Iodine Concentrations in Milk of Dairy Cattle Fed Various Amounts of Iodine as Ethylenediamine Dihydroiodide

Due to concerns about high I in milk, the dairy industry has proposed a voluntary standard of 500 micrograms of I/L as the maximum allowable I in milk sold for processing and human consumption. This study was undertaken to determine the amount of ethylenediamine dihydroiodide that could be fed to dairy cattle without exceeding this standard. Various amounts (0 to 45 mg/head per d) of the I compound were fed to a commercial dairy herd for 50 wk. Individual and bulk milk samples were analyzed for total iodine. Milk I in herd bulk milk was directly correlated (r = .92) with the amounts fed. However, the correlation of milk I of individual cows was not as high (r = .66), indicating some individual variation in metabolism and secretion of the I into the mammary gland. Milk production and number of lactations did not correlate with I in milk. Regression analysis indicated that 25 to 30 mg of ethylenediamine dihydroiodide per day can be fed to dairy cattle receiving a diet otherwise low in I without exceeding a 500 micrograms concentration in milk.