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Intestinal health has a major influence on growth performance of turkeys and broilers as it affects feed digestion, nutrient absorption, and mortality. Compromised intestinal health is associated with animal infectious diseases and enteric foodborne pathogen colonization that may contaminate poultry products for human consumption. Diet can influence enteric health and disease. Benefits associated with the presence of non-starch polysaccharides (NSP) in the diet have been identified, including the potential to change the microflora and promote intestinal health. Therefore, it was hypothesized that manipulation of dietary NSP content and dietary exogenous enzyme supplementation promotes intestinal health and discourages the colonization of Salmonella spp. in turkey intestine, improving growth performance and reducing the presence of potential pathogenic microorganisms in turkeys. To test this hypothesis, four experiments were performed. The first research trial evaluated the effect of three different supplemental enzymes on intestinal size and histomorphometry of turkeys fed wheat-based diets from 0-56 days. The three enzyme preparations used included (1) an enzyme blend of endoxylanase along with β-glucanase, hemicellulase, cellulase and protease; (2) an enzyme with predominantly endoxylanase activity, and (3) an enzyme with predominantly phospholipase activity. Ileum digesta viscosity, intestinal size and ileum histomorphometry were determined from 56 days old turkeys. Experiments 2 and 3 were conducted to study the effects of feed formulation and dietary enzyme supplementation on intestinal Salmonella spp. colonization and performance of turkeys. In experiment-2, turkeys raised on litter-covered floor were fed wheat/soybean meal- (SBM) and corn/SBM-based diets with and without xylanase blends (XY1 or XY2, respectively) from 0-126 days. In experiment-3, turkeys raised in battery cages were fed a corn/SBM-control diet, and wheat/SBM- and triticale/SBM-based diets with and without XY1 from 0-28 d. The XY1 contained a pure endoxylanase, whereas XY2 contained endoxylanase, protease and α-amylase blend preparation. Growth performance and intestinal size were measured in both experiments. Additionally, Salmonella spp. fecal prevalence and intestinal accessory gland weights were determined in experiment-2, and Salmonella enterica cecal population, cecal pH, ileum digesta viscosity, and ileum histomorphometry were measured in experiment-3. The fourth trial utilized cultivation-independent approach using polymerase chain reaction (PCR) denaturing gradient gel electrophoresis (DGGE) to analyze changes in ileum bacterial population of turkeys fed different diets and after infection with Salmonella spp. The animals used in this trial were from experiment-2. Microbial DNA was extracted from ileum content of the turkeys at 16 weeks of age, and 16S ribosomal-DNA (rDNA) gene was amplified by PCR and analyzed by DGGE. Diversity indexes, including richness (number of species or DGGE bands), evenness (the relative distribution of species), diversity (using Shannon's index that include richness and evenness), and Sorenson's pairwise similarities coefficient (measures the species in common between different habitats) were measured. Diversity indexes were associated with change of Salmonella colonization of turkey intestine determined in experiment-2. The first study showed that NSP increased intestinal weight and length, likely as an adaptation response to increased intestinal digesta viscosity, compromised nutrient digestibility, and increased intestinal microbial fermentation. The dietary supplementation of NSP-hydrolyzing enzyme alleviated the adverse effects of NSP and decreased intestinal size. In addition, endoxylanase supplementation increased crypt depth and decreased villus height:crypt depth ratio, indicating increased enterocyte turnover rate. Experiments 1 and 3 showed that ileum digesta viscosity increased as the NSP content in the diet increased, but xylanase supplementation decreased viscosity of both triti ale- and wheat-based diets, such that the triticale diet was equivalent to the wheat diet; and the wheat diet was equivalent to the corn diet. Experiments 1 and 2 demonstrated that the blend of enzymes provided better response on growth performance and intestinal health of turkeys than single enzyme preparations, presumably due to the synergistic activity among the different enzymes. In experiments 2 and 3, Salmonella colonization in turkey intestine was discouraged by the diets high in NSP content (wheat- and triticale-based diets) and NSP-enzyme supplementation, consequently enhancing growth performance. In the fourth study, diets with high levels of NSP from wheat increased microbial community diversity indexes, especially when the diets were supplemented with dietary exogenous enzyme preparations. Increased microbial diversity appeared to support a stable, resident flora that discouraged Salmonella colonization in turkey intestine. In contrast, turkeys fed the corn-based diets had lower intestinal microbial diversity indexes which was associated with a decreased level of competitive exclusion against Salmonella colonization. In conclusion, dietary NSP positively interacted with both the mucosa and the microflora, demonstrating that it played an important role in maintenance of health, anatomy, development, and function of the intestine. A more stable and healthy intestinal ecosystem discourages the colonization of unfavorable microbial communities, leading to improved growth performance and animal welfare. The data presented in this dissertation supports the following hypothesis: dietary exogenous enzyme supplementation and NSP promotes intestinal health and discourages the colonization of Salmonella spp. in turkey intestine, thereby, improving growth performance and reducing the presence of potential pathogenic microorganisms in turkeys.
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