Studies on quantitative and qualitative effects of lucerne silages with varying nitrogen fractions on ruminal nitrogen metabolism and the ruminal bacterial population

在反刍动物营养中，紫花苜蓿青贮是一种具有相当大的生态和营养潜力的牧草。然而，在青贮之前，植物材料中就已经发生了广泛的代谢反应，这可能会受到枯萎条件的很大影响，并可能对粗蛋白组成和所生产青贮饲料的蛋白质质量产生重大影响。在不同枯萎条件下的青贮料中，一方面青贮料的真蛋白含量较高，而其他青贮料在枯萎过程中粗蛋白的降解继续推进，导致非蛋白氮含量较高。我们推测，紫花苜蓿青贮料中也有类似的过程，它们对青贮料的品质有很大影响。由于瘤胃氮和碳水化合物代谢的相互依赖，可以推测，氮组分的不同组成导致了瘤胃代谢的广泛变化。提交的项目的基础是生产因枯萎条件不同而含有不同N组分的紫花苜蓿青贮料。在对这些青贮料进行广泛的化学表征后，将通过半连续的长期瘤胃模拟系统来研究它们对瘤胃氮和碳水化合物代谢的影响。由于底物供应的不同，可以假设瘤胃微生物种群将发生变化，并将通过分子遗传学方法采集特定样本来跟踪这些变化。尤其是游离氨基酸含量较高的青贮料品种，可能有利于氨基酸发酵菌种的生长，导致氮周转增加，瘤胃微生物粗蛋白合成效率降低。该项目的成果将对青贮饲料的制作有很大的促进作用。在枯萎期间，紫花苜蓿青贮料的后期质量可能会受到有意的影响。有了这一点，确保瘤胃内高效微生物粗蛋白质合成的紫花苜蓿青贮料可能会被生产出来。

In ruminant nutrition lucerne silage is a forage with considerable ecological and nutritional potential. However, already prior to ensiling are extensive metabolic reactions in the plant material occur, which may be considerably affected by wilting conditions and may have a significant influence on crude protein composition and, thus, protein quality of the silage produced. In the case of grass silages differing wilting conditions lead to silages with a high percentage of true protein on the one hand whereas, the degradation of crude protein during wilting continues to advance in other silages and leads to high percentages of non-protein N. We assume that there are similar processes in lucerne silage and that they influence the quality of the silages considerably. Because of the mutual dependence of ruminal N and carbohydrate metabolism it can be hypothesized that the differing composition of N fractions leads to extensive alterations in ruminal metabolism. The basis of the submitted project is production of lucerne silages with differently composed N fractions due to different wilting conditions. After an extensive chemical characterization of these silages, their effects on ruminal N as well as carbohydrate metabolism will be studied by means of a semi-continuous long-time rumen simulation system. Because of the differing substrate supply it can be assumed that shifts will be observed in the ruminal microbial population and there will be specific samples taken to track these changes by molecular genetic methods. Especially silage varieties with high percentages of free amino acids might facilitate growth of amino acid-fermenting species leading to an increase of N turnover accompanied by less efficient rumen microbial crude protein synthesis. The results of this project will significantly contribute to the knowledge of silage making. Already during wilting the later quality of lucerne silages could be purposefully influenced. With that lucerne silages that ensure efficient microbial crude protein synthesis in the rumen might be produced.