Probiotic and Gastrointestinal Microbiology in the Broiler Chicken
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Probiotics and prebiotics are used widely because of their benefits to digestive and immune health. While there is significant evidence to support their effectiveness in humans and livestock animals, interpretation of the results of this research is complicated by the wide differences in research. We have explored host-specific digestive physiology, experimental constraints, and probiotic and prebiotic functionality. The insight provided by an understanding of these important differences will provide a context in which results of host-specific studies and their broader implications to the science can be evaluated. Lactobacillus species are common inhabitants of the gastrointestinal tract and are widely used as probiotics because of their health promoting benefits. When used as Direct Fed Microbials (DFM) in poultry, they have been demonstrated to promote growth, stimulate immune responses, and reduce intestinal colonization of pathogens. While they are used widely, the mechanisms responsible for their functionality are not well understood. While genetic tools available for use in lactobacilli are advanced, they have not been applied to investigate the probiotic functionality of Lactobacillus cultures in poultry. The objective of this study is to demonstrate the functionality of the pORI28 system in L. gallinarum ATCC 33199 by insertional inactivation of lacL, encoding β-galactosidase. The establishment of an effective chromosomal integration system for L. gallinarum will provide a platform for functional genomic analyses to investigate the functionality of this model probiotic culture in poultry. DFM and exogenous enzymes have been demonstrated to improve growth performance in poultry and are potentially important alternatives to antibiotic growth promoters (AGP). We investigated the administration of a feed additive composed of a DFM products and enzymes in broiler chickens over a 42-day growth period. Evaluation of growth performance determined feed efficiency of broiler chickens which were administered the feed additive was comparable to those fed a diet containing AGPs. Characterization of the gastrointestinal microbiota using culture-dependent methods determined administration of the feed additive increased or decreased counts of bacteria enumerated from the gastrointestinal tract of the broiler chicken. Our results suggest the administration of DFMs and exogenous enzymes may potentially be an important component of antibiotic free poultry production.
Askelson, Tyler Edward (2017). Probiotic and Gastrointestinal Microbiology in the Broiler Chicken. Doctoral dissertation, Texas A&M University. Available electronically from