Boar studs need to refine isolation and acclimation (I/A) programs. They also need to focus on controlling people traffic and handling cull boars and dead animals.
That's the view of Darwin Reicks, DVM, Swine Vet Center (SVC), St. Peter, MN, who consults and audits about 12 area boar studs. All of the negative studs in his practice have stayed PRRS-free.
Meanwhile, 10-12 other Midwest boar studs were diagnosed with PRRS this winter, according to veterinary sources, raising a flurry of questions about biosecurity.
Following are biosecurity and management practices to guard against PRRS that Reicks has developed from several years of auditing.
One of the biggest biosecurity lapses Reicks has turned up is poor control of people traffic. “It used to be very common on a lot of farms and boar studs to exit and reenter the buildings without showering back in,” he says. Now, anyone that steps outside of the facility for any reason must shower back in.
By far the most common reason for violating this biosecurity rule was to check on feed bins. “That is a big problem because we have to assume that the yard and premise are contaminated with PRRS,” he says.
Field observations support his contention that PRRS spreads like TGE (Transmissible gastroenteritis), rather than by aerosol. “PRRS appears to spread best in frozen, wet material and during months when there is less daylight and sunshine,” Reicks says.
Some producers thought they could get by without showering if they wore plastic boots. But they are a huge safety hazard when conditions are icy, so the practice is often eliminated altogether.
The answer is to assign someone to check feed bins first thing in the morning prior to entry and the last thing as they leave the facility at night, he says.
Handling Culls, Deads
The Pork Storks I boar stud near New Ulm, MN, uses a portable chute that connects to the livestock trailer for loading out cull boars, Reicks explains. The trailer itself is not allowed to touch the building and the persons inside must not cross the threshold of the load-out door.
A second door at load-out, called a doghouse, serves as a barrier to prevent cull boars from being able to turn back and reenter the boar stud. Any PRRS-negative farm should have a covered chute or some kind of area that prevents an animal from reentering a building, he stresses.
The trailer that hauls cull stock must be cleaned and disinfected in a certified truck wash and most importantly, dried, before it is allowed to enter the boar stud premise. Reicks suggests dedicating a trailer specifically to a single boar stud.
For staff safety, trailers used at Pork Storks, a PIC-affiliated boar stud, have been modified to pen and transport boars individually.
A precise procedure is followed for removal of dead animals at boar studs, Reicks says. Boars are taken to the exit door where someone on the outside touches only the animal, hooking it up and pulling it outside. A tractor owned by the stud takes dead boars to an off-site location for pickup. The tractor is cleaned and disinfected before returning to the stud.
Typically, boar stud I/A facilities are off-site, relates Reicks. Common practice is to transport the acclimated boars onto the stud site and place them directly into the main stud. This procedure poses a potential weak link. Boars could be contaminated in transit when they are moved from the trailer to the stud barn.
Reicks suggests adding an on-site isolation unit under the same roof as the stud, so those new boars don't have to go outside just prior to entering the main stud. If a separate isolation unit is built on-site, he recommends a covered, connecting hallway to the main stud.
Reicks declares: “We think the most important part of I/A is to have animals in a separate area where they can stay under the same roof before they go into the main stud. We see a lot of people having off-site isolation, but not having on-site isolation. The on-site isolation is a lot more important.”
Other People Traffic
Ordinary traffic to the site is severely restricted, explains Reicks. Visitors and producers are prohibited.
Deliveries are diverted to an employee's home or designated business before they are brought into the stud.
The semen delivery driver must wear clean clothes and plastic boots and have the delivery vehicle completely washed before driving onto the stud premises, he points out. The driver carries an identification card that is validated at an automatic drive-up checkpoint.
Garbage pickup is well away from the main building and done first thing Monday morning. The propane delivery driver uses a long hose so his truck doesn't enter the main premise. Feed bins are positioned inside the perimeter fence. The only outside vehicle allowed within the inner fence is the one that picks up dead animals, he says.
Employees can't live on a hog farm or live with someone who works on a hog farm. If they visit a hog farm, they must have three days downtime before returning to the boar stud.
Showers and bathrooms are locked. Any necessary guests, including Reicks, must sign the logbook to document their visit.
Exterior Stud Biosecurity
Pork Storks I, also managed by SVC, was designed to provide heightened biosecurity. Built in 1996, the stud holds 400 boars. The site is completely enclosed by an electrified, high-tensile wire fence. An inner chain-link fence topped by barbed wire surrounds all access points 12 ft. from the building. The facility and main gates are locked when employees have left for the night.
Interior Stud Biosecurity
Pork Storks I boar stud manager Wayne Nienhaus says the whole stud gets washed down every other week to clean crevices, corners and spilled feed that harbor bugs and mice. Boar collection areas, including collection dummies, are washed every day. Once a week the dummies are pulled out, washed and disinfected.
Reicks reviews the main stud area. Each stud should have its own tools needed for repairs to avoid a repairman bringing in contaminated tools.
Water is cultured regularly for bacteria, he says.
For manure disposal, studs are urged to own the equipment that goes directly into the pit. Haulers are urged not to pump out manure from a hog facility before pumping out pits at a boar stud.
Reicks regularly audits boar stud labs for acceptable semen morphology and motility, equipment calibration, semen concentration, semen extending techniques and proper semen cooling before shipping.
Pork Storks I and II (Rushmore, MN) and Fairmont Artificial Breeders (FAB) boar stud at Fairmont, MN, are the only ISO-9000 certified boar studs in the U.S. This certification requires that a third-party auditor must review semen production and processing practices annually.
Those studs and Pipestone (MN) System's boar stud have a unique arrangement. If one closes due to a disease outbreak or other emergency, the other studs agree to provide backup until they resume operations. Pork Storks I filled the void for FAB when the stud was down three months after a PRRS outbreak last winter (see sidebar).
Every boar at Pork Storks must test negative for pseudorabies, brucellosis, leptospirosis, swine influenza virus, parvovirus, erysipelas and PRRS prior to stud entry. Boars are retested monthly.
Polymerase chain reaction (PCR) testing of semen for PRRS has done a good job. But using the mail service takes 2-3 days to get results, meaning most producers will have used the semen before test results are known.
In a new venture dubbed the “Minnesota Standard,” southern Minnesota boar studs are pooling resources to speed up PCR testing, Reicks explains. Semen samples dropped off early at SVC or Fairmont Veterinary Clinic are being driven by courier to the Minnesota Veterinary Diagnostic Laboratory in St. Paul. The lab has geared up to test the samples the same day to have results by the next morning.
Lab veterinarian Kurt Rossow says for samples that arrive by 1 p.m., the goal is to have the results faxed to the clinics by 7 a.m. the next day. The Minnesota lab is also expanding its diagnostic capabilities to process semen samples six days a week.
The expedited process means studs could hold semen one day and be assured that shipments are PRRS-free, explains Reicks. If the sample turns up positive, the shipment isn't sent.
Producers should take three steps to protect their herds from PRRS, according to SVC staff. Producers should hold semen on-farm one day until test results are back, check the health status and monitoring of their semen supplier and develop a contingency plan in case their supply of semen is interrupted.
Boar Stud Survey
The PRRS (porcine reproductive and respiratory syndrome) Committee of the American Association of Swine Veterinarians has sent out two questionnaires for a boar stud case study. Responses will be used to help identify risk factors to drive changes in boar stud procedures and processes.
The responses will be analyzed and a report prepared by Robert Morrison, DVM, University of Minnesota. Committee chair Joe Connor, DVM, Carthage, IL, expects the results of the survey will be presented during the Leman Swine Conference, Sept. 14-17, St. Paul, MN.
— Joe Vansickle
Boar Stud Bounces Back
Fairmont Artificial Breeders (FAB) is back at full strength selling semen after breaking with porcine reproductive and respiratory syndrome (PRRS) in January, reports manager Doug Faber.
The virus was discovered through routine, weekly polymerase chain reaction (PCR) semen testing, Faber says. The positive result was in a pooled semen sample of three boars. The boars in the stud near Fairmont, MN, showed no clinical signs of disease.
“That was what shocked us the most,” he says. “We thought with these boars being naïve, never being exposed to the virus, that when they were exposed, they would at least go off feed and we'd probably see some pretty sick animals.”
After the positive PRRS test, the stud was immediately shut down and their 75 producer clients notified. Further testing confirmed several boars were infected.
After boars were allowed to complete the shedding process, the seven-member FAB producer board took decisive action. A sample of every batch of semen shipped is now being tested every day to ensure that customers get clean semen, stresses Faber. This will be done indefinitely.
They also decided not to depopulate. FAB depopulated and repopulated a year ago. No one wanted to repeat the $500,000 process this soon, he says. With no clues as to where the PRRS virus came from, nor guarantees that it won't strike again, the risk of another break is too great, explains Faber.
Instead, all boars were vaccinated with an autogenous killed virus PRRS vaccine. All boars have tested negative for PRRS since that time, says Faber. Shipments to customers include a report from the university verifying health status of the semen.
Faber says biosecurity has been tight at FAB. But since the mysterious break, all protocols are being reviewed and tightened. A biosecurity audit is planned.
“We are scared of this disease. But we are not going to let it prevent us from leading the industry as a semen supplier,” he stresses.
— Joe Vansickle