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Journal of Dairy Science Vol. 64 No. 5 814-821
© 1981 by American Dairy Science Association ®
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Transfer of Selenium from Blood to Milk in Goats and Noninterference of Copper with Selenium Metabolism1

Jonathan C. Allen2 and W. J. Miller3

Department of Animal and Dairy Science, University of Georgia, Athens 30602

3 Reprint requests to W. J. Miller.

ABSTRACT

The mechanism of selenium secretion by the mammary gland and effects of dietary copper and selenium metabolism on selenium in milk were investigated. Radioactive sodium selenite was injected into the jugular vein of lactating goats fed concentrates containing 15 or 115 ppm copper. Blood and milk samples were collected hourly for 8 h and daily for 1 wk. Whole blood, plasma, whole milk, and casein, whey, and cream fractions of milk were counted for selenium-75. No significant differences due to dietary copper were seen. The selenium-75 was primarily associated with the casein in milk. The association of selenium with the whey fraction was greater for early periods than later and varied between animals. The specific activity based on protein content was greater in casein than in whey. Peak selenium-75 in whole milk occurred 2 h after the peak in plasma. On day 7 following selenium-75 dosing, kidney had the highest specific activity, and liver was slightly higher than mammary tissue. All subcellular organelle fractions of liver, kidney, and mammary tissue by homogenization and differential centrifugation contained significant selenium-75. Selenium normally is secreted from the mammary secretory cell in combination with protein through the secretory vesicles, metabolism of selenite prior to milk secretion is important, and copper does not interfere with normal metabolism of selenium.

FOOTNOTES

1 Supported by State and Hatch funds allocated to the Georgia Agricultural Experiment Stations.

2 Department of Physiology, University of Colorado Health Sciences Center, Denver, CO 80262.






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Copyright © 1981 by the American Dairy Science Association ®.