Managing curtains on calf barns can become tricky in spring and fall when the air is often cool and damp with intermittent periods of warm weather. While there aren’t any well-researched rules for managing curtains, we can apply some basic principles to ensure the air in calf barns is free and clear of problems this fall.
Natural ventilation in calf barns is primarily achieved by capturing wind through an opening in the eave or curtain sidewall. However, we need to balance ventilation with keeping calves warm. Given that a calf’s thermal neutral zone (the ambient temperature range in which calves don’t expend additional energy to cool off or stay warm) is 50-78 °F at birth and 32-73 °F at 1 month old, a starting set of guidelines for a nursery calf barn might be as follows:
- Below ~40 degrees F, curtains should completely cover the sidewall. A well-designed supplemental positive pressure ventilation system should be installed and run continuously throughout the year to provide the minimum ventilation rate regardless of curtain position, while not creating a draft on the calves.
- Between ~40-75 degrees F: adjust the top curtain opening "as needed", but what that exactly looks like depends on wind, rain, and sun.
- Above ~75 degrees F, the curtains should be completely open.
Older calves have a lower critical temperature of around 20 degrees F, so the above general guidelines should be adjusted downward accordingly. Wet, dirty, and matted hair coats on calves will not insulate as well as clean coats, and these calves will require more energy to stay warm before the mercury drops below their normal lower critical temperature, and require changing the above guidelines as well.
Mechanical curtain controllers are helpful, automatically adjusting curtains in relation to temperature and fancier systems also account for wind and even precipitation. A few mismatched weather events will require an override of the mechanical system, however. Also, winds can be calm or from a non-prevailing direction much of the time, as you can see on this wind rose from the NRCS for Madison in September, so a supplemental positive pressure ventilation tube system will also be important for these periods of time, not just when the curtains are closed.
Visit The Dairyland Initiative for more information.
Courtesy of The Dairyland Initiative NEWS, Fall 2012