IODINE AND THYROID-HORMONE STATUS OF DAMS AND THEIR PIGLETS

The iodine concentration in the chain sow feed --> blood serum of dams --> milk --> blood serum of piglets (2 per litter) was determined in 36 litters in two experiments with different dietary iodine levels and in 16 litters in the framework of field studies in two piglet product ion farms in each case at weaning after four weeks lactation. In the b lood serum also the concentration of thyroxine (T-4) and triiodothyron ine was determined. The serum concentration of iodine and T-4 did not indicate dietary iodine administration (sows)or showed only a weak res ponse (piglets). The iodine concentration of milk was very strongly af fected by iodine administration and by the iodine status of sows prior to the experiments. The highest milk iodine concentration was found i n the sows of piglet production farms, corresponding to the level of i odine administered. For diagnosis of the iodine supply status the iodi ne concentration of sow milk should be analyzed. The lower limit of mi lk iodine concentration is presently defined as 50 mu g/l, and the mea n of 5 random samples per sow herd should not fall below this limit. S erum concentrations of iodine and T-4 may remain moderate even in case of a low iodine supply (sow serum: 30 mu g iodine/l, 25 nmol T-4/l; p iglet's serum: 50 mu g iodine/l, 55 nmol T-4/l), and are unsuited for diagnosis of iodine status.