Posted March 26, 2017
The Mann Valley Farm at UW-River Falls is raising a new genetic line of pigs after it was hit last year with a disease called Porcine Reproductive and Respiratory Syndrome (PRRS).
PRRS (pronounced “purrs”), is a viral infection that was initially found in the U.S. in the 1980s, according to Iowa State University. When it breaks out in a herd of swine, as it did at the Mann Valley Farm in February 2016, it can have a couple different effects.
“In adult female swine, the most common symptom is abortion,” said Gary Onan, professor of animal science at UWRF. The female, he said, might abort an entire litter and give birth too soon, resulting in stillborn piglets or piglets that are too weak to last long. Less commonly, the fetus might also die in the uterus, but remain there full term and be born as a shriveled “mummy.” If the pigs contract the disease as piglets, the respiratory part of PRRS comes into play. They develop a form of pneumonia, which either kills them outright or weakens them and slows their growth rate.
“It usually doesn’t wipe you out like some swine diseases,” said Bill Connolly, director of the lab farms. However, the slower growth rate of infected piglets means that the farmer has to wait longer before selling them for market, during which time they will require more feed and cost more money. Some farmers, Connolly said, will simply live with the disease rather than try to get rid of it, but over a long period of time, that can be costly.
At the Mann Valley Farm, officials decided they would “depopulate.” First, Onan said, they stopped breeding new piglets. They sold their adult females for butchering, and then allowed their existing batches of piglets to grow up to market size. They then sold that batch of pigs for meat as well. The PRRS virus, Onan said, has no effect on humans, so selling infected pigs was safe so long as they were going to butcher rather than to other pig breeders.
With the old herds gone, the next step was to clean the barns. They pressure-washed the barns, Connolly said, got rid of manure, disinfected everything, and then left the place empty for three months over the summer. In September, they brought in a new batch of 40 gilts (unbred female pigs).
The new pigs are purebred Yorkshires, which are a white variety with erect ears. The advantage of raising purebreds, Onan said, is that it adds another educational layer for students working with the swine herds.
“One of the nice things about purebreds from a teaching standpoint is that it gives students the opportunity to track pedigrees,” Onan said. Students can also practice reporting performance data to the breed organization, and provide pigs to 4-H or Future Farmers of America members hoping to show a purebred pig.
Preventing another outbreak of PRRS in this new herd of pigs will be difficult. Transmission, for starters, happens very easily. Essentially, Onan said, all body fluids from an infected animal contain the virus. Manure on the bottom of someone’s boot can transmit it, or nose-to-nose contact between two animals. The virus can also become airborne when fluids from the pigs’ noses ends up sprayed into the air, and can drift as much as 5 miles on the breeze to other pig farms.
The other difficulty with PRRS is its high mutation rate. Vaccinations are developed to prevent individual strains of the virus, but the disease will simply mutate into a new version that the vaccination can’t prevent.
“It’s a very frustrating disease,” Onan said. PRRS has cost the swine industry more money than any other single disease ever, he added.
Prevention options at the lab farm will be limited. The big problem, Connolly said, is that the Mann Valley Farm needs to be open for classes of students. Intense biosecurity measures such as mandatory showers and special clothing are impractical as well as expensive for a farm that is so open to the public. The one advantage the lab farm has is that there are very few other swine operations in the surrounding area, which means that the virus likely won’t be blown in on the breeze from some other pig farm.
“You just hope for the best,” Connolly said. “There’s always gonna be conflict, and something going on.”
For now, the new Yorkshires are doing well, Connolly said. One batch of 60 piglets born in February has already been weaned off their mother’s milk, and another batch of 80 born at the beginning of March will probably be weaned around the end of the month. Because of a shortage of pigs to sell, there will be no spring auction this year. However, next year’s sale will likely go ahead as planned, and will take place either the last Saturday of March or the first Saturday of April.