By Sukie Kevane
Dairy and beef producers are feeling the strain of heat waves and so are their animals. Longer, hotter summers are making it harder for cows to stay healthy and productive. Heat stress lowers milk yields, weakens cows’ immune systems and can even threaten fertility.
For farmers, the impacts go beyond animal health: heat stress reduces milk yields and fertility in cows, which translates directly into financial losses from lower production and higher management costs. Lower productivity also increases the methane intensity of any milk or meat produced.
But across the world, producers, veterinarians and nutritionists are responding with new tools and time-tested strategies to help livestock cope. These solutions matter not only for animal health, but for food security, rural livelihoods and climate resilience.
How does extreme heat impact cows?
When cows are exposed to high temperatures and humidity, they struggle to stay cool. Unlike humans, cows cannot sweat effectively, and their natural cooling behaviors, like panting or standing more, aren’t as effective in extreme conditions where temperatures are hotter or prolonged. A cow’s normal body temperature is about 102°F, so even small increases can push them into dangerous territory. Scientists use the Temperature-Humidity Index (THI) to measure when conditions become stressful for livestock.
It’s important to keep the Temperature-Humidity Index (THI) below a critical threshold, because when cows overheat a condition known as “heat stress” it leads to lower feed intake, reduced milk production, and changes in milk quality. It also impairs fertility and weakens the immune system, leaving cows more vulnerable to illness. These effects can linger even after temperatures drop.
In the United States, dairy producers lose an estimated $1 to $2.5 billion each year due to heat-related impacts, with small and mid-sized farms often hit hardest.
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