Cows can feel the heat just like people.

Heat stress can significantly reduce cows' appetite, fertility and milk production levels during the summer, according to Cargill Inc. The stress can begin when the temperature-humidity index reaches 68, which is still a comfortable level for most people.

Cargill thinks it has a solution. The Wayzata-based company reported Tuesday that trials in Texas, Brazil and the Netherlands showed that new products called I.C.E. and Cooling Pack have helped protect cows at the ­cellular level.

Cargill's global ruminant technology director Ercole Zerbini said that adding key nutritional ingredients can help cows stay hydrated and avoid dramatic increases in overall body temperature. It can also help them recover faster after high heat and humidity, he said, and improve pregnancy and fertility rates that normally decline during hot weather.

Zerbini said the customized feeding solutions work best when they are started before a heat wave begins.

In the trials, one U.S. dairy operator was able to maintain 70 pounds of milk production per cow during each summer day instead of having it drop to 60 pounds per day when temperatures climbed.

Cargill officials said that the feeding solutions are now being marketed in the United States and eight other countries.