A new Israeli study has discovered that extreme heat reduces milk production by up to 10% and that adding cooling technologies offsets only about half of the loss.
ByJUDY SIEGEL-ITZKOVICH JULY 13, 2025
A cow named Kharta from Kibbutz Sa’ad in the South has produced 18,208 liters a year as the highest individual milk production record for a cow in Israel. It has also been recognized as a world record holder for milk production.
In addition to the individual record, Israeli dairy cows are known for their high average milk yield, with some farms reaching averages of over 14,000 liters per cow per year. Israel was far ahead of its closest competitors, with cows in Denmark and Estonia in second and third place but way behind.
But now, a new Israeli study has discovered that extreme heat reduces milk production by up to 10% and that adding cooling technologies offsets only about half of the loss. While recent studies have shown climate change will cut crop production, there has been less research into its impacts on livestock.
Dairy farmers already know their cows are susceptible to harm from heat.
One of the most comprehensive assessments of the impact of heat on dairy cows, a study in the journal Science Advances – the American Association for the Advancement of Science’s open-access multidisciplinary journal – and titled “High-Frequency Data Reveal Limits of Adaptation to Heat in Animal Agriculture” found that just one day of extreme heat can cut milk production by up to 10%. The effects of that hot weather can last more than 10 days later, with efforts to keep cows cool being inadequate.
“Climate change will have wide-ranging impacts on what we eat and drink, including that cold glass of milk,” said one of the study’s co-authors, Asst. Prof. Eyal Frank, now at the Harris School of Public Policy at the University of Chicago. “Our study found that extreme heat leads to significant and lasting impacts on milk supply, and even the most high-tech, well-resourced farms are deploying adaptation strategies that may be an insufficient match to climate change.”
His co-authors were economist Prof. Ayal Kimhi of Hebrew University’s Robert Smith Faculty of Agriculture, Food and Environment in Rehovot and vice president of the Shoresh Institution for Socioeconomic Research; post-doctoral student at the Harris School Dr. Claire Palandri; Dr. Yaniv Lavon and Ephraim Ezra of the Israel Cattle Breeding Association; and Associate Prof. of Public Policy and Sustainable Development at Tel Aviv University Ram Fishman.
Israel’s dairy industry has several unique attributes that make it a good testing ground: the dairy farms scattered throughout its region experience a wide range of temperatures and humidity that represent conditions for top milk-producing countries; prices are centrally controlled; and virtually all farms have adopted technologies to reduce heat stress.
Kimhi, who was born on Moshav Kfar Warburg in south/central Israel and continues to live there, is very familiar with dairy cows because his grandfather raised them.
“The increasing heat load due to climate change is not only reducing milk production but also threatens the cows’ health, as it creates physical stress that makes them more vulnerable to diseases. In fact, the cooling technologies themselves expose the cows to excess humidity that may lead to infections. Even more importantly, the heat stress affects cows’ fertility,” he explained to The Jerusalem Post.
He added that “Dry air is good, even if it’s hot, so the farms’ locations are less of a problem, just as Jerusalem’s summer is more pleasant than Tel Aviv’s. There has to be more research and implementation of how to cool cows off better, such as when they come to eat, a fan could be turned on automatically, and a breeze dispels pathogens through the sheds’ open roofs. Genetic improvements of cows should take into account resilience to heat in addition to high milk yields.”
Global implications of rising heat on livestock
EUROPEANS CONTINUE to drink a lot of milk, but in countries like China and India, where the standard of living has risen considerably, the consumption of milk has increased markedly. Many studies have predicted the impact of climate change on crops, but less is known about its effects on livestock. Dairy cows in particular have been shown to be vulnerable to heat, which can affect milk production, the authors wrote.
“This could have widespread implications both nutritionally and economically, with about 150 million households around the world raising dairy cows. While global milk production is expected to grow faster than most other main agricultural commodities to meet rising demand, it’s uncertain how much climate change could slow growth,” they added.
The researchers analyzed highly local temperatures and humidity and 320 million daily milk production observations over 12 years, representing records from more than 130,000 Israeli dairy cows. They then surveyed 306 dairy farm managers, asking whether they have taken steps to adapt through cooling technologies.
They found that milk output declined significantly on hot days – by up to 10% when daily temperatures exceeded 26°C. One additional hour of temperatures above 26°C reduces daily milk yield by 0.5%. The effects from extreme heat exposure lasted for more than 10 days. The researchers also noted a prolonged effect of humid heat exposure, with milk production seeing negative impacts for more than 10 days after exposure – with 10 consecutive days of extreme heat causing a 25.9% reduction in output on the 11th day.
While nearly all local farms keep cows in the shade, there are different systems that can either cool the cow directly or the surrounding environment. Owners have widely adopted cooling infrastructure over the past 20 years, but the researchers found these strategies only partially reduce the losses from extreme heat, and, the hotter it gets, the less helpful these cooling systems are.
Even in a high-tech, well-resourced setting like Israel, adaptation could not fully offset the damages.
The researchers conducted a cost-benefit analysis to assess the economic returns of adopting cooling technologies for the typical dairy farm. Compared with a one-time fixed cost of $30,804 for cooling equipment, the investment breaks even in about a year and a half, not taking into account operation and maintenance costs.
They also found that cows are much more sensitive to heat during specific times, such as early lactation, when they would ordinarily produce more milk. Those that have had more calves are also known to produce more milk, but they are also more sensitive to heat. The decline in milk output due to heat stress is more than twice as high for cows that have had two or more calves.
The team urged the relevant authorities to support research into a broader range of strategies to reduce stressors in dairy systems, particularly in regions with growing heat exposure and expanding dairy sectors. Reducing heat exposure through fully enclosed housing may introduce new stressors – like confinement – that undermine welfare and productivity.
Dairy farmers could also decide to reduce other stressors like confinement or cow-calf separation to minimize the compound effect on cow sensitivity and build resilience, they concluded.
DR. NAHUM ITZKOVICH, former director-general of the Agriculture Ministry, who many decades ago owned a dairy farm with 100 cows at Moshav Ometz in Emek Hefer before closing it 12 years later, said in an interview that “cows used to be cooled with mists of cold water and fans, but with global warming, this isn’t enough.
“Genetic engineering to develop cow varieties that are less affected by heat takes a very long time and is very expensive, and the public doesn’t like the idea of genetic engineering of food or animals. It’s easier to breed cows, even by artificial insemination, that are known to be resistant to heat. There are large farms in China that have purchased Israeli cows to increase their milk yields.”
Most Israeli dairy farms have music that the cows and farmers enjoy. “Thanks to research, farmers have formulated the best mix of grains at different ages of the cows to make them most productive. In most farms, milking robots developed here handle them gently and humanely; they are sold around the world,” he added.
Itzkovich concluded that the decision by Finance Minister Bezalel Smotrich to eliminate tariffs for Israeli dairy products sold in the US was “not a smart decision. We need to ensure that sophisticated Israeli agriculture will continue to exist and be strong and not depend on foreigners to feed us.”
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