Keeping Cows Cool as Temps Heat Up

On a warm summer day the lines for ice cream at the Daily Scoop on the University of Wisconsin- Madison campus are frustratingly long. Everyone is herded together, waiting their turn to order a cone filled with creamy, cold ice cream -- anything to take the edge off that overheated feeling. But securing a steady supply of this refreshing treat depends on keeping cows cool, too.

Cows create a lot of body heat and use a large amount of energy in the process of producing milk. “When you are comfortable, a cow is warm; when you are hot, a cow is miserable; and when you are cold, a cow is probably fine,” explained Dr. Lou Armentano, a professor in the Department of Dairy Science at the University of Wisconsin-Madison. On those hot summer days, cows immediately respond to the high temperature with decreased milk production.

Cows produce the most milk and are most comfortable when the temperature is between 15 and 85 degrees Fahrenheit. When the temperature increases to the 85- to 105-degree range, milk production is decreased by 20 percent, or more. Once it gets above 105 degrees it can be fatal. At that point, up to 5 percent of the herd can be expected to die.

“The big issue for all the farmers we work with is risk. Extreme weather is adding uncertainty to this already uncertain profession,” according to Michelle Miller, associate director of the UW-Center for Integrated Agricultural Systems.

In an average year Madison would expect 13 days above 90 degrees, but in the summer of 2012 there were 39 days when the temperature surpassed that mark. And scientists expect more hot summers like that in the future.

The Wisconsin Initiative on Climate Change Impacts (WICCI) predicts that summer days and nights in Wisconsin will become increasingly warmer. Climate models point toward an average temperature increase of as much as 3 to 9 degrees Fahrenheit in Wisconsin by mid-century. By 2055 Madison may be seeing an average of 37 days above 90 degrees and 4 above 100 degrees. Many cows are confined to barns with some measure of temperature control, so for them, extreme weather is not a major concern.

Various techniques are used in the barns to keep the cows cool. Open-stall barns have curtains that can be opened in the summer to allow natural breezes to blow through. Temperatures can also be held at bay by building the barn so that it’s in the shade during the hottest part of the day. And some farms have installed evaporating systems that mist and fan the cows on hot days.

According to Dr. Victor Cabrera, UW-Madison dairy science professor and extension specialist, “The trend is that milk production increases year to year because of genetics and/or better management practices, regardless of climate changes” for the cows that are kept indoors.

But not all cows spend their time in the barn. The cows at Rick Adamski’s Full Circle Farm, in Seymour, graze outdoors in the pastures. Shade trees are scattered throughout the pasture and provide shelter from the heat of the summer at this organic farm. Still, Adamski finds that his cows are vulnerable to heat stress once the temperature gets above 90 degrees. When it gets that hot, the cows wait to eat until the temperatures have cooled down.

When they’re ready to graze, “A good permanent pasture shades the soil to keep the soils cooler during the heat of summer,” according to

Adamski. He maintains permanent pastures consisting of dense grasses and clovers in about 85 percent of his 220-acre farm. The thick ground covering of these perennial plants retains moisture and provides additional hydration for the cows. And the diversity of the plants creates a natural insurance for the fluctuations in weather patterns.

Adamski believes that grazing is integral in maintaining this perennial system. “If we manage for both production of the pasture and the livestock, both can be productive.”

For organic operations committed to an outdoor grazing regimen, perennial agricultural systems with soil and herd management may help to meet milk production demands even if hotter summers become the norm.

Organic or not, all dairy farmers and ice cream lovers stand to reap the benefits of farming practices that help cows stay cool.