Proper Ventilation in Freestall Barns

Dairy farmers who build freestall barns for their cattle are faced with two choices in ventilation: natural and mechanical. The decision can make a vital difference in the health and milk production of the cattle, who benefit from a dry, moisture-free environment. Proper air exchange also removes odors and gases that can contribute to poorer milk production.

  1. About Ventilation

    • Freestall barn ventilation, note the authors of a Kansas State University study, "is influenced by sidewall opening, eave opening, building width, ridge opening and wind speed." Keeping proper ventilation in these barns is vital to the health of the lactating cows, who naturally produce great amounts of heat and moisture, and who spend up to 90 percent of their day in the barn. A well-ventilated freestall barn can mitigate heat stress and protect the animals from solar radiation.

    Natural Ventilation

    • Most freestall barns in temperate environments contain little or no insulation, as the cows typically are not washed or milked in these structures. In these barns, natural ventilation--- consisting of open windows supplemented by fans---protects the cows from wind, sun and rain; protection from normal winter conditions is less of an issue as cattle are typically more tolerant of cold weather than humans. The key issue is utilizing a barn design that creates a dry environment that provides consistent airflow. According to a study published by Pennsylvania State University, freestall barns that employ natural ventilation must include strategically placed openings to draw in breezes and foster thermal buoyancy, or what's called the "chimney effect."

    Tunnel Ventilation

    • A standard design for freestall barns, tunnel ventilation is a form of mechanical ventilation that draws fresh air into the barn through an open endwall. As the Cornell University Dairy Facilities Engineering website notes, tunnel fans mounted at the opposite endwall creates sight negative pressure that draws the air into the barn.

    Cross-Ventilation

    • Another example of mechanical ventilation is in the low-profile cross-ventilated (LPCV) barn, an eight-row-wide freestanding unit also known as the wide-body. The Milk Producer Magazine---in an article reposted by the Ontario Ministry of Agriculture---says this type of barn takes up less space and offers more ventilation than the four-row alternative. In an LPCV setup, two air sources, an open curtain wall and a bank of fans, sit at opposite sides of the barn. The sides contribute to air exchange at 60 to 120 seconds during warm weather. Baffles installed over the stalls can speed air flow and direct air downward to the cattle.