Effects of Elevated Iodine in Milk Replacer on Calf Performance

Abstract

Calves were fed milk replacer containing .57, 10, 50, 100, or 200ppm iodine (from ethylenediaminedihydroiodide) in DM, from 3 to 38 d of age, to estimate the minimum toxic concentration of iodine.Only the 200ppm iodine intake reduced weight gains, DM intake, feed efficiency, and DM digestibility. At the 100 and 200ppm iodine intakes, protein digestibility was reduced, and calves showed typical symptoms of iodine toxicity (nasal discharge, excessive tear and saliva formation) and coughing from tracheal congestion). Thyroid iodine increased with every elevation in iodine intake. Iodine in plasma, bile, and nonthyroid tissues started to increase at the 50ppm intake and, except for muscle, tended to increase again at the 100 and 200ppm intakes. Thus, the preruminant calf tolerated up to 50ppm iodine in milk replacer DM for 5 wk postpartum. However, as iodine concentrations in plasma and nonthyroid tissues started to increase at 50ppm iodine, an upper limit of 10ppm would be more preferable.