Urinary iodine level as an intake indicator in dairy cows

Urinary iodine concentrations were determined in 672 dairy cows of 22 herds. Less than 20 micrograms per L, 20 to 50 micrograms per L, 50 to 100 micrograms per L and more than 100 micrograms per L were found in 27.5, 24.6, 16.8, and 31.3% of the cows, respectively. In terms of the ICCIDD grading, moderate iodine deficiency was recorded in 68.9% and normal iodine intake in 31.3% of the cows. The mean urinary iodine concentrations were 94.8 micrograms per L at the peak of the lactation period (n = 300), 82.3 micrograms per L immediately before drying off (n = 122), 92.5 micrograms per L in the cows fed summer rations (n = 267), and 79.2 micrograms per L in those fed winter rations (n = 405). The differences in mean values were nonsignificant. Urinary iodine concentrations were examined in the herd LOS in cows fed iodine-supplemented (LOS E) or nonsupplemented (LOS C) rations. Mean concentrations were 316.2 micrograms per L for LOS E (n = 46) and 52.3 micrograms per L for LOS C (n = 41). The difference was highly significant (P < 0.01). The status of the group LOS C was classified as a medium iodine deficiency. The mean iodine concentrations at the peak of the lactation period and immediately before drying off were also significantly higher (P < 0.01) in this group. The supplementation of iodine resulted in an increase of urinary iodine concentration and, in terms of ICCIDD, the increase of iodine intake to the normal range. Normal intake and moderate, medium and serious deficits were found in three, two, one, and four herds, respectively. Special attention should be paid to herds showing higher grades of iodine deficiency.