Financial implications of installing air filtration systems to prevent PRRSV infection in large sow herds

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. The specific objectives of the 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 3000 sow farm. Variables included in the study were production variables (quarterly) from respective herds; air filtration status; number of pig sites within 4.7 km 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 5927 more pigs than unfiltered farms. The payback 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. Payback period sensitivity analyses were performed for both biological and financial inputs. The payback period was most influenced by the premium for weaned pig sales price for PRRSV-negative pigs, and the relative proportions of time that filtered vs. unfiltered farms produced PRRSV-negative pigs. A premium of $5 per pig for PRRS-negative weaned pigs reduced the estimated payback periods to 2.1 years for Scenario 2 and 2.8 years for Scenario 3.