Ventilation in the two-year-old calf barn seemed satisfactory. Still, pneumonia was a prevalent problem among calves housed in the naturally ventilated barn.

A field investigation by Ken Nordlund and colleagues at the University of Wisconsin School of Veterinary Medicine led to some answers.

During the investigation, the farm installed a positive-pressure ventilation system in the calf barn. It made a world of difference on airborne bacterial counts — particularly inside the pens. Colony-forming units (cfu) of bacteria per cubic meter of air were cut by 75 percent inside the pens. Plus, the farm saw a 25-percent decrease in pneumonia treatments.

Poor ventilation inside calf barns creates a respiratory-damaging environment. A study in the October 2006 Journal of Dairy Science confirms this and presents some compelling reasons for improving ventilation inside calf pens.

Keep it open

The study involved 13 naturally ventilated calf barns. During the study, airborne bacterial levels were much higher inside the calf pens than in the center alleys. (Please see the sidebar, “Pen vs. alley bacterial levels.”) One of the risk factors associated with this was the presence of solid panels on the front and back of calf pens.

The average airborne bacterial count in the pens was 112,280 cfu per cubic meter of air. Overall, pen bacterial counts ranged from 29,000 to more than 326,000 cfu per cubic meter of air. Bacterial counts that exceed 100,000 cfu per cubic meter are a risk factor for respiratory disease, Nordlund says.

Take-home message: Remove solid front and back panels on calf pens — even in winter. Enclosing pens only impedes ventilation and increases airborne bacteria. However, you should keep a solid panel between adjoining calf pens.

Reduce the risk

No surprise, the high bacterial levels in the calf pens were associated with more respiratory problems in the calves.

On 10 of the 13 farms in the study, more than 20 percent of the calves had respiratory scores greater than 5. On one farm, nearly 60 percent of the calves scored a 5 or more.

Take-home message: Decrease air counts inside calf pens to reduce the risk of calves falling victim to respiratory illness. You can make a difference in calf health.

A breath of fresh air

Read about a farm that added supplemental ventilation to a naturally ventilated calf barn and see pictures of the system at:

Pen CFU/cubic meter of air

Key factors for respiratory health

To reduce airborne bacterial counts in calf pens and improve calf respiratory health, follow these measures:

  • Remove solid front and rear panels on calf pens. This improves air exchange inside the pen.
  • Supply deep straw bedding in which the calf can nest. This reduces chilling in cold weather. “Nesting means that you cannot see the calf’s legs when it lies down in the bedding,” says Ken Nordlund, veterinarian at the University of Wisconsin.
  • Keep a solid panel between calf pens to reduce calf-to-calf contact and respiratory disease.
  • Lower the barn temperature.
  • Create larger pens. Shoot for 30 square feet of space inside the pen.