Variation of Superoxide Dismutase in Bovine Milk

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Abstract
Individual cow milk is highly variable in its resistance to oxidation. Variation in the enzyme (superoxide dismutase) concentration may have a minor effect on the oxidative stability of individual cow''s milk. Milk from 11 Holsteins and 11 Jerseys were analyzed for 17 wk for superoxide dimustase, xanthine oxidase, oxidized lipids as determined by thiobarbituric acid values, milk produced and fat content. All cows were of good health and on normal feed but varied in stage of lactation and age. Average superoxide dismutase concentration was 1.1 .+-. .48 units/ml with a range of .06 to 2.88 units/ml and a variance of .23. Concentration of superoxide dismutase in milk was approximately 102 lower than in bovine blood. Assay of individual cow milk indicated no significant difference in superoxide dismutase concentration between night and morning milkings. Superoxide dismutase concentration was affected by breed but not by stage of lactation or age. Superoxide dismutase decreased the minor pro-oxidant effect of xanthine oxidase. The concentration of superoxide dismutase in individual cow milk did not account for the large variability in oxidative resistance in raw milk that was not exposed to light.
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