Feed for Net Zero: Understanding the structure function relationships in forages driving rumen feed degradation

反刍动物是食物供应链的重要组成部分，从生产人类不可食用的食物的土地上提供营养产品。牧草是英国反刍家畜的主要营养来源。虽然瘤胃微生物群落的进化使纤维饲料发酵成为可能，但副产物是甲烷和氨的排放。甲烷释放与饲料中“纤维”部分的瘤胃消化效率有关。我们假设存在构成草料饲料的“纤维”部分的最佳组合物，其驱动使发酵最大化但使产甲烷最小化的定殖概况。此外，我们预测，环境压力会扰乱细胞壁的生物化学，改变殖民化，从而饲料利用efficiency. Livestock为基础的甲烷排放量减少，提高消化率和营养价值的牧草。这被称为中性可消化纤维（NDF）和酸性可消化纤维（ADF）。这些术语广泛地测量细胞壁中的纤维素、半纤维素、木质素和果胶，但没有描述草之间的基本成分差异如何影响定殖。我们已经证明了连续的殖民地摄入的饲料，确定的微生物群落形成阶段超过24小时。时间可能受到基质的影响，但需要更多关于基质对群落组成的影响以及微生物群在各个阶段的功能作用的信息。此外，未来的气候情景预测英国的天气模式越来越不稳定和极端。细胞壁占植物干重的约70%，适应其组成和结构以应对外部挑战，以保持细胞完整性。细胞壁成分与耐旱性有关，干旱胁迫降低了牧草的消化率。同样，暴露于风导致木质素含量增加和消化率降低。一个宏基因组学的方法与植物生物化学将被用来探索这些relationships.Aim和ObjectivesWe假设，环境压力将改变饲料细胞壁的组成和结构（从而质量/营养价值），从而导致温室气体排放量的变化。了解环境压力、细胞壁特征和温室气体之间的相互作用对于帮助实现基于草地的净零粮食系统至关重要1。我们将建立环境胁迫对牧草细胞壁质量的影响。在与牧草育种公司GERDESS协商后，将在受控环境下种植三种主要牧草品种，并将其暴露于一系列环境胁迫（干旱、高温、风、洪水），以检测处理诱导的细胞壁成分（木质素、纤维素、半纤维素）变化。环境胁迫也影响细胞壁果胶。用代表不同形式果胶的标记物的抗体进行的ELISA测定将提供关于应激诱导的果胶变化的信息。我们将确定是否应力诱导的细胞壁特性的变化影响牧草的体外消化率。将暴露于不同环境胁迫的每种牧草的生物质样品暴露于瘤胃液接种物，并测量总气体产量、CO2和甲烷。瘤胃接种物样品将用于FTIR分析，以探索代谢产物产生的差异。建立微生物组和定殖概况。来自草和瘤胃微生物群的体外孵育的样品将进行宏基因组学和元转录组学分析，以建立植物材料定殖期间的分类学概况以及响应于植物碳水化合物结构变化的微生物群落内和之间的相关转录组学概况。

Background & JustificationRuminants are a vital part of the food supply chain, delivering nutritious products from land that produces food inedible by humans. Forage grasses are the main source of nutrition for ruminant livestock in the UK. While the evolution of the rumen microbial community enables fermentation of fibrous feed, a by-product is emission of methane and ammonia. Methane release is linked to efficiency of rumen digestion of the "fibre" part in the feed. We hypothesise that there is an optimal composition making up the "fibre" part of the forage feed which drives a colonisation profile that maximises fermentation but minimises methanogenesis. Furthermore, we predict that environmental stress will perturb cell wall biochemistry to alter colonisation and hence feed use efficiency.Livestock-based methane emissions decrease with increased digestibility and nutritional value of forage grasses. This is described as Neutral Digestible Fibre (NDF) and Acid Digestible Fibre (ADF). These terms broadly measure cellulose, hemicellulose, lignin and pectin in the cell walls but do not describe how the fundamental compositional differences between grasses affects colonisation. We have demonstrated successional colonisation of ingested forage, with defined microbial communities forming in phases over 24h. The timing can be affected by substrate but more information is needed about the effect of substrate on community composition and the functional roles of the microbiota at the various stages. Also, future climate scenarios predict increasingly erratic and extreme weather patterns in the UK. Cell walls, representing ~70% of a plant dry weight, adapt their composition and structure in response to external challenges to maintain cell integrity. Cell wall components have been associated with drought tolerance and drought stress decreases the digestibility of forage grasses. Likewise, exposure to wind resulted in increased lignin content and reduced digestibility. A metagenomics approach linked to plant biochemistry will be used to explore these relationships.Aim and ObjectivesWe hypothesise that environmental stress will alter forage cell wall composition and structure (and thus quality/nutritive value) which leads to changes in GHG emissions. Understanding the interaction between environmental stresses, cell wall characteristics and GHGs is essential to help deliver Net Zero grassland-based food systems1. We will establish the effect of environmental stresses on cell wall quality of forage grasses. In consultation with the grass breeding company Germinal, three leading forage grass varieties will be grown under controlled environment and exposed to a range of environmental stresses (drought, heat, wind, flooding) to detect treatment induced changes in cell wall composition (lignin, cellulose, hemicellulose). Environmental stresses also affect the cell wall pectins. ELISA assays with antibodies that represent markers for different forms of pectins will provide information on stress induced changes to pectin.2. We will determine if stress induced changes in cell wall properties impact the in vitro digestibility of forage grasses. Biomass samples of each of the forage grasses exposed to the different environmental stresses will be exposed to a rumen fluid inoculum and total gas production, CO2 and methane measured. Samples of the rumen inoculum will be used for FTIR analysis to explore differences in metabolite production.3. Establish microbiome and colonisation profiles. Samples from in vitro incubation of grasses and rumen microbiota will be subject to metagenomics and metatranscriptomic analysis to establish the taxonomy profile during colonisation of the plant material and the related transcriptomic profiles within and between microbial communities in response to changes in the plant carbohydrate structure.