Over the years, Lance Baumgard has documented the physiological effects of heat stress on a cow.

During heat stress, a cow will partition nutrients differently when it is in a thermo-neutral state. Glucose that would normally be used for milk production often gets diverted for other uses during times of heat stress. Because it generates less metabolic heat to burn glucose than fat, a heat-stressed cow prefers to utilize more glucose in her muscle and organs, says Baumgard, an associate professor of animal science at Iowa State University. And, that means less glucose is reaching the mammary gland and the cow is deprived of an important building block for milk production.

But, in a research study in the November issue of Journal of Dairy Science, Baumgard and other researchers at Iowa State show that monensin-fed cows have a 10-percent higher rate of appearance (or production) of glucose per unit of dry matter intake than control cows. That can help maximimze glucose entry into the cow’s energy pool.