Theses & Dissertations (2011 - present)
Permanent URI for this collection
This collection contains all theses and dissertations produced at the University of Guelph since 2011 when the requirement to submit electronic theses to the Atrium was adopted by the University.
Graduate students should refer to the Atrium submission instructions for guidance related to submitting their thesis or dissertation to the Atrium.
Browse
Recent Submissions
Item Interactions between individual physiology and social information in the North American red squirrel (Tamiasciurus hudsonicus)(University of Guelph) Hare, Alexander; Newman, Amy; McAdam, AndrewAs the manner in which individuals respond to, and produce social information is intimately connected to their physiological state, it is not surprising that individual physiological responses to stress as mediated through endocrine axes, such as the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes may have impacts not just on the responding individual, but on the surrounding community through social information. Despite the important role that these interactions play in shaping individual responses to stimuli, interactions between conspecifics, and resource utilization, our understanding of how these physiological axes and social information interact remains relatively uninvestigated. My thesis aims to examine the role that the HPA axis and closely associated HPG axis play in directing how social information is produced and incorporated into both the physiology and ecology of free-living mammals. In order to do this, I have conducted field experiments and examined multi-year datasets from a natural population of North American red squirrels (Tamiasciurus hudsonicus) that have been studied continuously for the last 34 years. Conducting a playback experiment in which I manipulated the motivational state and relatedness of senders, I found that receiving red squirrels did not alter territorial behaviour, indicating that the physiological state of senders is less important than other factors, such as changes in resources for kin discrimination. Second, I examined a multi-year dataset of acoustic recordings in order to examine whether there were reliable vocal cues relating to estrus in female red squirrels. Despite finding no distinct cues relating to estrus, I did find that female vocal characteristics changed significantly during pregnancy, providing potential cues to conspecifics within an acoustic neighbourhood. Finally, in examining whether social information regarding circulating glucocorticoids influenced social partners, I found that red squirrel glucocorticoids were influenced by the glucocorticoids of neighbours. I also found novel sex differences in the glucocorticoid levels of males and females. This thesis expands our understanding of how individual physiology and social information influence each other, showing strong association between both the HPA and HPG axes and the social interactions of a natural population of mammals.Item Investigation of Cold Brew Extraction Phenomena in Continuous Circulation, Continuous Countercurrent and Multistage Batch Extraction Methods(University of Guelph) Zwicker, Matthew; Lim, Loong-TakCold brew coffee extraction methods, such as continuous recirculation and continuous countercurrent extraction have had limited investigation but could be advantageous over traditional full immersion batch extraction. Thus, continuous recirculation cold brewing was explored through modification of a single-serve brewer to allow recirculation of brew within a single-serve capsule. Continuous countercurrent cold brewing was explored through development of a prototype machine based on pairing countercurrent single-screw extraction with mechanical expression, and through lab-scale simulation of continuous cold brewing using a multistage batch extraction approach. The first objective of this research was to understand the effects of brewing process parameters (e.g., grind size, brewing ratio (BR), and extraction time) on the physicochemical properties of brew produced using the aforementioned methods. Using fine coffee grounds resulted in higher rates of extraction and water absorption than using medium coffee grounds: a consequence of the higher surface area of the fine coffee grounds. Regarding BR, increasing the mass of coffee grounds extracted typically resulted in increased brew concentration and decreased extraction yield (EY). Additionally, both a linear relationship between BR and equilibrium brew concentration was identified; however, the equilibrium brew concentration became practically independent of BR when large masses of water were used (i.e., lower than 1:20 coffee:water, w/w). Finally, comparisons of batch extractions indicated that 70% of the equilibrium concentration could be obtained in under 30 min. Moreover, through use of the extraction machine prototype a total dissolved solids of 6.44 ± 1.08 % and an EY of 17.9 ± 0.2 % in under 10 min of extraction time. The second objective was to elucidate the extraction phenomena occurring during continuous cold brewing processes. First, the Weibull cumulative distribution proved effective for describing the extraction of soluble material and the absorption of water by coffee grounds in cold brewing processes. Second, appropriate selection of process parameters (i.e., fine grind size and inclusion of agitation) was shown to reduce the extraction time required for concentrate production. Finally, the EY of cold brewing processes was increased through brew recovery from spent coffee grounds (via forced filtration or pressing the spent coffee grounds).Item Functionalization of Graphene-Based Nanomaterials for Energy Conversion and Storage(University of Guelph) Hung, Chi-Kai; Chen, AichengThe intensifying impacts of climate change underscore the critical importance of sustainable energy conversion and storage technologies by facilitating the integration of renewable energy sources and infrastructure. This thesis explores the synthesis and optimization of expanded graphite/reduced graphene oxide composites incorporating ruthenium nanoclusters for both hydrogen production and supercapacitor applications. For the alkaline hydrogen evolution reaction, varying the content of expanded graphite and annealing temperature resulted in an optimized nanocomposite outperforming the benchmark 20% Pt/C in both electrocatalytic activity and stability. The interconnected microstructure and the tuned ruthenium cluster size and quality contributed to the superior performance. Similarly in supercapacitor applications, varying the expanded graphite content and annealing temperature produced an optimized nanocomposite with outstanding energy storage capabilities and durability. This thesis highlights the importance of studying process-structure-property relationships and shows the potential for streamlined design strategies in developing advanced energy conversion and storage materials.Item Processivity Factor PCNA (POL30), Chromatin-Associated Factors, and Fork Protection Complex Maintain Epigenetic Stability in Saccharomyces cerevisiae(University of Guelph) Sauty, Safia Mahabub; Yankulov, KrassimirThe transcriptional profile of a eukaryotic cell is influenced by its genome organization and chromatin landscape. Post-translational modifications on histone tails, known as epigenetic marks, dictate the packaging of underlying genes into a compact or relaxed structure, rendering them transcriptionally silent or active, respectively. These epigenetic marks and their associated chromatin structures are faithfully inherited during multiple cycles of DNA replications to maintain cellular identity. Alterations in the epigenetic marks or disruptions in the inheritance pathway may result in epigenetic conversions between active and silent states of a gene. In this thesis, I investigated the role of the DNA processivity factor PCNA (Proliferating Cell Nuclear Antigen, POL30) in maintaining transcriptional silencing using S. cerevisiae as a model organism. Using combinations of low and high-sensitivity loss-of-silencing assays at the VIIL sub-telomeric locus, I have shown that mutations in POL30 (pol30-6, pol30-8, and pol30-79) and deletion of the histone chaperone CAC1 cause transient de-repression, while the deletion of the chaperone ASF1 causes epigenetic conversion, meaning a persistent conversion to the active state of the gene. Through biochemical assays, I demonstrated differential physical interactions of the mutant pcna proteins with Cac1p and the helicase Rrm3p. I extended my analysis to the FLO loci responsible for the flocculation in yeasts and showed that the deletions of fork stabilizing factors TOF1 and RRM3 reconstitute mild flocculation in pol30 mutant strains. The increase in flocculation correlates with increased FLO11 expression and epigenetic conversions at this locus. I conducted a parallel investigation of the SIR-dependent loci, demonstrating that the phenotype observed at the FLO loci is consistent with the effect of these factors at the sub-telomeres and mating-type loci. Data from this thesis strongly indicate that mutations in PCNA (POL30) predispose to heritable epigenetic instability that can result in epigenetic conversion upon disruptions in the nucleosome assembly pathway. Additionally, the effect of PCNA-mediated interactions of TOF1 and RRM3 indicates a mechanism-independent regulatory role of these factors.Item Investigating Representations and Students’ Challenges, Experiences and Perceptions of Equity, Diversity and Inclusion at Veterinary Colleges in Canada and the USA(University of Guelph) Dusome, Kassandra; Khosa , DeepThough important, equity, diversity and inclusion (EDI) is understudied and reported in veterinary medicine. Using two studies, this research aimed to investigate the representations, and students’ challenges, experiences and perceptions of EDI at veterinary colleges. First, the websites of all veterinary colleges in Canada and the USA were assessed using content and statistical analysis. Male or BIPOC people were more likely to be depicted without animals. BIPOC individuals were under-depicted on some USA websites and over-depicted on others. Website reading level, and access to supports for underrepresented students and mental health resources were inconsistently represented. Second, the survey responses of students at five Canadian and five American colleges were statistically analyzed. Students who were not white, with a disability or part of the LGBTQ2S+ community were more likely to agree or strongly agree that discrimination occurs at college. Overall, fewer students reported experiencing discrimination in colleges compared to workplaces.Item Plant response to severing access to arbuscular mycorrhizal networks differs between controlled and field environments(University of Guelph) Herlin, Olivier; Maherali, HafizArbuscular mycorrhizal (AM) fungi associate with 70% of plant species and increase the availability of nutrients in exchange for plant sugars. Research determining whether plants benefit from AM fungi is derived predominantly from controlled environments that may not represent the undisturbed field environment. To determine whether plant responses are equivalent between controlled greenhouse and field environments, we quantified 9 plant species responses to severing access to the AM network in both environments using a mesh barrier (48μm) preventing root entry but enabling ingrowth of AM hyphae. We found that in the greenhouse severing access to AM networks reduced plant biomass, but in the field severing increased plant biomass. The lack of correlation in plant mycorrhizal responsiveness between environments suggests that controlled environments may need to account for the surrounding plant density, plant community, and the larger carbon cost from AM networks in the field to observe field relevant plant responses.Item Novel Roles of Cardiac-derived Erythropoietin in Disease(University of Guelph) Marrow, Jade P.; Simpson, JeremyMyocardial infarction (MI) is a leading cause of death globally. Over 3 million individuals experience ST-segment elevation MI (STEMI) each year. Despite considerable research into cytoprotective mechanisms, no clinically available therapy has been developed that directly reduces ischemic cardiac injury. Understanding the pathophysiological mechanisms underlying MI should reveal novel strategies for treatment and diagnostic purposes (i.e., biomarkers). Emerging preclinical data shows erythropoietin (EPO), a canonically renal-derived erythropoietic cytokine, is also produced by the heart under hypoxic conditions in vitro and in vivo. However, whether these findings translate to functionally relevant outcomes post-MI is currently unknown. Therefore, the overarching purpose of this thesis was to define the contributions to cardioprotection by endogenously produced EPO in the heart and fundamentally improve our understanding of non-canonical EPO biology. My objective was to characterize the systemic (i.e., endocrine) and local (i.e., autocrine/paracrine) effects of cardiac EPO using two in vivo pre-clinical models (i.e., murine permanent occlusion MI and a cardiomyocyte-specific EPO knockout mouse). We hypothesized: 1) cardiac ischemia localized to the heart would induce cardiac Epo expression and contribute to erythropoiesis, and 2) loss of endogenous cardiomyocyte-derived Epo would increase myocardial susceptibility to ischemia-reperfusion injury and impair cardiac functional recovery. Here we show MI upregulates cardiac Epo, stimulating erythropoiesis, alongside the expression of a novel exon 4-deleted Epo splice variant (termed mV-Epo). Administration of recombinant human EPO (rhEPO) or a human orthologue to the mV-EPO variant (hV-EPO) was cardioprotective compared to vehicle-treated MI mice. Therefore, as a non-erythropoietic EPO isoform, hV-EPO represents a promising strategy for amplifying endogenous cardiac EPO signaling in post-MI patients without the rheological side effects posed by traditional rhEPOs. In our second model, cardiomyocyte-specific Epo deletion induced a compensatory increase in Epo expression by neighboring endothelial cells that enabled cellular hypertrophy and superior cardiac function, and reduced ischemia-reperfusion injury. Collectively, cardiac EPO has powerful physiological relevance as a cardioprotectant and erythropoietic cytokine. These findings fundamentally shift our understanding of EPO biology – confirming it as both an endocrine and autocrine/paracrine cardiac hormone – and reinvigorate its therapeutic potential for ameliorating MI-induced dysfunction.Item Growing tomato in controlled environments under continuous light requires dynamic LEDs to entrain the circadian rhythm, adjust canopy architecture, and balance photostasis(University of Guelph) Marie, Telesphore; Grodzinski, BernardControlled environment agriculture (CEA), including greenhouses and indoor production, offers tremendous opportunities to meet food security across the world. The success of CEA depends on electricity, with artificial lighting consuming a large fraction. Previous work has introduced a novel alternating LED strategy that extends the photoperiod in greenhouse production, taking advantage of off-peak electrical pricing while maintaining a healthy crop. Tomato (Solanum lycopersicum L.) is a model species in terms of its sensitivity to extended photoperiods, experiencing photoperiodic injury under continuous light. The alternating LED strategy alleviated photoperiodic injury and it was hypothesized that circadian rhythm entrainment was responsible, as the injury itself has been associated with circadian asynchrony previously. The presented thesis continues to explore and optimize the strategy in different chapters. First, the principles of circadian entrainment are detailed. A perspective centers on the “latitudinal rule”, where predictable chronotypes have evolved to the longer photoperiods in northern latitudes that can guide selectable traits for breeders and tailor ideal entraining cues for any genotype. Second, diurnal transpiration patterns revealed a great way to assess and measure circadian entrainment on a whole-plant level as they integrate cellular-stomata responses with whole-plant hydraulic status. Practically, transpiration, and associated thermal indices, can be sensed remotely to bring circadian data into smart-agriculture. Finally, a modified dynamic LED strategy (dynamic 1) significantly outperformed control (16hr photoperiod with unchanging spectrum), and by-far surpassed constant light (24hr), in total biomass accumulation via morphological and photosynthetic adjustments. A second modification (dynamic 2) attempted to extend the daytime photoperiod by 4hrs and resulted in a subtle photosynthetic stress response. A deep phenotyping gas exchange plus chlorophyll fluorescence multi-curve dataset revealed photorespiration as both beneficial and hazardous in photoperiodic injury. Also, a simple high throughput protocol distinguished dynamic 2 as engaging a nonphotochemical quenching dissipative type response, whereas dynamic 1 engaged an ATP:NADPH balancing response that upregulated ATP synthase activity. Cyclic electron flow at nighttime was also found to likely contribute much needed ATP. Overall, a philosophy is proposed that optimizing plant growth should start with entraining circadian rhythms, and then fine-tune timing/ dosage to choreograph morphology and balance photostasis.Item Transferable skills: A student perspective(University of Guelph) Boivin, Simone; Jacobs, ShoshanahUniversity graduates do not have the necessary skills to succeed in the workplace. To address this skills gap there have been calls for universities to improve transferable skill education. To accomplish this, it is important to understand students’ attitudes and motivations. To better understand Canadian undergraduate students’ attitudes about and motivation to develop transferable skills in their education I created and distributed a survey to students at the University of Guelph in all disciplines and year levels. I also developed and delivered a scientific inquiry workshop, delivered in two different contexts (biology-specific, and general). I found that students in all year levels have a positive attitude about and are motivated to develop transferable skills, with students mostly focused on the value of transferable skills for employment. Students are also frustrated with current transferable skill education. There is also indication that students feel differently about developing transferable skills in different contexts.Item How to Market Your Curator Team: The Role of Entitativity in Curation Subscriptions(University of Guelph) Wang, Huiquan; Wang, JuanCuration subscription is an emerging e-commerce business model which provides recurring deliveries of products selected by curators from companies but tailored to subscribers’ individual preferences. Focusing on the essential role of curators in curation subscriptions, the current research explores how subscription companies promote their curation services by managing the entitativity of their curator teams. Results from one study indicate that increasing the entitativity of a curator team can increase the perceived competence of the team, which in turn promotes consumers’ subscription intention. The positive effect of entitativity on subscription intention only presents for consumers with utilitarian purchase motivations. As consumers’ purchase motivations shift from utilitarian to hedonic, the effect attenuates to disappears. Findings of the study provide theoretical implications for future marketing research as well as managerial inspirations for subscription service providers.Item Analysis of the Immunomodulatory Properties of Mycobacterium Cell Wall Fraction on the Cytokine Production of Peripheral Blood Mononuclear Cells of Healthy Dogs(University of Guelph) Ward, Robert; Sharif, Shayan; Geoffrey, Wood; Khalil, Karimi; Charlotte, Pye; Anthony, YuMycobacterium cell wall fraction (MCWF) is a Toll-like receptor agonist that is derived from non-pathogenic Mycobacterium phlei. The objective of this research was to evaluate host responses induced by MCWF in canine peripheral blood mononuclear cells (PBMCs), using enzyme-linked immunosorbent assays (ELISA) and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) for quantifying cytokine protein and mRNA transcripts, respectively. PBMCs were isolated from eight healthy dogs and cells were cultured with MCWF. A significant increase of interleukin (IL)-10 mRNA was detected at all time points for all concentrations of MCWF (p<0.05). mRNA relative abundance reflected this finding. A post-stimulation elevation of interferon (IFN)-γ mRNA was noted at 24-hours with all concentrations of MCWF (p<0.01) and tumor necrosis factor (TNF)-α mRNA was increased for 0.5ng/dL MCWF only at 72-hours (p<0.05) compared to the negative control. Further research into the role of MCWF as a systemically administered immunomodulator or adjuvant to immunotherapy is warranted.Item Treated with Love: Understanding Dog and Cat Caregivers’ Perceptions, Decisions, and Experiences with Feeding Treats(University of Guelph) Nielson, Shelby; Khosa, DeepTreats are commonly fed by most dog and cat caregivers and can constitute a significant proportion of an animal’s diet, potentially contributing to obesity. Previous research has explored the nutritional aspects of the primary diet for companion animals, though factors surrounding treat feeding specifically have received far less attention. While reducing or eliminating treats is commonly recommended as a strategy for weight management, caregivers can struggle to adhere to such dietary recommendations. This research consisted of two sequential phases using a mixed-methods approach. The first phase utilized an online questionnaire to quantitatively explore dog and cat caregivers’ (n=1053) perceptions, decisions, and behaviours for feeding treats. Data were analyzed using descriptive statistics and multivariable modelling, and results were used to inform the development of a question guide for the subsequent qualitative phase. The second phase involved the use of five online focus groups to provide an in-depth exploration of caregivers’ (n=24) perceptions and behaviours surrounding treat feeding, including their motivations and barriers related to reducing treat feeding with dogs and cats. Findings elucidated a diverse spectrum of how caregivers incorporate treats in their pet’s diets, evident through a multitude of treat types, as well as how and why treats are provided. The research identified associations between certain treat feeding habits and obesity, including daily chews (OR=2.99) for dogs and table scraps (OR=4.22) for cats. Findings highlighted the importance of treats in the human-animal bond, which can influence caregivers’ willingness and capability to deny treats. Changing the pet’s routine (OR=1.67) was identified as a significant factor that was positively associated with caregivers’ reported capability to reduce their pet’s current treat intake as difficult. Overall, participating caregivers reported a low reliance on veterinarians for support in decisions and habits related to feeding treats. Outcomes of this research have both clinical and educational implications, offering a foundational framework for the development of targeted interventions. Findings highlight opportunities to enhance the available resources that can empower both veterinary professionals and caregivers to make well-informed decisions and foster sustainable treat feeding practices to support weight management and overall health, while fostering the human-animal bond.Item Histological Heterogeneity: Tissue-Level Diversity of Lizard Osteoderms(University of Guelph) Willan, Gabriella; Vickaryous, MatthewOsteoderms are bone-rich elements that form within the dermis of various vertebrates including many species of lizard. Lizard osteoderms demonstrate variability in size, shape, and body-wide distribution but a detailed comparative assessment of their microstructure is lacking. Here, I characterized the histological diversity of osteoderms from representative members of the lizard groups Gekkota (geckos), Scincomorpha (scincids, cordylids, Gerrhosaurids), and Anguimorpha (anguids, Shinisaurus, helodermatids, varanids). In virtually all lizards, osteoderms are composed primarily of bone, albeit with a heterogeneous and often laminated fibrillary organization. Histologically, most osteoderms are dominated by lamellar, woven-fibred, and/or Sharpey-fibred bone, although details of the organization and relative contribution of each bone matrix differs between genera. In addition, we found that multiple genera from each major group also develop a highly mineralized, collagen and cell-poor capping tissue – a feature previously restricted to only a handful of species. Singularly, the osteoderm-like elements from the gekkotan Geckolepis entirely lack bone and instead are composed of a plate of collagen topped with mineralized capping tissue.Item Integrating emergent data in decision-making tools characterizing foodborne antimicrobial resistance in Canada(University of Guelph) Chapman, Brennan; Parmley, JaneAntimicrobial resistance (AMR) is a preeminent health threat and ‘wicked problem’. The tools used to assess the risks posed by foodborne antimicrobial resistant pathogens must be continuously updated to make effective use of existing and emerging sources of data. The objective of this thesis is to explore the integration of emergent sources of data in decision-making and risk assessment tools and frameworks for the study of antimicrobial resistant foodborne pathogens, using ceftiofur-resistant Salmonella Heidelberg as an example organism. This thesis describes the creation of a tool to prioritize food animal species for antimicrobial resistance surveillance, the development of a publicly available database of factors potentially linked to the occurrence of AMR in the agri-food system, an integrated assessment model (IAM) of S. Heidelberg from broiler chickens, and the exploration of the use of beta diversity as a proxy measure for microbial transmission in exposure and risk models. The results of our prioritization concorded with current surveillance targets in Canada and was useful for identifying data gaps in the literature. The database is an important resource for ongoing work and can serve as a template for making data collected for individual projects findable, accessible, and reusable. We used the database to populate the IAM model, allowing us to explore scenarios to reduce Canadians’ risk of exposure to antimicrobial resistant S. Heidelberg. Using whole genome sequencing data from S. Heidelberg, we demonstrated that some measures of beta diversity may be useful for quantifying microbial transmission between production stages along the farm-to-fork continuum, which could improve the accuracy of future IAMs. There are still many questions to be answered with respect to the impact of AMR in the agri-food system on human health. This thesis lays the methodological groundwork for future tools that will be used to answer those questions, and embraces a forward-thinking, open science approach to their development.Item Glucose-Induced Memory Enhancement Mediated by Opioid Systems in Rats(University of Guelph) Soodeen, Keith; Leri, FrancescoThe mechanism of the memory enhancing effects of peripheral administered glucose is not well understood. This line of research is important because it may offer insight into food addictive seeking behaviours and obesity. The aim of the current study was to investigate the effect of subcutaneous glucose injections on memory consolidation and if the memory enhancement could be blocked by modulating the opioid or catecholamine systems. In this study, male Sprague-Dawley rats were tested on object recognition with post-training administration of glucose as well as with post-training administration of a contrave-like drug combination and glucose. It was found that glucose (100mg/kg) enhancing effect on object recognition tasks could be blocked with the contrave-like combination, naltrexone alone, and naloxone methiodide. This experiment concluded that opioid receptors are involved with the memory enhancement from glucose.Item Discovery and Testing of Plant Microbes for Enhancing Maize Growth Under Nitrogen and Water Stress(University of Guelph) Hewedy, Omar; Raizada, ManishMaize (Zea mays L.) stands as the second most important grain crop globally, yet its yields are significantly reduced by nitrogen and water limitations. Nitrogen is required for maize production, but synthetic nitrogen fertilizers contribute to climate change. Climate change-induced droughts are worsening, which also reduces nitrogen availability. Climate change is expected to exacerbate crop diseases. I hypothesized that root-associated microbiota, including endophytic bacteria, could enhance maize growth under conditions of water and nitrogen limitation. An endophytic bacterium (Bacillus sp.), previously isolated from the wild ancestor of modern maize, was investigated in this research. I discovered that under conditions of water and/or nitrogen limitation, Bacillus seed inoculation promoted the growth of maize shoots, root systems, and root hairs. To understand the mechanisms underlying this growth enhancement, Bacillus was tagged with green fluorescent protein (GFP) and visualized using fluorescence confocal microscopy. Under nitrogen/water limitation conditions, Bacillus -GFP inoculation resulted in the formation on root surfaces of a protective rhizosheath, consisting of elongated root hairs (RH) and mucilage, and remarkable nest-like structures, referred to as "rhizonests". Those rhizonests consisted of cross-stitched RH, acting as apparent mucilage scaffolds. It was found that Bacillus-GFP colonized these structures, especially during their biogenesis. Furthermore, Bacillus-GFP could intracellularly colonize root border cells after being shed into the rhizosphere. Bacillus triggered asymmetric growth of individual RH, apparently bending them to form the elaborate nest/cross-stitch patterns. Remarkably, under water limitation, Bacillus caused asymmetric initiation of RH, rhizosheath, and rhizonests along the primary root axis, suppressing their growth on the opposite side in an auxin-dependent manner. Thus, a eubacterium can control the fundamental property of eukaryotic symmetry. The mucilage produced in the root environment, rich in sugars, potentially supports nitrogen fixation. However, whole genome sequencing revealed that Bacillus is devoid of nitrogen-fixation genes. Instead, microbiome profiling showed that the mucilage under stress contained two companion nitrogen-fixing bacteria. The mature mucilage under low nitrogen contained scarce Bacillus ; thus, Bacillus built habitats for other bacteria, providing a remarkable example of cooperativity in a rhizosphere microbiome. Critically, this symbiosis delivered more nitrogen to maize shoots when nutrient/water limitation was combined.Item The Metabolic Cost of Keel Bone Fracture in End-Of-Lay Hens Using Doubly Labelled Water and Respirometry(University of Guelph) Brost, Jacob; Harlander, AlexandraThe prevalence and severity of laying hen keel bone fractures (KBF) is concerning to the poultry industry. There is a dearth of research on KBF during the end-of-lay. Little is known about the potentially chronic and long-term impact KBF, even when healed, may have on end-of-lay hens. To bridge this knowledge gap, studies were conducted that utilized metabolic measures such as respirometry (Chapter 2) and doubly labelled water (Chapter 3) to explore the impacts KBF have on end-of-lay hens. In both studies, the mean metabolic measurements between fractured and unfractured birds did not reveal statistically significant differences. However, intriguing findings related to the variation of results within groups, the duration of activity, and allometry suggest a potential interplay between KBF and metabolism during the end-of-lay phase. Future research is necessary to determine the exact effects KBF have on end-of-lay hens.Item Analysis of Stx4-Munc18c Interaction and Membrane-Type 1 Matrix Metalloproteinase Phosphorylation During Cell Invasion(University of Guelph) Battagin, Samantha; Coppolino, MarcMembrane-type 1 matrix metalloproteinase (MT1-MMP) plays a central role during invadopodium-based ECM degradation and subsequent cancer cell invasion through its proteolytic ability and as a signal transducer. Regulation of MT1-MMP function is not well understood but would provide better insight on the role of MT1-MMP and how it can be targeted to impair cell invasion in metastatic cancers. Previous research provides evidence that disrupting SNARE function, by competitively inhibiting Stx4’s interaction with its regulatory protein Munc18c, impairs MT1-MMP trafficking and cell invasion. Furthermore, previous research revealed a potential role for MT1-MMP phosphorylation at Thr567 in the activation of ERK signalling as a mechanism to upregulate cell invasion. The goal of this study was to examine Stx4 and Munc18c interaction across different breast cancer cell lines and to determine if ERK activation in breast cancer cells is mediated by MT1-MMP phosphorylation. The results of this study suggest Stx4-Munc18c interaction is conserved across breast cancer cell lines and in breast tumour tissues. Although we could not conclude the involvement of MT1-MMP phosphorylation at Thr567, our results confirm positive evidence of MT1-MMP’s potential role in ERK activation. This study expands the analysis on cellular mechanisms involved in regulating MT1-MMP activity.Item Barbering in Laboratory Mice (Mus musculus): Investigating Risk Factors and Behavioural Correlates(University of Guelph) Young, Lauren; Mason, GeorgiaBarbering is a behaviour in laboratory mice (mus musculus), where animals pluck the fur and/or whiskers out of themselves or conspecifics. It has been hypothesized this behaviour is related to social dominance, human hair-plucking disorders (trichotillomania) and environmental stressors, though there is no consensus in the literature. I sought to replicate past findings about environmental and demographic factors that increase the risk of whisker- and fur-barbering and test new hypotheses using a cross-sectional data collection approach. I also sought to simultaneously test three hypotheses about the etiology of whisker-barbering using time budget data. Overall, this work found differential factors that increase the risk of whisker- and fur-barbering. It also suggested that whisker-barbering in female C57BL/6 mice is related to social dominance, though only in older animals, and is reduced by environmental “enrichment”. Further research is thus needed to investigate the influences on, and welfare impacts of, different barbering phenotypes.Item Unlocking the Potential of Fat in Milk Replacer for Calves(University of Guelph) Wilms, Juliette Nina Roxanne; Steele, MichaelThe composition of milk from mammals likely evolved to ensure the survival and the optimal growth of the offspring. In the dairy industry, calves are often fed milk replacer (MR) or a combination of whole milk (WM) and MR. Despite advances in calf nutrition, MR still significantly differs from WM, particularly in fat content, which is half that of WM. Competition within the food industry also results in milk fat being unavailable for inclusion in MR formulations, requiring the use of alternative fat sources. Since nutrient imbalances can disrupt metabolic homeostasis in neonates, it is important to establish nutritional boundaries for MR formulation. To address these challenges, the objectives of this thesis were to 1) understand the impact of low-fat formulations on calf development and metabolic responses, 2) to investigate to which extent fat composition in WM and MR is important for the developing calf, and 3) to propose short-term improvement in fat composition by balancing individual fatty acids (FA) to enhance the well-being of calves in current production systems. All experimental analyses were performed on Holstein dairy calves within the first 3 mo of life. Calves were raised in two systems: individually housed and fed restricted volumes of milk or group-housed with ad libitum access to milk and starter feed. Unlike MR high in lactose or protein, increasing fat inclusion in MR shifted metabolic responses closer to those of calves fed a WM powder. Formulating the FA profile to resemble milk fat by incorporating dairy cream was beneficial for calves, improving preweaning intakes and growth. Finally, balancing individual FA in MR, as a means to further mimic the FA profile of milk fat without including dairy cream, improved gastrointestinal tract development in the preweaning phase, allowing calves to consume substantially more starter feed upon weaning. Taken together, these findings suggest that increasing the fat content and balancing the fat composition in MR is crucial for enhancing the growth and metabolic health of developing calves.