Changes in the Plasma Level of Protein-Bound Iodine in the Young Calf

Abstract

The plasma level of protein-bound iodine (PBI) in young dairy calves shows a marked rise shortly after birth and reaches a peak within about 24 hrs. By the end of 72 hrs. the concn. will have fallen to its initial level. The increase in plasma PBI appears to result from the ingestion of the first colostrum, which has a relatively large PBI fraction. The PBI in colostrum may be due to the transfer of PBI from the blood of the dam since her level at calving is significantly lower than the pre- or post-partum concns. Limited histological studies of the thyroid glands of calves under 1 wk. old showed marked increases in colloid storage and tissue differentiation with advancing age.