Jenkins K J, Hidiroglou M
Animal Research Centre, Agriculture Canada, Ottawa, Ontario.
J Dairy Sci. 1987 Nov;70(11):2349-54. doi: 10.3168/jds.S0022-0302(87)80295-3.
Milk replacers containing 100, 500, 1000, 2000, or 5000 ppm iron were fed to 3-d-old calves for 6 wk to estimate the lowest amount of dietary iron (added as ferrous sulfate) that would reduce calf performance. Calves tolerated all iron treatments except 5000 ppm. At this intake calves showed reduced weight gains, DM intake, feed efficiency, and digestibility of DM and protein. There were no other signs of iron toxicity and no gross abnormalities were found on postmortem examination. Percent of dietary iron in feces increased with higher dietary iron and ranged from 65 to 84%. Elevated iron intakes caused relatively small increases in iron concentration of blood plasma, bile, kidney, heart, and muscle but marked increased in spleen and liver iron, particularly in liver for the 2000 and 5000 ppm treatments. At 100 ppm iron intake, nonheme iron in liver, spleen, and kidney was composed of similar proportions of ferritin and hemosiderin, but at 5000 ppm iron intake, hemosiderin predominated in these tissues. Thus, the preruminant calf tolerated between 2000 and 5000 ppm iron in milk replacer. At toxic iron intake, calf performance and feed efficiency were reduced; there was a characteristic change to higher liver than spleen iron; and hemosiderin became the predominant iron storage compound in both tissues.
将含有100、500、1000、2000或5000 ppm铁的代乳品喂养3日龄犊牛6周，以评估可降低犊牛生长性能的最低日粮铁含量（以硫酸亚铁形式添加）。犊牛能够耐受除5000 ppm之外的所有铁处理。在此摄入量下，犊牛体重增长、干物质摄入量、饲料效率以及干物质和蛋白质消化率均降低。未发现铁中毒的其他迹象，死后检查也未发现明显异常。粪便中铁占日粮的百分比随日粮铁含量升高而增加，范围为65%至84%。铁摄入量增加导致血浆、胆汁、肾脏、心脏和肌肉中的铁浓度相对小幅升高，但脾脏和肝脏中的铁含量显著增加，尤其是在2000和5000 ppm处理组的肝脏中。铁摄入量为100 ppm时，肝脏、脾脏和肾脏中的非血红素铁由类似比例的铁蛋白和含铁血黄素组成，但铁摄入量为5000 ppm时，含铁血黄素在这些组织中占主导地位。因此，反刍前犊牛能够耐受代乳品中2000至5000 ppm的铁。在铁摄入量达到中毒水平时，犊牛生长性能和饲料效率降低；肝脏中铁含量高于脾脏，出现特征性变化；含铁血黄素成为这两个组织中主要的铁储存化合物。
