description
- 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.