concentration of serum total iodine and thyroid hormones in holstein cows in central iran

the aim of this study was to evaluate total iodine, triiodothyronine (t3) and thyroxine (t4) status in the blood serum of holstein cows on six farms in central iran. total iodine, t3 and t4 concentrations were measured in 90 blood serum samples (15 per farm). mean concentrations of total iodine (38.80 ± 1.52 µg/l) and t3 (1.57 ± 0.10 nmol/l) were lower but the mean concentration of t4 (45.60 ± 1.53 nmol/l) was greater than the critical levels (p < 0.01). deficiency of total iodine, t3 and t4 was diagnosed in 82%, 85% and 35% of the cows, respectively. it was concluded that cows in central iran were deficient in total serum iodine concentration. increasing dietary iodine and further studies on the interaction between iodine and other minerals is recommended.