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

背景与正义反刍动物是食品供应链中的重要组成部分，它们从生产人类不能食用的食物的土地上运送营养产品。牧草是英国反刍动物的主要营养来源。虽然瘤胃微生物群落的进化使纤维饲料的发酵成为可能，但副产品是甲烷和氨的排放。甲烷的释放与饲料中“纤维”部分的瘤胃消化效率有关。我们假设，存在一个最优的成分，组成饲料的“纤维”部分，它驱动着最大限度地发酵但最大限度地减少甲烷生成的定殖率。此外，我们预测，环境压力将扰乱细胞壁生物化学，从而改变定居，从而改变饲料利用效率。牧草的消化能力和营养价值增加，牲畜甲烷排放量减少。这被描述为中性可消化纤维(NDF)和酸性可消化纤维(ADF)。这些术语广泛地衡量了细胞壁中的纤维素、半纤维素、木质素和果胶，但没有描述草类之间的基本成分差异如何影响定居。我们已经证明了摄取的饲料的连续性定植，在24小时内分阶段形成了特定的微生物群落。这一时间可能会受到底物的影响，但需要更多关于底物对群落组成的影响以及微生物区系在不同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反复无常和极端。细胞壁约占植物干重的70%，它们根据外界的挑战调整自己的组成和结构，以保持细胞的完整性。细胞壁成分与牧草的耐旱性有关，干旱胁迫会降低牧草的消化率。同样，暴露在风中会导致木质素含量增加，消化率降低。我们将使用与植物生物化学相关的元基因组学方法来探索这些关系。目的和目的我们假设环境胁迫会改变饲料细胞壁的组成和结构(从而改变品质/营养价值)，从而导致温室气体排放的变化。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提供净零草原食物系统至关重要。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Geral协商后，将在受控环境下种植三个主要牧草品种，并将其暴露在一系列环境压力(干旱、高温、风、洪水)中，以检测处理引起的细胞壁成分(木质素、纤维素、半纤维素)的变化。环境压力也会影响细胞壁的果胶。用代表不同形式果胶标记物的抗体进行的酶联免疫吸附试验将提供有关压力引起的果胶变化的信息。我们将确定胁迫引起的细胞壁特性的变化是否会影响牧草的体外消化率。将暴露在不同环境胁迫下的每种牧草的生物量样本暴露在瘤胃液接种中，并测量总产气量、二氧化碳和甲烷。瘤胃接种样品将用于FTIR分析，以探索代谢物产生的差异。建立微生物组和定殖区概况。来自牧草和瘤胃微生物群体外培养的样本将受到元基因组学和元转录分析的影响，以建立植物材料定植期间的分类图谱，以及微生物群落内和微生物群落之间的相关转录图谱，以响应植物碳水化合物结构的变化。

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.