Pathologic features of iodide toxicosis in calves
Mangkoewidjojo, S.; Sleight, S.D.; Convey, E.M.
American Journal of Veterinary Research 41(7): 1057-1061
1980
ISSN/ISBN: 0002-9645 PMID: 7436098 Document Number: 163894
Forty Holstein-Freisian heifer calves were divided into 4 groups of 10 each and dosed orally with ethylenediamine dihydriodide [a drug used in veterinary medicine for the treatment and prevention of foot rot and actinomycosis (lumpy jaw)] to provide 0, 50, 250 or 1250 mg of iodide[I]/animal each day. Five calves in each group were given thyrotropin-releasing hormone [thyroliberin, TRH] at 4-wk intervals. Two calves given 1250 mg of I (active ingredient)/day died by 70 days and had severe bronchopneumonia. At 6 mo., the remaining 38 calves were killed. Pneumonia was evident in calves given I, with the severity apparently dose-related. Squamous metaplasia of tracheal epithelium occurred in all calves given 1250 mg of I. Similar changes were seen in the interlobular duct of the parotid gland of 2 calves given 1250 mg of I and in 1 calf given 250 mg. Scanning electron microscopy revealed changes in the tracheal mucosa, the severity of which were related to the dose of I fed. Changes in the thyroid glands of calve given 1250 mg of I included large follicles, flat epithelium, and large amounts of colloid. In calves given 1250 mg of I plus TRH, the histologic features of the thyroid glands were similar to controls. Serum vitamin A concentrations were less in calves given 1250 mg of I relative to that of control calves. In general, calves were able to compensate for excessive dietary I after an initial period of an apparent increased susceptibility to respiratory tract infection.