Selenium (adding 0.3 ppm or 6 milligrams/cow/day), copper (adding 10 ppm or a total of 15-20 ppm), and zinc (adding 40 ppm or a total of 60-80 ppm) can lower somatic cell counts in uninfected cows or lower the severity and/or duration of mastitis. Also there seems to be some effect from manganese. All of these minerals, as well as vitamins A, D, and E, should be fed at levels meeting 2001 NRC guidelines. (The values in parentheses are Illinois Cooperative Extension guidelines.)
Mike Hutjens, Extension Dairy Specialist, University of Illinois - Illini DairyNET
