Are too many minerals in water a bad thing for cows?

By Lois Caliri

Cows are thirsty and with good reason — they need to drink almost 30 gallons of water a day to produce milk and stay healthy. That water needs to be of good quality because much of the ingested water becomes milk, which is made up of about 87 percent water.

Cows’ drinking water includes a variety of minerals that are beneficial for cows. The various minerals provide the nutritional value of milk to calves and humans. But when that balance is off-kilter, the milk composition could be altered and that could cause problems for cows.

A potential for decreased availability of groundwater for dairy farming exists. Western dairy farms are already seeking alternative sources of drinking water to reduce the burden on natural groundwater reservoirs. High levels of minerals, including iron, may be in some water sources. That could be problematic.

Susan Duncan, a professor in food science and technology, Katharine Knowlton, a professor in dairy science, and Andrea Dietrich, a professor in civil and environmental engineering, are leading research into how excess amounts of iron and other minerals impact dairy cow productivity and health, nutrient digestibility, milk synthesis, and dairy product quality. Duncan and Knowlton are in the College of Agriculture and Life Sciences.

This research project will provide preliminary data for establishing mineral recommendations for water reuse in dairy herd health. The project will benefit water and dairy managers in the U.S. and around the globe.

“Excess amounts of iron and copper in milk can lead to flavor problems in the milk, making it taste bad,” Duncan said. “Additionally, changes in the milk’s mineral composition may reduce the quality of manufactured dairy products, such as cheese and yogurt.”

How the cows’ health and milk composition are affected by high iron content in drinking water is unknown.

“But we do know that iron from feed sources can affect calcium absorption,” Duncan said. Calcium is stored in cow bones, just as it is in humans. In any species, a mother’s body can respond to dietary changes in order to protect the infant from harm. Many questions about how that relationship is affected remain.

The research seeks to answer several questions, including: Will the cow’s natural response to excess iron in the water protect the calf by maintaining the normal milk calcium content? If so, will this cause changes in the cow’s metabolic mineral balance at the expense of her bone health? Will iron from the water source change the way the cows synthesize milk proteins so that there are more iron-binding proteins in the milk?

Georgianna Mann, a graduate student in food science and technology, is conducting the initial studies on milk composition and processing.

Changes in milk composition can impact the quality of dairy products, which may be noted by a decrease in flavor, odor, and texture, and a shortened shelf life of milk and dairy products, Duncan said.

Georgianna Mann, a graduate student in food science and technology, is conducting the initial studies on milk composition and processing. Aili Wang, a doctoral student in the same department, will join the study in  August to examine the changes in milk proteins. Xin Feng, a doctoral student in dairy science, is studying the effects on cows. Katherine “Kat” Phetxumphou, a graduate student in civil and environmental engineering, is evaluating the chemistry of water on dairy farms in Virginia.

The College of Agriculture and Life Sciences Pratt Endowment at Virginia Tech partially funded this research project.