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Abstract：
In New Zealand, the recommended intake of Se for dairy cattle (0.03 mg/kg dry matter (DM)) is lower than in the United Kingdom and Australia (0.1 and 0.04 mg/kg DM, respectively), and much lower than in the United States of America (0.3 mg/kg DM). Advisors in New Zealand often suggest that New Zealand intake recommendations are far too low and that recommendations from the United States of America should be used. This has created confusion as farmers are given very different advice depending on which recommendations their advisor uses. In this review, we assess whether the published evidence supports the existing dietary requirements and associated Se status thresholds, or if change is required. We focus particularly on the evidence-base in cattle fed a primarily pasture-based diet, as it is critical that dietary recommendations are derived from data created using cows fed similar diets. Accordingly, we also consider whether the increased use of fodder crops, especially during the dry period, is likely to have altered the Se requirements of dairy cows in New Zealand. We report that the science behind the dietary requirements for Se is robust, being supported by factorial models validated using New Zealand data, and on-farm experimental studies. Published nutritional data suggest that the increased use of fodder crops is unlikely to have altered the dietary balance of pro- and antioxidant factors in New Zealand dairy cows in a way that would meaningfully affect Se requirements. However, the lack of specific data on the vitamin E and fatty acid content of the crops being fed in New Zealand means that more information is needed to confirm this conclusion. In general, the existing New Zealand recommendations for Se-status thresholds are supported, although studies are still lacking to properly characterise the upper threshold of the marginal range. Nevertheless many studies in New Zealand, of herds with marginal or low adequate Se status (using New Zealand recommendations), have failed to show an effect of Se supplementation on milk production, intramammary infection or reproductive performance, so it is highly unlikely that the upper threshold of the range is much higher than the current recommendation. Proponents of the hypothesis that Se intakes in New Zealand dairy cattle should be increased by at least 10 times the current recommendations are therefore not using the evidence base correctly.
摘要：
在新西兰,奶牛推荐的硒摄入量（0.03mg/kg干物质（DM））低于英国和澳大利亚（0.1和0.04mg/kgDM，分别)，远低于美国（0.3mg/kgDM）。新西兰的顾问经常建议，新西兰的建议摄入量太低，应使用美利坚合众国的建议。这造成了混乱，因为根据他们的顾问使用的建议，农民会得到非常不同的建议。在这次审查中,我们评估已发表的证据是否支持现有的饮食要求和相关的硒状态阈值，或者如果需要更改。我们特别关注以牧场为主要饮食的牛的证据基础，因为至关重要的是，饮食建议来自使用饲喂类似饮食的奶牛创建的数据。因此，我们还考虑是否增加饲料作物的使用，尤其是在干旱时期，很可能改变了新西兰奶牛对硒的需求。我们报告说，硒的饮食需求背后的科学是强有力的，由使用新西兰数据验证的阶乘模型支持，和农场实验研究。已发布的营养数据表明，增加饲料作物的使用不太可能改变新西兰奶牛的促和抗氧化因子的饮食平衡，从而对硒的需求产生有意义的影响。然而,缺乏有关新西兰饲喂作物的维生素E和脂肪酸含量的具体数据，这意味着需要更多的信息来证实这一结论。总的来说,支持新西兰现有的硒状态阈值建议，尽管仍缺乏适当表征边际范围上限阈值的研究。尽管如此，新西兰的许多研究，具有边际或低充足硒状况的牛群(使用新西兰建议)，未能显示出硒补充对牛奶产量的影响，乳房内感染或生殖表现，因此，该范围的上限阈值远高于当前建议的可能性很小。因此，支持新西兰奶牛的硒摄入量应至少增加10倍的假设的支持者没有正确使用证据基础。
