Hidiroglou M, Thompson B K, Ho S K, Proulx J G
Can J Comp Med. 1981 Apr;45(2):124-9.
A field experiment was undertaken in northern Ontario in order to assess the magnesium status of beef cattle raised in the area. Magnesium status was assessed using several criteria including blood and urine magnesium levels, and bone biopsy samples. Eighteen groups each containing four pregnant Shorthorn beef cows were used. Each of the following three mineral feeds were offered to six groups throughout the experiment: a mineral feed without magnesium, a mineral feed containing 8% magnesium in the form of magnesium oxide and the third containing sequestered magnesium with a magnesium level of about a tenth of that in the mineral feed containing magnesium oxide. During the winter, when the cows were housed indoors, they were fed grass silage. Six groups, two of each mineral feed, remained indoors throughout the summer. The other 12 groups were turned out to pasture on May 25 and continued receiving the appropriate mineral feed. There were no differences in serum magnesium owing to magnesium-supplementation treatments observed at any time during any experiment. Serum magnesium levels fell drastically in all groups before the cows were released to pasture, implying that the hypomagnesaemic condition was attributable to the stress of yarding. The rate of recovery from hypomagnesaemia was slower in the cows released to pasture than in those kept indoors. Urine samples from cows returned to the pasture were indicative of low magnesium status. At the end of the experiment, the magnesium levels in the bones of the housed animals were higher than for those on pasture. In spite of severe cases of hypomagnesaemia, no clinical signs of this metabolic condition were observed.
在安大略省北部进行了一项田间试验，以评估该地区饲养的肉牛的镁状况。使用包括血液和尿液镁水平以及骨活检样本在内的多个标准来评估镁状况。使用了18组，每组包含4头怀孕的短角肉牛。在整个实验过程中，向6组提供以下三种矿物质饲料中的每一种：不含镁的矿物质饲料、含8%氧化镁形式镁的矿物质饲料以及第三种含螯合镁且镁水平约为含氧化镁矿物质饲料中镁水平十分之一的饲料。在冬季，当母牛圈养在室内时，给它们喂青贮草。6组，每种矿物质饲料两组，整个夏天都留在室内。其他12组在5月25日被放到牧场，并继续接受适当的矿物质饲料。在任何实验期间的任何时候，均未观察到因补充镁处理而导致的血清镁差异。在母牛被放到牧场之前，所有组的血清镁水平均大幅下降，这意味着低镁血症状况归因于圈养应激。放到牧场的母牛从低镁血症中恢复的速度比留在室内的母牛慢。回到牧场的母牛的尿液样本表明镁状况较低。在实验结束时，圈养动物骨骼中的镁水平高于牧场动物。尽管存在严重的低镁血症病例，但未观察到这种代谢状况的临床症状。
