- Title
- Investigation of the potential application of dairy propionibacteria for the treatment and prevention of ruminal acidosis
- Creator
- Luo, Jianbiao
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2013
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- In this thesis the physiology and acid metabolism of dairy propionibacteria under different growth environments including SLB medium, fortified NB medium with inoculation of Streptococcus bovis and simulated rumen samples with or without fortifications were investigated. The main aim of this thesis was to assess the feasibility of applying dairy propionibacteria for the prevention of ruminal acidosis in cattle. Ruminal acidosis is one of the most prevalent disorders in digestive system in the cattle industry especially in dairy cow and feedlot beef cattle. The main cause of this disorder is the high percentage of readily fermentable concentrates in the rations of high producing cows which leads to an imbalance of the rumen fermentation process. Dairy propionibacteria is a group of bacteria isolated from the dairy environment which has a characteristic metabolic feature of producing a large quantity of propionic acid by utilizing lactic acid as the favoured carbon source. In the past 100 years, many efforts have been dedicated to the comprehension of the mechanism of its metabolism and their application in cheese making and propionic acid production. In the present studies, a potential application of the unique capability of dairy propionibacteria to utilise lactic acid in ruminal acidosis was explored. The ability of lactic acid consumption and acetic and propionic acid production exhibited in the dairy propionibacteria during the present investigations demonstrated great potential for its application in ruminal acidosis. Their characteristic metabolism provides a good match to the metabolic conditions in the rumen during the ruminal acidosis. Theoretically, the excessive accumulated lactic acid in rumen can be converted into acetic and propionic acid absorbed as an energy source for animal by the application of dairy propionibacteria. The arrangement of the chapters is followed the order of a review of the previous knowledge of dairy propionibacteria and ruminal acidosis (Chapter One); studying and comparing the physiology and acid metabolism in different strains of dairy Propionibacterium (Chapter Two); investigation of the application of dairy propionibacteria in a simulated ruminal acidosis environment (Chapter Three) and finally, the assessment of the interaction and influence of the application of dairy propionibacteria on two main indigenous bacteria involved in ruminal acidosis S. bovis and Megasphaera elsdenii (Chapter Four). The studies described in Chapter Two examined the growth curve, lactic acid utilization and acetic and propionic acid production in seven different strains of dairy Propionibacterium as well as the activity of nicotinamide adenine dinucleotide (NAD)-independent lactate dehydrogenases (iD-LDHs) and the prevalence of lactate permease coding sequence in their genome. All strains used in the studies belong to the dairy propionibacteria. A similar pattern of physiology and metabolic features were observed in all strains. However, significant differences between strains were also exhibited. Strain PF 2207, had the highest growth rate, strain PA 341 had the lowest final pH, and strain PJ 702 had the highest conversion rate of lactic acid to acetic and propionic acid. Significant differences were also found between strains in the L-iD-LDH and D-iD-LDH specific activity. The possession of the lactate permease coding sequence in their genome was universal. In Chapter Three, different stains of dairy Propionibacterium were inoculated into a simulated ruminal condition. In the studies, rumen content with fortification of lactic acid was applied as the base growth environment for the bacteria. The results have confirmed that dairy propionibacteria were able to survive and remain metabolically active in the high lactic acid rumen environment. More importantly, the excessive lactic acid in the rumen environment was not only reduced, but also completely eliminated by the introduction of propionibacteria. However, there was a significant difference between strains for their metabolic activity in the rumen environment. Strains PA 341, PF 2207, PJ 572 and PJ 702 showed more rapid reduction of lactic acid than others. Furthermore, the dosage study also demonstrated that the efficacy of this application was dosage related. In Chapter four, the interaction and influence of dairy propionibacteria on the growth and acid metabolism of S. bovis and M. elsdenii was studied. S. bovis is the main lactic acid producer during the course of ruminal acidosis and M. elsdenii is the main lactic acid utiliser in a normal healthy rumen. These two bacteria play important roles in ruminal acidosis. In the medium and the rumen cultures which were fortified with glucose, the accumulation of lactic acid which was produced by S. bovis was significantly reduced by the introduction of dairy propionibacteria and M. elsdenii alone or together. The dairy propionibacteria were able to achieve better prevention of the lactic acid accumulation than M. elsdenii. In the present studies, the potential of the application of dairy propionibacteria for the treatment and prevention of ruminal acidosis was confirmed by investigating the acid metabolism of these bacteria in different growth environments. All the strains of Propionibacterium used in the studies have exhibited typical physiology and metabolic characteristics as dairy propionibacteria. The ability of utilization of lactic acid and production of acetic and propionic acid appeared universal within dairy propionibacteria at both the metabolic level and molecular level. Nevertheless, high variations were found between strains for the acid metabolism. Therefore, careful study and comparison of each strain of dairy propionibacteria is essential for the selection of a suitable candidate for its application in the treatment of ruminal acidosis.
- Subject
- propionibacteria; rumen; acidosis
- Identifier
- http://hdl.handle.net/1959.13/938558
- Identifier
- uon:12639
- Rights
- Copyright 2013 Jianbiao Luo
- Language
- eng
- Full Text
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