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<OL> <LI> To etermine the effects of dietary modifications on the microecology of the gastrointestinal tract and colonization of poultry by enteropathogens <LI> to understand the potential role of the crop for enteropathogen virulence expression while birds are undergoing dietary regimen stress <LI> to understand genetics of virulence expression while birds are undergoing dietary regimen stress and determine if key genes can be linked with limiting colonization and virulence expression.
The ability of enteropathogens to colonize the gastrointestinal tractof an animal is dependent on bacterial factors that permit the organism to survive in the gastrointestinal environment.Comparisons will be made of the indigenous microbial response in crops of birds that have been stressed by various dietary regimens. The hypothesis is that dietary modifications will cause a slight reduction in feed intake but the crop microflora will retain active fermentation to the point of being inhibitory to enteropathogen colonization and invasion. The key indicators of an active fermentation in the crop, low pH and high concentration of lactate, will be measured as well as quantitation of fermentation products and enumeration of crop lactobacilli. Whether these key characteristics in the chicken crop microenvironment can be linked with limiting enteropathogen invasion will be determined by examining virulence activity with a gene fusion strain for in vitro assays of crop contents.