Checking heat stress in dairy cows as climate warms

June 19, 2014 |

Wisconsin dairy farm
Wisconsin dairy farm. (WI DNR photo)

There’s an old saying: The best year a farmer ever had is next year.


Year-to-year weather variability is normal, but extreme weather events are on the rise as a consequence of the state’s warming climate. UW-Madison climate scientists expect Wisconsin to see higher humidity levels, heavier storms (but an overall reduction in summer rains), and more days with temperatures above 90 degrees F. According to projections developed for the Wisconsin Initiative on Climate Change Impacts, these changes are likely to occur within a single generation, making our state’s climate more closely resemble Missouri’s.

Hotter summers could ramp up stress on dairy herds.

“Cows are fine with cold, with frostbite being the only real concern,” says Victor Cabrera, an associate professor and extension specialist for dairy management at UW-Madison. “But when it’s hot and humid, with temperatures rising above 72 degrees F, cows will feel the impact.”

Annual losses due to heat stress reported by the U.S. dairy industry exceed $1.5 billion, mostly in the South and California.

“Heat-stressed dairy cows could give as much as 10 percent less milk from their daily 60-pound average,” says Cabrera.

Heat-stressed cows are also less likely to conceive, and if they do, they are at higher risk for losing the developing calf and delaying lactation. Heat with humidity also increases bouts of mastitis, an inflammation of the mammary gland and udder tissue typically caused by microorganisms. The condition can lead to lower milk production and render milk unusable, because antibiotics frequently used for treatment appear in the milk.

Moving cows indoors is a common solution. Innovative barn designs where air flow can be optimized and mechanized to maximize cooling, along with regular monitoring of ambient temperatures, humidity levels, and animal body temperatures, can protect livestock and livelihoods.

“The thing about cooling cows is, you have to work ahead—once the cow gets overheated, she starts to pant and it’s over with,” says Lloyd Holterman, co-owner of Rosy-Lane Holsteins, LLC in Watertown, Wisconsin. A cow’s normal temperature is 101.5 degrees. Most start panting when their core temperature reaches 104 degrees, and at 107, they die.

Rosy-Lane is home to 830 dairy cows, most housed in a modern, cross-ventilated barn where 38 large, powerful fans keep the air moving. Fans start to run as temperatures approach 60 degrees F. Additional fans automatically turn on as the barn warms up.

Like many farmers who consistently cope with weather variability, Holterman is not convinced about climate change. But he is interested in sustainable solutions to water and power demands that can help his farm run more efficiently, keeping his animals comfortable and productive.

Cow drinking water
Cows drinking from a water tank. (WI DNR photo)

Two years ago, during that record-setting March heat, Holterman’s farm spent $225 more per day to cool the cows. In addition to the mechanically ventilated barn, his cows are cleaned and cooled by recycled cooling water as they wait in the holding pen for milking.

Water usage varies across dairies, but more hot summer days will mean higher costs for preventing heat stress. So too will energy and water demands from other water-intensive industries, as well as residential communities—needs that may bump against one another.

Even within the dairy industry, highly monitored and efficiently run large-scale operations such as Rosendale Farm in Pickett, Wisconsin, can take a significant bite out of available resources. Here, all 8,500 cows are confined in a cross ventilated barn that includes water drips for cooling. But facilities of this scale require a huge capital investment, precision management, access to enough water, and power to run the facility.

Bill Harke, spokesman for Rosendale owners Milk Source, LLC, says total water usage at the facility breaks down to 30 gallons per day per cow.

In April, at UW-Madison, Kifle Gebremedhin, a Cornell University professor of biological and environmental engineering and a UW alumnus, presented his latest efforts documenting modern cow bioenergetics (how heat moves in and out of the animals) to lay the groundwork for better-designed cooling strategies that save on water and energy. They include airflow optimizations and chilled beds for cows, a simple innovative coupling of existing products and technologies to achieve better cooling.

Gebremedhin presented a simple scenario for drawing heat out of the cow and into a cooled waterbed. The group modified mattresses currently used for cushioning cows, pumping chilled water through them.

Gebremedhin reported that cows lying on the chilled mattresses had significantly higher milk production, lower body temperatures, and lower respiration rates than a control group. His group is also working with a farm equipped with an anaerobic digester for generating biogas, which is converted to electricity to power the mattress water chillers, thus creating a closed system to use waste heat and recycle cooling water.

“The heat-exchange water mattress idea is a good one if it provides enough cooling to offset enough heat,” says Holterman. “But it depends on how well and how long the system lasts before a ton of ongoing maintenance comes up—our modern day cows weigh 1,600 pounds and they have sharp feet, and in Wisconsin, there are very few farms with digesters. But the concept is great if they can make it work effectively and economically.”

The Cornell-based project is funded by the state of New York, where climate change conditions are expected to be similar to Wisconsin. “When we mentioned climate change, state officials suddenly sat up straight and listened,” says Gebremedhin.