As a consequence of preventive consumer protection, the European Food Safety Authority proposed a reduction in the iodine upper level for lactating ruminants from 5 to 2 mg/kg complete feed.

Supplementation of animal feed with iodine influences the iodine content of milk and therefore, in addition to salt iodination, provides another possibility for improving the human iodine supply. On the other hand, excessive iodine intake by humans through drinking milk must be avoided. Furthermore, the iodine content of milk varies, depending on the presence of iodine antagonists in feed (e.g., glucosinolates in rapeseed) and the applied iodine species. This study evaluated the impact of various feed iodine supplementation levels up to the permitted maximum level, the effect of applying rapeseed compared with a glucosinolate-free ration, and the impact of 2 different iodine species on the iodine content of milk. A total of 32 dairy cows were divided into 4 groups with 8 animals each. Two groups received distillers dried grains with solubles (DDGS) as the protein source, and the others received rapeseed meal (RSM, 16.5% of total diet). In each case, half the animals received feed supplemented with iodine in the form of potassium iodide, and the other half received feed supplemented with iodine in the form of calcium iodate. Iodine supplementation levels of 0, 0.5, 1, 2, 3, 4, and 5 mg/kg of dry matter (DM) were tested in consecutive periods of 21 d each. The milk iodine concentration increased with increasing iodine supplementation of the feed. Rapeseed meal in the ration (0.58 mmol of glucosinolates/kg of diet DM) diminished the milk iodine concentration by up to one-half to one-third of the concentration achieved by DDGS. At iodine supplementation levels of 2 mg/kg of DM and higher, the differences were significant. The application of iodate predominantly resulted in higher milk iodine concentrations compared with iodide, but not significantly in any period. At the highest tested iodine supplementation (5 mg/kg of DM), the milk iodine concentration increased up to 1,464 (iodide) and 1,578 microg/kg (iodate) when feeding DDGS and up to 718 (iodide) and 620 microg/kg (iodate) in the RSM groups. The carry over of iodine from feed into milk amounted to 30 to 56% when using DDGS, and 11 to 25% when using RSM. The maximum level of iodine currently allowed in the feed of dairy cows in Europe could lead to high milk iodine concentrations. As a result, the Tolerable Upper Intake Level in human nutrition could be exceeded. Therefore, this maximum level needs to be reevaluated. In addition to iodine supplementation, the application of RSM in the ration must be considered when estimating the iodine content of milk.

During the last decade the iodine supply in Germany has increased significantly, but there is still a high frequency of goitre. Therefore the question of iodine bioavailability has arisen. In a two-period study 12 women were given a mixed diet of ordinary foods with milk and milk products of different batches. None of the volunteers suffered from an iodine deficiency according to WHO-criteria. Each period ended with a 9-day balance-study protocol in which all foods were provided. Food and fluid intake were registered, and urine and faeces were quantitatively collected. The iodine content was determined by ICP-MS. The mean intake in the form of solid food amounted to 175 +/- 10 micrograms I/d and to 27 +/- 15 micrograms I/d in fluid form. Milk and dairy products represented the main source of iodine (37%). Iodine was predominantly excreted in the urine (89%, 171 +/- 45 micrograms I/d) and the faeces 11% (20 +/- 11 micrograms I/d). The resulting iodine balance was approximately . In one case an iodine-rich erythrosine preparation with a low iodine bioavailability was used. Between the two periods of consuming different batches of milk and milk products no differences were observed concerning the high bioavailability of iodine.

Summary Hypericin is a molecule of high pharmaceutical importance that is synthesized and stored in dark glands (DGs) of St. John's Wort (Hypericum perforatum). Understanding which genes are involved in dark gland development and hypericin biosynthesis is important for the development of new Hypericum extracts that are highly demanded for medical applications. We identified two transcription factors whose expression is strictly synchronized with the differentiation of DGs. We correlated the content of hypericin, pseudohypericin, endocrocin, skyrin glycosides and several flavonoids with gene expression and DG development to obtain a revised model for hypericin biosynthesis. Here, we report for the first time genotypes which are polymorphic for the presence/total absence (G+/G−) of DGs in their placental tissues (PTs). DG development was characterized in PTs using several microscopy techniques. Fourier transform infrared microscopy was established as a novel method to precisely locate polyaromatic compounds, such as hypericin, in plant tissues. In addition, we obtained transcriptome and metabolome profiles of unprecedented resolution in Hypericum. This study addresses for the first time the development of dark glands and identifies genes that constitute strong building blocks for the further elucidation of hypericin synthesis, its manipulation in plants, its engineering in microbial systems and its applications in medical research.

No abstract