Tissue Iodine in Sheep Fed Diets Containing Ethylenediamine Dihydriodide

Twenty-four male lambs, produced by crossing commercial blackfaced ewes with purebred Suffolk rams and averaging 40.1 kg body wt., were fed one of two ethylenediamine dihydriodide (EDDI)-supplemented diets. A total of eight pens (four pens per treatment) containing three animals each were assigned at random to the two diets. Dietary treatments consisted of a basal diet containing 0.79 ppm I as EDDI and EDDI-supplemented diets providing an additional 12 mg of EDDI/head/d. The diets were fed for 42 d, after which the animals were slaughtered and various tissues collected for I analysis. Iodine concentration in the serum of sheep fed the EDDI-supplemented diet increased fivefold (62 vs. 12 μg/dl) over the control animals within a week and this difference was maintained throughout the experiment. There was a trend toward increased I in semimembranosus, psoas major, longissimus and trapezius muscles, although this was statistically nonsignificant. Increases (P<0.01) in the I concentration in liver (0.085 vs. 0.166 μg/g) and kidney (0.143 vs. 0.409 μg/g) were observed. Analysis of thyroid tissue indicated no increase in I concentration (1732 vs. 2166 μg/g). Based on these results, it is concluded that feeding EDDI to sheep at 12 mg/head/d until slaughter increased I in edible tissues. The rate at which iodine depletes from these tissues is unknown.