Comparison of the Metabolism of Iodine from Ethylenediamine Dihydriodide, Sodium Iodide, and Potassium Iodide

Nineteen dairy cows were used in three different experiments to determine if there was a difference in the metabolism of iodine from EDDI, an organic iodine compound, and iodine from the inorganic compounds, Nal or KI. The first experiment was conducted on two sets of twin lactating cows with one member of each twin receiving a single oral dose of EDD¹²⁵I and Na¹³¹I and the other member receiving an intravenous dose of EDD¹²⁵I and Na¹³¹I. Collection of milk, urine, feces, and blood taken for six consecutive days indicated that the metabolism of iodine from a single dose of EDDI and Nal was similar. In Experiment II, three nonlactating cows received daily oral doses of EDD¹²⁵I and Na¹³¹I, and ⁴⁶Sc simultaneously for six days. Blood, urine, and feces were sampled for six days, and 24 hours after the last dose the animals were sacrificed. Samples were taken from different sections of the digestive tracts and a number of tissues and organs. There was 17% more ¹³¹II than ¹²⁵I excreted in the feces and 11% more ¹²⁵I recovered from the tissue samples, which indicated that EDDI was retained more efficiently in tissues than was Nal. Twelve lactating dairy cows were fed KI and EDDI at varying levels for seven weeks. Samples of blood, milk, urine, and feces were taken every seventh day. The results indicated that when EDDI and KI were compared on an equal iodine basis similar amounts of iodine from the two compounds appeared in the feces, serum, and serum PBI. However, twice as much iodine was recovered from the urine of KI cows as from that of EDDI cows, while twice as much iodine from EDDI fed cows was recovered in the milk. The results indicated a difference in the metabolism of iodine from EDDI and iodine from KI and Nal. Whether these differences are of economic or therapeutic importance has not been elucidated. The greater affinity of EDDI for tissues, especially cartilage, may explain its apparent effectiveness as a preventive agent for foot rot in cattle.