By Samantha Nelson
Marinus Dijkstra and his 1,550 dairy cows all felt the effects of the 100-degree temperatures that blasted Southern California last summer.
As a result of the heatwave, Dijkstra's Lakeview Dairy Farm in Riverside County saw a significant decrease in milk production, a drop that cost the dairy about $2,250 a day. Dijkstra had to spend an additional $1,500 each month on electricity, trying to keep his cows cool in the summer's extreme heat.
California dairy farmers spend hundreds of thousands of dollars each year trying to keep their cattle cool, as increasingly high summer temperatures, driven by climate change, heat up the country's biggest dairy state.
Cows are especially sensitive to heat and produce less milk when they are overheated, so farmers in California try to keep them cool using shade, fans and sprinkler systems. But these cooling systems use huge amounts of water and electricity, adding costs and wasting resources in an already resource-stretched state.
The state's dairy industry is so threatened by the shifting climate that scientists have begun to explore innovative ways to keep cows cool in hot weather. Since 2018, researchers from the University of California Davis' Western Cooling Efficiency Center have tried out a variety of methods and now believe they have found a solution in a simple algorithmic modification of the existing fan-and-sprinkler systems.
The new system takes account of the climate where cows are located and determines when fans and water need to be used, how fast the fans need to run and how much water is necessary to keep cows comfortably and consistently cool.
"Cows love it cold," said Tyler Ribeiro, a fourth generation farmer in California's Central Valley. "Happy cows produce milk."
'Milk Is Last'
With a normal body temperature of 101.5 degrees Fahrenheit, cows create a large amount of heat as their bodies work to break down feed and produce milk.
"Producing milk is like an athletic activity for cows," said Jennifer Van Os, an assistant professor and extension specialist in animal welfare in the University of Wisconsin-Madison's Department of Animal & Dairy Sciences.
According to the University of Minnesota Extension, cows generally start to feel the heat when ambient temperatures are in the high 60s and lower 70s.
Around 72 degrees, with 50 percent humidity, the animals start to feel mild to moderate heat stress. Higher producing cows, which eat more and create more heat, can begin to experience heat stress in temperatures as low as 65 degrees, even in well-ventilated barns.
When cows struggle to get rid of body heat, their respiration rates start to rise and they begin to drool and breathe with their mouths open. As their systems work to bring their body temperatures down, they produce less milk, an adaptive response to alleviate heat stress, Van Os said.
"They're going to use their energy to take care of themselves first," said Ribeiro, who runs Rib-Arrow Dairy in Tulare County. "Milk is last."
To help cattle regulate their body temperature, California dairy farmers turn on fans and sprayers, gently misting the animals for up to five hours each day before they are milked.
This system might not be enough as periods of extreme heat become more frequent. This year alone, California has experienced several record-breaking heat waves throughout the summer and autumn.
But a changing climate is only part of the problem for dairy farmers. With rising demand for dairy products, scientists have worked to breed cows that are more productive and efficient. These breeding improvements have helped the average California dairy cow produce 55 percent more milk than in the mid-1980s, but the improvements also have effectively stoked the animals' internal temperatures, making it more difficult for them to cope with climbing external temperatures.
"Cows have had problems with heat stress for a while due to changes in climate, with warmer temperatures for longer seasons," said Alycia Drwencke, a dairy management specialist for Cornell Cooperative Extension who was involved in the UC Davis cooling research as a student. "But then we've also seen genetic changes within cows that cause them to produce more milk."
The Right Amount of Cool
The Western Cooling Efficiency Center first began exploring better options for cooling cows to help California's dairy industry during the drought that ended in 2017.
The researchers began by comparing four different systems for cooling cows.
One used mats buried underneath the cows' sand bedding. In theory, water flowing through the mats would absorb heat from the cows through conduction, then the heated water would be transferred to a chiller and cycled back to the mats. Another method used a "swamp cooler," with ducts blowing water-cooled air over the animals while they rested.
Researchers also tested a method that used traditional water and fans but moved the fans closer to the water to promote evaporation from the cows' bodies. In another trial, the sprayers were used for a shorter period of time.
None of the systems was able to cool the animals sufficiently.
Controlling the controls
Theresa Pistochini, engineering manager at the center, realized there were opportunities within the cooling systems that farmers were already using.
If they could predict how long it would take a cow's fur to dry based on ambient conditions, that timing could determine how frequently the cows needed to be sprayed and when and how fast to run the fans.
The researchers came up with an algorithm that uses ambient temperature and humidity levels to guide the output of water and air in the sprayers and fans used to cool the cows. The formula helps optimize water and electricity usage, while ensuring that cows are properly cooled.
The researchers successfully tested the model on a dairy farm in Tulare County this summer by installing a controller unit in a barn's existing cooling system.
They projected that the savings demonstrated by the model-based controller could reduce annual electricity consumption by 20 percent and water consumption by 40 percent.
Van Os and her students also tried out a new cooling system at Rosy Lane Holsteins in Watertown, Wisconsin.
Before, the farm would cool its cows in a holding area using sprinklers, right before they were milked.
"We saw how inefficient that was because a lot of water wouldn't hit the cows," said Lloyd Holterman, a farmer and member of Rosy Lane Holsteins.
The farm moved its showerheads into the milking parlor, where it now sprays the cows as they are being milked. According to Holterman, Van Os' students tested the cows and confirmed that their new method was working to cool them.
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