Understanding the role of host genetics in regulating the bovine gut microbiome

牛肉是饮食中营养丰富的组成部分，以相对较少的份量提供容易获得的蛋白质和必需的微量营养素。在世界许多地方，相当一部分人口营养不良，甚至在加拿大也是如此。肉牛还利用不适合或低效的土地资源来生产作物。因此，在许多国家，反刍动物蛋白质是人类饮食的一个组成部分，其生产有助于人类社会的发展和消除贫困。然而，反刍动物被认为对全球变暖做出了重大贡献。这方面可以通过选择提高饲料效率或将饲料转化为肉来减轻。提高牛的饲料效率是工业和社会面临的重大挑战之一，以满足日益增长的人类消费者需求，同时降低生产成本，减少每公斤产品产生的温室气体量以及粪便浪费。迄今为止，反刍动物的牛饲料效率和甲烷生产背后的生物过程在很大程度上仍然未知。我实验室过去的研究表明，饲料效率高的牛与饲料效率低的牛的瘤胃微生物群的组成和活性不同。反刍动物已经进化到在其瘤胃中拥有多样化的微生物种群，使它们能够将饲料转化为动物生长所需的营养物质。这种共生菌群可以降解大多数复杂的植物多糖，产生短链脂肪酸、蛋白质和维生素，满足动物维持和生长所需的能量。由此可见，“瘤胃发酵”作为营养物质消化的起点，是决定个体饲料效率的重要生物过程。虽然饮食是影响瘤胃微生物群的关键因素，但最近的研究强调，在相同环境中饲喂相同饮食的动物之间，微生物群可能存在很大差异。目前，我们还不清楚是什么影响了这方面。本项目旨在增加我们对瘤胃功能及其受宿主遗传影响的理解，以提高其功能和效率。我们将提出以下问题：1)宿主基因型是否部分解释了饲养场牛瘤胃微生物群落的变化，表现出饲料效率的差异？2)。牛下肠的微生物群是否也导致了这种变化，又是如何导致的？例如，通过影响宿主基因表达和氨基酸吸收和/或宿主影响下肠道微生物的相互作用和功能？对这种相互作用的理解可以形成新方法的基础来操纵它，以帮助实现更可持续或更环保的牛生产，这是我研究计划的最终目标。

Beef is a highly nutritious component of the diet providing readily accessible protein and essential micronutrients in a relatively small serving. In many parts of the world significant parts of the population is undernourished, even in Canada. Beef cattle also make use of land resources that are unsuitable or inefficient for producing crops. Thus, in many nations, ruminant protein is an integral component of the human diet and its production has contributed to the development and elimination of poverty in human society. However, ruminants are seen as contributing significantly to global warming. This aspect can be mitigated by selecting for improved feed efficiency or conversion of forage to meat. Improving feed efficiency of cattle is one of the grand challenges for industry and society in order to meet increased human consumer's demand but also to lower production cost and to reduce the amount of greenhouse gas produced per kg of product as well as the manure waste. To date, the biological processes underlying cattle feed efficiency and methane production in the ruminants are still largely unknown. Past studies from my laboratory have revealed that the composition and activity of the rumen microbiota in cattle with high feed efficiency differs from those with low feed efficiency. Ruminants have evolved to possess a diverse population of microbes in their rumen that enable them to convert forage into nutrients for animal growth. This symbiotic microbiota can degrade most complex plant polysaccharides to produce short chain fatty acids, proteins, and vitamins, which provide satisfy the animal's energy requirement for maintenance and growth. This suggests that “rumen fermentation”, as the starting point of nutrient digestion, is a major biological process determining individual feed efficiency. Although diet is a key factor for the rumen microbiome, recent research has highlighted that the microbiome can vary widely between animals fed the same diet in the same environment. Currently, we do not understand what impacts this aspect. This project seeks to increase our understanding of rumen function and how it is impacted by host genetics in order to improve its function and efficiency. We will ask the following questions: 1) Does the host genotype partially explain the variation in rumen microbial communities in feedlot cattle exhibiting differences in feed efficiency? 2). Can the microbiome of the lower gut of cattle also contribute to this variation and how? E.g. by impacting host gene expression and amino acid absorption and/or the host impacting microbial interactions and function in the lower gut? An understanding of this interaction can then form the basis of new approaches to manipulate it to help achieve more sustainable or environment friendly cattle production, the ultimate goal of my research program.