Veterinarian’s Corner: Manage Calf Barn Ventilation During Temperature Swings – Courtney Halbach, The Dairyland Initiative
Fall and spring are tricky times of the year to manage ventilation in calf and heifer barns because of fluctuating temperatures. The goal of any calf ventilation system is to provide a sufficient number of air exchanges per hour without creating a chilling draft. An appropriately designed naturally ventilated barn with a 1-to-4 roof pitch, open eaves (1 inch of opening on each sidewall per 10 feet of building width), and an open ridge (2 inches per every 10 feet of building width) ventilates when air enters the barn through the eave openings and exits out of the ridge as it warms up; this is called the chimney or stack effect.
Estimating ventilation rates based on natural wind currents and the stack effect is challenging. The minimum winter ventilation rate is four air changes per hour (ACH), which can be consistently achieved with an appropriately designed positive pressure tube system. As temperature increases, so does the required ventilation rate. In mild fall and spring weather, we target a ventilation rate of 15 to 20 ACH; in the summer months, we target a minimum of 40 ACH. This can be done by opening the sidewall curtains in stages on a naturally ventilated barn.
Keeping in mind that a calf’s thermal neutral zone (the ambient temperature range in which calves do not expend additional energy to stay warm or cool off) is between 50 and 78 degrees F at birth, and between 32 and 73 degrees F at one month old, a starting set of guidelines for a calf barn might be as follows:
- Curtains should be completely closed at temperatures below 40 degrees F, while the eaves and ridge should remain open. A well-designed supplemental positive pressure tube ventilation (PPTV) system should be installed and ran continuously year-round to provide the minimum ventilation rate of four ACH while not creating a draft on the calves, regardless of curtain position.
- Between 40 and 75 degrees F, adjust the top of the curtain opening “as needed” depending on wind, rain, and sun.
- As temperatures approach 75 degrees F and above, curtains should be completely open to capture as much of the prevailing winds as possible.
Because older calves have a lower critical temperature around 20 degrees F, the above general guidelines should be adjusted downward accordingly. Calves and heifers with wet, dirty, and matted hair coats will require more energy to stay warm than animals with clean, dry coats, so the above guidelines would again have to be adjusted accordingly.
Automatic controllers can help minimize the chore of opening and closing curtains, while ensuring that calves get the fresh air they need. Basic controllers adjust curtains in relation to temperature, while more advanced controllers also account for wind and precipitation.
For mechanically ventilated calf barns, you will want to work with the consultant who designed the system to stage the fans depending on the indoor temperature of the barn and/or outdoor temperature.
Spring and fall are good times of the year to perform regular maintenance on PPTV systems and to check that eaves, soffits, and PPTV weatherhoods are free of debris.
It is important to remember that bedding provides the necessary insulation and shelters calves from large temperature swings. For information about recommended bedding depth, type of bedding and calf barn ventilation, visit The Dairyland Initiative website.
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