Despite enormous efforts to control and eradicate porcine reproductive and respiratory syndrome (PRRS) virus, the disease continues to cause large losses to the North American swine industry. Air filtration takes biosecurity to a higher level and allows producers to effectively produce negative piglets for a longer period of time.

A study at the University of Minnesota compared the PRRS outbreak history of 20 filtered and 17 control (non-filtered) sow farms. Data was collected from October 2004 to June 2011. The information encompassed 120,000 sows from high-density regions in the Midwest.

Overall, implementation of air filtration was associated with improved performance on the farm and financial advantages to filtered sow farms.

(Pictured above: Example of an air filter box.)

Based on the data, farms that were filtered experienced an 80% reduction in the risk of PRRS breaks compared to non-filtered farms. Filtered farms had a 4% higher farrowing rate, an extra 1.9 pigs weaned/sow/year and a 2.3% decrease in sow mortality rate.

As a result of these improvements, production models predicted a total benefit of almost 6,000 pigs weaned/year for the modeled filtered farms vs. the non-filtered farms.

In this study, non-filtered farms had a PRRS virus break every 1.4 years and filtered farms had an outbreak every 7.9 years, on average.

Using actual production data from the sow farms and assuming a $5 premium for PRRS-negative weaned pigs translates into a mean difference of $1.70/pig in weaned pig value between filtered and non-filtered farms. According to the researchers, this value will significantly influence the payback period of this investment.

Minnesota researchers calculated a payback period of 2.1 years for an initial investment of $150/sow/year (attic-filtered farms) and a payback period of 2.8 years for a $200/sow/year investment (attic and sidewall panel-filtered farms).

Those figures are based on a weaned pig premium of at least $5/pig for PRRS-negative piglets and a filter replacement schedule of six months for pre-filters and three years for filters.

Researchers caution that these figures are long-term averages and are not intended to apply to individual herds. Also, the calculations would not apply to herds at low risk of PRRS or herds with less comprehensive biosecurity. Biosecurity should be first rate before investment in filtration is considered.

Researchers: Carmen Alonso, DVM, and Peter Davies, DVM, College of Veterinary Medicine, University of Minnesota; Dale Polson, DVM, Boehringer Ingelheim Vetmedica, Inc., Kansas City, MO; Scott, Dee, DVM, Pipestone (MN) Veterinary Clinic; and William Lazarus, Department of Applied Economics, University of Minnesota.  For more information, contact Alonso by phone (651) 315-0233 or e-mail