Strategic use of carbohydrase enzymes in broiler diets to increase productivity by improving gut health

拟议项目的目的是研究在饮食中补充碳水化合物酶（木聚糖酶和β-葡聚糖酶）对促进生长性能，肠道水平免疫和炎症反应，肠道细胞发育和完整性以及肠道微生物群变化的有益影响。假设以高补充水平补充糖酶将通过促进肠道健康而不仅仅是改善营养利用来改善禽类的生长性能。家禽的饮食以谷物和豆类为主。英国最重要的谷物是玉米、小麦和大麦。小麦和大麦含有大量的非淀粉多糖（NSP），通过减少营养物质的利用，导致肠道中有害微生物的增殖和损害肠道细胞发育来损害动物生长。碳水化合物酶补充到家禽饮食中以增加能量可用性，但它们也可以对肠道健康有益。例如，在一项研究中，在饮食中掺入NSP水解产物（从谷物发酵中获得）可减少肉鸡粪便中的沙门氏菌计数。看来NSP水解产物可以促进肠道健康，因为NSP水解产生的寡糖可以充当益生元。然而，水解NSP作为谷物颗粒预处理并将预处理的谷物颗粒掺入实际饮食中既不实际也不可行。实用和现实的途径是战略性的膳食补充剂的NSP酶，可以帮助提供NSP水解产物的肉鸡肠道，从而刺激动物的生长和增强肠道健康。因此，这个博士项目将研究NSP酶在饮食中的战略用途，以促进肠道健康和提高肉鸡生产力。该项目的第一部分旨在显示NSP在体内的水解程度。据认为，NSP水解成较大的寡糖具有生长刺激作用，而较小的寡糖对消化道具有健康益处。然而，目前还没有系统的研究在何种程度上，碳水化合物的补充提高NSP水解活禽。使用HPLC，分析从沿着消化道的不同部分收集的肠杆菌，以显示不同类型的NSP水解产物的相对丰度。NSP水解的数据将与生长性能和营养物质消化率数据相关联，使研究具有行业相关性。随后的实验将设计研究各种可能的作用模式，通过这些模式，碳水化合物酶引起生长性能的提高和肠道环境的改善。将使用组织学和形态学测量来研究小肠中吸收细胞的细胞发育。NSP水解产物在调节肠道水平的炎症和免疫反应中的可能作用将使用肠道炎症和免疫的分子标志物进行检查。这些将与使用消化道中的形态学和分子反应以及血液中的化学标记物测量细胞完整性相结合。在改进优化反应的酶产品的水平和组合后，将使禽类暴露于中度疾病挑战，例如可能发生在典型的鸡群中，并将使用炎症、生长性能和营养利用反应以及肠道微生物群的动态来研究禽类对疾病挑战的反应。该项目福尔斯属于BBSRC研究的职权范围，证明了牲畜物种的营养和健康之间的联系。该项目将展示碳水化合物酶促进肉鸡生长性能和肠道健康的可能方法，因此这些研究将提供有关营养-健康相互作用的有价值信息，从而促进进一步的酶发现。

The objective of the proposed project is study the beneficial effects of supplementing diets with carbohydrases (xylanase and beta-glucanase), in promoting growth performance, gut level immunity and inflammatory responses, intestinal cell development and integrity, and changes in gut microbial population. It is hypothesised that supplementation of carbohydrases at high supplemental levels will improve growth performance of birds via promotion of gut health rather than improved nutrient utilisation only. Poultry diets are based on cereal grains and legume meals. The most important cereal grains in the UK are maize, wheat and barley. Wheat and barley have high amounts of non-starch polysaccharides (NSP) which impair animal growth by reducing nutrient utilisation, causing proliferation of harmful microorganisms in the gut, and impair intestinal cell development. Carbohydrases are supplemented to poultry diets to increase energy availability, but they can have gut health benefits as well. For example, incorporation of NSP hydrolysis products (obtained from fermentation of grains) in diets is shown to reduce salmonella count in the droppings of broilers in a study. It appears that NSP hydrolysis products can promote gut health, because the oligosaccharides produced by NSP hydrolysis can act as prebiotics. However it is neither practical, nor feasible, to hydrolyse NSP as a cereal grain pre-treatment and incorporate the pre-treated cereal grains in practical diets. The practical and realistic route is the strategic dietary supplementation of NSP enzymes that can help deliver NSP hydrolysis products to broiler gut and thus stimulate animal growth and enhance gut health. Consequently this PhD project will investigate the strategic use of NSP enzymes in the diets to promote gut health and enhance broiler productivity. The first part of the project is designed to show the extent of NSP hydrolysis in vivo. It is thought that hydrolysis of NSP to larger oligosaccharides have growth stimulation effects whereas the smaller oligosaccharides have health benefits for the digestive tract. However, there have been no systematic study on the extent to which carbohydrase supplementation enhance NSP hydrolysis in live birds. Using HPLC, the digesta collected from different sections along the digestive tract will be analysed to show the relative abundance of the different types of NSP hydrolysis products. The data on NSP hydrolysis will be related back to growth performance and nutrient digestibility data to make the study industry-relevant.Subsequent experiments will be designed to study various possible modes of action by which carbohydrases elicit increased growth performance and improved gut environment. The cellular development of the absorptive cells in the small intestine will be study using histological and morphological measures. The possible roles of NSP hydrolysis products in modulating gut-level inflammatory and immune responses will be examined using molecular markers of gut inflammation and immunity. These will be combined with measurement of cellular integrity using both morphological and molecular responses in the digestive tract as well as chemical markers in the blood. After refining the level and combination of enzyme products that optimize responses, the birds will be exposed to moderate disease challenge such as can occur in a typical flock and the response of birds to the disease challenge will be studied using inflammatory, growth performance and nutrient utilisation responses, as well as the dynamics of gut microbial population. The project falls within the remit of BBSRC research demonstrating the link between nutrition and health of livestock species. The project will demonstrate possible ways by which carbohydrases promote growth performance and gut health in broilers and the studies will thus provide valuable information on nutrition-health interaction which can stimulate further enzyme discovery.