Change in the ileal bacterial population of turkeys fed different diets and after infection with Salmonella as determined with denaturing gradient gel electrophoresis of amplified 16S ribosomal DNA
Article
Santos, A. A., Jr., Ferket, P. R., Santos, F. B. O., Nakamura, N., Collier, C.
abstract
Changes in ileal bacterial populations of Salmonella-infected turkeys fed different diets were analyzed by using 16S-V3 PCR denaturing gradient gel electrophoresis. Turkeys raised on litter flooring were fed wheat-and corn-based diets with and without enzyme preparations (XY1 and XY2, respectively) from 0 to 126 d. Preparation XY1 contained exclusively endoxylanase, whereas preparation XY2 contained endoxylanase, protease, and alpha-amylase (Danisco,, Wiltshire, UK). The dietary activity levels of XY1 and XY2 were 2,500 and 650 endo1,4-beta-xylanase units/kg of feed, respectively. Microbial DNA was extracted from the ileal content of 16-wk-old turkeys, and the 16S rDNA gene was amplified by PCR and analyzed by denaturing gradient gel electrophoresis. Diversity indexes, including richness (number of species, S), evenness (relative distribution of species, E-H), diversity (using Shannon's index, H'), and Sorenson's pairwise similarities coefficient (measures the species in common between different habitats, C-s) were calculated. Additionally, diversity indexes were associated with Salmonella prevalence determined from fresh fecal droppings collected from each pen. On the basis of contrast analysis, the wheat-based diets resulted in higher microbial diversity indexes than the corn-based diets (S = 10 vs. 12; E-H = 0.9 vs. 0.8; H' = 2.2 vs. 1.9, P < 0.05). Likewise, enzyme supplementation stimulated growth of the microbiota and increased the diversity indexes in comparison with unsupplemented treatments (S = 13 vs. 10; E-H = 0.9 vs. 0.8; H' = 2.2 vs. 1.9, P < 0.05). Salmonella prevalence was higher (P < 0.05) at 15 wk in turkeys fed the corn-based diet (Salmonella prevalence = 50%) than in turkeys fed the corn-enzyme (Salmonella prevalence = 13%) and wheat-based (Salmonella prevalence = 0%) dietary treatments. Therefore, contrast analysis showed that birds fed the corn control diet had lower microbiota diversity but higher Salmonella prevalence than birds fed the enzyme-supplemented and wheat-based diets. In contrast, birds fed the wheat-based diets had higher diversity but lower Salmonella prevalence than birds fed the corn-based diets. High dietary nonstarch polysaccharides from wheat and dietary exogenous enzyme supplementation promoted microbial community diversity and apparently discouraged Salmonella colonization through competitive exclusion. Nonstarch polysaccharides and dietary exogenous enzyme supplementation may be practical tools to control enteric pathogens and benefit the intestinal health and food safety of the birds.