The objectives of this research were to evaluate non-invasive measures of bone mineral content (BMC) and bone mineral density (BMD) as rapid, on-farm tools to assess phosphorus (P) status in dairy cows. In addition, the effects of parity and stage of lactation on measures of BMC of the fused 3rd and 4th metacarpal bone and of caudal vertebrae 14 and 15 were assessed. The caudal vertebrae and right front metacarpal (sample pairs) were excised from 107 Holstein cull cows following slaughter. Parity, age, and days in milk (DIM) of the donor animal were obtained for 43 pairs of samples. Samples were grouped by parity (1, 2, 3, and >4) and stage of lactation (Stage 1 = < 90 DIM, Stage 2 = > 90 and < 150 DIM, Stage 3 = >150 and < 250 DIM and Stage 4 = > 250 DIM). Samples were analyzed for BMC and BMD with dual energy X-ray absorptiometry (DXA), BMC with radiographic photometry (RP), breaking strength with mechanical methods, and mineral content with chemical procedures. Estimates of BMC obtained with RP and DXA were poorly related to chemical measures of actual BMC and to measures of breaking strength. In caudal vertebrae 14 and 15, increasing stage of lactation decreased energy to peak load with the lowest values observed in late lactation. Stage of lactation had no effect on BMC measured chemically in the caudal vertebrae or metacarpal. Parity did not affect breaking strength of the metacarpal or caudal vertebrae or total ash or P content of any bone. Results indicated that imaging techniques are not useful measures of BMC in mature dairy cattle. / Master of Science

Osteoporosis is one of the most common diseases experienced in the older adult population. This condition is not only costly to manage and treat, particularly so when osteoporotic fractures occur, but also negatively impacts functional health and health-related quality of life for many individuals. This indicates the need for more to be done to prevent osteoporosis from developing initially. While bone mineral density (BMD) testing recommendations are in place for women aged 65 and older and men aged 70 and older to diagnose osteoporosis, there currently are no BMD testing recommendations for preventive or screening purposes in the general, healthy, adult population. One potential screening tool for bone strength is a peak vertical jump test. Peak vertical jump height can be used as a proxy for lower body muscle power, which has been identified as an influential factor in determining bone mass and geometry, both of which are critical aspects of bone strength. This study ascertained the relationship between muscle power and bone strength, as well as the capacity of a peak vertical jump test to identify young adults with below-average areal BMD (aBMD). A total of 303 young adults (18 to 22 years, n=136 males, n=167 females) participated in these cross-sectional analyses. DXA was used to assess aBMD for total hip and femoral neck, and DXA images were used to calculate femoral neck section modulus (FN Z) values. Peripheral quantitative computed tomography (pQCT) was used to assess indices of bone strength at the tibia. Cortical bone area (CoA) and density-weighted polar section modulus strength-strain index (SSIp) were assessed at the 38% midshaft site, and bone strength index (BSI) was assessed at the 4% midshaft site. Lower body muscle power was predicted using peak vertical jump height and the Sayers et al. (1999) equation. Data were analyzed using Pearson bivariate and partial correlations to examine associations among bone strength outcomes and muscle power. Logistic regression was used to examine the probability of below-average bone strength based on muscle power. Receiver Operating Characteristic (ROC) curve analysis was used to show the tradeoff between sensitivity and specificity and to display the accuracy of a peak vertical jump test as an assessment tool for aBMD. Logistic regression indicated the odds ratio of below-average height-adjusted femoral neck aBMD decreased 5.4% for females and 3.6% for males per 50 Watts of power. ROC curve analysis showed the best sensitivity-specificity trade-off for identifying individuals with and without below-average aBMD was 5,038 Watts in males (sensitivity = 73.7%; specificity = 62.4%; AUC = 0.709, 95%CI = 0.572 - 0.847) and 3,261 Watts in females (sensitivity = 71.4%; specificity = 58.9%; AUC = 0.708, 95%CI = 0.586 - 0.829). These cut off values correspond to a vertical jump height of 54.39 cm and 36.16 cm for males and females, respectively. Taken together, the results of these analyses suggest acceptable sensitivity and specificity and moderate discriminate ability for using a measure of muscle power, assessed with a peak vertical jump test, to identify young adults with below-average aBMD.

Exercise during growth may increase peak bone mass; if the benefits are maintained it may reduce the risk of fracture later in life (1). It is hypothesised that exercise will preferentially enhance bone formation on the surface of cortical bone that is undergoing bone modeling at the time (2). Therefore, exercise may increase bone mass accrual on the outer periosteal surface during the pre- and peri-pubertal years, and on the inner endocortical surface during puberty (3). An increase in bone formation on the periosteal surface is, however, more effective for increasing bone strength than medullary contraction (4). While exercise may have a role in osteoporosis prevention, there is little evidential basis to support this notion. It is generally accepted that weight-bearing exercise is important, but it is not known how much, how often, what magnitude or how long children need to exercise before a clinically important increase in bone density is obtained. In this thesis, the effect of exercise on the growing skeleton is investigated in two projects. The first quantifies the magnitude and number of loads associated with and in a moderate and low impact exercise program and non-structured play. The second project examines how exercise affects bone size and shape during different stages of growth. Study One: The Assessment of the Magnitude of Exercise Loading and the Skeletal Response in Girls Questions: 1) Does moderate impact exercise lead to a greater increase in BMC than low impact exercise? 2) Does loading history influence the osteogenic response to moderate impact exercise? 3) What is the magnitude and number of loads that are associated with a moderate and low impact exercise program? Methods: Sixty-eight pre-and early-pubertal girls (aged 8.9±0.2 years) were randomised to either a moderate or low impact exercise regime for 8.5-months. In each exercise group the girls received either calcium fortified (-2000 mg/week) or non-fortified foods for the duration of the study. The magnitude and number of loads associated with the exercise programs and non-structured play were assessed using a Pedar in-sole mobile system and video footage, respectively. Findings: After adjusting for baseline BMC, change in length and calcium intake, the girls in the moderate exercise intervention showed greater increases in BMC at the tibia (2.7%) and total body (1.3%) (p ≤0.05). Girl's who participated in moderate impact sports outside of school, showed greater gains in BMC in response to the moderate impact exercise program compared to the low impact exercise program (2.5 to 4.5%, p ≤0.06 to 0.01). The moderate exercise program included -400 impacts per class, that were applied in a dynamic manner and the magnitude of impact was up to 4 times body weight. Conclusion: Moderate-impact exercise may be sufficient to enhance BMC accrual during the pre-pubertal years. However, loading history is likely to influence the osteogenic response to additional moderate impact exercise. These findings contribute towards the development of school-based exercise programs aimed at improving bone health of children. Study Two: Exercise Effect on Cortical Bone Morphology During Different Stages of Maturation in Tennis Players Questions: 1) How does exercise affect bone mass (BMC) bone geometry and bone strength during different stages of growth? 2) Is there an optimal stage during growth when exercise has the greatest affect on bone strength? Methods: MRI was used to measure average total bone, cortical and medullary areas at the mid- and distal-regions of the playing and non-playing humerii in 47 pre-, peri- and post-pubertal competitive female tennis players aged 8 to 17 years. To assess bone rigidity, each image was imported into Scion Image 4.0.2 and the maximum, minimum and polar second moments of area were calculated using a custom macro. DXA was used to measure BMC of the whole humerus. Longitudinal data was collected on 37 of the original cohort. Findings: Analysis of the entire cohort showed that exercise was associated with increased BMC and cortical area (8 to 14%), and bone rigidity (11 to 23%) (all p ≤0.05). The increase in cortical bone area was associated with periosteal expansion in the pre-pubertal years and endocortical contraction in the post-pubertal years (p ≤0.05). The exercise-related gains in bone mass that were accrued at the periosteum during the pre-pubertal years, did not increase with advanced maturation and/or additional training. Conclusion: Exercise increased cortical BMC by enhancing bone formation on the periosteal surface during the pre-pubertal years and on the endocortical surface in the post-pubertal years. However, bone strength only increased in response to bone acquisition on the periosteal surface. Therefore the pre-pubertal years appear to be the most opportune time for exercise to enhance BMC accrual and bone strength

Introduction. Wrist (Colles') and forearm fractures commonly occur when a person falls on the outstretched forearm and the force exceeds bone strength. There is lack of experimental evidence testing the available force prediction models and assessing factors that determine forearm forces during a fall.<p> Objective. The primary objective was to compare experimentally measured force peaks (F1max-E and F2max-E) to the force peaks that were predicted by an engineering based force prediction model (F1max-M and F2max-M), at heights greater than 5cm. The second objective was to describe the relationships between the experimentally measured peak forces and forearm bone and muscle strength properties, body mass, and stature as a function of fall height.<p> Methods. Using 3D motion tracking, we assessed the first (F1max) and second (F2max) peak forces from 10 young adults (5 male; 5 female) who volunteered to fall from heights up to 25cm onto a foam covered force plate. Peripheral QCT was used to determine the bone strength index (BSIc), strength-strain index (SSIp), and muscle cross sectional area (MCSA) of each participant. Two 2x8 between-within factorial ANOVAs determined the difference between the experimental and model force peaks, with post hoc analyses at all fall heights. Pearson's correlation was used to determine the relationship between the pQCT-derived bone and muscle strength indices and the force peaks.<p> Results. There was no significant differences between F1max-E and F1max-M across all fall heights, but the model significantly over-predicted the F2max-E across all fall heights. After controlling F1max-E and F2max-E for body mass, the force peaks appeared to be weakly related to the anthropometric as well as bone and muscle strength outcomes (r=0.2-0.7, p>0.05). The relationship between bone and muscle strength outcomes appeared to have a tendency to get stronger at higher fall heights.<p> Conclusion. The model predicted experimental F1max, but not experimental F2max. This study presents preliminary pilot results. Larger sample size is needed to confirm whether incorporating bone and muscle strength estimates into fall force prediction models could enhance forearm fracture risk assessments.

Introduction. Wrist (Colles') and forearm fractures commonly occur when a person falls on the outstretched forearm and the force exceeds bone strength. There is lack of experimental evidence testing the available force prediction models and assessing factors that determine forearm forces during a fall.<p> Objective. The primary objective was to compare experimentally measured force peaks (F1max-E and F2max-E) to the force peaks that were predicted by an engineering based force prediction model (F1max-M and F2max-M), at heights greater than 5cm. The second objective was to describe the relationships between the experimentally measured peak forces and forearm bone and muscle strength properties, body mass, and stature as a function of fall height.<p> Methods. Using 3D motion tracking, we assessed the first (F1max) and second (F2max) peak forces from 10 young adults (5 male; 5 female) who volunteered to fall from heights up to 25cm onto a foam covered force plate. Peripheral QCT was used to determine the bone strength index (BSIc), strength-strain index (SSIp), and muscle cross sectional area (MCSA) of each participant. Two 2x8 between-within factorial ANOVAs determined the difference between the experimental and model force peaks, with post hoc analyses at all fall heights. Pearson's correlation was used to determine the relationship between the pQCT-derived bone and muscle strength indices and the force peaks.<p> Results. There was no significant differences between F1max-E and F1max-M across all fall heights, but the model significantly over-predicted the F2max-E across all fall heights. After controlling F1max-E and F2max-E for body mass, the force peaks appeared to be weakly related to the anthropometric as well as bone and muscle strength outcomes (r=0.2-0.7, p>0.05). The relationship between bone and muscle strength outcomes appeared to have a tendency to get stronger at higher fall heights.<p> Conclusion. The model predicted experimental F1max, but not experimental F2max. This study presents preliminary pilot results. Larger sample size is needed to confirm whether incorporating bone and muscle strength estimates into fall force prediction models could enhance forearm fracture risk assessments.

The mechanical properties of the cancellous bone in the laboratory rat animal model are of great interest to the research community for the evaluation of treatments for osteoporosis. Cancellous bone responds rapidly and dramatically to disuse, various pathologies, nutritional deficiencies, and hormonal deficiencies and hence is often a primary focus in animal studies. Previous methods for evaluating the mechanical properties of cancellous bone in rat test specimens included both cortical and cancellous bone. This thesis introduces a new method to core cancellous specimens using a diamond wire saw in concert with specially designed fixtures. This method has been termed Isolated Cancellous Coring (ICC). The location and the geometry of the cored specimens were determined based on uCT analysis. The isolated cancellous specimens were subjected to uni-axial compression testing to evaluate the mechanical properties. Furthermore, the new method is evaluated by directly applying it to a study investigating the effects of estrogen replacement therapy in post-menopausal osteoporosis as simulated by the ovariectomized rat model. The results show that the ICC method can be applied to bone specimens with a large range in density and micro-architecture parameters. The compression testing of the isolated cancellous specimens provides a sensitive indicator of the effects of osteoporosis and treatment on the mechanical properties of the cancellous bone in the distal rat femur. Also, the results indicate a possible discordant relationship between bone mineral density and bone strength with respect to estrogen treatment. Power law regressions show that approximately 50% of the variation in ultimate strength can be accounted for with bone mineral density and the percent of bone volume per total volume.

There is a pressing need for better assessment of bone strength as current clinical tools do not directly measure bone mechanical properties, but offer only surrogate measures of bone strength. We conducted an ex-vivo study of emu bones to examine how two investigative devices, hr-pQCT and MRTA, compare to current clinical tools (DXA and QUS) in predicting true bone mechanical properties. We found that hr-pQCT parameters were able to assess bone strength as well as DXA and better than QUS, while MRTA was able to predict bone strength well in low-density but not high-density bones. Our results suggest that both hr-pQCT, which has the unique ability to specifically assess the various determinants of bone strength, and MRTA, which measures a bone mechanical property (stiffness), have great potential for use as clinical tools that can assess various components of bone strength not measured by current devices.

A variety of pathologies exist which increase the likelihood of bone fracture. Present methods for determining the fracture risk of a specific patient are based exclusively on the amount of bone present. While the quantity of bone tissue is correlated with strength, it neglects to account for bone’s intricate microarchitecture. To assess the effect of bone quality on strength, a methodology was developed for the structural analysis of cancellous bone biopsies. Thirty biopsies were selected from a pre-existing biopsy bank, and scanned using a SCANCO µCT-40 at a resolution of 30 microns. Cortical bone was removed from the resulting three-dimensional geometry, and the remaining cancellous bone was meshed with solid tetrahedral elements. A linear static uniaxial compression test was performed using ANSYS v14.0 to determine the apparent-level Young’s modulus. The maximum von Mises stress was also investigated, but showed poor convergence with increased mesh density. Consistent with the methodology of Pistoia et al., the failure load was assumed to occur when 2% of the bone volume exceeded 7000 µstrain. The results of the finite element analysis compared favorably with known values for cancellous bone strength.

There is a pressing need for better assessment of bone strength as current clinical tools do not directly measure bone mechanical properties, but offer only surrogate measures of bone strength. We conducted an ex-vivo study of emu bones to examine how two investigative devices, hr-pQCT and MRTA, compare to current clinical tools (DXA and QUS) in predicting true bone mechanical properties. We found that hr-pQCT parameters were able to assess bone strength as well as DXA and better than QUS, while MRTA was able to predict bone strength well in low-density but not high-density bones. Our results suggest that both hr-pQCT, which has the unique ability to specifically assess the various determinants of bone strength, and MRTA, which measures a bone mechanical property (stiffness), have great potential for use as clinical tools that can assess various components of bone strength not measured by current devices.

Made available in DSpace on 2014-06-11T19:33:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-28Bitstream added on 2014-06-13T19:04:38Z : No. of bitstreams: 1 boiago_mm_dr_jabo.pdf: 456558 bytes, checksum: 5fedc7f36c4c91c58db0f60b0bc4ccb5 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Avaliou-se o desempenho, qualidade e composição química da carne, resistência óssea e empenamento de frangos de corte arraçoados com dietas contendo selênio, zinco e manganês complexados ou não a moléculas orgânicas e criados sob condições de estresse térmico. Foram utilizados 980 pintos machos Cobb de um dia de idade, criados até 42 dias de idade em três câmaras climáticas, que proporcionaram temperaturas alta, termoneutra e baixa. Foi utilizado o delineamento inteiramente casualizado, em esquema fatorial 3 X 2 + 1, sendo três temperaturas de criação, duas fontes de selênio, zinco e manganês: inorgânica e “orgânica”, mais o tratamento testemunha (criação em câmara termoneutra sem adição de Se, Zn e Mn na ração). As aves criadas em condições de estresse térmico apresentam desempenho inferior e ossos com densidade óssea e resistência à quebra menores. A fonte orgânica proporcionou melhor desempenho, principalmente em condições de temperaturas elevadas. Selênio e zinco foram melhor absorvidos na forma orgânica, já o manganês teve absorção similar nas duas formas. As aves criadas em temperaturas baixas apresentaram carne menos macia. O empenamento das aves não foi influenciado pelos fatores testados / It were evaluated performance, meat quality and composition, bone strength and feathering of broilers fed supplemented diets with different selenium, zinc and manganese sources (organic and inorganic) and raised under different environmental temperatures. Nine hundred and eighty one d. old Cobb male broilers were used during 42 days. It were used three climatic chambers (high, neutral and low temperatures) and twenty chickens per pen. It was used a 3x2 + 1 factorial arrangement (three breeding temperatures, two mineral sources and a control treatment that provided neutral temperature without mineral supplementation) with seven replicates. The means were compared by Tykey's test (5%).The thermal stressed broilers showed lower performance, bone density and strength. The organic source took to a better performance, mainly under high temperatures. Organic sources of selenium, zinc and manganese were highly absorbed, however, the absorption of both sources of manganese was similar. Chickens raised under low temperatures presented lower values of tenderness. The factors didn't influence the feathering of the chickens