Cows in heat stress: a hot day, ten percent less milk

Heat stress is also noticeable in dairy cows: an extremely hot day can reduce the milk quantity of a cow by up to ten percent. The effect has an effect for up to ten days, as a research team reports in the “Science Advances” journal. In the course of climate change, there is a noticeable decline in milk production.

If the emissions of greenhouse gases are not reduced, the cows in the ten countries with the world’s highest milk production could give up to four percent less milk in the period 2045 to 2055, the researchers around Ayal Kimhi from Hebrew University of Jerusalem in Rechovot (Israel) report. In Germany, the losses could be about 1.4 percent. In addition to the temperature, the air humidity also has an impact on the milk yield.

Fans and water showers for cows

The scientists had data from the Israeli cattle breeder association for the years 2009 to 2020, which were compared with the weather data during this period and measures by farmers for heat protection. “Dairy farmers are aware of the negative effects of heat stress on their herds and use different forms of adaptation,” said Kimhi. Fans and water spray systems are mainly used.

Even after only a very hot day, it takes around ten days for the milk quantity to normalize. During this time, milk losses add up to 25.6 percent compared to a time without a hot day.

Losses cannot be prevented

In order to reduce such losses, more and more dairy farmers in Israel have taken measures against the heat stress of their animals, which they mostly keep open to the surrounding area. The loss can be reduced, but not prevented.

“The dairy industry in Israel is well suited as a test field, since the companies are distributed all over the country and exposed to a wide range of temperature and moisture that corresponds to the conditions in the leading milk production countries worldwide,” said Mit author Ram Fishman from Tel Aviv University.

“Our study showed that extreme heat has significant and permanent effects on milk production; even the most modern and best -equipped companies use adaptation strategies that may not do justice to climate change,” said MitAutor Eyal Frank from the University of Chicago.