Utilisation of iodine from different sources in pigs.

Balance experiments have demonstrated that growing pigs fed a ration consisting of wheat, barley, extracted soya meal, dicalciumphosphate, and iodine-free feeding salt utilised 48.8% of the received iodine. The tested supplementary iodine sources included potassium iodide (KI), ethylenediamine dihydroiodide (EDDI), iodine humate (HUI) prepared from iodine acid (HIO3), and the product P containing 0.004% iodine in an oil base (P). The amount of the supplemented iodine was in all cases 1 mg per 1 kg feed. The utilisation of iodine from the supplements reached 93.6, 92.6, 90.7, and 67.9% for KI, EDDI, P, and HUI, respectively. The values were significantly higher compared with controls (P < 0.01). Compared with KI and EDDI, the utilisation of iodine from HUI was significantly lower (P < 0.01). The lower availability of iodine from HUI was probably due to the high binding capacity of humate. The amount of urinary iodine excreted by control pigs receiving in the non-supplemented ration 147.5 micrograms iodine per day, was 40.3 micrograms per day (27.3%). In the pigs receiving in the supplemented ration 1647.5 micrograms iodine per day, the amount of urinary iodine reached 734.9 to 805.0 micrograms per day (44.6 to 48.9%). The corresponding values of faecal excretion were 75.6 micrograms iodine per day (51.2%) for the control pigs and 106.2 to 121.1 micrograms iodine per day (6.45 to 7.35%) for the pigs fed the supplemented rations. A high amount of 528.6 micrograms iodine per day (32.1%) was excreted in the faeces by pigs of the group HUI.