Summer heat takes a toll on Missouri’s dairy cattle and milk production

ST. JOSEPH, Mo. (News-Press NOW) -- This summer's heat has been hard on people across Northwest Missouri, but it's also taken a toll on other residents: cattle.

When temperatures climb above 72 degrees Fahrenheit, cattle begin to experience heat stress. Unlike humans, they can't run and escape to an air conditioner. A combination of high temperatures and humidity can also leave herds exhausted.

"The cow starts stressing over 72 degrees. And so you're talking on a day when it's 95, you know, 25 degrees warmer plus heat index. Milk production is seriously affected by that," said local Buchanan County farmer Tim Gach, who raises beef cattle and previously operated a dairy farm.

This summer, temperatures across northwest Missouri soared into the 90s, with heat indices over 100 F for several days. Humidity makes sweating more difficult and raises the "feels-like" temperatures or heat index.

Storm Tracker Chief Meteorologist Jared Shelton explained the science behind humidity and sweating.

"The way sweat works is you get the cool-off when it evaporates. And when you have higher humidity, you have a lower rate of evaporation. So temps could be far away from 100, but if the humidity is high enough, you could have feels-like temperatures over 105," said Shelton.

Cows are especially vulnerable because they can only produce about 10% as much sweat as humans. This makes it harder for them to regulate body heat and more susceptible to heat-induced stress.

"They can sweat fairly effectively, but of course not nearly as good as humans,” said Jay Johnson, associate professor of animal welfare and stress physiology at the University of Missouri. “That’s really why the humidity can play a large role in a cow’s ability to deal with heat stress."

Researchers and farmers use a scale called the "temperature humidity index", which helps provide an easy visual and indicates when cattle might experience stress.

Even with mild temperatures in the 70s, elevated humidity percentages can push cattle into that stress threshold.

Heat stress in cattle isn’t just about comfort — it directly affects their biology. When cows overheat, their feed intake drops dramatically, which lowers the energy available for milk production.

Then, when cows do produce and consume energy, it's redirected to cooling their body instead of milk production.

Over time, this nutritional imbalance can weaken immune systems, making cows more vulnerable to illnesses. Researchers note that prolonged periods of heat stress can even affect reproductive performance, delaying calving cycles and further impacting farm productivity.

According to research done by the University of Missouri, heat stress can reduce milk production by three to 20%.

This loss in milk production can add up quickly, especially across the Midwest, where dairy farming is a key industry.

A four-year trend has shown a steady decrease in milk production between May and August, some of the warmest months of the year.

While Dairy is still retally available on store shelves, the strain on farmers is evident.

Tune in to News-Press NOW at 5 p.m. on Thursday to watch this Special Report.