Environmental management practices in U.S. pork production differ greatly by geography, according to Eric Bush, DVM and NAHMS staff veterinarian for USDA's Animal and Plant Health Inspection Service. He recently presented results of an environmental study contained in the NAHMS Swine 2000 report.

The environmental study had two major goals: to estimate frequency of good environmental practices on hog farms, and to determine the extent to which odor control methods have been tried or adopted.

In assessing those goals, the survey evaluated manure storage and handling; manure application; nutrient management plans; testing of manure, water, soil and air; and carcass disposal, explains Bush.

Last spring's survey compared methods used in 17 states in four regions — Minnesota, Wisconsin, Michigan and Pennsylvania (north); Iowa, Illinois, Indiana and Ohio (east central); Colorado, South Dakota, Nebraska, Kansas and Missouri (west central); Oklahoma, Texas, Arkansas and North Carolina (south).

Manure Systems Used

Mechanical scraper was the most typical means of waste management used in gestation, particularly in the northern and east central regions, with 32.5% of respondents using that technology, reports Bush. In those areas, half the sites use open buildings with outside access (see Table 1).

Table 1. Waste Management Systems (Gestation)
Type Northern West Central East Central Southern All Sites
Holding pit, % 23.9 14.6 20.3 14.6 19.4
Mechanical scraper/tractor, % 41.3 10.1 41.9 3.7 32.5
Hand-cleaned, % 14.6 20.0 21.2 12.0 19.1
Flush-under slats, % 3.9 5.8 3.3 37.2 5.9
Flush-open gutter, % 1.7 3.0 0.7 7.8 1.8
Other, % 5.3 12.4 6.1 2.7 7.2
None, % 9.3 34.1 6.5 22.0 14.1
Total, % 100.0 100.0 100.0 100.0 100.0


The pit recharge system of shallow pits and pull-plug waste removal was the second most frequently used system on gestation sites.

Notably in the western and southern regions, where facilities were located on a lot or pasture, no waste management method was used during gestation on several sites, Bush explains.

For farrowing, holding pit (34.7%) and hand cleaning (23.6%) were the top two waste management systems used. In the south, flush under slats predominated (see Table 2).

Table 2. Waste Management Systems (Farrowing)
Type Northern West Central East Central Southern All Sites
Holding pit, % 37.3 22.6 40.9 16.0 34.7
Mechanical scraper/tractor, % 19.9 6.5 14.2 3.3 13.0
Hand-cleaned, % 26.2 30.7 21.0 10.1 23.6
Flush-under slats, % 10.5 17.8 12.7 45.9 15.3
Flush-open gutter, % 4.2 4.2 4.6 4.6 4.4
Other, % 0.4 6.6 3.7 1.7 3.6
None, % 1.5 11.6 2.9 18.4 5.4
Total, % 100.0 100.0 100.0 100.0 100.0


Flush under slats was also the most common waste-holding method used in southern nurseries (46.6%). For the rest of the country, holding pits were most commonly used by 51.6% of respondents (see Table 3).

Table 3. Waste Management Systems (Nursery)
Type Northern West Central East Central Southern All Sites
Holding pit, % 53.2 31.2 62.3 18.7 51.6
Mechanical scraper/tractor, % 13.7 10.4 9.9 2.4 10.4
Hand cleaned, % 17.3 21.9 8.0 10.5 12.9
Flush-under slats, % 9.8 21.2 12.2 46.6 15.5
Flush-open gutter, % 4.4 3.6 0.8 3.3 2.3
Other, % 0.6 4.8 1.6 1.7 2.0
None, % 1.0 6.9 5.2 16.8 5.3
Total, % 100.0 100.0 100.0 100.0 100.0


Holding pits, with 47.1% of sites reporting, were most frequently used for manure collection in grow-finish systems, except in the south, where flush under slats was more common. Registering second was mechanical scraper/tractor as indicated by 28.4% of respondents (see Table 4).

Table 4. Waste Management Systems (Grow-Finish)
Type Northern West Central East Central Southern All Sites
Holding pit, % 59.9 33.6 48.3 27.7 47.1
Mechanical scraper/tractor, % 28.0 18.5 33.7 4.1 28.4
Hand cleaned, % 5.6 14.2 9.9 6.6 9.6
Flush-under slats, % 2.2 6.9 2.2 44.5 5.1
Flush-open gutter, % 0.5 7.7 1.4 4.4 2.5
Other, % 1.8 8.2 2.2 1.7 3.1
None, % 2.0 10.9 2.3 11.0 4.2
Total, % 100.0 100.0 100.0 100.0 100.0


Manure Management

Overall, deep pits are the most frequently used method of manure storage. Lagoons are used for storage, but are also a common means of manure treatment, says Bush.

Lagoon systems show a 70-80% loss of nitrogen-phosphorus, while solid manure, daily-scrape-and-haul systems have nutrient losses of only 15-30%, notes Bush. “The two systems reflect differing goals in manure management — utilization of manure on crops or reduction of manure nutrients,” he adds.

Producers use one of two ways to manage manure — natural fertilizer to enhance crop yields and reduce synthetic fertilizer, or handling and storage treatments for reduction of nutrients in manure. On 83% of sites, handling and storage to reduce nutrients in manure is considered unimportant, although this varies tremendously by farm size, Bush says.

In contrast, on 65% of sites utilization of natural fertilizer to enhance crop yields is viewed as very important.

Figure 1 depicts the various lagoon liners used. Producers surveyed report that more than half (53.2%) of lagoons are over 10 years old. About 21% of sites include multi-stage lagoons.

In the study, more than 90% of the sites surveyed with 10,000 or more hogs had formal, written nutrient management plans, says Bush. That compares to 67% with an inventory of 2,000-9,999 head and 19.4% under 2,000 head.

Sites that were surveyed used four methods of manure application: irrigation, broadcast, surface and injection. Broadcast is still common in many parts of the country, except in the south, where irrigation is most commonly used. Surface application and injection predominate in east central states.

Except for soil sampling, relatively little environmental testing has been done in the last three years, according to the NAHMS report. Soil testing was done on more than 75% of sites. However, less than 40% of sites had one or more tests of groundwater. Manure testing was done at about 25% of sites, but a majority of large sites reported testing groundwater and manure. Testing of air quality was done on less than 5% of sites.

Odor Control

The NAHMS environmental report surveyed whether diet manipulation, manure treatment or facility modifications have been tried or adopted as odor reduction strategies.

Of that group, diet manipulation is the most frequently used strategy, points out Bush. One of the most common means by which this is achieved is reducing crude protein and supplementing with amino acids to limit the amount of nitrogen in the manure.

About 20% of sites use pelleted feed, nearly 40% feed finely ground corn and 10-15% feed phytase. About 30% control feed dust.

Very few sites report having tried a variety of available manure management methods to reduce odors. Only 15% of sites reported using biological additives, though another 15% reported trying them. Another 5% indicated use of chemicals, solid/liquid separation systems and composting solids, according to Bush.

For air quality management, producers reported that about 18% of sites have shelterbelts and 15% have windbreaks.

An impressive 96% of producers surveyed said they hadn't received an odor complaint in the last year.

Carcass Disposal

Rendering accounted for just over half of carcass disposal methods for preweaned pigs. Another 15% of young pigs were buried on-site or composted, while just under 15% were burned on the operation.

For weaned and larger pigs, 68% were handled by rendering. Almost 13% were disposed of by composting, 11.5% were buried on site and 6% were burned on the operation.