Schöne Friedrich, Spörl Kathrin, Leiterer Matthias
Thuringian State Institute of Agriculture, Investigation Unit - Laboratory, Naumburger Str. 98, D-07743, Jena, Germany.
Thuringian State Institute of Agriculture, Investigation Unit - Laboratory, Naumburger Str. 98, D-07743, Jena, Germany.
J Trace Elem Med Biol. 2017 Jan;39:202-209. doi: 10.1016/j.jtemb.2016.10.004. Epub 2016 Oct 11.
Milk may be an iodine source for humans, but its magnitude depends on the iodine content of cow feed. The present investigation focused on the iodine level of feed and milk in German feeding practice in comparison with the results of previous milk monitoring and dose-response experiments with dairy cows. In 73 samples of straight feedstuffs (41 concentrates, 32 silages prepared from grass or green maize) and a total of 83 vitamin mineral premixes and compound feeds, respectively, the iodine content was determined and along with the expected daily iodine intake of cows. In six Thuringian cow herds, the total cow diets (51 total mixed rations, TMR) as well as the bulk milk (n=77) were analysed for iodine. Cereal and legume grains and extracted meals from oilseeds had very low native iodine contents at<9-43μg iodine/kg dry matter (DM). Silages showed higher contents than the concentrates. In grass silage, the median amounted to 173μg iodine/kg DM. The significant relationship between the silages' ash and iodine content indicates contamination of grass during harvesting by soil. With regard to supplements, dairy cows received via premixes a mean of 1.2mg iodine/kg diet DM and this was in the magnitude of 0.8mg iodine/kg DM determined in TMR on farm. However, the resulting mean milk concentration of 105μg iodine/kg, median 100μg/kg, is only a half of that in dose-response experiments with 200μg iodine/kg milk at 1mg iodine/kg cow feed DM. The decrease of iodine transfer into the mammary gland and milk is caused by rapeseed meal (RSM) with the glucosinolates and their degradation compounds, e.g. isothiocyanates. By compensating for the iodine antagonist effects of diets containing RSM, more iodine should be added. Twice the current mean feed iodine supplement would optimize the contribution of animal-source food to the human iodine supply in Germany.
牛奶可能是人类的碘源，但其含量取决于奶牛饲料中的碘含量。本研究聚焦于德国饲养实践中饲料和牛奶的碘水平，并与之前牛奶监测结果以及奶牛剂量反应实验结果进行比较。分别测定了73份单一饲料样本（41份精饲料、32份由青草或青玉米制成的青贮饲料）以及总共83份维生素矿物质预混料和复合饲料中的碘含量，以及奶牛预期每日碘摄入量。在图林根州的六个奶牛群中，分析了奶牛的全日粮（51份全混合日粮，TMR）以及散装牛奶（n = 77）中的碘含量。谷物、豆类籽实以及油籽粕的天然碘含量非常低，每千克干物质（DM）中碘含量<9 - 43μg。青贮饲料的碘含量高于精饲料。在青草青贮饲料中，中位数为每千克DM含173μg碘。青贮饲料的灰分与碘含量之间的显著关系表明，收割青草时受到了土壤污染。关于补充剂，奶牛通过预混料摄入的碘平均为每千克日粮DM含1.2mg碘，这与农场TMR中测定的每千克DM含0.8mg碘的水平相当。然而，由此产生的牛奶平均碘浓度为每千克105μg，中位数为每千克100μg，仅为剂量反应实验中每千克奶牛饲料DM含1mg碘时每千克牛奶含200μg碘的一半。油菜籽粕（RSM）及其硫代葡萄糖苷和降解产物（如异硫氰酸盐）导致碘向乳腺和牛奶中的转移减少。通过补偿含RSM日粮的碘拮抗作用，应添加更多碘。将目前平均饲料碘补充量增加一倍，将优化动物源食品对德国人类碘供应的贡献。
