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The Evaluation of the Physiologic and Microbial Parameters in Laying Hens during an Induced Molt Using Alternative Molting Diets


<OL> <LI> To determine the effects of dietary modifications on the microbial ecology of the gastrointestinal tract and colonization of poultry by food-borne pathogen. <LI> To evaluate the physiological and immunological effects in birds undergoing dietary regimen stress. <LI> To understand the genetics of virulence expression while birds are undergoing dietary regimen stress and determine their role in colonization and virulence expression.

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APPROACH: Identify potential alternative molting diets (Alfalfa-commercial feed grade, Tomato Extract, Alfalfa-purified protein extract) that can be utilized as pre-harvest intervention strategies and determine how these alternative diets control poultry enteropathogen colonization. The ability of pathogens to colonize the gastrointestinal tract depends on several factors including host responses and microbial responses. We will investigate the interactions of bacterial populations including Salmonella within the gastrointestinal tract of layers and using molecular based techniques (DGGE, PFGE) in order to determine the dynamics between commensal gut bacterial populations and Salmonella. Evaluating the dietary effects on physiological and immunological responses will include weight loss, ovary weight regression, feed consumption, and antibody responses (IgG and sIgA) that can be measured by ELISA. The dietary influence on virulence expression will also be evaluated. Previous work in our laboratories has indicated that feed withdrawal greatly increases virulence expression and infection of organs in laying hens. Therefore, it is important to develop ways to quantify the level of virulence in the gut to predict the ability of dietary regimes to limit invasion by pathogens of susceptible hens. Both in vitro and in vivo approaches will be used to accomplish this. In vitro screening on virulence gene expression and survivability using alternative molt diets as the substrate and layer hen cecal inocula in fermentation flasks will be conducted to determine the best diet combinations to limit pathogen survival. In vivo measurement of mRNA expression of key virulence genes of pathogens in the intestinal and cecal lumen contents will also be measured using RT-PCR to quantify the amount of expression of key virulence genes and compare these with the levels of organ infection. In addition, generation of mutant libraries of pathogens may reveal other genes that are required for successful colonization and invasion. The outcome of this series of experiments should give us some molecular indicators for large-scale screening of multiple dietary/antimicrobial combinations that are most likely to be effective. Identification of key virulence genes may also lead to alternative nondietary approaches to limit pathogen colonization and invasion.

PROGRESS: 2005/11 TO 2006/06<BR>
Project scientists, in close collaboration with the poultry industry, conducted a series of in vitro and in vivo studies that demonstrated the utility of alternative molting diets, and of fructooligosaccharide and zinc supplemented diets. Project work also focused on an experimental chlorate product added to the drinking water in combination with an alternative molting diet. These studies overall have identified methods to support beneficial microbial activity, specific microbial populations, and fermentation actions that limit Salmonella colonization and infection in laying hens. This research will provide the poultry industry with alternative molting strategies that reduce Salmonella incidence while maintaining the production benefits of a second egg laying cycle and that are more acceptable by the general population. This project expired in FY 2006.

Ricke, Steven; McReynolds, Jackson
Texas A&M University
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