Positive-pressure ventilation makes a comeback to reduce PRRS transmissions
A ventilation system that fell out of favor when it caused deterioration in swine buildings is making a comeback.
Producers looking for ways to reduce porcine reproductive and respiratory syndrome (PRRS) find positive-pressure ventilation with some modifications works well now, especially in older building, according to Aaron Lower, DVM, Carthage Veterinary Clinic, Carthage, Iowa.
“For a period of time, we controlled swine barns through positive-pressure ventilation,” Lower said.
Fans blew air into the barn and air escaped through special outlets. These systems were easy to manage and air distribution was excellent. However, warm, humid air could move into an attic or other dead areas and cause building deterioration.
Producers had no choice but to return to negative-pressure ventilation systems where fans create a slight vacuum in the barn to draw air in through special inlets, he explained.
PRRS changed ventilation
Then PRRS arrived and the swine industry needed new ways to manage this costly virus. One option was a system to filter incoming air and minimize PRRS outbreaks. The system was proven effective in reducing PRRS transmissions, Lower told Pig Health Today.
However, in an older barn with leaks and cracks, it was impossible to expect 100% of the air to enter through the filters, he explained. “But if you turn it around and push filtered air into the barn, the leaks and cracks don’t matter because air is pushing out of the barn.”
It still is a “little risky” putting a positive-pressure ventilation system in new construction, Lower added. But new designs address past problems. All areas including attic spaces are positive pressure to prevent dirty air from entering and deteriorating building trusses. New, fully sealed building materials are used for sidewalls to reduce damage from dust and humidity.
The cost to add an air filtration system is $75 to $90 per sow plus long-term recurring costs of $1 to $2 per sow for changing filters, etc., according to Lower.
Upgrading the entire ventilation system costs $100 to $300 per sow, depending on the age of the facility. Because ventilation upgrades are expensive, producers usually upgrade only sow farms, he said.
Investment in an upgraded ventilation system with filtration can pay for itself over time, depending on the frequency of PRRS outbreaks.
“If a sow farm has a PRRS break history of every 3 to 5 years, then the return is good enough to go ahead and spend the money to filter those farms,” Lower said.
The effectiveness of a filtration system on a ventilation system is being studied on several large-scale projects. Lower said early indications suggest farms are five to eight times less likely to break with PRRS if filtration is added.
“And if you have a good ventilation system, it makes my job a lot easier,” he quipped.