Cows grazed on pastures have five times
more of a fatty acid called conjugated
linoleic acid (CLA) in their milk. The
incidence of cancer in laboratory rats
declines after they've consumed CLA. (K5176-4)
There is a new reason why it may be
beneficial to allow cows to graze on pasture. That reason involves a compound
called conjugated linoleic acid (CLA).
CLA is a fatty acid found in beef and dairy fats. Scientific interest in CLA
was stimulated about 12 years ago when a University of Wisconsin researcher
discovered its cancer-fighting properties in a study of rats fed fried
hamburger. CLA cannot be produced by the human body, but it can be obtained
through foods such as whole milk, butter, beef, and lamb.
"The interesting thing is that dairy cattle that graze produce higher
amounts of CLA in their milk than those which receive conserved feed, such as
grain, hay, and silage," says ARS
dairy scientist Larry Satter. This is true even when the nongrazers eat pasture
grass conserved as hay.
Satter, who is based at the Dairy Forage Research Center in Madison, Wisconsin,
conducted a study comparing the amount of CLA in milk from cows grazing on
pasture to the amount from cows fed hay or silage. His findings: Pasture-grazed
cows had five times more CLA in their milk than those fed silage.
Do dairy producers need to graze cows to get them to produce more CLA?
"Not necessarily," says Satter. Instead, he devised a way to nudge
the production of CLA by dairy cows fed typical confinement diets. He added
extracted whole soybean and linseed oils to the corn-alfalfa diet. The added
oils boosted CLA content in the cows' milk to equal the levels obtained from
ARS and the Wisconsin Alumni Research Foundation (WARF) subsequently patented
the method to increase CLA in cows' milk. The patent, issued in the spring of
1999, was based on a study conducted by Satter and his University of Wisconsin
"Animal fats have been criticized for years, but now the potential
benefits of CLA in milk and meat from ruminant animals is being seriously
studied. Milk fat is one of the richest natural sources of CLA. If human trials
show the same benefits as studies with laboratory animals, the benefit of
consuming milk products could improve the economics of dairy producers
everywhere," says Satter.By Linda McGraw, Agricultural
Research Service Information Staff.
This research is part of Animal Production Systems, an ARS National Program
(#102) described on the World Wide Web at