Biosecurity and Health Management on U.S. Swine Operations
By USDA NAHMS - Biosecurity includes the use of certain management practices to prevent the introduction of new disease and the spread of existing disease on swine operations.
Examples of these practices include:
proper handling of new breeding stock; the use of
multiple-site production; proper pig flow
management; strict rodent control; and controlling
human and vehicle entry between and within
operations.
The USDA’s National Animal Health Monitoring
System (NAHMS) collected data on swine health
and management practices from a stratified random
sample of swine production sites in 17 states1 as
part of the Swine 2000 study.
These sites
represented 94 percent of the U.S. pig inventory
and 92 percent of U.S. pork producers with 100 or
more pigs.
Overall, 2,499 swine production sites
participated in the first interview from June 1, 2000,
through July 14, 2000. A second interview was
completed by 895 of these sites between August
21, 2000, and November 3, 2000. A final interview
was completed by 799 of these sites between
December 1, 2000, and February 28, 2001.
For
estimates in this report, small, medium, and large
sites refer to sites with less than 2,000, 2,000 to
9,999, and 10,000 or more pigs in total inventory,
respectively.
For estimates involving breeding
females, small, medium, and large sites refer to
sites with less than 250, 250 to 499, and 500 or
more breeding females, respectively.
Isolation and Health Testing
A common threat to biosecurity of the breeding
herd is the addition of new animals. Isolating
incoming animals prior to introduction into the herd
minimizes the risk of disease entry.
During
isolation, animals can be observed for clinical signs
of disease, tested for pathogens they may be
carrying, and acclimated to organisms already
present in the breeding herd.
Typically, new breeding females were
introduced onto 51.5 percent of small sites, 80.5
percent of medium sites, and 90.2 percent of large
sites. The majority of these sites always isolated
newly arriving females, while almost 30 percent
never isolated them (Figure 1).
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The Swine 2000 study found that 66.6 percent
of small sites (those with less than 250 breeding
females that introduced new breeding females)
either isolated them always or sometimes,
compared to 78.8 percent of medium sites and 84.3
percent of large sites.
New breeding males were added to 86.3
percent of sites. Almost two-thirds of these sites
always isolated new breeding males, while less
than one-quarter never isolated new breeding
males. For sites that introduced new breeding
males, 75.6 percent of small sites either isolated
them always or sometimes, compared to 78.8
percent of medium sites and 84.7 percent of large
sites.
There was little difference between the length of
time breeding females and males were isolated.
Large sites tended to isolate their new arrivals
longer than small sites.
For instance, new breeding
females were isolated for an average of 35 days on
small sites compared to 51 days on large sites.
For sites that isolated or quarantined new
breeding animals, 43.5 percent tested all new
females and 51.8 percent tested all new males
either before or after isolation.
Acclimatization
Acclimatization introduces new breeding stock to viral and bacterial pathogens present on the receiving farm. The Swine 2000 study found that 84.1 percent of sites that isolated new breeding females vaccinated them as part of the acclimatization process. Other practices used commonly to acclimate gilts were: exposure to cull females (49.0 percent of sites); feedback of feces from other swine (25.1 percent of sites); feedback of mummies/placentas/stillborns (11.3 percent of sites); and exposure to sick pigs (7.7 percent of sites).
Use of Artificial Insemination and Sources of Semen
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Artificial insemination (AI) reduces the risk of
disease transfer between the boar and breeding
female. However, certain pathogens can be
transmitted in semen. Nearly one-fourth (23.2
percent) of all sites with sows or gilts used AI;
however, this varied tremendously by site size.
Most large sites (91.3 percent) used AI, while 61.4
percent of medium sites and only 12.1 percent of
small sites used it.
Nearly three-fourths (72.9 percent) of sites that
used AI purchased semen, while 17.1 percent
collected semen on-site and 20.8 percent collected
semen off-site, such as with an owner boar stud.
Some sites used more than one semen source.
There were significant differences among the
different regions regarding the source of purchased
semen. More than three-fourths of sites in the
northern, west central, and east central regions
purchased semen, but less than one-third of sites in
the southern region purchased semen (Figure 2).
Use of Separate Sites and Segregated Early Weaning (SEW)
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The Swine 2000 study found that 36.4 percent
of sites with farrowing facilities moved weaned pigs
to “separate-site” nurseries. Of sites with nurseries,
50.0 percent moved pigs to separate-site
grower/finisher facilities. Three-quarters of large
sites (10,000 or more pigs) used a separate site for
either nursery or grower/finisher facilities, while less
than half of small sites did so.
Segregated early weaning (SEW) is an
important disease-control management strategy.
For this study, sites that had a maximum weaning
age of 20 days or less and moved weaned pigs to a
separate-site nursery were defined as SEW sites.
Overall, only 4.7 percent of sites used SEW;
however, many more large sites used SEW than
medium or small sites. Because of this, 21.4
percent of all weaned pigs and 28.7 percent of
pigs on large sites were raised using SEW
(Figure 3).
Sources of Weaned Pigs
Weaned pigs may enter the grower/finisher
phase of production from several sources. The
biosecurity practices of these sources and the risk
associated with using mulitple sources should be
considered.
More pigs entering the grower/finisher
units from December 1999 through May 2000 (52.8
percent of pigs) came from farrowing or nursery
units that belonged to the site (either on or off the
site) than any other source. Feeder pig producers
(both contract and non-contract) supplied 40.8
percent of pigs that entered grower/finisher units.
Only 0.7 percent of all pigs originated from an
auction, salebarn, or livestock market.
Over three-quarters (76.1 percent) of sites that
obtained pigs from off-site units or feeder-pig
producers obtained pigs from only one other
source. Only 16.3 percent of sites acquired pigs
from two sources, and 7.6 percent received pigs
from three or more sources. Large and medium
sites tended to use more sources for pigs than
small sites. For sites that received feeder pigs from
more than one source, 43.2 percent commingled
pigs from different sources in the same building.
Pig Flow Management
All-in/all-out management means that every animal is removed from a room, building, or site prior to restocking. These facilities are then cleaned and disinfected before placing new animals in them, which greatly reduces the transmission of type of pig flow management was used on 51.1, 60.2, and 53.7 percent of sites that had farrowing, nursery, and grower/finisher phases, respectively, accounting for 79.4, 87.4, and 83.0 percent of all farrowed females, nursery pigs, and grower/finisher pigs.To further decrease the chance of disease transmission among different groups of pigs, 16.6 percent of sites with weaned market pigs used wean-to-finish buildings to reduce the need to resort and move pigs.
Visitor and Employee Restriction
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Nearly two-thirds (65.5 percent) of sites
restricted entry to swine facilities by allowing
access to employees only. For sites that allowed
visitors, large sites (57.7 percent) were much more
likely than small sites (4.1 percent) to require that
visitors shower before entry. Almost all large sites
(98.3 percent) required visitors to wear clean
coveralls and boots before entry, while only 43.2
percent of the small sites did so.
To prevent visitors from accidentally introducing
organisms, such as through nasal secretions, a 24-
hour “no-swine-contact” period prior to entering the
swine facilities was required on 23.6 percent of
sites that allowed visitors (Figure 4).
To prevent employees from accidentally
introducing diseases into the herd, 89.7 percent of
all sites did not allow employees to have contact
with swine not owned or managed by the operation.
For large sites, the percentage was 96.4 percent.
Cleaning and Disinfection of Livestock Trucks
Trucks entering the site can be a serious
biosecurity risk. Overall, 56.8 percent of sites
allowed trucks transporting livestock to enter the
site perimeter. Small sites were more restrictive
than large sites. Only 52.0 percent of small sites
allowed trucks or trailers transporting livestock to
enter the pig site, whereas 79.6 percent of medium
sites and 86.8 percent of large sites did so.
Thorough cleaning and disinfection of livestock
trucks and trailers before entry into a swine site can
reduce the risk these vehicles pose to swine. Most
sites required trucks be cleaned before entering the
pig site, particularly the inside. However, fewer
sites required disinfection of trucks. For sites that
allowed trucks on the premises, small sites were
less likely than large sites to require cleaning or
disinfection of trucks (Table 1).
Table 1. Percent of Sites* Requiring Cleaning and/or Disinfection of Livestock Trucks and Trailers. |
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Percent Sites |
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Size of Site (Total Inventory) |
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Required Practices | Small (Less than 2,000) |
Medium (2,000- 9,999) |
Large (10,000 or More) |
All sites |
Clean inside of truck | 58.2 | 87.7 | 96.3 | 65.4 |
Disinfect inside of truck | 37.2 | 77.1 | 90.5 | 47.0 |
Clean outside of truck | 46.9 | 77.0 | 91.4 | 54.4 |
Disinfect outside of truck | 25.6 | 59.2 | 68.9 | 33.8 |
*For sites that allowed trucks or trailers transporting livestock onto the pig site. |
Carcass Disposal
Dead pigs were most commonly disposed of by having a renderer pick up the carcasses at the operations. This method accounted for the disposal of 40.4 percent of dead preweaned pigs and 55.9 percent of dead weaned or older pigs. Having a renderer pick up carcasses outside the operations accounted for the disposal of only 12.7 percent of dead preweaned pigs and 12.1 percent of dead weaned and older pigs.
Rodent Control and Exclusion of Cats from Facilities
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Rodents, cats, and some wildlife may serve as
a reservoir for various swine diseases. A welldesigned
rodent control program is essential for all
swine operations. The most common method of
rodent control was bait or poison (88.5 percent of
sites) followed by cats (60.6 percent of sites),
despite the fact that cats may spread disease to
swine. Using cats to control rodents was much
more common on small sites (68.0 percent) than on
medium (25.9 percent) or large (5.2 percent) sites.
The percentage of sites where all buildings
used to house swine were constructed and
maintained to keep out cats or rats and mice
increased as the size of the site increased
(Figure 5).
Overall, 46.4 percent of sites maintained all
feed storage buildings in a manner that kept out
rats and mice, and 58.6 percent of sites maintained
all of these buildings to keep out cats.
1Arkansas, Colorado, Illinois, Indiana, Iowa, Kansas, Michigan,
Minnesota, Missouri, Nebraska, North Carolina, Ohio, Oklahoma,
Pennsylvania, South Dakota, Texas, Wisconsin.
For more information, contact:
USDA:APHIS:VS, CEAH, NRRC, Building B., M.S. 2E7
2150 Centre Ave., Bldg. B.,
Fort Collins, CO 80526
(970) 494-7000
Email:
Web: www.aphis.usda.gov/vs/ceah/cahm
Source: USDA National Animal Health Monitoring Service - March 2003