Purdue Pork Page Archive

The concept of SEW and the rules to make it work


Segregated early weaning is a term used to describe a management technology for producing high health status pigs from sow herds endemically infected with a multitude of disease agents. Vaccines and antibiotics are used strategically to aid the control or elimination of some diseases. The operational theories behind the success of SEW technology are not new, but are used in combination such that producing high health status pigs is consistent and predictable. For ease of understanding, the components of the technology are separately described below.

Weaning age -- Pigs weaned from their dams at less than 21 days benefit from high concentrations of colostral antibodies and are usually protected from colonization of infectious agents carried by their dams. Weaning ages and strategice use of vaccines and antibiotics vary for the control of transmission of specific diseases.

Biosecurity - Cleaning, disinfection, and other biosecurity measures are required to prevent disease agents present in the environment from being transmitted to growing pigs.

Segregation - Rearing batches of pigs (usually no more than a 7 day age variation) all-in, all out by room, building, or site is required. Facilities with the best segregation usually result in pigs with the highest health status.

Weaning age rules

Rule 1. Bacterial transfer

Bacterial transfer from sows to pigs can be controlled by weaning age

a) Except for S. suis and H. parasuis

b) weaning age less than 14 days will eliminate most bacteria

--Varies with pathogen

--Varies among pigs in litters, litters, and herds (passive antibody status)

Rule 2. Virus transfer

Virus transfer from sows to pigs is not influenced by weaning age

Equalizing immune status among sows most important

This can be done by exposure or vaccination

Rule 3. Cross fostering

Cross fostering may enhance sow to pig transfer of pathogens

Don not cross foster after pigs are 24 hours old

Cross fostering age may vary from herd to herd


The major source of new diseases for the breeding herd comes from purchased animals. Thus, the rules for breeding herd additions will be listed first in this section. The sources of disease agents to growing pigs are related to moving groups of pigs from farrowing to nursery and then to finishing as each subsequent environment must be free of potential pathogens that might infect the high health status pigs produced by early weaning. The following is a list of some, but probably not all, biosecurity measures required to raise high health status pigs.

Rule 1. Placement

Isolation facility must be at least 300 yards east of breeding herd

Isolation facility must have a 60 day capacity

Rule 2. Disease matching

Incoming stock must not have diseases new to the herd

--Test results

--Vet to vet conference

Incoming stock must be exposed to or vaccinated for diseases of the recipient herd

Rule 3. Preparation of gestating sows

Viral infections--PRRSV, PRV, SIV, TGE?

--Keep sows vaccinated when these diseases are endemic in the herd

Bacterial infections

--Vaccinate sows as needed

--May need to vaccinate sows for M. hyopneumoniae

Rule 4. Cleaning

All rooms that hold a batch of pigs must be cleaned with a high pressure washer

Cleaning includes all equipment

Rule 5. Disinfection

All rooms and equipment need to be disinfected

Disinfectant to be determined with veterinary input

Rule 6. Down time

After disinfection, rooms need to be left empty for drying and organism killing

Down time varies dependent on diseases present

Rule 7. Work sequence

When multi-aged pigs are at one site always work from youngest to oldest pigs

Never go back without clean boots, coveralls, and washing of hands

Rule 8. Rodents

Before adding a new batch of pigs, check for rodents

Repair rodent barriers

Hire professional exterminator to eliminate rodents

Rule 9. Worker cleanliness

Workers must start the day with clean boots and coveralls

Workers exposed to older pigs (adults or finishers) should shower before entering nursery

Rule 10. Building sites

SEW nurseries must be placed 300 yards upwind (west) of a breeding and finishing facilities

Greater distances increase security

Rule 11. Vehicles

Vehicles from outside the premises must be cleaned and disinfected before entry

Rule 12. Dead animals

Dead animals must be placed outside the premises for pick up

Rule 13. Load out

Load out facilities must be placed at the perimeter of the premises

Rule 14. Visitors

Visitors should be minimized

Visitors must follow rule 9 before being allowed to enter facilities

Rule 15. Perimeter security

A fence around the perimeter of the facilities is preferred

If site is isolate, the perimeter fence may not be needed

Rule 16. General

If a biosecurity issue has no rule, be conservative on rule development


The best case pig segregation scenario would be to place each batch of weaned pigs (no more than 7 day age variation) in a room, building, and site separate from all other pigs. In addition to this separation, the best herd size would be 4000 to 5000 sows such that 1600 to 2000 pigs would be placed in the building/s by sex for phase and sex feeding. Obviously, except for a very small group of producers, these conditions would be impossible to emulate. Nonetheless, nearly all producers, no matter what their herd size or current facilities configuration, can take advantage of this new technology after some thought and planning.

The minimal change towards segregated rearing would be to separate age groups of pigs by room in existing facilities (all-in, all-out production). A more advanced step would be to build an off-site nursery that would accommodate 7 or 8 weekly groups of pigs in rooms off a common hallway. These pigs could be sold as feeder pigs or returned to all-in, all-out finishing units. From these 2 scenarios to the most advanced system described above are about as many segregation possibilities as there are producers to create them. These possibilities also can be expanded to accommodate production networking. No matter what system of SEW technology is used by a producer, pig performance will generally be enhanced. Additionally, the more the segregation mimics the best case scenario described above, the nearer producers can come to attaining the genetic growth potential of their pigs.

Segregation rules

Rule 1. Placement of batches

By room--least biosecure

By building--reasonably biosecure

By site--most biosecure

Rule 2. Age range of batches

Three days (twice a week weaning) is best

Seven days is common

Fourteen days is risky, but has worked

Rule 3. By herd vs by age

One batch from 1 herd at 1 site--best

Multiple ages from 1 herd at 1 site--OK

One age from multiple herds at 1 site--OK (Herds must be of equal health status)

Rule 4. All-in/all-out management

All batches of pigs are to be moved all-in/all-out (no exceptions)

Rooms, buildings or sites can be filled over time (10 day maximum) as long as maximum weaning ages are maintained

Only at slaughter can groups of smaller pigs be moved back with younger pigs

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