Jenkins K J, Hidiroglou M
Animal Research Centre, Research Branch Agriculture Canada, Ottawa, ON.
J Dairy Sci. 1991 Mar;74(3):1047-53. doi: 10.3168/jds.S0022-0302(91)78254-4.
In two experiments, calves were fed milk replacer containing 40, 200, 500, 1000, or 5000 ppm Mn or 40, 200, 500, 700, or 1000 ppm Zn in DM, from 3 to 38 d of age, to estimate the minimum toxic concentrations of Mn and Zn. Starting at 1000 ppm Mn, weight gains and feed efficiencies were decreased slightly; none of the calves fed 5000 ppm Mn survived the 5-wk experiment. Liver and bile showed the largest increases in Mn concentration. In the Zn experiment, only at 700 and 1000 ppm Zn were weight gains, DM intake, and feed efficiency reduced. Largest Zn increases were in liver, kidney, and plasma. Thus, performance of the preruminant calves was not affected adversely by 500 ppm Mn or 500 ppm Zn in milk replacer, concentrations that are markedly higher than the NRC recommendations of 40 ppm Mn and 40 ppm Zn. However, Mn and Zn concentrations increased in some tissues, and toxicities might have arisen if the trial had been continued. Evidence was not obtained indicating that the calf benefits from Mn or Zn intakes above the NRC recommendations.
在两项试验中，给犊牛饲喂干物质中含40、200、500、1000或5000 ppm锰或40、200、500、700或1000 ppm锌的代乳料，从3日龄至38日龄，以估计锰和锌的最低中毒浓度。从1000 ppm锰开始，体重增加和饲料效率略有下降；饲喂5000 ppm锰的犊牛在为期5周的试验中无一存活。肝脏和胆汁中的锰浓度增加最多。在锌试验中，仅在700和1000 ppm锌水平时，体重增加、干物质摄入量和饲料效率降低。锌增加最多的是肝脏、肾脏和血浆。因此，代乳料中500 ppm锰或500 ppm锌对反刍前犊牛的生长性能没有不利影响，这两个浓度明显高于美国国家研究委员会（NRC）建议的40 ppm锰和40 ppm锌。然而，某些组织中的锰和锌浓度有所增加，如果试验继续进行，可能会出现中毒情况。没有证据表明犊牛摄入高于NRC建议量的锰或锌会有益处。
