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Financial Implications of Installing Air Filtration Systems to Prevent PRRSV Infection in Large Sow Herds

14 August 2013

Using modelling, researchers in the US found that the installation of air filters to pig houses to keep out the porcine reproductive and respiratory syndrome (PRRS) virus could result in almost 6,000 more pigs being produced from a 3,000-sow herd. This additional output alone led them to calculate a pay-back period of around five to seven years for the investment.

Air filtration systems implemented in large sow herds have been demonstrated to decrease the probability of having a porcine reproductive and respiratory syndrome virus (PRRSV) outbreak. However, implementation of air filtration represents a considerable capital investment, and does not eliminate the risk of new virus introductions, according to a paper soon to be published in the journal, Preventative Veterinary Medicine.

Carmen Alonso from the University of Minnesota and co-authors there and with Boehringer-Ingelheim and Pipestone Veterinary Clinic explain that the objectives of their study were:

  1. to determine productivity differences between a cohort of filtered and non-filtered sow farms, and
  2. to employ those productivity differences to model the profitability of filtration system investments in a hypothetical 3,000-sow farm.

Variables included in the study were production variables (quarterly) from respective herds; air filtration status; number of pig sites within 4.7km of the farm; occurrence of a PRRSV outbreak in a quarter and season.

For the investment analyses, three scenarios were compared in a deterministic spreadsheet model of weaned pig cost:

  1. control
  2. filtered conventional attic, and
  3. filtered tunnel ventilation.

Model outputs indicated that a filtered farm produced 5,927 more pigs than unfiltered farms.

The pay-back periods for the investments were estimated to be 5.35 years for Scenario 2 and 7.13 years for Scenario 3, based solely on sow herd productivity.

Pay-back period sensitivity analyses were performed for both biological and financial inputs.

Alonso and co-authors found that the pay-back period was most influenced by the premium for weaned pig sales price for PRRSV-negative pigs, and the relative proportions of time that filtered versus unfiltered farms produced PRRSV-negative pigs. A premium of $5 per pig for PRRS-negative weaned pigs reduced the estimated pay-back periods to 2.1 years for Scenario 2 and 2.8 years for Scenario 3.

For more information, please click here.


Alonso C., P.R. Davies, D.D. Polson, S.A. Dee, W.F. Lazarus. 2013. Financial implications of installing air filtration systems to prevent PRRSV infection in large sow herds. Preventive Veterinary Medicine. 111(3–4): 268–277. doi: 10.1016/j.prevetmed.2013.05.001

Further Reading

You can view the full report (fee payable) by clicking here.

Find out more about PRRS by clicking here.

August 2013

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