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Impact of probiotics on commensal and pathogenic swine intestinal microbes
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- Author / Creator
- Wang Weilan
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The application of probiotics is considered an effective approach to improve overall health conditions and growth performance in swine. Understanding the properties of these probiotics is a prerequisite for the selection of probiotics for pigs. Here, a rational selection criteria of swine probiotics is discussed mainly based on divergent probiotic effects of different strains and practical purposes in swine production (Chapter 2). The systematically investigated ecological history rather than the source of isolates should be regarded as the natural origin of probiotic strains, which helps to correct the inconsistencies arising from incorrect identification of the source. Host-adapted probiotic strains are likely to associated with exclusive colonization while the nomadic or environmental strain exert better immune stimulating functions. Strains with potent enzymatic activity are fitter for grower pigs favoring feed digestion and enhancing growth performance.
Enterotoxigenic Escherichia coli (ETEC) is known to be a major pathogen in swine, however, this group of pathogens has a variable profile. Monitoring this profile of ETEC virulence factors could supply novel strategies to develop ETEC vaccines or fimbriae receptor analogues. In this thesis, a multiplex high-resolution melting curves-based qPCR (HRM-qPCR) assay was developed which enabled quantification of predominant ETEC fimbriae types and additionally monitored the presence or absence of other fimbriae types related to post-weaning diarrhea. Inclusion of host-adapted L. reuteri effectively reduced ETEC abundance in swine intestine (Chapter 4 and 5). In contrast, nomadic L. fermentum and L. casei did not show inhibitory effects on ETEC but eliminated Clostridium spp.. Furthermore, probiotic intervention showed limited alteration of commensal gut microbiota.
The feed transition after weaning also induces an increasing ability of intestinal microorganisms to harvest energy from dietary carbohydrates. To unravel the adaptation of the swine microbiome to the dietary shift after weaning, a total of 360 high-quality microbial genomes were assembled as the first metagenomic-assembled-genomic reference for swine intestinal microbiota (Chapter 6). The reconstructed gut microbiome allowed identification of key microbial contributors to the degradation of starch, fructans, and lactose. Starch is a substrate for colonic microbiota and its metabolism is dependent on metabolic cooperativity between Firmicutes and Bacteroidetes. The functional prediction of the most abundant extracellular starch degrading enzyme in Firmicutes was further validated by protein purification and activity assays (Chapter 7). Fructans and lactose are fermented by simple enzymatic systems present in Bacteroides and Lactobacillus spp., respectively. The improved understanding of carbohydrate fermentation in the swine intestine enables the development of feeding models with higher feed efficiency and better pathogen control for weanling pigs. -
- Subjects / Keywords
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- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.