Defined iodine intake and changes of its concentration in urine and milk of dairy cows

Changes in iodine concentrations in urine and milk were monitored in dairy cows. receiving rations without iodine supplementation but ensuring the standard requirement, after termination of its supply and in the course of application of a preparation containing iodine (Jodonal B) to the skin of mammary gland. When Feeding the ration comprising meadow and lucerne hay, cereal meals (wheat and barley 1 : 1), wheat brans and barley straw ad libitum, it means without iodine supplement, iodine concentrations in urine and milk were 44 +/- 8.3 and 20 +/- 5.2 mu g/l (Figs. 1 and 2). Iodine sources were potassium iodide (KI) and ethylenediamine dihydroiodide (EDDI) with iodine contents 70.45 and 80.53%, respectively, which were applied in doses corresponding to 33, 66 and 100%, of iodine daily requirement. Ensuring of 33% of iodine requirement (Figs. 1 and 2) by administration of KI or EDDI resulted in an increase of its urinary contents to 108 +/- 5.8 (P < 0.01) or 98 +/- 49.1 mu g/l, respectively. iodine content in milk increased from 20 mu g/l to 50 +/- 15.2 or 37 +/- 9.0 mu g/l (P < 0.01). Significant increase (P < 0.01) of urinary iodine concentrations (154 +/- 6.3 or 157 +/- 2.5 mu g/l) occurred after covering of 66% of the requirement. Milk iodine concentrations also increased significantly (P < 0.01) to 80 +/- 3.0 or 64 +/- 13.9 mu g/l. At 100% coverage the urinary iodine concentrations were 321 +/- 88.3 or 346 +/- 78.2 mu g/l, it means significantly higher compared with the control (P < 0.01) and on the following days the values further moderately increased. Milk iodine concentrations rose to 173 +/- 39.3 (P < 0.05) or to 121 +/- 52.8 mu g/l Elimination of iodine supplement from the ration (Fig. 3) was accompanied by a significant decrease (P < 0.01) of urinary iodine concentrations on Day 8 to 90 +/- 16.7 mu g/l, and on Day 11 the recorded concentration was 44 +/- 24.6 mu g/l. No linear decrease was observed in milk, on Day 4 after iodine elimination the values were nonsignificantly lower, on Day 8 a significant decrease to 61 +/- 39.0 mu g/l was observed but on Day 11 a moderate increase of the concentrations (103 +/- 23.0 mu g/l) was recorded. Prior to the application of Jodonal B on the skin of mammary gland the average iodine concentrations in milk of control and experimental cows were 36.4 and 47.3 mu g/l, respectively. Differences between the average values are nonsignificant from Day 2 to Day 5 of the experiment to the values in control animals ranged between 16.4 and 42.7 mu g/l. In experimental cows a highly significant increase of the values (185.5 mu g/l) was recorded on Day 2 already and further gradual increase was observed, reaching the value 377.2 mu g/l on Day 5. Statistical significance was confirmed on Days 2? 3: 4 and 5 (P < 0.05, or 0.01) between control and experimental cows and in comparison with the original values prior to application of Jodonal B (Fig. 4).