Nutritional programming in replacement dairy heifers: Future-proofing herd performance, health and behaviour

背景和依据：乳牛一生的性能受到早期健康、营养和环境的严重影响。如果这些因素是次优的，则它们将对动物实现其遗传潜力的能力具有不利影响，因此损害生产力、健康和福利（例如，海因里希斯等人，2011年）。在乳牛中，在生命早期摄入的营养素的平面和组成与未来的泌乳性能相关（例如Soberon等人，2012; 2013）。从初乳、乳汁或乳汁中摄取营养和非营养成分的变化可能与小牛代谢的变化有关，并在生产寿命期间持续存在。此外，在生命早期提供的营养素可以影响肠道微生物群（例如，Dill-McFarland等人，2018年）。例如，在单胃物种中，消化道内的饮食和微生物群对免疫力和健康具有强烈的影响（Maslowski和Mackay，2011），在与消化道细菌接触的肠道中出现几种免疫细胞的发育。然而，在反刍动物中，这些机制需要在它们可以用于操纵微生物群以有利于牛的健康和免疫之前进行表征（Plaizier等人，2018; Skelly等人，2019年）。此外，越来越多的证据强调了肠道微生物群在脊椎动物关键生理功能发育中的关键作用，这不仅包括生长和代谢，而且还包括脑发育和行为（Kraimi等人，2019年）。此外，表现出较少反应行为的奶牛具有改善的牛奶质量和生产参数（Cziszter等人，2016）。因此，更好地了解微生物-肠道-大脑轴之间的联系可能对动物生产，健康和福利产生影响。这些方面可以通过考虑肠道微生物群作用的营养和管理实践来改善（Kraimi等人，2019年）。假设：本研究将检查在早期生活中喂食不同饮食处理的动物的代谢型及其长期稳定性以及与成年生活中生产概况的关联。它将测试以下假设：从饮食中摄入不同的早期营养和非营养物质将导致不同的肠道微生物群和代谢型，这些微生物群和代谢型影响动物的能量代谢，表型（包括饲料效率和牛奶产量和质量）和行为。目的：确定可能与断奶前犊牛营养摄入量相对应的血浆代谢途径（代谢型）改变的生物标志物。研究日粮营养素和非营养素对断奶前和断奶后犊牛胃肠道中稳定的微生物组的影响，以及它们到成年期的长期稳定性。分析从生命早期到成年期确定的代谢型的纵向稳定性，以寻找代谢型与动物表型之间的相关性（包括对系统恢复力和可持续性有直接影响的体重、饲料效率、BW和牛奶产量和质量）。确定早期犊牛肠道菌群、代谢型和气质之间的关联，并检查这些特征是否持续到成年。确定改善免疫系统功能的生物标志物，以减少疾病和动物损失。该项目的结果将扩展我们对早期生命营养影响的理解，并有助于制定犊牛营养策略，以促进未来泌乳奶牛的代谢规划。这将有助于制定有针对性的性状选择策略，这将有助于建立一个环境可持续、高福利和多产的乳制品系统。提高奶制品的生产质量也将对人类营养产生积极影响。

Background and justification:Dairy calf lifetime performance is heavily influenced by early life health, nutrition and environment. If these factors are sub optimal they will have detrimental impacts on the ability of the animal to achieve its genetic potential, therefore compromising productivity, health and welfare (e.g. Heinrichs et al., 2011). In dairy calves, the plane and composition of ingested nutrients during early life has been associated with future lactation performance (e.g. Soberon et al., 2012; 2013). Variations in the intake of nutritive and non-nutritive components from colostrum, milk or milk replacers may be associated with changes in calf metabolism and persist during the productive lifespan. Additionally, nutrients provided in early life can impact on the gut microbiota (e.g. Dill-McFarland et al., 2018). For example, in monogastric species the diet and microbiota within the digestive tract have a strong influence on immunity and health (Maslowski and Mackay, 2011), with the development of several immune cells occurring in the intestines at contact with digestive tract bacteria. However, in ruminants these mechanisms need to be characterized before they can be utilised to manipulate the microbiota to favour bovine health and immunity (Plaizier et al., 2018; Skelly et al., 2019). Furthermore, an increasing body of evidence has highlighted the pivotal role of the gut microbiota in the development of key physiological functions in vertebrates, this not only including growth and metabolism, but also on brain development and behaviour (Kraimi et al., 2019). Furthermore, dairy cattle which display less reactive behaviours have improved milk quality and production parameters (Cziszter et al., 2016). As such, a better understanding of the links between the microbiota-gut-brain axis could have implications for animal production, health and welfare. These aspects could be improved through nutrition and management practices which take into account the role of gut microbiota (Kraimi et al., 2019). Hypothesis:This study will examine metabotypes from animals fed different dietary treatments in early life and their long-term stability and association with production profiles in adult life. It will test the hypothesis that different early life nutrient and non-nutrient intakes from the diet will result in different gut microbiota and metabotypes that affect the energy metabolism, phenotype (these including feed efficiency and milk production and quality) and behaviour of the animal. Objectives:Identify biomarkers for altered plasma metabolic pathways (metabotype) that may correspond to the intake of nutrients fed to pre-weaned calves.Study the effect of dietary nutrients and non- nutrients on the microbiome that stablishes in the gastrointestinal tract of pre- and post-weaned calves, and their long term stability to adulthood.Analyse the longitudinal stability of metabotypes identified in early life through to adulthood, to look for correlations between metabotypes and animal phenotype (including DMI, feed efficiency, BW and milk production and quality which have a direct impact on system resilience and sustainability). Identify associations between the gut microbiota, metabotype and temperament in early calfhood and examine if these traits persist to adulthood.Identify biomarkers for improved immune system function as a means of reducing ill-health and animal losses.Results from this project will extend our understanding of the effects of early life nutrition and help to develop nutritional strategies in calves for metabolic programing of future lactating cows. This will enable the development of strategies for targeted selection of traits which will contribute to an environmentally sustainable, high welfare and productive dairy system. Improving the production quality of milk products will also have a positive impact on human nutrition.