Iodine Deficiency in Newborn Sheep and Swine

Abstract

The gross and microscopic anatomy and the iodine content of thyroid glands from 338 newborn lambs and 407 newborn pigs were studied in three central Indiana sheep flocks and two swine herds. In one sheep flock fed a commonly used ration not supplemented with iodine the average thyroid weight was 5.71 gm. and ranged from 0.90 gm. to 49.15 gm. Hyperplasia of the thyroid epithelium was observed in over 60 percent of the glands and the iodine content of only three of 147 thyroids fell within the reported normal range (0.10 to 0.25 percent on a dry weight basis). The average iodine content was 0.021 percent in this flock. In a second flock when stabilized iodized salt was fed only one of 86 glands was hyperplastic, only 14 weighed more than one gram and none exceeded 1.8 gm. Iodine content ranged from 0.126 to 0.721 percent and only three glands contained less than 0.20 percent. In one swine herd fed a ration not supplemented with iodine of III glands studied 39 percent contained only a trace of iodine, 45 percent showed only a trace of stored colloid and over 30 percent were hyperplastic. When stabilized iodized salt was used only five of 106 glands weighed more than 0.47 gm., only 14 contained less than 0.20 percent iodine and none was hyperplastic. There were highly significant differences in thyroid weight and iodine content of newborn lambs and pigs when different rations, not supplemented with iodine, were fed. There were highly significant differences between the thyroid glands of newborn lambs and swine when iodine supplemented rations for the pregnant dams were compared to non-supplemented rations. Significant correlations of −0.646 in sheep and −0.525 in swine between iodine content and height of the thyroid epithelium were found. Significant correlations of −0.-321 and −0.350 were found between iodine content and thyroid weight in lambs and pigs respectively.