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

牛肉是饮食中高度营养的组成部分，在相对较少的份量中提供容易获得的蛋白质和必要的微量营养素。在世界许多地区，即使在加拿大，也有很大一部分人口营养不良。肉牛还利用不适合或低效生产农作物的土地资源。因此，在许多国家，反刍动物蛋白是人类饮食中不可或缺的组成部分，其生产有助于人类社会的发展和消除贫困。然而，反刍动物被认为是全球变暖的重要原因。可以通过选择提高饲料效率或将饲料转化为肉类来缓解这一方面。提高牛的饲料效率是工业和社会面临的重大挑战之一，既要满足日益增长的人类消费需求，又要降低生产成本，减少每公斤产品产生的温室气体和粪便废物。到目前为止，牛饲料效率和反刍动物甲烷产生的生物学过程在很大程度上仍不清楚。本实验室过去的研究表明，饲料效率高的牛和饲料效率低的牛的瘤胃微生物区系的组成和活性不同。反刍动物已经进化到在它们的瘤胃中拥有不同的微生物种群，使它们能够将饲料转化为动物生长所需的营养物质。这种共生微生物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，为动物提供维持和生长所需的能量。这表明，瘤胃发酵作为养分消化的起点，是决定个体饲料效率的主要生物学过程。虽然饮食是瘤胃微生物群的关键因素，但最近的研究强调，在相同环境下喂食相同饲料的动物之间，微生物群可能会有很大差异。目前，我们还不清楚是什么影响了这一方面。本项目旨在加深我们对瘤胃功能以及宿主遗传学如何影响瘤胃功能的了解，从而提高瘤胃的功能和效率。我们将提出以下问题：1)宿主基因是否部分解释了饲料效率不同的饲用牛瘤胃微生物群落的差异？牛的肠道下部的微生物群是否也会对这种变异产生影响，以及如何造成这种差异？例如，通过影响宿主基因的表达和氨基酸的吸收和/或宿主影响肠道下部微生物的相互作用和功能？对这种相互作用的理解然后可以形成新的方法的基础，以操纵它，以帮助实现更可持续或环境友好的牛生产，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.