Convey E M, Chapin L T, Thomas J W, Leung K, Swanson E W
J Dairy Sci. 1978 Jun;61(6):771-5. doi: 10.3168/jds.S0022-0302(78)83647-9.
The objective was to determine whether dairy cows fed supplemental iodine daily at 2.5 or 5.0 mg per kg body weight for 49 wk had altered thyroid status relative to controls fed no supplemental iodine. Average daily dose of iodine was 1.6 and 3.3 g. Iodine as ethylene diamine dihydriodide was fed to Holstein cows beginning at 8 to 10 wk of lactation, for the remainder of that lactation, through the dry period, and into the next lactation. On day 341 after onset of iodine feeding, each cow was injected intravenously with 15 microgram thyrotropin releasing hormone per 100 kg body weight. Thyrotropin in jugular blood collected before injection of releasing hormone averaged 7.6, 6.1, and 8.2 ng/ml for cows given 0, 2.5, and 5.0 mg iodine/kg body weight; there were no differences between means. Releasing hormone increased thyrotropin, thyroxine, and tri-iodothyronine in serum of all cows, but increases were not affected by quantity of dietary iodine.
目的是确定每天按每千克体重2.5毫克或5.0毫克的剂量给奶牛补充碘，持续49周后，与不补充碘的对照组相比，其甲状腺状态是否发生了改变。碘的平均日剂量分别为1.6克和3.3克。以二氢碘化乙二胺形式的碘从荷斯坦奶牛泌乳期的第8至10周开始投喂，直至该泌乳期剩余时间、干奶期，并进入下一个泌乳期。在开始投喂碘后的第341天，每头奶牛按每100千克体重静脉注射15微克促甲状腺激素释放激素。对于每千克体重分别给予0毫克、2.5毫克和5.0毫克碘的奶牛，在注射释放激素前采集的颈静脉血中促甲状腺激素平均分别为7.6、6.1和8.2纳克/毫升；各平均值之间无差异。释放激素使所有奶牛血清中的促甲状腺激素、甲状腺素和三碘甲状腺原氨酸增加，但增加幅度不受日粮碘量的影响。
