Potential and Limitations of plant polyphenols to reduce methane emissions from ruminants in grassland systems

反刍农业的甲烷排放量占欧盟27国温室气体总排放量的12-17%。然而，在欧洲，在不降低动物生产力的情况下减少这些排放的可能性是有限的。目前存在的几种可能性之一是食用含有单宁酸的饲料植物。尽管关于这一主题的研究已经进行了好几年，但关于饲料物种减少甲烷排放的潜力的结果却变化很大。这阻碍了含单宁的饲料植物在农业中的广泛应用，尽管它有增加草地生物多样性的有益副作用。其中一个主要原因是观察到的变化在反产甲烷的潜力是，以前的实验通常只量化总酚类化合物。这是有问题的，因为它忽略了单宁的结构特征，这已被证明对生物活性有很大影响。此外，只分析了很少的物种，而且是在池样品中而不是在单个植物中，因此忽略了物种内部的可变性，使先前的结果更加难以解释。然而，最近在单宁分析方面的进展使得对单宁浓度及其结构特征的分析变得更快、更好。此外，这些新方法允许同时定量类黄酮或其他具有潜在生物活性的多酚，这些多酚也可能存在于饲料物种中。我们提出了以下假设：1)对单宁的准确和改进的表征将允许改进对其抗甲烷潜能的评估，2)这些单宁的作用可以减少或增加，取决于额外多酚的共同存在，3)生长条件的差异影响了先前研究中的单宁含量，从而使这些研究之间的比较变得困难。为了解决这些问题，我们将在相同的环境条件下培养8种含单宁的牧草品种的不同个体，然后用最先进的设备分析它们的生物活性化合物。此外，它们的甲烷还原潜力将通过Hohenheim气体测试进行量化。本实验的实验设计进行了优化，以统计分析化学特性与观察到的生物活性之间的联系，并允许将结果外推到其他物种。最后，在这个实验中，我们将首次分析蛋白质和纤维结合的单宁，因为它们可能有助于抗甲烷作用。因此，本研究为后续体内试验提供了良好的基础。该研究项目得益于小组成员在植物化学分析、草料生产、草地系统和动物营养方面的经验。

Methane emissions from ruminant agriculture account for 12-17% of all EU-27 GHG emissions. However, possibilities to reduce these emissions are limited in Europe without risking decrements in the animal’s productivity. One of the few existing possibilities is the feeding of forage plants that contain tannins. Although research on this topic has been conducted for several years already, results about the potential of forage species to reduce methane emissions were highly variable. This prevented a widespread application of tannin-containing forage plants in agriculture, despite the beneficial side effect of increasing grassland biodiversity. One of the main reasons for the observed variability in antimethanogenic potential is that previous experiments usually only quantified total phenolic compounds. This is problematic as it ignores the structural characteristics of tannins, which have been proven to affect the bioactivity substantially. Additionally, only very few species were analysed and also in pool samples rather than individual plants, hence ignoring the variability within species and making previous results even more difficult to interpret. Nevertheless, recent advances in the analysis of tannins permitted faster and better analyses of both tannin concentration and their structural characteristics. Additionally, these new methods permit a simultaneous quantification of flavonoids or other polyphenols with potential bioactivity that might be present in the forage species as well.We put forward the following hypotheses: i) an accurate and improved characterisation of tannins will permit an improved assessment of their antimethanogenic potential, ii) the effect of these tannins can be reduced or increased, dependent on the co-presence of additional polyphenols, and iii) differences in growing conditions have affected the tannin content in previous studies, thus making comparisons among these studies difficult. To solve these issues, we will cultivate different individuals of several cultivars from eight tannin containing forage species under identical environmental conditions, and subsequently analyse their bioactive compounds with the most modern equipment available. Furthermore, their methane reducing potential will be quantified using the Hohenheim gas test. The experimental design for this experiment was optimized for the statistical analysis of the link between the chemical characterization and the observed bioactivity, and to permit extrapolation of results to additional species. Finally, in this experiment, we will analyse protein and fibre bound tannins for the first time, as they might contribute to the ant-methanogenic effect. Hence, this study provides an excellent basis for subsequent in vivo trials.This research project benefits from the experience of the group members in phytochemical analyses, as well as regarding forage production, grassland systems and animal nutrition.