López-Alonso Marta, Miranda Marta
Department of Animal Pathology, Faculty of Veterinary Medicine, Universidade de Santiago de Compostela, Campus Terra, 27002 Lugo, Spain.
Department of Anatomy, Animal Production and Clinical Veterinary Sciences, Faculty of Veterinary Medicine, Universidade de Santiago de Compostela, Campus Terra, 27002 Lugo, Spain.
Animals (Basel). 2020 Oct 15;10(10):1890. doi: 10.3390/ani10101890.
Ensuring adequate copper supplementation in ruminants is a challenging task due to the complexity of copper metabolism in these animals. The three-way interaction between copper, molybdenum and sulphur (Cu-Mo-S) in the rumen makes ruminants, particularly cattle, very susceptible to suffering from secondary copper deficiency. Paradoxically, excessive copper storage in the liver to prevent deficiency becomes a hazard when ruminants are fed copper-supplemented diets even slightly above requirements. While cattle were traditionally thought to be relatively tolerant of copper accumulation, and reports of copper poisoning were until recently somewhat rare, in recent years an increased number of episodes/outbreaks of copper toxicity in cattle, particularly in dairy cattle, have been reported worldwide. The growing number of lethal cases reported seems to indicate that copper intoxication is spreading silently in dairy herds, urging the development of strategies to monitor herd copper status and improve farmers' awareness of copper toxicity. In fact, monitoring studies carried out on numerous samples collected from culled animals in slaughterhouses and/or diagnostic laboratories have demonstrated that large numbers of animals have hepatic copper concentrations well above adequate levels in many different countries. These trends are undoubtedly due to copper supplementation aimed at preventing copper deficiency, as dietary copper intake from pasture alone is unlikely to cause such high levels of accumulation in liver tissue. The reasons behind the copper overfeeding in cattle are related both to a poor understanding of copper metabolism and the theory of "if adding a little produces a response, then adding a lot will produce a better response". Contrary to most trace elements, copper in ruminants has narrow margins of safety, which must also be formulated considering the concentrations of copper antagonists in the diet. This review paper aims to provide nutritionists/veterinary practitioners with the key points about copper metabolism in cattle to guarantee an adequate copper supply while preventing excessive hepatic copper loading, which requires à la carte copper supplementation for each herd.
由于反刍动物铜代谢的复杂性，确保其充足的铜补充是一项具有挑战性的任务。瘤胃中铜、钼和硫（Cu-Mo-S）之间的三方相互作用使反刍动物，尤其是牛，极易患继发性铜缺乏症。矛盾的是，当给反刍动物喂食即使略高于需求的补充铜的日粮时，肝脏中为防止铜缺乏而过度储存的铜会成为一种危害。传统上认为牛对铜积累的耐受性相对较高，直到最近铜中毒的报告还比较少见，但近年来，全球范围内报告的牛，尤其是奶牛铜中毒事件/疫情有所增加。报告的致命病例数量不断增加似乎表明铜中毒正在奶牛群中悄然蔓延，这促使人们制定监测牛群铜状态的策略，并提高农民对铜中毒的认识。事实上，对从屠宰场和/或诊断实验室采集的大量淘汰动物样本进行的监测研究表明，在许多不同国家，大量动物的肝脏铜浓度远高于适当水平。这些趋势无疑是由于旨在预防铜缺乏的铜补充，因为仅靠牧草的日粮铜摄入量不太可能导致肝脏组织中如此高的铜积累水平。牛过量喂食铜背后的原因既与对铜代谢的了解不足有关，也与“如果添加一点会产生反应，那么添加很多会产生更好的反应”这一理论有关。与大多数微量元素不同，反刍动物体内的铜安全边际很窄，在制定补充方案时还必须考虑日粮中铜拮抗剂的浓度。这篇综述旨在为营养学家/兽医从业者提供有关牛铜代谢的关键点，以确保充足的铜供应，同时防止肝脏铜负荷过高，这需要为每个牛群量身定制铜补充方案。
