoff (Follett, 1995).
Animal wastes contain both organic and inorganic forms of phosphorus (P). As with nitrogen, the organic form must mineralize to the inorganic form to become available to plants. This occurs as the manure ages and the organic P hydrolyzes to inorganic forms. The phosphorus cycle is much simpler than the nitrogen cycle because phosphorus lacks an atmospheric connection and is less subject to biological transformation.
Phosphorus is of concern in surface waters because it can lead to eutrophication. Phosphorus is also a concern because phosphate levels greater than 1.0 mg/l may interfere with coagulation in drinking water treatment plants (Bartenhagen et al., 1994). A number of research studies are currently underway to decrease the amount of P in livestock manure, primarily through enzymes and animal ration modifications that make phosphorous in the feed more available (and usable) by the animal. This means that less phosphorus must be fed to ensure an adequate amount for the animal and, as a result, less phosphorous is excreted in the manure.
Phosphorus predominantly reaches surface waters via direct discharge and runoff from land application of fertilizers and animal manure. Once in receiving waters, the phosphorus can become available to aquatic plants. Land-applied phosphorus is much less mobile than nitrogen since the mineralized form (inorganic Phosphate) is easily adsorbed to soil particles. For this reason, most agricultural phosphorus control measures have focused on soil erosion control to limit transport of particulate phosphorus. However, soils do not have infinite phosphate adsorption capacity and with long-term over-application, inorganic phosphates can eventually enter waterways even if soil erosion is controlled.
Both manure and animal carcasses contain pathogens (disease-causing organisms) which can impact human health, other livestock, aquatic life, and wildlife when introduced into the environment. Several pathogenic organisms found in manure can infect humans.
Table 1. Some Diseases and Parasites Transmittable to Humans from Animal Manure
|Anthrax||Bacillus anthracis||Skin sores, fever, chills, lethargy, headache, nausea, vomiting, shortness of breath, cough, nose/throat congestion, pneumonia, joint stiffness, joint pain|
|Brucellosis||Brucella abortus, Brucella melitensis, Brucella suis||Weakness, lethargy, fever, chills, sweating, headache|
|Colibaciliosis||Escherichia coli (some serotypes)||Diarrhea, abdominal gas|
|Coliform mastitis-metritis||Escherichia coli (some serotypes)||Diarrhea, abdominal gas|
|Erysipelas||Erysipelothrix rhusiopathiae||Skin inflammation, rash, facial swelling, fever, chills, sweating, joint stiffness, muscle aches, headache, nausea, vomiting|
|Leptospirosis||Leptospira Pomona||Abdominal pain, muscle pain, vomiting, fever|
|Listeriosis||Listeria monocytogenes||Fever, fatigue, nausea, vomiting, diarrhea|
|Salmonellosis||Salmonella species||Abdominal pain, diarrhea, nausea, chills, fever, headache|
|Tetanus||Clostridium tetani||Violent muscle spasms, “lockjaw” spasms of jaw muscles, difficulty breathing|
|Tuberculosis||Mycobacterium tuberculosis, Mycobacterium avium||Cough, fatigue, fever, pain in chest, back, and/or kidneys|
|Q fever||Coxiella burneti||Fever, headache, muscle pains, joint pain, dry cough, chest pain, abdominal pain, jaundice|
|Foot and Mouth||Virus||Rash, sore throat, fever|
|Coccidioidycosis||Coccidioides immitus||Cough, chest pain, fever, chills, sweating, headache, muscle stiffness, joint stiffness, rash wheezing|
|Histoplasmosis||Histoplasma capsulatum||Fever, chills, muscle ache, muscle stiffness, cough, rash, joint pain, join stiffness|
|Ringworm||Various microsporum and trichophyton||Itching, rash|
|Coccidiosis||Eimeria species||Diarrhea, abdominal gas|
|Cryptosporidiosis||Cryptosporidium species||Watery diarrhea, dehydration, weakness, abdominal cramping|
|Giardiasis||Giardia lamblia||Diarrhea, abdominal pain, abdominal gas, nausea, vomiting, headache, fever|
|Toxoplasmosis||Toxoplasma species||Headache, lethargy, seizures, reduced cognitive function|
|Ascariasis||Ascaris lumbricoides||Worms in stool or vomit, fever, cough, abdominal pain, bloody sputum, wheezing, skin rash, shortness of breath|
|Sarcocystiasis||Sarcosystis species||Fever, diarrhea, abdominal pain|
The treatment of public water supplies reduces the risk of infection via drinking water. However, protecting source water is the best way to ensure safe drinking water. Cryptosporidium parvum, a protozoan that can produce gastrointestinal illness, is a concern, since it is resistant to conventional treatment. Healthy people typically recover relatively quickly from such illnesses. However, they can be fatal in people with weakened immune systems such as the elderly and small children.
Runoff from fields where manure has been applied can be a source of pathogen contamination, particularly if a rainfall event occurs soon after application. The natural filtering and adsorption action of soils typically strands microorganisms in land-applied manure near the soil surface (Crane et al., 1980). This protects underlying groundwater, but increases the likelihood of runoff losses to surface waters. Depending on soil type and operating conditions, however, subsurface flows can be a mechanism for pathogen transport.
Soil type, manure application rate, and soil pH are dominating factors in bacteria survival (Dazzo et al., 1973; Ellis and McCalla, 1976; Morrison and Martin, 1977; Van Donsel et al., 1967). Experiments on land-applied poultry manure have indicated that the population of fecal organisms decreases rapidly as the manure is heated, dried, or exposed to sunlight on the soil surface (Crane et al., 1980).
Antibiotics, Pesticides, and Hormones
Antibiotics, pesticides, and hormones are organic compounds which are used in animal feeding operations and may pose risks if they enter the environment. For example, chronic toxicity may result from low-level discharges of antibiotics and pesticides. Estrogen hormones have been implicated in the reduction in sperm counts among Western men (Sharpe and Skakkebaek, 1993) and reproductive disorders in a variety of wildlife (Colburn et al., 1993). Other sources of antibiotics and hormones include municipal waste waters, septic tank leachate, and runoff from land-applied sewage sludge. Sources of pesticides include crop runoff and urban runoff.
Little information is available regarding the concentrations of these compounds in animal wastes, or their fate/transport behavior and bioavailability in waste-amended soils. These compounds may reach surface waters via runoff from land-application sites.
With the trend toward larger, more concentrated production operations, odors and other airborne emissions are rapidly becoming an important issue for agricultural producers.
Whether there is a direct impact of airborne emissions from animal operations on human health is still being debated. There are anecdotal reports about health problems and quality-of-life factors for those living near animal facilities have been documented.
Source of Airborne Emissions
Odor emissions from animal production systems originate from three primary sources: manure storage facilities, animal housing, and land application of manure.
In an odor study in a United Kingdom county (Hardwick 1985), 50% of all odor complaints were traced back to land application of manure, about 20% were from manure storage facilities, and another 25% were from animal production buildings. Other sources include feed production, processing centers, and silage storage. With the increased use of manure injection for land application, and longer manure storage times, there may be a higher percentage of complaints in the future associated with manure storage facilities and animal buildings and less from land application.
Animal wastes include manure (feces and urine), spilled feed and water, bedding materials (i.e., straw, sunflower hulls, wood shaving), wash water, and other wastes. This highly organic mixture includes carbohydrates, fats, proteins, and other nutrients that are readily degradable by microorganisms under a wide variety of suitable environments. Moisture content and temperature also affect the rate of microbial decomposition.
A large number of volatile compounds have been identified as byproducts of animal waste decomposition. O'Neill and Phillips (1992) compiled a list of 168 different gas compounds identified in swine and poultry wastes. Some of the gases (ammonia, methane, and carbon dioxide) also have implications for global warming and acid rain issues. It has been estimated that one third of the methane produced each year comes from industrial sources, one third from natural sources, and one third from agriculture (primarily animals and manure storage units). Although animals produce more carbon dioxide than methane, methane has as much as 15 times more impact on the greenhouse effect than carbon dioxide.
Dust, pathogens, and flies are from animal operations also airborne emission concerns. Dust, a combination of manure solids, dander, feathers, hair, and feed, is very difficult to eliminate from animal production units. It is typically more of a problem in buildings that have solid floors and use bedding as opposed to slotted floors and liquid manure. Concentrations inside animal buildings and near outdoor feedlots have been measured in a few studies; however, dust emission rates from animal production are mostly unknown.
Pathogens are another airborne emission concern. Although pathogens are present in buildings and manure storage units, they typically do not survive aerosolization well, but some may be transported by dust particles.
Flies are an additional concern from certain types of poultry and livestock operations. The housefly completes a cycle from egg to adult in 6 to 7 days when temperatures are 80 to 90°F. Females can produce 600 to 800 eggs, larvae can survive burial at depths up to 4 feet, and adults can fly up to 20 miles. Large populations of flies can be produced relatively quickly if the correct environment is provided. Flies tend to proliferate in moist animal production areas with low animal traffic.
Emission Movement or Dispersion
The movement or dispersion of airborne emissions from animal production facilities is difficult to predict and is affected by many factors including topography, prevailing winds, and building orientation. Prevailing winds must be considered to minimize odor transport to close or sensitive neighbors. A number of dispersion models have been developed to Airborne Emission Regulations.
Most states and local units of government deal with agricultural air quality issues through zoning or land use ordinances. Setback distances may be required for a given size operation or for land application of manure. A few states (for example, Minnesota) have an ambient gas concentration (H2S for Minnesota) standard at the property line. Gas and odor standards are difficult to enforce since on-site measurements of gases and especially odor are hard to do with any high degree of accuracy. Producers should be aware of odor- or dust-related emissions regulations applicable to their livestock operation.
Source: Lesson 40 of the LPES: Adapted from Livestock and Poultry Environmental Stewardship curriculum, lesson authored by Larry Jacobson, University of Minnesota; Jeff Lorimor, Iowa State University; Jose Bicudo, University of Kentucky; and David Schmidt, University of Minnesota, courtesy of MidWest Plan Service, Iowa State University, Ames, Iowa 50011-3080, Copyright (c) 2001.
Environmental Impacts of Animal Feeding Operations Study Questions
Identify the definition that best fits the following terms:
Comprehensive Nutrient Management Planning
Recently, the concept of Comprehensive Nutrient Management Planning (CNMP) was introduced by the U. S. Environmental Protection Agency (EPA) and U.S. Department of Agriculture’s (USDA’s) Natural Resources Conservation Service (NRCS). It is anticipated that the CNMP will serve as a cornerstone of environmental plans assembled by animal feeding operations to address federal and state regulations. EPA and NRCS guidelines for CNMP are given in Table 1.
|Table 1. Summary of Issues addressed by a CNMP as initially defined by EPA's Guidance|
|Planning components of CNMP||Issues addressed|
|A manure handling and storage plan||
|Land application plan||
|Site management plan||Soil conservation practices that minimize movement of soil and manure components to surface and groundwater|
|Record keeping||Manure production, utilization, and export to off-farm users|
|Other utilization options||Alternative safe manure utilization strategies such as sale of manure, treatment technologies, or energy generation|
|Feed management plan||Alternative feed programs to minimize the nutrients in manure|
Beef Production Study Questions
Identify the definition that best fits the following terms: