Veterinary Wisdom

Warm barns

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In my neighborhood, a warm dairy barn used to mean a tiestall or stanchion barn, and those barns had temperatures well above freezing even on the coldest winter days. As freestall barns became the norm, almost all were designed to be cold. Cold usually means natural ventilation with an open ridge and open eves. On very chilly winter days, the temperature in those barns might only be 10 degrees warmer than the outside temperature, for example.

Cows did not seem to mind, unless the sand in the stalls froze, were covered with snow or alleys developed significant buildup of frozen manure. Humans mostly did not like cold barns in the winter. We had to wear so many clothes that we could no longer get through the pass-throughs. Some of us could barely fit through normal-sized doors. Plus, we needed thick gloves or those big chopper mitts, which really made it hard to draw up 2 cc of GnRH and inject it into the neck of a cow, for example. But, we adapted because we knew it was best for the cows.

Recently, farmers have pioneered ways to keep naturally ventilated barns warmer in the winter. The most successful efforts use power ridge vents instead of a completely open ridge. Most farmers leave the eve vents open when remodeling, but some make the vents smaller. Some others even close the eve vents. Some farmers add insulation to non-insulated roofs, and others do not. However, if done correctly, power vents do seem to result in significantly warmer barns in winter without significant detriment to animal health and production. Humans really like these barns.

There are challenges, however. First, when it is really cold, the screens over the power vents may freeze up and require thawing, which is accomplished by turning the fans off until the frost melts. This can create challenges to animal health. Second, particularly in barns where the eve vents are closed, farmers may need to regulate the curtain openings much more frequently. This commonly happens as the outside air temperatures rise above roughly 20 degrees, but the temperature when the curtains need to be opened varies between barns. If farmers do not open curtains, the barns may become very humid and smelly. Summers also create challenges.

According to retired Kansas State University agricultural engineer Joe Harner, these barns are warmer in the summer. There is simply no way that power vents spaced 40 feet apart, for example, can remove as much air as a 24-inch-wide open ridge. However, my own observation is that if the barn did not have an insulated roof before, adding insulation may make the barn cooler during late morning and early afternoon on sunny, hot days. Harner is correct that these barns do not remove as much air on hot, still afternoons as an open ridge would and, thus, probably are hotter in the afternoon and retain heat much longer as the outside temperatures drop at night. Still, even with these challenges, most producers are happy with the results.

When used in calf barns, the results are less clear. Trying to keep a newborn calf barn significantly warmer than outside air usually results in poor air quality and impaired animal health. Calves do not generate much heat, so barns need to be kept very tight with a few vent fans running on very cold days if one wants to keep them warm.

Of course, one could add heat, but doing this while maintaining adequate ventilation is not economically feasible for most farms. However, power vents might work in calf barns if enough fresh air is brought into the barn. Installing positive pressure tubes is one way to get this done. Four exchanges of air per hour is the recognized minimum standard of winter. It may be that this is too low or too high, but any power ventilation system should be designed to maintain at least four changes per hour in very cold weather.

This applies to calf and cow barns. In general, keeping calf barns cold seems to be the best practice for animal health. It is, however, imperative that calves in group housing inside cold barns have jackets and deep, dry bedding. Truthfully, no one really knows how to mechanically ventilate calf barns in such a way that both humans and calves are warm and healthy during winter in the Upper Midwest.

For now, it looks like we can keep freestall barns warmer than we used to think without negatively affecting cow health and production. That has made life easier for farmers and their workers on those frigid winter days.

Jim Bennett is one of four dairy veterinarians at Northern Valley Dairy Production Medicine Center in Plainview, Minnesota. He consults on dairy farms in other states. He and his wife, Pam, have four children. Jim can be reached at bennettnvac@gmail.com.

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