Influence of substrate and aerobic exposure on chemical composition and the metabolome of silages and on the preference behavior of ruminants

青贮饲料已成为世界各地奶牛和其他反刍动物日粮中最重要的饲料。在饲喂过程中，青贮料可能会发生好氧降解过程和加热，伴随着饲料质量的下降和反刍动物接受度的降低。在这段时间里，几种挥发性有机化合物(VOC)正在排放，这会对空气质量产生负面影响，并有助于对流层臭氧的形成。此外，在饲料摄入量方面，VOC通过影响青贮料的感官特性或动物在摄食后获得的摄食后反馈而发挥重要作用。在好氧暴露过程中，由于微生物的活动或挥发，VOC的组成不断变化。然而，对它们的组成是如何变化的，以及哪些特定的VOC影响了反刍动物对饲料的接受，缺乏了解，因此仍然缺乏对观察到的饲料采食量减少的解释。在这方面，计划中的研究项目将首次使用青贮料的代谢组分析，以及广泛的化学特性和偏好试验。代谢组学的使用可以帮助获得比以前更详细的青贮料的化学和分子组成的描述，如底物、青贮和有氧暴露的影响。玉米、紫花苜蓿和多花黑麦草的全作物青贮料将在四个重复中使用，并在三种状态下进行比较：“预青贮”、“青贮新鲜”和“青贮再加热”(高于环境温度3K)。其目的是对完整的青贮料组成和与以前未被检测和研究但可能影响饲料选择行为的化合物的联系进行概述。在有氧暴露期间浓度发生显著变化的化合物随后将作为纯物质添加到山羊和奶牛的偏好试验中，以研究它们对饲料选择和饲料接受的影响。在这方面，我们将第一次能够概述与牧草有氧变质有关的物质，并评估它们对反刍动物饲料接受度的影响。

Silage has become the most important feedstuff in rations for dairy cows and other ruminants worldwide. During feed-out aerobic degradation processes and heating of the silage can take place, accompanied by a decrease in feed quality and reduced acceptance by ruminants. In this time, several volatile organic compounds (VOC) are emitting, which can impact the air quality negatively and can contribute to ozone formation in the troposphere. Also with regard to feed intake VOC play an important role by influencing the sensory characteristics of the silage or the post-ingestive feedback received by the animal after ingestion. The composition of the VOC is changing continuously during aerobic exposure, as a consequence of microbial activity or volatilization. However, there is a lack of knowledge how their composition is changing and by which specific VOC the feed acceptance of ruminants is influenced such that explanations for the observed reduction in feed intake are still missing. For the first time in this extend, the planned research project will use metabolome analyses of the silages in addition to an extensive chemical characterisation and preference trials. The use of metabolomics can help to obtain a more detailed description of the chemical and molecular components of silages than before, as influenced by substrate, ensiling and aerobic exposure. Whole-crop silages of maize, lucerne and Italian ryegrass will be used in four replicates and compared in the three states “pre-ensiled”, “ensiled fresh” and “ensiled re-heated” (>3 K above ambient temperature). The aim is to get a overview about the complete silage composition and links to compounds that have not been detected and studied before but that possibly impact the feed choice behaviour. Compounds that change significantly in concentration during aerobic exposure will afterwards be added as pure substance in preference trials with goats and dairy cows to study their effect on forage choice and feed acceptance. For the first time in this extend we will be able to give an overview about substances that are linked to the aerobic deterioration of forages and to evaluate their effect on the feed acceptance of ruminants.