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Item Broken shoulders in dairy heifers in New Zealand : investigating the relationship between live weight and bone morphology in the bovine forelimb : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2021) Gibson, MichaelaSpontaneous humeral fractures in first lactation dairy heifers are a significant economic and welfare issue in the New Zealand dairy industry. With approximately 4% of dairy farms being affected and, within farm, up to 25% of replacement heifers lost, the cost to the dairy industry is estimated to be over $10 million. Preliminary observations from Dittmer et al. (2016), showed the presence of growth arrest lines in bones from affected heifers, indicating a period of malnutrition in the heifer’s life. However, with little known about how heifer’s bones grow within the New Zealand pastoral system, it is difficult to identify developmental time periods that have the greatest impact on long bone growth and, therefore, greatest potential to affect the risk of fracture. Therefore, the aim of this thesis was to investigate the relationship between live weight and bone morphology in the bovine forelimb to identify potential risk periods for spontaneous humeral fractures in first-lactation dairy heifers. In this thesis, the metacarpus and humerus were opportunistically collected from cattle from a variety of experiments carried out at Massey University and from samples submitted from farms throughout New Zealand. Measures of bone morphology in the metacarpus were highly correlated with the same measure in the humerus (R²=0.89-0.98). Measures of the humerus and metacarpus were also highly correlated with live weight at all ages. However, the relationship between bone and live weight changed over time demonstrating differences in bone maturity. Distal regions of the forelimb such as the metacarpus matured by one year of age as indicated by a different relationship between live weight and pQCT measures of the humerus at 24 months compared with 8-12 months of age. However, proximal regions of the forelimb such as the humerus continued to grow after a year of age. Differences in proximal and distal bone growth were reflected in the pattern of stature growth. A cohort of dairy heifers (Holstein Friesian, Jersey, and Holstein-Friesian cross Jersey) were measured for live weight, height, wither-rump length, girth, and distal and proximal forelimb length (stature) from birth to 15 months of age. As live weight increased, the contribution of the distal limb to increases in height decreased, which is consistent with knowledge that physeal closure in cattle occurs earlier in distal limb bones, such as the metacarpus, than in proximal limb bones, such as the humerus. Finally, bones collected from heifers affected and unaffected by spontaneous humeral fractures were compared and the effect of copper status on bone measures was examined. The mid diaphysis of the humerus of the affected group had reduced cortical bone mineral density (p<0.05) and a trend for reduced cortical content and total bone content which contributed to a reduced stress-strain index. A trend for reduced bone length in affected humeri provides additional support for the hypothesis of inhibited humeral growth. Heifers with low liver copper concentration had reduced humeral length and reduced cortical bone mineral density (p<0.05). Growth and fracture data presented in this thesis support the hypothesis that the most likely developmental period in which inadequate bone growth occurs in heifers subsequently affected by humeral fracture is in the months leading up to the event, which coincides with the animal’s second winter.Item Predicting horse limb responses to surface variations with a 3D musculoskeletal model : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biomechanics at Massey University, Palmerston North, New Zealand(Massey University, 2020) Bardin, AliénorThoroughbred racehorses are often affected by musculoskeletal injuries, leading to involuntary rest periods, early retirement or death. A number of studies have focused on identifying risk factors. A major focus of research has been track surface properties because it should be possible to modify these so that the risk of musculoskeletal injury is minimised. Among all the track surface properties studied to date, consistency of the surface is reported to be one of the main injury risk factors. The aim of this study was to develop a preliminary 3D musculoskeletal model of the whole equine forelimb based on data published in the literature and derived from anatomical measurements; and to determine the effects of the perturbations by the ground surface on the limb response with the musculoskeletal model developed and to assess whether the response occurs acutely in the perturbed stance phase or in the next stance phase. To answer these questions, gait data were collected from ridden Thoroughbreds passing through a perturbation area, where the surface hardness was changed by adding wood or foam under the baseline sand surface. The horses changed their joint flexion/extension patterns in response to changes in hardness. In response to the hard perturbation, the proximal limb spring was more compliant, evidenced by increased shoulder flexion. The elbow and carpal joints were more flexed in the intervening swing phase. In response to the soft perturbation, more coffin joint flexion was observed during both the perturbed and the following stance phase. The preliminary musculoskeletal model of the equine forelimb developed in this thesis allow the observation and study of the forelimb reaction to hardness perturbation through the joint excursions and tendon and ligament strains.