When a fire destroyed the calf barn at Hanke Farms four years ago, they did not hesitate to rebuild and install the same positive-pressure ventilation system in the new calf barn.
This group-housing calf barn with automatic feeders features a supplemental positive pressure ventilation system. The tube is made of a flexible woven plastic material. “I knew I wanted to put the positive-pressure tubes back in — that was a no-brainer for me because we had such good results in our previous barn,” says Heidi Hanke, herdsperson at the 700-cow dairy in Sheboygan Falls, Wis. “You are giving the calves fresh air without creating a draft on the calves,” she says.
This is one of the hallmarks of positive-pressure systems that have spurred their increased use in nursery and grower barns within the last five years or so, particularly in cooler regions of the country.
But, as with any ventilation system, they are not without their share of challenges, as Hanke knows.
“We didn’t have enough cables suspending (the ventilation tubes) from the rafters,” she says.
When the wind came from a certain direction or the barn was wide open, the tubes tended to bounce around a lot, especially on windy days. The tubes broke, and consequently, did not perform like they should.
“We added a few more cables, and now it doesn’t blow around as much on windy days,” Hanke says.
Fixing the problem has helped maintain good respiratory health among the calves. Here is some design and installation advice to help you head off problems with tube ventilation that can jeopardize calf health.
Focus on fan capacity, not diameter
Essentially, there are three primary components in a positive-pressure ventilation system: a fan, a tube and cables that suspend the tube from the rafters.
During the design phase, it is important to account for three key physical properties within the tube: static pressure, aperture ratio and discharge coefficient. Without going into a lot of detail, just remember that if the system is not designed with these factors in mind, you can end up with a poor match between the fan and the tube. Ultimately, this can result in insufficient air flow through the tube and uneven air distribution at calf level.
“We don’t fix the problem that we set out to fix (i.e., poor air quality at calf level) without accounting for those properties,” says Becky Brotzman, veterinarian and associate outreach specialist at the University of Wisconsin-Madison School of Veterinary Medicine.