Throughout the history of man, and today more than ever, the ruminant animal has played and continues to play a role of great economic importance. The reason for this importance is due to the presence in these animals of the reticulo-rumen as part of their gastro-intestinal system,which enables the ruminant to utilize roughages as sources of energy, protein, vitamins, and other nutrients. The ruminant has traditionally been the intermediary for the conversion of forage crops into meat, milk and wool. Probably, without ruminant animals, much of the crops now consumed by them would be returned to the soil or consumed by organisms that cannot be utilized by man. [...]

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Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / Feed is the largest single cost factor (60%) in production of chicken meat with cost of energy being a major consideration given that birds eat to satisfy an energy requirement. The Australian chicken meat industry is highly dependent on supply of energy from cereals such as wheat and barley that are known to vary widely in apparent metabolisable energy (AME). In contrast, sorghum is a relatively consistent source of energy. Diets for broiler chickens are comprised mainly of cereal grains, legumes and protein-rich meals of plant and animal origin. The diets are formulated to provide essential nutrients for maintenance and rapid growth of the flock as a whole. However, some dietary ingredients may also have chemical and physical properties that can be detrimental to the processes of ingestion, digestion, absorption, transport and utilisation of nutrients. Soluble non-starch polysaccharides (NSP) in cereal grains such as wheat and barley can depress digestion of energy by broiler chickens. This thesis examined the general hypothesis that the effects of soluble NSP in cereal grains on gut structure and function, digesta transit time, and gut microflora differ substantially between individual chickens within a flock, thus contributing to variation in the digestion of energy by the flock as a whole. A major goal of the research was to determine what characteristics of the gastrointestinal tract of broiler chickens were the key determinants of digestion of energy. Twelve experiments were conducted during this study. Breath tests involving measurements of carbon dioxide, hydrogen and methane were developed as noninvasive indicators of digestive function, and were used in conjunction with conventional methods for measuring energy digestion in commercial strains of chickens. Sex of the chicken had a significant effect (P<0.05) on AME values obtained for a diet based on wheat with a high soluble NSP content. Females were superior to males (14.6 vs 14.0 MJ/kg DM), but strain of chicken had no effect on AME. Villus height and crypt depth in the intestinal epithelium were measured to determine if any relationships between gut morphology and AME could explain why males and females differed. Males had significantly greater ileal villus height than females (P<0.05). In one of the two strains of chickens studied, villus heights in the duodenum and jejunum tended to be greater in males than females (0.05<P<0.10). In the second strain of chicken, villus heights in the duodenum and ileum were lower (P<0.05) than those in the first strain, with little differences observed between males and females. Crypt depth was unaffected by strain or by sex of the chickens. Thus, individual measurements of gut morphology were poor indicators of AME. Furthermore, only 33% of the total variation in apparent metabolisable energy (AME) could be accounted for by combinations of measurements of villus height and crypt depth in the duodenal, jejunal and ileal sections of the small intestine. It was concluded that other determinants of digestive capacity were collectively more important than gut morphology. Energy excretion by male chickens was observed to rise in an exponential manner relative to energy intake, whereas the increase in females was linear. It was reasoned that increased energy excretion by males could be due to increased endogenous energy losses from the distal part of the intestinal tract, reduced production of volatile fatty acids (VF A) by microbial fermentation in the caeca, or reduced absorption of VFA by caeca. These possibilities pointed to the need for a closer examination of the role of gut microbiota on the digestive function of chickens. It was also clear that further studies should differentiate between digestion of energy in the small intestine (by measurement of ileal digestible energy) and whole of tract digestion (by measurement of AME). ileal digestible energy (DE) values for wheat and barley were unaffected by sex of chickens, whereas AME values were lower in male chickens compared with females. These results suggested that the sex-specific effects of microbiota occurred mainly in the hindgut. Furthermore, the influence of the gut microbiota on between-bird variation in AME was partially dependent on the type of cereal grain used in the diet, as indicated by the observation that the differential between males and females in expiration of hydrogen and methane in the breath changed according to the type of grain consumed. That is, the metabolic activity of the gut microbiota was influenced both by the sex of the chicken and by the properties of the diet. The results of these studies provided evidence that microbial colonisation of the gut is a key determinant of the digestive function of chickens. Further work is needed to determine why microbial colonisation of the gut is variable and why it differs substantially between male and female chickens. Then it may be possible to control the initial colonisation of newly hatched chicks and to maintain a health-promoting profile throughout the life of chickens in order to enhance efficient production, and product quality and safety. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1080042 / Thesis (Ph.D.) -- University of Adelaide, Dept. of Animal Science, 2003

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 110-122). Also available in electronic version.

Thesis (Ph. D.)--University of Sydney, 2003. / Title from title screen (viewed Apr. 28, 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Biological Sciences, Faculty of Science. Degree awarded 2003; thesis submitted 2002. Includes bibliographical references. Also available in print form.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 120-124). Also available via the Internet.

Thesis--Academic Board of Wageningen University and Academic Board of the UNESCO-IHE Institute for Water Education, 2008. / Description based on print version record. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 62-72).

Introduction: Wheat is one of the most cultivated cereal grains in the world and is used for the manufacture of a wide range of food products; however its consumption has been linked to several health issues. Food products containing wheat flour commonly elicit a high glycaemic response (GR) through rapid breakdown of starch and absorption of the resulting glucose. Regular over-consumption of such foods has been linked to obesity and development of type 2 diabetes. Dietary fibre may alter GR after meal consumption indirectly through modification of chyme viscosity. Wheat can also elicit immune-mediated adverse reactions, such as immunoglobulin E(IgE)-mediated wheat allergy and coeliac disease (CD), which are most often associated with gluten proteins consisting of gliadins and glutenins. Resistance to digestion may impact the allergenicity of such protein components. Digestion of gluten and its epitopes important for CD have been enhanced in vitro and in vivo using a prolyl endopeptidase from Aspergillus niger (AnPEP) however the impact on IgE-mediated allergy has yet to be considered. Additional information is needed about the digestion of wheat. Specifically the impact of food matrix, digestion conditions and effect of AnPEP require further investigation. Methods: First, the effect of food matrix on proteolysis was tested by in vitro batch oral-gastric digestion of a purified total gliadin fraction (TGF), flour and bread. As the most physiologically relevant material, bread was also processed through the duodenal/intestinal phase in varying conditions to assess the impact of enzyme inclusions on macronutrient breakdown. Second, results from the batch digestions were compared to bread digestion in dynamic models, where the effect of natural variations in soluble fibre was also tested. Increasing levels of AnPEP were used in two in vitro batch oral-gastric models. Protein breakdown in digestions was assessed using a combination of 1D PAGE, immunoblots with a variety of wheat-specific antibodies, kinetic analysis and inhibition ELISA. Immunoassays were performed with sera from 23 wheat-allergic patients and some digestions were analysed in terms of starch digestion. Finally, LC-MS/MS was used to obtain specific sequence information and relative intensity of peptides from in vitro batch model digestions. Thus, digestion of selected allergens and key epitopes was monitored. Results and Discussion: Wheat proteins were very resistant to in vitro batch gastric digestion in bread compared to the TGF, with flour proteins somewhat intermediate. Thus, studies digesting purified proteins are not always indicative of protein digestion in a processed food matrix. Digestion of bread protein was enhanced by starch digestion and vice versa. This has implications for patients with deficiency in pancreatic amylase, which is often observed in childhood, so may play a role in food allergy development by influencing polypeptides reaching the gut mucosa. Digestion model conditions also had a large impact on wheat protein digestibility with differences observed between batch and dynamic models, and the two batch models used. This may reflect biological variations observed in vivo. Unexpectedly, the wheat cultivar with higher soluble fibre digested slightly more quickly which may be due to alterations in other macronutrients present. In most cases patient sera were poly-sensitized to a number of wheat proteins and IgE-binding was mostly unaffected by baking. Gastric digestion reduced IgE-reactivity of bread but large polypeptides of high relative intensity remained. Addition of AnPEP further reduced IgE-reactivity of digestion samples by digesting gluten proteins into smaller peptides of lower relative intensity. This reduced the presence of epitopes important for IgE-mediated allergy and CD. Therefore, AnPEP may have an application for treatment of accidental wheat consumption for patients with IgE-mediated wheat allergy.

Anaerobic digestion is a useful method for stabilizing and reducing the waste activated sludges (WAS) produced from biological secondary treatment. Pretreatments can make anaerobic digestion more efficient. However, the study of anaerobic digestion and pretreatments is limited to a focus in treating conventional WAS. Therefore, WAS from three non-conventional municipal wastewater treatment systems, a rotating biological contactor (RBC), a lagoon, and a moving bed bioreactor (MBBR), were digested anaerobically to determine the sludges’ biogas potentials compared to a conventional WAS. All three WAS had lower biogas potential normalized per volatile solids than conventional sludge by 46% + 6 (MBBR), 63% + 6 (RBC), and 77% + 7 (lagoon). The four sludges were pretreated with ultrasonic energies of 800 - 6550 kJ/kg TS to illustrate impact of sludge type on biogas production, solubilization, and digestion kinetics. All four sludge types responded uniquely to the same levels of sonication energies. The greatest increase in biogas production over the control of pretreated sludge did not coincide consistently with greater sonication energy but occurred within a solubilization range of 2.9 – 7.4% degree of disintegration (DD) and are as follows: 5% + 3 biogas increase for conventional sludge, 12% + 9 for lagoon, 15% + 2 for MBBR and 20% + 2 for RBC. The yield of biogas production related to soluble COD decreases with increased sonication energy. Hence it is likely that sonication produces refractory COD or causes inhibition in biogas production. The effect of sonication on digestion kinetics was inconclusive with the application of Modified Gompertz, Reaction Curve, and First Order models to biogas production. Diauxic growth patterns of biogas production of sonicated conventional waste demonstrates that the active time of digestion can be decreased through the conversion of less preferential substrates into existing, preferential substrates.