A South Dakota State University study, reported in the November 2000 Journal of Dairy Science, found that feeding cows fish oil at 2 percent of the ration’s dry matter resulted in approximately 3.6 times the amount of conjugated linoleic acid, or CLA, being produced in the cows’ milk. Recent research has suggested that CLA may ward off cancer.

At 2 percent of the dry matter, the diet was able to increase CLA production without causing great declines in milk production, says David Schingoethe, dairy nutritionist at South Dakota State University. Cows fed 1 percent fish oil per pound of dry matter produced 4 pounds more milk and had a higher milkfat percentage than the cows fed 2 percent. However, those fed 2 percent fish meal produced 0.82 more grams of CLA per 100 grams of milkfat.

Researchers do not know for sure why fish oil — a product with little linoleic acid — enhances CLA production. However, Schingoethe theorizes that the fish oil may serve as a rumen modifier to stimulate additional production of CLA from linoleic acid present in other feed ingredients.