The following information is from: http://www.princeagri.com/tmo-i.html
Production of Animal Feed Grade Iodine Products The forms of iodine most commonly used in animal feed are calcium iodate, ethylenediamine dihydriodide (EDDI), and potassium iodide.
Crude iodine (99.9% iodine) is refined as a co-product from brines associated with underground gas and oil wells in Japan and the U.S. In Chile, it is refined as a co-product with potassium nitrate from caliche deposits which are mined by open pit methods.
Iodine salts are manufactured from crude iodine and are very pure. There are three major converters of crude iodine to feed grade salts in the U.S. and Canada.
Factors Affecting Iodine Pricing and Supply Historically, iodine price fluctuations occur due to varying yen vs. dollar exchange rates, as well as supply and demand factors. Chilean iodine is handled by one marketing agent, while the Japanese own most of the U.S. iodine production. Consequently, Chile and Japan control market prices of crude iodine. Pricing of elemental iodine has generally ranged between $2-$8/lb, but reached a new high in 1997 when it averaged $8.60/lb.
Crude iodine supplies have been tight since 1995. As Chile brings new capacity on line, market tightness should be alleviated and pricing will stabilize.
(C) Average Crude Iodine Prices
Function of Iodine in the Animal Feed Industry Iodine is a key component in the formation of thyroid hormones thyroxin and mono-, di-, and tri-iodothyronine.
Typical Deficiency Symptoms of Iodine in Animals
Excessive ethylenediamine dihydriodide (EDDI) may interfere with vitamin A metabolism. High dietary calcium nitrate, thiocyanate, glucosinolate, perchlorate, rubidium, and cobalt interfere with iodine metabolism and can increase iodine requirements. Supplemental iron reduces iodine toxicity, but can increase iodine requirements.
Major Sources of Iodine Approved by AAFCO for Use in Animal Feed
Quality Considerations Iodine level should meet specification. Poor quality sources may cause caking. Ethylenediamine dihydriodide (EDDI) may react with sulfates in an all-sulfate premix and release free iodine
Potassium iodide is the most water soluble iodine source. It is also the least chemically stable and least used source in animal feed. Calcium iodate is usually the most stable source of iodine. All three major sources of iodine (calcium iodate, EDDI, and potassium iodide) are roughly equivalent in biological availability.
DOT-Hazardous Materials (Class 5.1) include calcium iodate. Ethylenediamine dihydriodide (EDDI) is restricted to GRAS as a nutrient source of iodine only (21 CFR 582.80). FDA exercises regulatory discretion with regard to supplementation up to 50 mg/head/day, per Compliance Policy Guide 7125.18 (May 2000). No therapeutic claims are allowed.
Iodine deficiency is the world’s leading cause of mental defects, such as severe retardation, deaf-mutism, partial paralysis, frequent clumsiness, lethargy, and reduced mental capacity. Iodine is an essential part of a thyroid hormone that contributes to brain development during fetal life and metabolism thereafter.