By Joe Vansickle Sometimes it's hard to feel secure about biosecurity when boars are being culled and replaced fairly often.

That's today's commercial boar stud where, to consistently upgrade genetics, boars are turned within two years.

At that pace, a strategy for biosecurity becomes paramount to survival of the boar stud, stresses Malcolm De Kryger, vice president of business development for Belstra Milling Co. Inc., DeMotte, IN.

"Our boar stud is more or less considered sacred ground by all of our employees and service people," he says. "We have a separate staff that never goes into anybody else's farm and none of the farm staff ever go into the boar stud. They just don't do it."

De Kryger, who supervises Belstra Milling's four gilt multiplier farms, and consulting swine veterinarian Tom Gillespie, Rensselaer, IN, are only allowed in Belvarken AI Center at St. Anne, IL, after being away from hogs for 96 hours. The 84-head boar stud sells semen on contract to its PIC producer customers. The boar stud is 31/2 miles away from any other hogs.

Minnesota swine practitioner Darwin Reicks says producer customers shouldn't fear they are "buying" disease when they make their semen purchases.

"For the producer, I think it is important to realize that the risk of transmitting disease in semen is very, very minor compared to the risk of live animals transmitting disease," the St. Peter, MN, veterinarian says.

In terms of live animal introductions, the bigger biosecurity risk is to the boar stud itself. If that stud goes down with a serious disease break, semen sales stop, income goes immediately to zero and clients are without a source of semen, points out Reicks. Expensive stud boars quickly become culls worth $100 or less, he explains.

Establishing Disease Status Reicks recommends setting up a two-phase biosecurity program of isolation and acclimation. The first-phase, 30 to 60-day isolation should be done, if possible, in an off-site facility at least a mile from the main boar stud and any other hog farms. After 30 days of isolation, new boars should be blood tested for pseudorabies (PRV), porcine reproductive and respiratory syndrome (PRRS), and brucellosis.

Other diseases should be tested for as needed. Explains Reicks: "Probably one of the most important things is to have a good vet-to-vet relationship with the genetic supplier; that will dictate what your testing program needs to be."

For instance, if your genetic supplier is free of Actinobacillus pleuropneumonia (APP), there is certainly no need to test every boar for APP.

If transmissible gastroenteritis (TGE) has been a problem in the area, it might be wise to blood test for the disease.

Reicks also suggests using highly sensitive PCR (polymerase chain reaction) to test for PRRS.

During the isolation phase, stud boars are vaccinated, as the client, animal status and geographic area dictate. The only boar stud client requiring PRV vaccination is located in Iowa, where the prevalence of the disease is higher. Normally, Reicks advises vaccination for PRRS, swine influenza virus, parvovirus, leptospirosis and sometimes Mycoplasmal pneumonia. One boar stud that is negative for PRRS has chosen not to vaccinate for the disease, he notes.

Isolation Is Not A Cure-All Indiana swine practitioner Larry Rueff, who is part-owner in a 50-head boar stud near Greensburg, IN, doesn't see isolation as a cure-all. "I always tell clients that isolation should have a purpose. We would be naive to think that we can eliminate all of the diseases through isolation. It's more a case of disease matching. You can't do disease elimination. That's not the name of the game.

"Isolation should have a purpose, and that purpose should be a definitive list of things you are trying to keep out, and that you can truly monitor through isolation," he says.

According to Reicks the second phase of the 30-60-day acclimation should occur in a separate facility on-site at the boar stud. "In most of the studs I am working with, we are trying to train these young boars prior to their entry to the main barn and also acclimate them in the facility," he says.

Reicks uses acclimation to accomplish two goals. First is to expose new boars to pathogens in the main barn so they don't get sick when they enter the stud. This is done by fenceline contact of the young, cull boars with the new boar stud candidates. "If the culls get sick, then you know the new ones aren't ready to move on into the stud," he explains. Young cull boars are those that weren't trainable for AI collection.

Second goal of acclimation is prompted by the notion that it is usually better not to vaccinate boars in the main stud barn because it increases stress, believes Reicks. Because of that, those animals in the main boar stud tend to become fairly naive over time. To protect them, after the young cull boars are removed from the acclimation area, old cull boars are introduced to the acclimation area. If the old cull boars get sick, then the boar stud staff knows the new boars are infected with something that could possibly make all the boars in the stud sick, says Reicks. Clinical observation of those old cull boars is really important in providing a disease barrier for the stud. Blood testing is also done to determine the cause of illness in the old cull boars.

As added insurance, Reicks does a lot of PCR testing for PRRS during acclimation while boars are being trained for artificial insemination (AI). "We will use PCR testing on the semen and make sure the new boars are negative prior to entering the boar stud," he notes. (See sidebar on page 30. )

Biosecurity Checklist Sherry Clark, DVM, University of Illinois, provides a summary checklist of recommended steps she devised for isolation and acclimation for boar studs. It appeared recently in the IMV International newsletter.

1. Understand health of source herd(s). Communication between herd veterinarians concerning disease profiles is key.

2. Isolation (first 25-30 days): Boars arrive at stud for isolation. While performing daily chores/feeding of isolated boars, monitor boars daily for any clinical signs of disease such as coughing, loss of appetite and loose stools. Begin training boars with the dummy sow for semen collection. Clean coveralls, boots are essential.

Blood test at 14 days and start preventive medicine program (deworming and vaccination).

3. Acclimation (second 20-30 day period): Continue to monitor boars daily for any signs of clinical disease. Continue training boars with the dummy. Expose boars to microorganisms of the main stud herd through material feedback from most recently introduced boars and/or direct exposure to cull boars. Do second blood test 2-4 days into the acclimation period. Re-treat for internal and external parasites and give booster vaccinations.

4. Other considerations: If boars are clinically healthy throughout the isolation period andhave passed the blood tests, they are then introduced into the boar stud.

Clean and disinfect isolation facility and equipment before bringing in the next group.

Monitoring Program "Monitoring feed intake is probably the best single indicator of a problem with individual boars in the boar stud," suggests Reicks. A boar may be off feed for many reasons, but if he is sick and has a fever, it will affect his sperm quality in 10 days to two weeks. These boars should be blood tested to check for infection. Also, have a diagnostic workup done on any boars that die while in the stud, he says.

Make sure external boar stud biosecurity is maintained. Besides limiting people traffic, make sure all vehicles - feed trucks, manure handling equipment or other delivery trucks - observe guidelines requiring them to be away from pigs for two to three days before entering the stud site. Semen delivery drivers should alternate work days, advises Reicks. The Genetipork USA, Inc. boar stud at Morris, MN, has added a fumigation room in the stud as a biosecurity tool, says Tom Spaeth, AI program director. All coolers, gel packs, paper products, pails, veterinary products and equipment and repairman's tools are fumigated before entry into the stud.

"With a fumigation room, if you've got any question about something, take 10-15 minutes and you've eliminated the risk," he says.

For external biosecurity, studs should be totally enclosed, bird and rodent proof.