Dairy farmer Megan McAllister knows what it looks like when her cows start getting toasty and extreme heat worsens dairy quality along with quantity.

They clump together in groups. Their four-chambered stomachs working on digestion create what she calls their own little “onboard furnace.” And she can measure a drop in how much milk they produce.

“If the girls aren’t comfortable, they aren’t going to be as productive,” McAllister tells Sentient about extreme heat worsening dairy.

Each year, she says her family tries to invest in technology to keep her cows more comfortable, especially cooling. Since they added more fans to their 290-cow operation in New Vienna, Iowa, they’ve noticed less of a dip in milk production on the hottest days of the summer. Now they lose two to six pounds per cow, down from 10 to 12 pounds.

But a new study finds that the heat does more than limit the quantity of milk a cow produces. It also changes the quality, steadily deteriorating nutritional components like fat and protein as temperatures rise, according to a paper out last month in the journal Environmental Research Letters.

This matters to the dairy industry because farmers get paid not by the overall weight or volume, but are instead priced using a formula that takes those nutritional components into account. As climate change increases the intensity and duration of heat events, industrial dairies with more capital tend to be better equipped to handle the added strain on their margins, coauthor and Cornell University associate professor of applied economics Ariel Ortiz-Bobea tells Sentient.

As a result, Ortiz-Bobea sees heat events adding to the trend of consolidation toward bigger farms in the dairy industry, with small farms unable to invest enough to adapt. Another concern is that industry efforts to breed cows to maximize protein and fat content will be inconsistent with a quest for other protective traits like heat resilience.

Read the full article about heat stress and dairy quality by Melina Walling at Sentient Media.