Milk from pastured cows could help fight cancer, according to new Wisconsin research.

In studies at USDA's Dairy Forage Research Center in Madison, milk from cows fed only grazed forages contained nearly three times as much conjugated linoleic acid (CLA) as milk from cows fed mostly stored feeds.

CLA, an 18-carbon fatty acid, is a "kissing cousin" to linoleic acid, which is found in many vegetable oils, explains dairy scientist Larry Satter, who conducted the research with Tilak Dhiman.

While human trials on the benefits of CLA have just begun at several research institutions, the acid has proved effective at reducing several types of cancers and the progression of atherosclerosis in laboratory animals. Atherosclerosis is a contributor to heart disease.

"For once, the dairy industry can be recognized for producing a good fatty acid," says Satter. "Everything we've heard about animal fats has tended to be bad, but here is one that definitely seems to have some very desirable effects. These findings on CLA have some interesting possibilities and could develop into a big positive for the ruminant industry. Within the next five years, we'll know a lot more."

He divided 54 Holstein cows into three groups to start grazing in May. The first group received all pasture and no stored feed, except for vitamins and minerals. The second group received two-thirds of its dry matter intake from pasture and one-third from stored feed. A third group ate a ration of one-third grazed forages and two-thirds stored feed.

For groups two and three, the stored feed consisted of alfalfa hay, high-moisture ear corn, protein supplements, minerals and vitamins. The pasture was a mix of bluegrass, quackgrass, timothy, brome, and red and white clover.

The cows grazed through September and then Satter analyzed the results. The milk from group one contained 22.1 milligrams of CLA per gram of fatty acids, compared with 14.3 and 8.9 milligrams, respectively, for groups two and three.

"Typically, cows fed under confinement would have 3-5 milligrams of CLA per gram of fatty acids," he says.

Satter isn't sure why the pasture-based diet boosted CLA levels. "It could be a combination of things. Perhaps there's an abundance of building blocks for CLA in standing grass and legumes; perhaps there are other indirect effects we just don't know about."

While Satter's encouraged by the findings, he says their practical application may be difficult to establish.

"Of course, all milk gets mixed together during processing. At this time, the relatively small percentage of milk coming from pasture-fed cows would have little or no impact on human health. But the findings point to the possibility of being able to manipulate the diets of cows so that they can produce milk with higher amounts of CLA on a routine basis."