Even on well-managed hog farms, some animals die before being marketed. For example, a 1,200-sow farm that produces 2.2 litters per sow per year and sells weanling pigs may need to dispose of 36 sow carcasses and 7,920 stillborn and other dead piglets annually. A finishing farm producing 10,000 market hogs annually should plan for the disposal of approximately 300 pigs each year (Table 1). These examples are based on a 3 percent annual mortality rate for breeding sows and market hogs and the loss of three stillborn and nursing piglets per litter produced. Farms with lower mortality rates will have lower disposal needs, and those with higher rates will have higher disposal needs. To meet this need, a practical, cost-effective, and environmentally sound means to dispose of routine death losses is essential on all hog farms.
|Table 1. Typical Swine Mortality Rates*|
|Mortality at various performance levels|
|Production stage||Weight range||Excellent||Good||Poor||Your farm|
|Birth (stillborns)||3 - 5 lb||1 pig/litter||2 pigs/litter||3 pigs/litter||___________|
|Birth to weaning||3 - 15 lb||< 10%||10 - 12%||> 12%||___________|
|Nursery||15 - 45 lb||< 2%||2 - 4%||> 4%||___________|
|Growing-finishing||45 - 270 lb||< 2%||2 - 4%||> 4%||___________|
|Breeding sows||300 - 525 lb||< 2%||2 - 5%||> 5%||___________|
|*Adapted from Mayrose and co-authors, Pork Industry Handbook Fact Sheet No. 100, 1991.|
Traditional mortality disposal methods on hog farms include burial, on-farm incineration, and transport to rendering plants. Mortality composting was initially developed as a means of disposing of dead birds on poultry farms. More recently, composting has become an accepted method of dead swine disposal in some states. Table 2 summarizes the advantages and disadvantages of the traditional methods of dead swine disposal and mortality composting. For producers willing to learn the principles of composting and who can provide adequate management, composting is an effective method of dead swine disposal that is safe, biosecure, and environmentally sound.
|Table 2. Advantages and Disadvantages of Swine Mortality Disposal Methods|
|Method||Advantage (+) or Disadvantage (-)|
|Burial||(+) Prompt burial gets dead stock out of public view.|
(+) Prompt burial coverage prevents odor, flies, and scavengers.
(-) Poor or delayed coverage can result in odor, flies, and scavengers.
(-) Burial pits can collect rainwater.
(-) Depending on burial location, groundwater could be contaminated.
(-) Virginia regulations require permits for the burial of waste materials including animals.
(-) Burial pits can be difficult to dig in winter.
|Incineration||(+) Prompt incineration gets dead stock out of public view.|
(+) Modern incinerators reduce carcasses to ash and are biosecure.
(-) Older, less efficient incinerators may generate smoke and odor.
(-) Modern incinerators have large capital costs and fuel requirements of one to two gallons per hour.
(-) Virginia law requires that incinerators be equipped with an "afterburner" for pollution control.
(-) Virginia law requires a separate Department of Environmental Quality Permit for on-farm incinerators.
|Rendering||(+) Rendering converts animal mortality to useful by-products.|
(+) Prompt transport to rendering plants removes dead stock from the farm.
(-) Storage of dead hogs in "dead boxes" or other methods prior to hauling can cause odor and attract flies and scavengers.
(-) There are only a few rendering plants in Virginia that process dead stock.
(-) Some rendering plants charge fees for accepting carcasses.
(-) Vehicles and personnel traveling to and from the farm and rendering plant can compromise biosecurity.
|Composting||(+) Proper composting generates minimal odor, fly, or scavenger problems.|
(+) Prompt composting gets dead stock out of public view.
(+ Proper composting has low potential for pollution and produces a final product that can improve soil tilth and fertility.
(+) On-farm composting is considered biosecure.
(-) A readily available supply of carbon-rich bulking material such as sawdust, cotton-gin trash, or other suitable material is required.
(-) Some initial capital cost is necessary for construction of composting facilities.
(-) Poorly managed compost units (inadequate bulking material, delayed carcass coverage, etc.) will result in odors and attract flies and scavengers.
The Process. When composting swine mortality, the dead animals, which are nitrogen-rich, are fully covered with and allowed to react with carbon-rich materials such as sawdust, cotton-gin trash, chopped cornstalks, or other similar material. Naturally occurring bacteria in the mixture then cause the conversion of these components into humic acids, bacterial biomass, and compost. During the process, carbon dioxide, water vapor, and heat are generated as by-products. In mortality composting, it is essential that each carcass, large or small, be fully covered and surrounded with the bulking agent to allow for the complete interaction of the carbon- and nitrogen-rich materials and to absorb the moisture and odors released by the carcass. The bulking agent also serves as an insulator to retain the heat and moisture that is generated during the composting process.
The bacteria involved in the composting process are aerobic, meaning they require oxygen. They are also thermophilic, meaning they thrive in warmer temperatures. Since the bacteria do the work of reducing dead swine to compost, it is important to understand their requirements. In fact, the compost pile and the resident bacteria can be considered a "living" organism that must be cared for if it is to process swine mortality successfully.
Nutrient Balance. Composting bacteria require the appropriate balance of carbon and nitrogen in the medium. Observations of successful composting units indicate that a carbon to nitrogen ratio of 20:1 to 35:1 directly around carcasses within the pile is optimum. Using high-carbon bulking agents such as sawdust, cotton-gin trash, chopped straw, or chopped corn stalks will generally produce a good balance of carbon to nitrogen in and around the carcasses. Poultry litter has been used successfully as a bulking agent. However, poultry litter and pig carcasses alone result in a lower carbon to nitrogen ratio. Blending higher carbon material such as sawdust with broiler litter will elevate the carbon to nitrogen ratio and improve composting performance.
Particle Size, Porosity, and Quantity of Coverage Material. Demonstration work with composting indicates that the physical characteristics of the bulking agent are also important. For aerobic bacteria to thrive, bulking agents that allow 25 percent to 30 percent free airspace within the pile should be used. Coarse, damp sawdust has excellent physical properties for composting dead swine because it forms a stable pile around the carcasses, provides airspace within the pile, and helps retain heat and moisture. Ginning trash obtained from cotton gins has also performed effectively as a bulking agent in swine mortality composting. Straw or cornstalks, if chopped to reduce particle size, can be used for composting. However, long straw or cornstalks tend to form mats in a compost pile that restrict the composting process. Extremely light materials, such as peanut hulls, do not hold moisture or heat adequately and allow flies to enter the pile and odors to escape. When very low-density carbon sources such as peanut hulls are used, they should be mixed with greater quantities of denser material such as sawdust or cotton-gin trash.
The amount of high-carbon bulking material needed for a composting operation depends mainly on the quantity of mortality to be processed and on the extent to which secondary compost is recycled back into primary composting (see discussion on recycling secondary compost). Workers at the University of Missouri have recommended 100 cubic feet of sawdust per 1,000 pounds of mortality to be composted. Depending on moisture content, hardwood sawdust typically weighs about 20 to 25 pounds per cubic foot. Manager experience and judgment are the most important factors for keeping adequate quantities of material on hand to insure proper coverage of all mortalities as they occur in the operation.
Moisture. Composting bacteria require water; therefore, the compost pile should have a 45 percent to 60 percent moisture level for optimum results. To promote the heat-generating process of composting, it is often necessary to add water to compost piles when carcasses are added and covered. However, too much moisture also can restrict the composting process. Excessively wet or water-logged compost restricts free air space and loses aerobic activity. One simple test for compost pile moisture content is to take a handful of bulking material from inside the pile, firmly squeeze it, and then gently release. If water drips from the material when squeezed, it is too wet. If the material crumbles apart easily when released, it is too dry. If the material remains in some intact form when released, it is approximately the correct moisture content for composting.
Primary and Secondary Compost Phases. As with poultry composting, static pile and bin composting are the most common methods used on commercial hog farms. The main difference between swine mortality composting and poultry composting is that, for larger hogs, composting pile space and the required composting times are greater. Managing swine mortality composting in primary and secondary phases can promote a more rapid and complete breakdown of carcass material.
A primary phase compost pile starts with a base layer of absorbent, high-carbon bulking material at least 12 inches deep. Add mortalities as they occur and promptly cover them with bulking material. Assess the moisture conditions of the material each time carcasses are added. If moisture levels are too low, add water as the carcasses are placed. Place each additional carcass such that there is about eight inches of bulking material separating it from other carcasses or from the compost bin wall (Figure 1). Do not pile carcasses directly in contact with other carcasses or with compost bin walls. Take care to avoid protruding carcass parts or very thin coverage. When these situations occur, composting action on the carcass is poor and odor and fly activity will result.
Once a primary pile has been built up to a height of approximately six feet, top it off with a protective layer of bulking material and leave it to compost for two to three months. If the pile contains several large carcasses or a large number of carcasses in general, allow a primary composting time of three months. For piles containing mostly small pigs and afterbirth tissue, the required primary composting time is substantially less. Be sure that the intended primary composting time occurs from the time the last carcasses were placed in the pile. The effective management of primary and secondary mortality compost piles requires a record of the numbers, the estimated weights, and the dates carcasses were placed.
By the time a pile completes its primary phase, the internal pile moisture level and temperature will have declined substantially. You may then turn the pile to form a secondary compost pile (Figure 1). Typically, you should add water to the material as it is turned. The added air and moisture associated with turning primary compost into secondary piles reinvigorate the composting action and cause the temperature to rise. The reinvigorated secondary compost allows for further breakdown of the remaining carcass tissues, cartilage, and bones. After two to three months in a secondary phase pile, the remaining mortality material is sufficiently broken down to allow for further storage or agricultural land application. Some larger bony material, such as skulls, femur bones, and blade bones may remain after the secondary phase of composting (Figure 2); however, these are usually easily broken and are relatively non-odorous and inert.
Recycling Secondary Compost Material. One valuable use for compost material that has completed or nearly completed a secondary composting phase is recycling it as bulking material for primary compost piles. Experience at the Virginia Tech Tidewater Agricultural Research and Extension Center (AREC) swine unit and other locations indicates that secondary compost material can replace up to half of the bulking material when loading carcasses into new primary piles. In fact, using some secondary material in primary compost piles actually enhances composting when fresh carcasses are placed into primary piles.
Determining if the Process Is Working. The most practical means of determining if a compost pile has the correct blend of ingredients and is functioning properly is to check the internal pile temperature. A long-stem compost thermometer is an essential tool for anyone employing composting for mortality disposal (Figure 3). Within two to four days after loading carcasses into a pile, or after mechanically turning a primary compost pile, the internal temperature should increase. The carcass decomposition rate in a compost pile is most rapid within a temperature range of 110° to 150°F. Maintaining a temperature range between 130° and 150°F for five days is considered necessary for the destruction of pathogens. Ideally, a freshly loaded or recently turned compost pile will maintain an internal pile temperature of 130° to 150°F for about two weeks followed by a gradual decline in internal pile temperature. Internal pile temperatures above 160°F are excessive and are actually detrimental to the compost bacteria population. They may also increase the risk of pile combustion. For these reasons, limit the height of active compost piles to approximately six feet (see discussion on troubleshooting in Table 5).
Surfaces on which to Compost Mortality. If properly located, it is feasible to safely compost swine mortalities on compacted earth surfaces. However, experience has demonstrated that composting on a hard, impervious surface has significant advantages. The most commonly used surface is formed concrete that has been designed to support heavy equipment such as a tractor equipped with a front-end loader. A concrete surface facilitates pushing and scooping compost material with mechanical equipment and completely eliminates the potential for leaching at the pile base. Another important consideration is that the USDA Natural Resources Conservation Service (USDA-NRCS) Conservation Practice Standards (Code 316, Animal Mortality Facility) require that mortality composting units be constructed on concrete. Therefore producers seeking to participate in the USDA backed cost share or other conservation programs must follow these guidelines.
Roofed Structures for Composting. A well-planned roofed structure with multiple bins allows for better moisture control and better overall management of mortality composting. A pole-type structure with a concrete slab floor may be constructed using treated poles and lumber with trusses or rafters covered with metal roofing (Figure 5). Typically, the treated support poles are set first and the concrete floor is then formed and poured around the poles. An alternative construction method that has been used successfully is to construct both the floor and bin sidewalls out of formed concrete (Figure 6). You should consult a public (USDA-NRCS or Cooperative Extension) or private design engineer when planning a composting structure.
Siting a Mortality Composting Unit. Factors to consider when determining a site for a swine mortality composting unit include ease of operation, public perception, and environmental safeguards. A composting unit should be convenient to the hog barns so that dead pigs can be moved and placed in the compost promptly. There should be easy access and operational room for equipment used in loading, turning, and unloading compost from bins or stationary piles.
Although it is an essential component of livestock production, moving and handling dead animals is not aesthetically pleasing. If possible, it is best to site composting facilities out of direct public view. Trees or other visual screens may be helpful for this purpose. A well-constructed, well-maintained composting facility looks similar to other practical farm structures and can actually improve the overall appearance of mortality handling on the farm.
The site must be well drained and not prone to flooding or the pooling of water around the composting unit. All-weather access is essential. The required minimum distance from a well is 100 feet; a distance of at least 200 feet is recommended. Plumbing a water source to the unit is important so that water can be added to compost piles as needed. The site should be chosen and managed to prevent any seepage or direct runoff from compost piles into ditches, streams, or any other surface waters or sensitive areas. Maintaining grass or other vegetative ground cover around the compost work area helps to assure runoff prevention and improves overall appearance.
Sizing a Mortality Composting Unit. Compost units must be properly sized for individual swine operations. Indeed, adequate size of compost bins can be considered another requirement for composting bacteria. A composting unit is intended for routine mortality, not large, single event death losses such as a major disease outbreak or a barn fire. To properly size the composting unit, you need an estimate of the weight of average daily mortalities. You can determine the weight using farm production records or industrywide averages (Table 1).
Secondly, you must calculate the necessary volume of primary and secondary composting bins. There should be at least 20 cubic feet of primary bin volume for every pound of average daily mortality. Moreover, the number and volume of secondary composting bins should equal that of the primary bins. Some storage space for additional bulking agent material may also be built into the system or located close by.
The bin dimensions must also be determined. The height of a compost bin should accommodate a maximum compost pile height of six feet and bin width should be at least 1-1/2 times the width of the mechanical equipment that will be used to load and unload the bins. Sows and larger market hogs require a minimum bin size that allows laying individual carcasses in the bin for complete coverage with bulking material. Minimum compost bin floor dimensions of 7-1/2 by 10 feet are suggested for sows and 5-1/2 by 8 feet for market hogs. Table 3 provides examples of calculating the primary and secondary composting bin space needed for a swine finishing farm and a farrow-to-wean sow farm.
|Table 3. Example calculations for determination of bin volume and number of bins for swine mortality composting|
|Example A: Finishing farm marketing 10,000 head annually|
|Farm death loss rate:||3% of all pigs placed|
|Average weight of dead pigs:||150 lb|
|Calculate average daily mortality weight:||3% x 10,000 pigs = 300 dead pigs annually|
300 deads x 150 lb average wt = 45,000 lb annually
45,000 lb ÷ 365 days/year = 124 lb average daily mortality
|Calculate volume of primary bin space needed:||124 lb x 20 cu ft/lb = 2,480 cu ft|
|Calculate number of primary bins to construct:||Assume 400 cu ft bins (8' x 10' x 5' [width x depth x height])|
2,480 cu ft ÷ 400 cu ft/bin = 6.2 or 7 primary bins
|Secondary bins to construct:||Equal to primary bins or 7 secondary bins|
|Total 400 cu ft bins:||14 bins with 8' x 10' x 5' dimensions for each bin|
|Example B: 1,200-Sow farrow-to-wean farm producing 2.2 litters/sow/year|
|Stillborn and nursing piglet losses:||3 pigs per litter|
|Average weight of stillborn and dead piglets:||4 lb|
|Weight of dead piglets per litter:||3 dead pigs/litter x 4 lb/pig = 12 lb/litter|
|Annual weight of stillborn and dead piglets:||2.2 litters/sow/year x 1,200 sows x 12 lb/litter = 31,680 lb|
|Sow death loss rate:||3% of all sows in herd|
|Average weight of dead sows:||440 lb|
|Annual weight of dead sows:||3% x 1,200 sows x 440 lb/sow = 15,840 lb|
|Calculate average daily mortality weight:||31,680 lb dead piglets/year + 15,840 lb dead sows/year = 47,520 lb|
47,520 lb ÷ 365 days/year = 130 lb average daily mortality
|Calculate volume of primary bin space needed:||130 lb x 20 cu ft/lb = 2,600 cu ft|
|Calculate number of primary bins to construct:||Assume 500 cu ft bins (10' x 10' x 5' [width x depth x height]) 2,600 cu ft ÷ 500 cu ft/bin = 5.2 or 6 primary bins|
|Secondary bins to construct:||Equal to primary bins or 6 secondary bins|
|Total 500 cu ft bins:||12 bins with 10' x 10' x 5' dimensions for each bin|
Like other types of compost, properly processed swine mortality compost has beneficial characteristics as a soil amendment. The granular organic material that comprises finished compost can improve the tilth and water holding capacity of soils. Mortality compost also contains substantial quantities of plant nutrients. When applied properly, these nutrients can be used in crop production systems similar to the ways other organic fertilizer sources are used. In this regard, swine mortality compost has many of the same attributes as livestock manures and poultry-house litter.
The nutrient content of finished compost varies depending on the carbon sources used and the quantity of mortalities that are processed through the system. The degree to which secondary compost is recycled into primary compost piles will also affect the nutrient content of the final product and the frequency of land application. In general, as more mortalities are processed and secondary compost is recycled through the system, the more the nutrient density of the final product will increase. Table 4 illustrates variation in nutrient concentration of mature swine mortality compost from selected bins at the Virginia Tech Tidewater AREC mortality compost unit. The carbon source used as a bulking agent was primarily hardwood sawdust but some cotton-gin trash was used as well. The typical nutrient concentration for poultry litter is included for comparison.
As with all fertilizers, mortality compost should be applied in a manner that is agronomically sound and environmentally safe. Periodic analysis is important for land application systems because the nutrient composition of mortality compost varies substantially. You can use conventional manure spreading equipment to spread compost on crop or forage fields. You can also use gravity flow spinner-type spreaders if the compost moisture level is not excessive. On farms that maintain a Virginia Pollution Abatement (VPA) permit, land application of compost must be done in accordance with the farm nutrient management plan. This plan is an enforceable component of the VPA permit. Even on farms not required by permit to file a nutrient management plan, it is highly recommended that mortality compost be land applied in a manner that is consistent with crop nutrient needs and to prevent nutrient runoff. Specialists with the Virginia Department of Conservation and Recreation, USDA-NRCS, Soil and Water Conservation Districts, or Virginia Cooperative Extension can offer assistance in development of waste nutrient management plans.
|Table 4. Assayed nutrient content of mature secondary phase swine mortality compost|
|Moisture||Total N||N as NH4||P as P2O5||K as K2O|
|Mortality Compost - 1||39||52||11||14||14|
|Mortality Compost - 2||32||50||9||13||11|
|Mortality Compost - 3||36||45||10||11||13|
|Mortality Compost - 4||31||69||11||29||15|
|* Mortality compost samples are from the Virginia Tech Tidewater AREC swine mortality compost unit in 2002. Poultry litter values are for comparison and represent an average of 1,054 samples reported by the Virginia Department of Conservation and Recreation.|
Varmints. Mice in search of nesting places may be attracted to the crevices between compost bins, but they generally are harmless. More troublesome varmints, such as stray dogs, foxes, opossums, and scavenging birds, such as vultures and buzzards, can become problems at mortality composting sites. Inadequate carcass coverage, exposed carcass parts, and low composting temperatures will encourage these varmints. However, in properly constructed, well-managed composting facilities, unwanted animals are not a problem.
Insects. A variety of insects and arthropods such as earwigs, red-legged ham beetles, and centipedes may inhabit mortality compost piles. The vast majority of these should be considered beneficial or harmless. The most negative potential insect pests associated with compost piles are common house flies and green bottle flies. Some fly activity around livestock and poultry facilities is normal. But elevated fly populations at mortality compost units are indicators of poor compost management. Poor carcass coverage, low composting temperatures, excessive moisture, and seepage at the base of compost piles all contribute to heavy fly activity.
Troubleshooting. Correcting problems that may occur in mortality composting involves understanding the principles of effective composting. Consistently low temperatures or the failure of temperatures to increase after turning or carcass placement indicate that the compost requirements are not being met. Things to check for include poor carcass placement, inadequate aeration inside the pile, excessively wet or excessively dry compost. If the compost pile is too wet it should be turned and drier bulking material added to the pile during the process. If it is too dry, the pile should be turned and water added during the process. In some circumstances, the internal pile temperature may become excessively high (greater than 160°F). In this situation, the pile should be turned to release heat and part of the pile moved to reduce pile depth.
If excess fly activity or intense odors are observed, piles should be checked for exposed carcass parts or shallow coverage. Add fresh bulking material or recycled secondary compost for proper coverage. Low compost temperatures may also contribute to greater fly activity and may indicate that the moisture content or particle size of the bulking material may not be acceptable. Seepage at the base of compost piles is unsightly, attracts flies, and generates odor. Small amounts of seepage can be corrected in future piles by having a sufficient layer of absorbent bulking material form the base of the pile. If excessive seepage is observed, the piles causing the problem should be turned and absorbent bulking material added during the process.
At this writing, the only entry in the Virginia Code related to swine mortality disposal is item 18.2-510 entitled "Burial or cremation of animals or fowls which have died." This law, originally written in the 1950s, does not acknowledge that now the burial of waste is regulated by the Virginia Department of Environmental Quality (DEQ). Permits for the burial of waste materials, including animals, are required. The DEQ recommends that burial should take place only as a last resort and primarily in cases where the spread of disease is a concern as determined by the State Veterinarian. In addition, the DEQ recommends that the preferred methods of dead stock disposal include rendering, composting, and, when applicable, disposal in a permitted sanitary landfill.
Regulatory consultants at the DEQ have indicated that, when it is performed properly, composting to dispose of routine swine farm mortality is exempt from permitting requirements under an agricultural exemption.
Technical assistance for establishing mortality composting systems and facility design is available from Virginia Cooperative Extension, the Virginia Department of Conservation and Recreation, and state and local offices for the USDA-NRCS. Technical standards for composting animal mortality in Virginia have been developed by the USDA-NRCS as Conservation Practice Standard Code 316, Animal Mortality Facility. In some cases, producers who wish to construct mortality composting facilities for improved mortality disposal and soil and water protection may be eligible for programs that offer cost-share assistance, low-interest loans, or tax-credit benefits. Participation in such programs typically requires that USDA-NRCS technical specifications for the practice be met in order to receive program benefits.
|Table 5. Summary of general operating procedures for composting swine mortality|
|Site for composting|
|Sizing of compost unit|
|Management (Primary bins)|
|Management (secondary bins)|
Collins, E.R. 1992. Composting Dead Poultry, Virginia Cooperative Extension publication 442-037. Virginia Cooperative Extension, Virginia Tech, Blacksburg, Virginia.
Fulhage, C.D., and Ellis, C. E. 1996. Composting Dead Swine, University of Missouri Cooperative Extension publication WQ351, University of Missouri, Columbia, Missouri.
Langston, J., Carman, D., Van Devender, K., and Boles, J.C. Jr. 1997. Disposal of Swine Carcasses in Arkansas, University of Arkansas Cooperative Extension publication MP392. University of Arkansas, Little Rock, Arkansas.
Murphy, D.W., Estienne, M.J., Dobbins, C.N., and Foster, K.A. 1995. Disposal of Dead Swine, Pork Industry Handbook Fact Sheet no. 133. Purdue University Cooperative Extension, West Lafayette, Indiana.
Natural Resource, Agriculture, and Engineering Service (NRAES). 1999. Field Guide to On-farm Composting. Cornell University Cooperative Extension, Ithaca, New York.
University of Minnesota. 1999. Composting Animal Mortality - Resource Handbook, University of Minnesota West Central Research and Outreach Center, Miscellaneous publication 100-1999. University of Minnesota, Minneapolis, Minnesota.
USDA Natural Resources Conservation Service (NRCS). 2003. Virginia Interim Conservation Standard: Animal Mortality Facility, Technical Guide, Section IV, 316-Interim-VA-1. USDA Natural Resources Conservation Service, Richmond, Virginia.
USDA Natural Resources Conservation Service (NRCS). 2003. Virginia Interim Conservation Standard: Composting Facility, Technical Guide, Section IV, 317-VA-1. USDA Natural Resources Conservation Service, Richmond, Virginia.
Financial support for composting work at the Virginia Tech Tidewater Agricultural Research and Extension Center and the development of this publication was provided by:
The Virginia Agricultural Council
P.O. Box 1163
Richmond, VA 23218
The Virginia Pork Industry Board
1100 Bank Street
Richmond, VA 23219
The thoughtful reviews by these individuals are gratefully acknowledged.
Extension Agent, Environmental Sciences
Rockingham County Extension Office
925 Pleasant Valley Road
Harrisonburg, VA 22801
Regulations and Program Consultant
Virginia Department of Environmental Quality
P.O. Box 10009
Richmond, VA 24061
Extension Soil Scientist
421 Smyth Hall
Virginia Tech (0403)
Blacksburg, VA 24061
1606 Santa Rosa Road
Richmond, VA 23229
Nutrient Management Specialist
Virginia Department of Conservation and Recreation
11632 Highway 15 South
Clarksville, VA 23927
Associate Professor of Animal Science
3420 Litton-Reaves Hall
Virginia Tech (0306)
Blacksburg, VA 24061
Service, Illustration, and Informational Assistance
Terry Lee, Virginia Tech Tidewater AREC
Doug Redd, Virginia Tech Tidewater AREC
Phil Taylor, Virginia Tech Tidewater AREC
Gene Whitley, Virginia Tech Tidewater AREC
Gail White, Virginia Tech Tidewater AREC
Duane Reese, University of Nebraska
Gary Thome, National Pork Board Swine Educators Committee
Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Interim Administrator, 1890 Extension Program, Virginia State University, Petersburg.
May 1, 2009