High temps stress Minn. dairy cows

This week's high temperatures have dairy farmers across central and southern Minnesota on alert as the heat and humidity can hamper a cow's ability to produce milk.

Cows produce lots of heat when they eat. They're happy at temperatures around 45 to 50 degrees. Hot weather can put cows under a lot of stress, said Marcia Endres, an associate professor of dairy science at the University of Minnesota. Stress can cut a cow's food intake and drive down its milk production by as much as 15 percent, she added.

Minnesota is home to about 430,000 dairy cows. In 2011, unusually hot weather killed thousands of head of cattle with losses totaling about $1 million.

It's hard for cows to recover from long stretches of heat that last more than a few days, she added, but farmers can help ease the heat by placing oversized fans and sprinklers inside the barns.