The Importance of Iodine

Iodine is an essential trace mineral critical for animal health, primarily due to its role in the synthesis of thyroid hormones—thyroxine (T₄) and triiodothyronine (T₃)—which regulate metabolism, growth, reproduction, and thermoregulation. 

  • Deficiency leads to goiter (thyroid gland enlargement), reduced growth, poor fertility, impaired lactation, weakened immunity, and fetal developmental issues.  Regions with iodine-deficient soils (e.g., Great Lakes and Northwest U.S., parts of Canada) pose higher risk, especially when relying on local forages.

  • Toxicity from excessive iodine intake (e.g., overuse of supplements) can cause iodism—marked by cough, nasal discharge, dermatitis, weight loss, and increased mortality, particularly in dairy cattle and sheep. 

  • Optimal supplementation is key: National Research Council (NRC) recommends 0.2–0.3 ppm for dairy cattle and 0.33 ppm for beef cattle.  For pigs and beef cattle, 120–250 μg/kg dry matter is advised to maintain performance and thyroid function.

  • Iodine is efficiently absorbed (70–80%) in the rumen and intestines and is concentrated in the thyroid, milk, and eggs—making animal-derived foods a significant source of iodine for humans. 

Proper iodine management ensures animal productivity, food safety, and human nutrition.