Veterinary Science Collected Works - Theses
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ItemBiomechanical and microstructural properties of subchondral bone from three metacarpophalangeal joint sites in Thoroughbred racehorses( 2022)Reasons for performing the study: Fatigue induced subchondral bone (SCB) injury is common in racehorses. Understanding how subchondral microstructure and microdamage influence mechanical properties is important for developing injury prevention strategies. Mechanical properties of the disto palmar third metacarpal condyle (MCIII) correlate poorly with microstructure, and it is unknown whether the properties of other sites within the metacarpophalangeal (fetlock) joint are similarly complex. Objectives: We aimed to investigate the mechanical and structural properties of equine SCB from three sites within the metacarpophalangeal joint: the disto-palmar MCIII, disto-dorsal MCIII and proximal sesamoid bone. Two regions of SCB within each specimen were compared, a 2 mm superficial and underlying 2 mm deep layer. Methods: Cartilage-bone specimens were analysed with micro-computed tomography to determine bone volume fraction (BVTV) and bone mineral density (BMD), then loaded in cyclic compression for 100 cycles at 2 Hz. Disto-dorsal MCIII specimens were loaded to 30 MPa (n = 10), while disto-palmar MCIII (n = 10) and proximal sesamoid (n = 10) specimens were loaded to 40 MPa. Digital image correlation was performed on the first nine cycles to determine local strains. Specimens were stained with lead-uranyl acetate for volumetric microdamage quantification. Results: The dorsal MCIII SCB had lower BVTV, BMD, and stiffness compared to the palmar MCIII and sesamoid bone (P < 0.05). Superficial SCB had higher BVTV and lower BMD than deeper SCB (P < 0.05), except at the palmar MCIII site where there was no difference in BVTV between depths (P = 0.419). At all sites the deep bone was stiffer (P < 0.001), although the superficial to deep gradient was smaller in the dorsal MCIII. Hysteresis (energy loss) was greater superficially in palmar MCIII and sesamoid (P < 0.001), but not dorsal MCIII specimens (P = 0.118). Stiffness increased with cyclic loading in total cartilage-bone specimens (P < 0.001), but not in superficial and deep layers of the bone, whereas hysteresis decreased with cycle for all sites and layers (P < 0.001). Main limitations: Small sections of bone from each site were examined. Surface staining complicated volumetric microdamage quantification. Unconfined compression and end artefacts may have contributed to initial changes in stiffness and hysteresis. Conclusions: Superficial equine SCB is uniformly less stiff than deeper bone despite non uniform differences in bone density and damage levels. The more compliant superficial layer has an important role in energy dissipation, but whether this is a specific adaptation or a result of microdamage accumulation is not clear.
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ItemStudies of Exercise induced pulmonary haemorrhage in Thoroughbred and Standardbred Racehorses( 2022)Exercise induced pulmonary haemorrhage (EIPH) or ‘bleeding’ is an important disease of exercising horses. Though it is a disease commonly identified by equine veterinary practitioners, there is a lack of information regarding the impact of an episode of EIPH to career after examination or whether occurrence of EIPH is predictive of a horse’s lifetime athletic potential. There also exists a lack of consensus as whether the commonly used treatment, frusemide (a loop diuretic) is an effective medication to reduce or prevent EIPH. This research project addresses these two questions, with the aim of producing high quality information which can be used to underpin evidence based clinical recommendations for EIPH in horses.
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ItemHeterogeneity of Horse Fibrinogen( 2021)Fibrinogen has long been used diagnostically as a positive acute phase protein in horses. Fibrinogen heterogeneity has been observed in humans and can influence fibrinogen measurements when using the modified Clauss assay. To date, no studies have evaluated fibrinogen heterogeneity in other species. In this thesis we investigate the existence of fibrinogen heterogeneity in horses, and evaluate the precision of a method for fibrinogen fraction purification and relative quantification. Lastly, we evaluate the stability of fibrinogen fractions with freezing.