A microbial basis for Atlantic Salmon energetics

目前，全球鲑鱼养殖业的年产量已超过240万吨。欧洲主要生产商希望在未来五年内将产量扩大30-50%。如此大规模的扩张雄心引发了人们对鱼类福利、生态影响和鲑鱼饲料成分可持续性的担忧。营养是问题的核心。在野外，大西洋鲑鱼是专门的食肉动物。在水产养殖方面，为了摆脱对野生鱼类蛋白质和鱼油的不可持续使用，植物来源的蛋白质现在占其饮食的大部分（约60%）。相关的消化异常是常见的。此外，植物性饮食可能会影响营养物质的吸收速度和相关的鲑鱼生长速度，这决定了它们在海洋网箱中的生长速度。快速的海洋生长是可取的，因为它允许更广泛地跟踪沿海水产养殖场，从而减少养殖鱼类对海洋环境的影响（病原体转移、营养物污染）。最后，野生鱼类的蛋白质可以用植物蛋白代替，但鱼油不能。关键的omega-3脂肪酸必须来自海洋环境；对野生渔业造成重大负担。确保鲑鱼饲料中脂肪酸成分的有效同化对于保障海洋资源的可持续开发至关重要。鲑鱼的能量表型是由几个相互关联的性状组成的：代谢率、体脂含量、生长、从食物中获取能量、饥饿时的能量经济性。这些特征让人们更加关注鲑鱼的营养。在野生和养殖鲑鱼中都存在着显著的能量变异，有多种可能的驱动因素——遗传和环境因素。重要的是，大量的新数据表明，肠道微生物群（生活在所有脊椎动物肠道中的细菌）在决定宿主能量代谢方面发挥着重要作用。因此，了解肠道细菌如何影响大西洋鲑鱼的能量是理解它们在营养中的作用的基础。这是这个项目的主要目的。为了实现这一目标，我们将建立肠道细菌对野生和水产养殖环境中生活在盐和淡水中的鲑鱼能量学的影响。首先，在梅奥郡的Burrishoole（海洋研究所/科克大学学院，ROI）建立的一个独特的实验河流系统中，我们将通过其淡水生命周期跟踪引入的幼年鲑鱼，测量代谢和肠道微生物组的变化。这个“野生”队列将包括野生和放生的养殖鱼，以确定肠道微生物群的差异是否导致了野生养殖幼鱼的不良表现。其次，我们将在英国格拉斯哥大学（UoG）的实验室进行模拟水产养殖条件下的平行淡水实验。最后，与Marine Harvest合作，我们将在挪威对咸水阶段的成年前鲑鱼进行相应的实验。除了用活鱼进行实验外，我们建议利用工程学院的生物工程专业知识，UoG和行业合作伙伴Alltech的生物技术专业知识来构建人工鲑鱼肠道系统。通过将来自养殖和野生环境中代谢不同的鱼类的肠道细菌转移和维持到我们的肠道模型中，我们的目标是确定细菌发酵如何支撑饲料中能量收获的差异。一旦这些“人工”细菌群落建立起来，项目的最后探索阶段将包括将它们移植到实验室饲养的幼年鲑鱼中，以评估它们对宿主代谢的潜在影响。了解鲑鱼肠道细菌如何改变能量表型将为改善鱼类健康、营养和生产力开辟新的途径。在一个世界级的英国生物工程实验室里，大西洋鲑鱼肠道模型为英国鲑鱼养殖提供了一个宝贵的工具

Production of the global salmonid aquaculture industry now exceeds 2.4 megatons per annum. Major European producers expect to expand their outputs between 30-50% over the next five years. Ambitions for expansion on this scale create major concerns around fish welfare, ecological impact and the sustainability of salmon feed components. Nutrition lies at the heart of the issue. In the wild, Atlantic salmon are specialized carnivores. In aquaculture, in a move away from the unsustainable use of wild fish protein and oil, proteins of plant origin now constitute the majority (>60%) of their diet. Associated digestive abnormalities are common. In addition, plant-based diets may affect the rate at which nutrients are absorbed and the associated growth rate of salmon, which determines how quickly they grow in marine cages. Rapid marine growth is desirable since it permits more extensive fallowing of coastal aquaculture sites, which reduces the impact of farmed fish on the marine environment (pathogen transfer, nutrient pollution). Finally, while wild fish protein can be replaced by plant protein in salmon diets, oils cannot. Key omega-3 fatty acids must be sourced from the marine environment; a significant burden on wild fisheries. Ensuring the efficient assimilation of fatty acid components from salmonid diets is of paramount importance to safeguard the sustainable exploitation of marine resources.Salmon energetic phenotypes are composites of several interlinked traits: metabolic rate, body fat content, growth, energy harvest from food, energy economy in times of starvation. These traits underpin concerns around salmon nutrition. Significant energetic variation exists in both wild and farmed salmon with multiple possible drivers - both genetic and environmental. Importantly a wealth of new data indicates a role for intestinal microbiota - the bacteria that live in the guts of all vertebrates - in determining host energy metabolism. Understanding how gut bacteria influence Atlantic salmon energetics is thus fundamental to understanding their role in nutrition. This is the principal aim of this project. To achieve this we will establish the influence of gut bacteria on the energetics of salmon living in salt and freshwater, in both wild and aquaculture settings. First, in a unique experimental river system established in Burrishoole, Mayo (Marine Institute/University College Cork, ROI) we will track introduced juvenile salmon through their freshwater lifecycle, measuring both metabolic and gut microbiome variation. This 'wild' cohort will include wild and released farmed fish to establish whether differences between gut microbiota contribute to the poor performance of farmed juveniles in the wild. Secondly, we will undertake parallel freshwater experiments in simulated aquaculture conditions in the laboratory at the University of Glasgow (UoG),UK. Finally, in association with Marine Harvest, we will carry out corresponding experiments on saltwater phase pre-adult salmon in Norway. Alongside experiments with live fish, we propose to harness bioengineering expertise at the School of Engineering, UoG and biotechnological expertise via industry partner Alltech to build an artificial salmon gut system. Via the transfer and maintenance of gut bacteria from metabolically different fish from farmed and wild settings into our gut model we aim to establish how bacterial fermentation underpins differences in energy harvest from feed. Once these 'artificial' bacterial communities are established, a final exploratory phase of the project will involve their transplantation into laboratory reared juvenile salmon to evaluate their potential impact on host metabolism.Understanding how salmon gut bacteria change energetic phenotypes will open new avenues to improve fish health, nutrition and productivity. A model Atlantic salmon gut in a world class UK bio-engineering laboratory puts in place an invaluable tool for salmon aquaculture in the UK