US ARS: Grazing cows produce more cancer-fighting compound in milk.

April 10, 2000

A change in the way U.S. dairy cows are fed may give consumers one more healthful reason for drinking milk. Cows grazing pastures, or fed diets containing vegetable oil, produced five times more of a cancer-fighting compound–conjugated linoleic acid (CLA)–than cows fed conventional diets, according to Agricultural Research Service studies in Madison, Wis.

CLA is a fatty acid found in beef and dairy fats. The human body doesn’t produce CLA on its own, but CLA is available through foods such as whole milk, butter, beef and lamb.

ARS dairy scientist Larry Satter at the ARS U.S. Dairy Forage Research Center showed how to increase CLA levels in milk from cows fed typical confinement rations. He added whole soybean and linseed oils to a typical corn-alfalfa diet, boosting the CLA content in the cows’ milk to equal the levels obtained from grazing. ARS and the Wisconsin Alumni Research Foundation (WARF) patented this method to increase CLA in cows’ milk.

These studies may increase interest in grazing for dairy cows. Currently, only 10 to 12 percent of U.S. dairy cows are grazed, according to Satter.

A University of Wisconsin researcher is credited with discovering CLA’s cancer- fighting properties in a study of rats fed fried hamburger. Today, human studies of CLA are underway at several research institutions.

Laboratory animals given CLA in their diets have shown a reduction in several types of cancers and a slower progression of atherosclerosis, a contributor to heart disease.

If human trials show the same benefits as studies with laboratory animals, the benefit of consuming milk products could impact the economy of dairy producers everywhere.