United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Veterinary Services 

Centers for Epidemiology and Animal Health March 2008 

_________________________________________________________________________________________________________________________ 

Biosecurity on U.S. Swine Sites

Biosecurity involves the use of certain management 

practices designed to prevent the introduction and 

spread of disease. Examples of these practices include: 

housing features, pig-flow techniques within and 

between management phases, restriction of new animal 

sources, quarantine and testing of new arrivals, rodent 

control and control of other animals that may be vectors 

for pathogens, and monitoring human and vehicle entry 

between and within sites. 

In 2000 and 2006, the USDA’s National Animal 

Health Monitoring System (NAHMS) conducted studies 

on swine health and management practices from a 

random sample of swine production sites with 100 or 

more pigs in 17 States*. These States represented 

approximately 94 percent of U.S. pig inventory and 94 

percent of U.S. pork producers with 100 or more pigs. 

Housing and pig-flow management 

How animals are raised in terms of confinement 

level and flow management within stages of production 

and marketing processes is a facet of herd biosecurity. 

For example, pigs that are not confined or are rotated in 

and out of facilities continuously may have a better 

chance of acquiring and spreading certain disease 

agents. 

 Total confinement was the most common type of 

facility for all phases of production, except gestation. 

However, the percentage of sites that managed 

gestating pigs in total confinement increased from 22.4 

percent in the 2000 swine study to 34.6 percent in the 

2006 study. 

 A similar trend occurred for grower/finisher pigs, with 

the use of total confinement facilities increasing from 

42.9 percent of sites in 2000 to 53.2 percent in 2006, 

and the use of an open building with outside access 

decreasing from 33.2 percent in 2000 to 23.3 percent in 

2006 (table 1). 

____________ 

*States 

Arkansas, Colorado, Illinois, Indiana, Iowa, Kansas, Michigan, 

Minnesota, Missouri, Nebraska, North Carolina, Ohio

Oklahoma, Pennsylvania, South Dakota, Texas and Wisconsin. 

Table 1. For Sites with the Specified Production 

Phases, Percentage of Sites by Facility Type Used 

Most, 2006 

 Percent Sites 

 Production Phase 

 Gestation Farrowing Nursery

Grower 

/Finisher

Facility Type Percent Percent Percent Percent

Total 

confinement 34.6 67.7 74.0 53.2 

Open building 

with no outside 

access 13.3 10.6 10.7 20.4 

Open building 

with outside 

access 37.3 15.1 11.3 23.3 

Lot with hut or 

no building 8.6 3.3 1.8 1.8 

Pasture with hut 

or no building 6.2 3.3 2.2 1.3 

Total 100.0 100.0 100.0 100.0 

Except for the gestation phase, most sites used 

some form of all-in/all-out management. During the 

gestation phase, the majority of sites in 2006 (61.5 

percent) used continuous flow management, a decrease 

from 71.4 percent in 2000. During the grower/finisher 

phase, continuous flow management decreased from 

40.5 percent of sites in 2000 to 26.1 percent in 2006 

(table 2). No significant decrease occurred in the 

percentage of sites that used continuous flow 

management during the other phases of production. 

 

Photo courtesy of National Pork Board 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Table 2. For Sites with the Specified Production 

Phases, Percentage of Sites by Pig-flow 

Management Style, 2006 

 Percent Sites 

 Production Phase 

 Gestation Farrowing Nursery

Grower/ 

Finisher 

Management 

Style Percent Percent Percent Percent

Continuous flow 61.5 33.5 25.0 26.1 

All swine 

removed without 

cleaning and 

disinfecting 4.6 4.7 3.6 6.2 

All-in/all-out by 

room, with room 

cleaned and 

disinfected 10.0 37.1 30.5 17.5 

All-in/all-out by 

building, with 

building cleaned 

and disinfected 7.7 16.1 29.8 35.0 

All-in/all-out by 

site, with site 

cleaned and 

disinfected 1.4 1.9 7.1 12.1 

Not applicable 

(no housing) 14.8 6.7 4.0 3.1 

Total 100.0 100.0 100.0 100.0 

Biosecurity for breeding pigs 

When new breeding stock are brought to a site, 

there is concern that they might introduce a pathogen to 

the herd. In addition, existing pathogens in the herd 

might infect new arrivals. These risks can be reduced by 

minimizing new arrivals, isolating new arrivals, or by 

acclimating new arrivals to disease agents. Less than 

one-half of sites (43.7 percent) did not have new arrivals 

of breeding females during the last 12 months. A higher 

0

10

20

30

40

50

60

70

No new arrivals

Never

Sometimes

Always

Frequency

Percent

Small (Fewer than 250) Medium (250-499) Large (500 or more) All Sites

Size of Site (Sow and Gilt Inventory)

Figure 1. Percentage of Sites by Frequency New Breeding Females 

were Typically Isolated or Quarantined, and by Size of Site

26.5

5.5

17.0

51.0

37.4

6.4

21.9

34.3

61.1

2.5

15.0

21.4

34.3

5.0

17.0

43.7

percentage of small sites (51.0 percent) had no new 

arrivals compared with large sites (21.4 percent). 

Conversely, a higher percentage of large sites (61.1 

percent) always isolated new arrivals compared with 

small sites (26.5 percent) [figure 1]. 

 Table 3 shows the percentage of sites by methods 

used to acclimate new arrivals. A higher percentage of 

large sites used feedback of feces from other swine and 

feedback of mummies, placentas, or stillborn pigs as 

methods of acclimating newly arriving breeding stock 

than small sites. Approximately 6 of 10 medium sites 

(59.6 percent) and 5 of 10 large sites (50.9 percent) 

used exposure to cull females as a method of 

acclimation compared with about 3 of 10 small sites 

(29.0 percent). A higher percentage of large sites (90.5 

percent) used vaccinations to acclimate new arrivals 

compared with small sites (59.7 percent). 

Table 3. For Sites with Newly Arriving Breeding 

Stock, Percentage of Sites by Method Used to 

Acclimate New Arrivals and by Size of Site 

 Percent Sites 

 Size of Site (Sow and Gilt Inventory)

Small 

(Fewer 

than 250) 

Medium 

(250-499) 

Large 

(500 or 

More) All Sites

Method Percent Percent Percent Percent

Feedback of 

feces from 

other swine 12.6 34.1 44.7 20.8 

Feedback of 

mummies, 

placentas, or 

stillborn pigs 4.6 10.9 23.0 8.8 

Exposure to cull 

females (gilts 

and sows) 29.0 59.6 50.9 35.8 

Exposure to 

sick pigs 4.5 9.6 9.9 6.0 

Give vaccinations 59.7 74.8 90.5 67.1 

Other 6.8 2.9 2.0 5.5 

The percentage of sites that used these different 

acclimation methods remained relatively unchanged 

from 2000 to 2006, with the exception of vaccination. 

The percentage of small sites that used vaccinations to 

acclimate newly arriving breeding stock decreased from 

the swine 2000 study to the swine 2006 study (81.6 and 

59.7 percent, respectively. The percentage of sites that 

used these different acclimation methods remained 

relatively unchanged from 2000 to 2006. 

About 40 percent of all sites used artificial 

insemination (AI) as the predominant mating technique 

for sows during at least one mating. This practice varied 

widely by size of site. Most large sites (91.6 percent) 

used AI as the predominant mating technique for sows, 

while 65.7 percent of medium sites and 20.8 percent of 

small sites did so. For sites that used AI, nearly 80 

percent purchased semen, while16.8 percent collected 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

semen on-site, and 15.9 percent collected semen off-site 

but did not purchase it. Semen itself can be a source of 

pathogens, and some producers improve biosecurity by 

using commercial semen screened for pathogens. 

From December 2005 through May 2006, nearly 90 

percent of sites with a gestating phase brought their 

sows and gilts into the gestation phase from on-site 

sources. Many producers, therefore, keep their breeding 

herd fairly closed. However, weaned pigs used for 

marketing or replacement of breeding stock often come 

from a variety of sources, particularly when trying to 

keep facilities full on larger sites. The health practices of 

these sources are a biosecurity consideration. 

Biosecurity for weaned pigs 

 On sites with a nursery phase, 69.3 percent of small 

sites primarily obtained pigs for the nursery from on-site 

farrowing or nursery units (figure 2). Over 6 of 10 

medium sites (65.8 percent) and five of 10 large sites 

(52.1 percent) obtained pigs for the nursery from another 

producer, while fewer than 3 of 10 small sites (25.0 

percent) did so. Less than 1 percent of sites used an 

auction, sale barn or livestock market as a source of 

nursery pigs. 

0

20

40

60

80

Large (5,000 or more)

Medium (2,000-4,999)

Small (fewer than 2,000)

Figure 2. For Sites With a Nursery Phase, Percentage of Sites that 

Brought or Placed any Pigs Into the Nursery Phase from December 

2005 through May 2006, by Source of Pigs and by Size of Site

Percent

Source

Size of Site (Total Inventory)

69.3

22.9

33.8

7.4

10.7

15.2

25.0

65.8

52.1

0.8 0.5 0.0 0.0 0.9 0.4

On-site 

farrowing

or nursery 

units

Another farrowing 

or nursery unit 

belonging to same 

operation

Another 

producer

Auction, sale

barn, or 

livestock market

Other

Half of sites with a grower/finisher phase (49.9 

percent) obtained new pigs for grower/finisher units onsite, such as their own nursery. The majority of small 

sites (54.7 percent) brought pigs into the grower/finisher 

phase from on-site. The most common source of 

grower/finisher pigs on medium sites was other pig 

producers (47.9 percent of sites). For large sites, the two 

most common sources of grower/finisher pigs were onsite and other pig producers (42.7 and 41.4 percent of 

sites, respectively) [Figure 3]. 

0

20

40

60

80

Large (5,000 or more)

Medium (2,000-4,999)

Small (fewer than 2,000)

Figure 3. For Sites With a Grower/finisher Phase, Percentage of 

Sites that Brought or Placed any Pigs Into the Grower/Finisher 

Phase from December 2005 through May 2006, by Source of Pigs 

and by Size of Site

Percent

Source

Size of Site (Total Inventory)

On-site 

farrowing

or nursery 

units

Off-site farrowing 

or nursery units 

belonging to same 

operation

Another 

producer

Auction, sale

barn, or 

livestock market

Other

54.7

36.3

42.7

10.3

14.915.7

35.1

47.9

41.4

2.2 1.1 0.6 0.4 1.7 0.9

Visitor restrictions 

About 80 percent of sites in 2006 did not allow 

anyone except employees to come in contact with areas 

where swine were housed, compared to about 65 

percent of sites in 2000. For sites where nonemployees 

were allowed to enter swine facilities in 2006, 95.4 

percent allowed business visitors (e.g., an electrician), 

but only 68.1 percent allowed nonbusiness visitors. 

 A higher percentage of small sites (77.6 percent) 

allowed nonbusiness visitors compared to medium and 

large sites (42.9 and 32.0 percent, respectively). When 

nonbusiness visitors were allowed to enter swine 

facilities, the most common preventive measures 

required were to change to clean boots and coveralls 

before entering (26.5 percent of sites) and/or wait at 

least 24 hours after visiting another swine site before 

entering swine facilities (25.7 percent of sites). 

 When business visitors were allowed to enter swine 

facilities, the most common preventive measure required 

was to change to clean boots and coveralls before 

entering the facilities (48.4 percent of sites). 

Vehicles can be a mechanism for disease spread. 

Certain restrictions are often placed on commercial 

haulers before entry into a site. Slightly more than half of 

sites (51.3 percent) allowed commercial trucks or trailers 

on sites where pigs were kept. A higher percentage of 

large and medium sites (61.1 and 64.9 percent, 

respectively) allowed commercial trucks or trailers than 

did small sites (45.5 percent). Cleaning and disinfecting 

commercial livestock trucks and trailers before entry into 

a swine site may reduce the risk these vehicles pose to 

swine. 

Nearly three of four sites (72.3 percent) required 

cleaning of the animal area inside the truck or trailer 

before entering the pig area. Three of five sites (60.5 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

percent) required animal areas to be disinfected, and 

three of five sites (59.7 percent) required cleaning of the 

outside of the truck. Fewer than one-half the sites (44.8 

percent) required disinfection of the outside of trucks 

(figure 4). All of these practices increased as size of site 

increased. 

0

20

40

60

80

Animal area inside 

truck cleaned

Animal area inside 

truck disinfected

Outside of 

truck cleaned

Outside of 

truck disinfected

72.3

60.5 59.7

44.8

Figure 4. For Sites that Allowed Trucks or Trailers from Commercial 

Livestock Transporters or Animal Haulers to Enter the Pig Site, 

Percentage of Sites by Required Cleaning and Disinfecting 

Practices for Livestock Trucks or Trailers

Practice Required

Percent

Rodent control

Rodents, domestic animals, and some wildlife may 

serve as reservoirs for various swine diseases. Nearly all 

sites (97.3 percent) used some manner of rodent control. 

The most common method of rodent control used was 

bait or poison (87.9 percent of sites) followed by cats 

(51.2 percent of sites). The placement of bait stations in 

a building used to house swine or structures used to 

store feed may affect the efficacy of this rodent control 

method. When sites had at least one building used to 

house swine, nearly half of these buildings (47.7 

percent) had rodent bait stations placed inside, and 32.0 

percent of the buildings had bait stations placed outside 

at 50-foot intervals or less. Large sites had a higher 

percentage of buildings equipped with bait stations 

placed outside at 50-foot intervals or less than medium 

and small sites. Similarly, for sites that stored feed in a 

structure (open or closed) the most commonly used 

rodent control method was the placement of bait stations 

outside these structures at 50-foot intervals or less apart 

(29.4 percent of sites). 

Housing biosecurity 

 For sites with at least one building used to house 

swine, over 60 percent of sites indicated that all 

buildings used to house swine were constructed and 

maintained to keep out birds, cats, and dogs. A higher 

percentage of large and medium sites housed swine in 

buildings that kept out birds, cats, rats, mice, and dogs 

than did small sites (table 4). 

Table 4. For Sites with at Least One Building Used 

to House Swine, Percentage of Sites in Which All 

Buildings Used for Swine were Constructed and 

Structurally Maintained to Keep Out the Following 

Types of Animals, by Size of Site

 Percent Sites 

Size of Site (Total Inventory)

Small 

(Fewer 

than 2,000)

Medium 

(2,000-

4,999) 

Large 

(5,000 or 

More) All Sites 

Animal 

Type Percent Percent Percent Percent

Birds 49.3 85.2 91.3 62.0 

Rats 

and 

mice 

36.1 70.3 69.7 47.3 

Cats 50.5 88.6 94.8 63.9 

Dogs 56.6 92.1 95.1 68.8 

 Complete descriptive reports and other information 

sheets from NAHMS Swine Studies are available at: 

http://nahms.aphis.usda.gov 

For more information, contact: 

USDA–APHIS–VS, CEAH 

NRRC Building B, M.S. 2E7 

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000 

E-mail: NAHMS@aphis.usda.gov 

http://nahms.aphis.usda.gov 

#N500.0308 

____________________________________ 

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