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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #95334
Title: CONJUGATED LINOLEIC ACID CONTENT OF MILK FROM COWS FED DIFFERENT DIETS

Author
item DHIMAN, TILAK - UTAH STATE UNIV-LOGAN, UT
item ANAND, G - UTAH STATE UNIV-LOGAN, UT
item Satter, Larry
item PARIZA, MICHAEL - UNIV OF WISCONSIN-MADISON

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Conjugated linoleic acid (CLA) is an unsaturated fatty acid found primarily in foods derived from ruminant meat or milk products and is essentially absent or present in only small amounts in vegetables, grains, fruits, or poultry and pork products. It has been demonstrated that CLA can reduce the incidence of tumor formation in laboratory animals and can decrease the proportion of fat and increase the proportion of lean tissue in several avian and mammalian species. The implications CLA has for human health are attracting much attention. The objective of this research was to determine if CLA content of milk could be increased by manipulating the cow's diet. In four different experiments, diets were manipulated by feeding high oil corn and corn silage, by supplementing with fish meal and/or monensin, feeding different proportions of grain and forage, and by providing access to pasture such that one-third, two-thirds, or all of the cows' feed came from pasture. Feeding fish meal increased the CLA content of milk slightly but cows grazing pasture secreted much more CLA in milk than cows that were not grazed. The amount of CLA in milk was related to the proportion of grazed forage in their diet. When cows obtained all of their feed by grazing, then milk CLA content was about five times the normal amount. This research suggests that manipulation of the cow's diet might be a way of increasing CLA content of milk, and perhaps be a tool for increasing its health-promoting features in milk.

Technical Abstract: Four experiments were conducted to determine the content of conjugated linoleic acid in milk from cows fed different diets. In experiment 1, cows were fed either normal or high oil corn and corn silage in a 50% forage and 50% grain diet. Conjugated linoleic acid was 3.8 and 3.9 mg/g of milk fat in normal and high oil treatments, respectively. In experiment 2, cows consumed 1/3, 2/3 or all of their daily feed from a permanent pasture. The balance of feed for the 1/3 and 2/3 pasture treatments was supplied by alfalfa hay and concentrates. Conjugated linoleic acid was 8.9, 14.3, and 22.1 mg/g of milk fat in the 1/3, 2/3 and all pasture treatments, respectively. Cows grazing pasture and receiving no supplemental feed had 500% more conjugated linoleic acid in milk than cows fed typical dairy diets (experiment 1). In experiment 3, cows were fed either a control diet containing 55% alfalfa silage and 45% grain or similar diets supplemented with 3% fishmeal, 12 ppm monensin/cow/d, or fishmeal and monensin together. Conjugated linoleic acid was 5.3, 8.6, 6.8, and 8.9 mg/g of milk fat in the control, fishmeal, monensin and fishmeal plus monensin treatments, respectively. In experiment 4, cows were fed finely chopped alfalfa hay and finely ground corn (Trt 1), coarsely chopped alfalfa hay and coarsely ground corn (Trt 2) in a 50% forage and 50% grain diet, 66.6% grass hay and 33.4% grain (Trt 3), or 98.2% grass hay (Trt 4). Conjugated linoleic acid was 7.3, 8.3, 9.0, and 7.9 mg/g of milk fat in treatments 1 through 4, respectively.