The objective of this study was to examine the link between radiographic measures of bone quality and total knee implant migration as measured by radiostereometric analysis (RSA). Two uncemented total knee arthroplasty studies (n=65) with RSA and bone mineral density (BMD) exams up to two years post surgery, and one study with cemented total knees with one year RSA data (n=18) were examined. Radiograph image texture analysis was used to characterize the bone microarchitecture, and a feasibility study was conducted to determine if a given x-ray machine could be used to obtain bone mineral density at the same time as the RSA exams. Random ForestTM ensemble classification tree statistical models classified patients into groups based on implant migration with a range of cut-points. Models based on bone texture parameters measured from the two year radiographs had a sensitivity of 87.5% and specificity of 80% when classifying patients who had more than 0.3mm maximum total point motion (MTPM) at two years using the one year exam as reference. Other cut-points were examined, with models generally having a lower specificity if the acceptable migration was smaller, and lower sensitivity if higher migrations were tolerable. In a predictive model, post-operative bone texture could be used to create a model with a sensitivity of 75% and a specificity of 80% when predicting those subjects with cemented implants who went on to more than 0.4mm total migration by one year. Bone mineral density of the proximal tibia, as determined by clinical scanners, was not found to increase the accuracy of implant migration group classification. An empirical fit to central regions of a purposed-built cross-wedge calibration phantom returned residuals of less than ±1.5% for the bone-equivalent thicknesses. The coefficient of variation of the region greyscale values in three images spread over three days is under 4%, showing the stability of the system to hold a calibration between phantom exams and patient scans. Scatter and dynamic range issues will need to be considered for an accurate calibration across the full range of areal bone mineral densities in the distal femur and proximal tibia.

La fracture ostéoporotique du col fémoral et la coxarthrose constituent aujourd'hui deux enjeux majeurs de santé publique chez les sujets âgés. L'ostéoporose est définie par une diminution de la masse osseuse et une altération de la structure osseuse. La coxarthrose d'autre part associe la perte progressive du cartilage d'encroûtement articulaire, une sclérose osseuse sous-chondrale, des géodes sous-chondrales, et des ostéophytes marginaux. Bien qu'une masse osseuse élevée semble prédisposer à l'arthrose, les relations métaboliques et biomécaniques entre ostéoporose et coxarthrose sont complexes. L'évaluation de l'architecture osseuse de l'extrémité proximale du fémur est un des enjeux majeurs de recherche actuels visant à la caractérisation des modifications du tissu osseux liées au vieillissement. Notre travail de thèse s'est inscrit dans un projet pluridisciplinaire de recherche sur les altérations de la structure osseuse de l'extrémité proximale du fémur, reposant sur une analyse en imagerie médicale et une étude biomécanique de cette région anatomique fondamentale. / Fracture of the proximal femur and hip osteoarthritis are nowadays a major public health problem in elderly persons. The current definition of osteoporosis is a low bone mass associated with microarchitecture deterioration. On the other hand, osteoarthritis corresponds to progressive articular cartilage loss, subchondral bone sclerosis, subchondral bone cysts, and marginal osteophytes. Although a higher bone mass may increase the risk of osteoarthritis, osteoporosis and hip osteoarthritis present a complex metabolic and biomechanical relationship. The proximal femur architectural evaluation and characterization of age-related osseous alterations are currently one of the main challenges in bone and mineral research. Our work was based on a multidisciplinary project which aimed at evaluating the age-related structural deterioration of the proximal femur using medical imaging and biomechanical testing in this crucial anatomical region.

Bone drilling is an essential part of many orthopaedic surgical procedures, including those for internal fixation and for attaching prosthetics. Drilling into bone is a fundamental skill that can be both very simple, such as drilling through long bones, or very difficult, such as drilling through the vertebral pedicles where incorrectly drilled holes can result in nerve damage, vascular damage or fractured pedicles. Also large forces experienced during bone drilling may promote crack formation and can result in drill overrun, causing considerable damage to surrounding tissues. Therefore, it is important to understand the effect of bone material quality on the bone drilling forces to select favourable drilling conditions, and improve orthopaedic procedures.

Submitted by Simone Souza (simonecgsouza@hotmail.com) on 2017-08-23T14:00:22Z No. of bitstreams: 1 DISS_2014_Emanuele Brusamarelo.pdf: 1193853 bytes, checksum: ed950682d57e5c216154b030d0087cae (MD5) / Approved for entry into archive by Jordan (jordanbiblio@gmail.com) on 2017-08-24T15:13:12Z (GMT) No. of bitstreams: 1 DISS_2014_Emanuele Brusamarelo.pdf: 1193853 bytes, checksum: ed950682d57e5c216154b030d0087cae (MD5) / Made available in DSpace on 2017-08-24T15:13:12Z (GMT). No. of bitstreams: 1 DISS_2014_Emanuele Brusamarelo.pdf: 1193853 bytes, checksum: ed950682d57e5c216154b030d0087cae (MD5) Previous issue date: 2014-03-11 / A nutrição vitamínica e mineral interfere no desempenho e nas características ósseas das aves. O suplemento de vitamina D utilizado sem restrição nas rações para frangos de corte é o colecalciferol inativo e o 25-hidroxicolecalciferol. O objetivo foi avaliar o desempenho, o rendimento de cortes comerciais e de carcaça e os parâmetros ósseos de frangos de corte machos suplementados com 1,25-dihidroxicolecalciferol e redução de cálcio e fósforo disponível nas rações. Um total de 648 machos foi distribuído, em delineamento em blocos ao acaso, com seis tratamentos: dieta controle - atendendo a exigência nutricional; dieta controle negativo - com redução em 15% dos níveis de cálcio e de fósforo disponível; dieta controle negativo suplementada com: 0,5; 1,0; 1,5 e 2,0 μg de vitamina D3 ativa/kg ração respectivamente, com seis repetições (boxes). O desempenho foi avaliado pelo ganho de peso (kg), consumo de ração (kg/ave) e conversão alimentar. As aves foram pesadas com um dia e aos 42 dias de idade, para obtenção do ganho de peso. O consumo de ração foi obtido pela diferença entre a quantidade de ração fornecida, descontando-se as sobras em cada fase da criação. A razão entre o consumo de ração corrigido e o ganho de peso originou a conversão alimentar. Quatro aves/unidade experimental foram amostradas, pesadas e sacrificadas por deslocamento cervical para avaliação dos rendimentos de carcaça e de cortes comerciais no 42º dia de idade. Uma ave/unidade experimental foi amostrada, pesada e sacrificada para a remoção dos tibiotarsos utilizados na avaliação dos parâmetros ósseos no 21º e 33º dias de idade. As características ósseas avaliadas foram: o peso (mg) e comprimento (mg) do osso, índice de Seedor (mg/mm), cinzas ósseas (%) e resistência à quebra (kgf). O suplemento de vitamina D3 ativa com redução de cálcio e de fósforo disponível nas rações não influenciou o desempenho e os rendimentos de carcaça e cortes comerciais (peito, coxa + sobrecoxa e asa) das aves. A redução em 15% dos níveis de cálcio e de fósforo disponível e o suplemento de vitamina D3 ativa nas rações não afetou o peso e o comprimento do osso, o índice de Seedor e a resistência à quebra. O percentual de deposição de cinzas em ossos de frangos de corte aos 21 e 33 dias de idade foi diferente entre tratamentos. Os menores valores para cinzas, sem interferência na resistência à quebra dos tibiotarsos, demonstra a possibilidade de reduzir em 15% os níveis de cálcio e de fósforo disponível nas dietas sem compromoter a estrutura óssea das aves. / The vitamin and mineral nutrition interferes with the production performance and bone characteristics of birds. The vitamin D supplement used without restriction in the feed for broilers is inactive cholecalciferol and 25-hydroxycholecalciferol. The objective of this study was to evaluate the performance, and yields of carcass and commercial cuts and bone parameters of male broilers supplemented with 1,25-dihydroxycholecalciferol and reduction of calcium and available phosphorus in feed. A total of six hundred and forty-eight males, was used in a randomized-block design, with six treatments: control diet - meeting nutritional requirement; negative control diet - with 15% reduction in the levels of calcium and available phosphorus; negative control diet supplemented with: 0.5; 1.0; 1.5 and 2.0 μg of vitamin D3 active/kg diet respectively, with six replicates (boxes). The performance was evaluated by weight gain (kg), feed intake (kg/bird) and feed conversion. The broilers were weighed one day and at 42 days of age, for obtaining the weight gain. Feed intake was calculated as the difference between the amount of feed, discounting the leftovers at each stage of creation. The ratio between feed intake and weight gain corrected feed conversion originated. Later, four broilers of each experimental unit were sampled, weighed and slaughtered by cervical dislocation to evaluate carcass yield and commercial cuts yield at 42 days of age. Later, a one bird of each experimental unit was sampled, weighed and sacrificed for removal of tibiotarsos for the assessment of bone parameters at 21 and 33 days of age. The bones were identified and cleaned of all adhering tissue and frozen (-20°C) until analysis begins. The bone parameters were evaluated weight (mg) and length (mg) of the bone Seedor index (mg/mm) bone ash (%) and breaking strength (kgf). The active vitamin D3 supplement with reduced calcium and available phosphorus in the diets did not influence performance and carcass and commercial cuts (breast, thigh + drumsticks and wing) of poultry. A 15% reduction in the levels of calcium and available phosphorus and vitamin D3 supplement active in the diets did not affect the weight and length of the bone, the index Seedor and resistance to breakage. The percentage of bone ash deposition in bones of broilers at 21 and 33 days of age was different between treatments. The lowest values for ash, without interference in breaking resistance force of tibiotarsos, demonstrates the possibility of reducing in the 15% levels of calcium and available phosphorus in diets without compromising the bone structure of birds.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The study was conducted at the experimental aviary of broiler chickens in the Poultry Laboratory (LAVIC) at the Federal University of Santa Maria (UFSM), Brazil. The objective of the study was to evaluate the effect of Canthaxanthin associated with 25-hydroxycholecalciferol (25-OH-D3) in the feed of broilers. The research was divided into two experiments, one with males and the other with females. In the first experiment were used in 1500 one-day-old Cobb-500TM males were distributed in a completely randomized design, totaling two treatments with fifteen replicates of 50 birds each. In the second experiment were used in 1680 one-day-old Cobb-500TM females were distributed in a completely randomized design, totaling two treatments with fifteen replicates of 56 birds each. For both experiments the treatments were: Treatment one (control diet) and Treatment two (control diet + Canthaxanthin associated with 25-OH-D3 added in diet up to 21 days of age). The experimental phase comprised a continuous period of 42 days for the experiment with males and 43 days for the experiment with females, after the birds were slaughtered for performing laboratory tests. The parameters measured were, production performance (weight gain, feed intake, feed conversion and carcass yield and cuts), physicochemical characteristics of carcass (pH, color, water-holding capacity, shear force, cooking loss, lipid oxidation of meat at different shelf times 0, 30, 60 and 90 days "post-mortem" and paw pigmentation), bone characteristics (Black Bone Syndrome, Gait Score, tibial rupture strength and percentage of calcium, phosphorus, and ashes of the tibia). For both experiments the data were submitted to analysis of variance using the statistical program SAS. For the experiment with males, significant results were found for dietary supplementation with Canthaxanthin + 25-OH-D3, where they presented better (P<0.05) body weight gain in the periods of 1-14 and of 1-21 days of age. Besides that, at 42 days of age presented higher (P<0.05) content of yellow in the breast meat, greater (P<0.05) paw pigmentation and greater (P<0.05) tibial rupture strength when supplemented with Canthaxanthin + 25-OH-D3 in the diet. For the experiment with females significant results were found for the variables of carcass coloration, where females supplemented with Canthaxanthin + 25-OH-D3 in the diet in the period of 1-21 days of age presented a higher (P<0.05) red (a*) and yellow (b*) content in the breast meat when slaughtered at 28 days of age. When they were slaughtered at 43 days of age, they presented only higher (P<0.05) breast yield in relation to the control group. It was concluded that males supplemented with Canthaxanthin + 25-OH-D3 in the diet of 1-21 days of age, presented better body weight gain in the initial production period, better breast color and paw pigmentation at 42 days of age and greater rupture force of the tibia. Females supplemented with Canthaxanthin + 25-OH-D3 in the diet of 1-21 days of age presented better breast coloration when slaughtered at 28 days of age, and when slaughtered at 43 days of age presented only higher breast yield. / O estudo foi realizado no aviário experimental de frangos de corte do Laboratório de Avicultura (LAVIC) da Universidade Federal de Santa Maria (UFSM), Brasil. O objetivo principal do estudo foi avaliar o efeito da Cantaxantina associada ao 25-hidroxicolecalciferol (25-OH-D3) na alimentação de frangos de corte. A pesquisa foi dividida em dois experimentos sendo, Experimento I com machos e Experimento II com fêmeas. No Experimento I foram utilizados 1500 machos Cobb-500® de um dia de idade, distribuídos em um delineamento inteiramente casualisado (DIC), totalizando dois tratamentos com quinze repetições de 50 aves cada. No segundo experimento foram utilizadas 1680 fêmeas Cobb-500® de um dia de idade, distribuídas em um delineamento inteiramente casualisado (DIC), totalizando dois tratamentos com quinze repetições de 56 aves cada. Para ambos experimentos os tratamentos foram: Tratamento 1 (dieta controle) e Tratamento 2 (dieta controle + Cantaxantina associada a 25-OH-D3 adicionado na dieta até 21 dias de idade). A fase experimental compreendeu um período continuo de 42 dias para o experimento com machos e de 43 dias para o experimento com fêmeas, após foi realizado o abate das aves, para realização das análises laboratoriais. Os parâmetros mensurados, foram, desempenho zootécnico (ganho de peso, consumo de ração, conversão alimentar e rendimento de carcaça e cortes), características físico-químicas da carcaça (pH, coloração, capacidade de retenção de água, força de cisalhamento, perda por cocção, oxidação lipídica da carne nos diferentes tempos de prateleira 0, 30, 60 e 90 dias “post-mortem” e pigmentação da pata), características ósseas (Black Bone Syndrome, Gait Score, força de ruptura da tíbia e percentual de cálcio, fósforo e cinzas da tíbia). Para ambos os experimentos os dados foram submetidos à análise de variância, através do programa estatístico SAS. Para o experimento com machos foram encontrados resultados significativos para a suplementação com Cantaxantina + 25-OH-D3 na dieta, onde estes apresentaram maior (P<0,05) ganho de peso corporal nos períodos de 1-14 e de 1-21 dias de idade. Além disso, aos 42 dias de idade apresentaram maior (P<0,05) teor de amarelo (b*) na carne de peito, maior (P<0,05) pigmentação da pata e maior (P<0,05) força de ruptura da tíbia quando suplementados com Cantaxantina + 25-OH-D3 na dieta. Já para o experimento com fêmeas foram encontrados resultados significativos, para as variáveis de coloração da carcaça, onde fêmeas suplementadas com Cantaxantina + 25-OH-D3 na dieta no período de 1-21 dias de idade, apresentaram maior (P<0,05) teor de vermelho (a*) e amarelo (b*) na carne de peito quando abatidas aos 28 dias de idade. Quando abatidas aos 43 dias de idade apresentaram somente maior (P<0,05) rendimento de peito em relação ao grupo controle. Concluiu-se que machos de corte suplementados com Cantaxantina + 25-OH-D3 na dieta de 1-21 dias de idade, apresentaram melhor ganho de peso corporal no período inicial de produção, melhor coloração de peito e pata aos 42 dias de idade e maior força de ruptura da tíbia. Já fêmeas de corte suplementadas com Cantaxantina + 25-OH-D3 na dieta de 1-21 dias de idade, apresentaram melhor coloração de peito quando abatidas aos 28 dias de idade, e quando abatidas aos 43 dias de idade, apresentaram somente maior rendimento de peito.

O rastreio de osteoporose utilizando imagens de tomografia computadorizada de feixe cônico (TCFC) é um procedimento ainda discutível. O objetivo deste estudo foi avaliar a qualidade óssea de mulheres de diversas faixas etárias (AG) através de índices de radiomorfométricos obtidos em TCFC. Setenta e cinco imagens de TCFC de mulheres (idades compreendidas entre 40 - 70 anos) foram avaliadas. Os pacientes foram agrupados de acordo com AG, em três maneiras diferentes, de acordo com a prevalência de osteoporose em mulheres brasileiras. Os índices avaliados foram: índice cortical mandibular (ICM), índice mentual (IM) e os índices de tomografia computadorizada superior e inferior (ITC). Dois examinadores calibrados avaliaram as imagens em três tempos: Abertura / reconstrução de imagens (1), repetindo este procedimento e salvando a reconstrução (2), e a avaliação das imagens reconstruídas (3). As reconstruções panorâmicas (variando as espessuras: 0,30, 10, e 20 mm) e imagens transaxiais foram avaliadas. A concordância intra e inter-examinador foram avaliadas por meio do teste Kappa e estatísticas de coeficiente de correlação intraclasse. A correlação de Pearson foi utilizada para verificar a relação entre os índices avaliados e AG. O teste de quiquadrado foi utilizado para comparar a prevalência de osteoporose de acordo com cada parâmetro e AG. Os índices avaliados não apresentaram correlação com AG. Alta concordância intra e inter-examinador foi encontrada para IM e ITC, mas não para ICM. A prevalência da osteoporose variou grandemente, de acordo com o índice avaliado e o valor de corte utilizado para definir a doença (com base na qualidade do osso). Os índices radiomorfométricos quantitativos obtidos na TCFC podem ser avaliados de uma forma reprodutível. Não houve correlação entre os índices e AG, o que sugere que as imagens de TCFC não devem ser utilizadas para o rastreio de osteoporose. / Screening for osteoporosis using cone beam CT images (CBCT) is a datable procedure. The aim of this study was to evaluate the bone quality of women from diverse age groups (AG) using CBCT-based radiomorphometric indices. Seventy-five CBCT images of women (age range 40 - 70) years were evaluated. Patients were grouped according to AG, in three diverse manners, according to prevalence of osteoporosis in Brazilian women. The mandibular cortical (MCI), mental (MI), and the superior and inferior computed tomography (CTI) indices were assessed. Two calibrated examiners assessed the images in three instances: opening/reconstructing the images (1), repeating this procedure (2), and assessing the reconstructed images once again (3). Panoramic reconstructions (0.30, 10, and 20 mm thicknesses) and cross-sectional images were assessed. Intra and inter-examiner agreement were assessed by means of Kappa and intraclass correlation coefficient statistics. Pearson correlation was used to verify the relationship between the assessed indices and AG. Chi-square statistics was used to compare the prevalence of osteoporosis according to each index and AG. Assessed indices showed no correlation with AG. High intraand inter-examiner agreement was found for MI and CTI but not to MCI. The prevalence of osteoporosis varied widely, according to the assessed index and to the cutoff used to define the disease (based on bone quality). Quantitative CBCT-based radiomorphometric indices can be assessed in a reproducible manner. No correlation between AG and the assessed indices was found, suggesting that CBCT images should not be used for the screening of osteoporosis.

Ossos trabeculares possuem uma microestrutura porosa e podem ser modelados como um sólido elástico linear, heterogêneo e anisotrópico. A microtomografia tridimensional por raios-x (uCT) tem sido mundialmente utilizada para a caracterização de osso trabecular em pesquisas relacionadas à qualidade óssea e à doenças do metabolismo ósseo como a osteoporose. Na literatura há poucas investigações comparando as análises morfométricas 2D e 3D de osso trabecular. Nesta investigação amostras de osso trabeculares cilíndricas extraídas da cabeça femoral bovina foram utilizadas para a comparação dessas análises por \'mü\'CT. O software CT-Analyser foi utilizado para medidas em três direções (crânio-caudal, lateral-medial e anterior-posterior) de diversos parâmetros da microestrutura trabecular tais como espessura trabecular, separação trabecular, número trabecular e os autovalores do tensor de anisotropia (M). A comparação entre os valores dos parâmetros medidos por análises morfométricas 2D e 3D foi realizada pelo teste-t pareado com nível de significância p < 0,05 e por correlação linear de Pearson. Os autovalores da matriz M mostram que a microestrutura trabecular bovina tem uma tendência para a simetria transversalmente isotrópica. Os resultados obtidos mostram que a microtomografia tridimensional por raios-X é uma técnica de grande potencial para caracterização da qualidade óssea gerando bons parâmetros para o diagnóstico de doenças do metabolismo ósseo. / Trebecular bones have a porous microstructure and can be modeled as a linear elastic solid, heterogenous and anisotropic. The x-ray tridimensional microtomography (\'mü\'CT) has been worldwide used for the assessment of trabecular bone in investigations related to bone quality and aimed to the diagnostic of bone metabolic diseases such as osteoporosis. In the literature few investigations have compared the 2D and 3D morphometric analysis of trabecular bone. In this investigation cylindrical trabecular bone samples were harvested from bovine head femur to carry out that comparison by \'mü\'CT. The CT-Analyser software was used to measure in three directions (superior-inferior, lateral-medial and anterior-posterior) several microstructural trabecular parameters such as trabecular thickness, trabecular separation, trabecular number and the eigenvalues of the fabric tensor (M). The comparison between the parameters values measured by 2D and 3D morphometric analysis was performed by the paired-sample t test with a level of significance p < 0,05 and the Pearson\'s linear correlation. The eigenvalues show that the bovine trabecular microstructure has a tendence to transverse isotropy symmetry. The results show that x-ray tridimensional microtomography (\'mü\'CT) is a technique of great potential for characterization of generating good bone quality parameters for the diagnosis of diseases of bone metabolism.

Ratas adultas foram tratadas com 2.5, 5, 10, 20 e 40x a dose fisiológica de triiodotironina (T3) por 10 semanas. Houve redução, dose-dependente, da massa óssea, volume e espessura trabecular (Tb.Th), e espessura de osso cortical. Até a dose de 10xT3, houve aumento na taxa de formação óssea (BFR). Doses maiores de T3 reduziram a BFR, e a reabsorção óssea. Esses dados mostram que, até um certo grau de tireotoxicose, a osteopenia é resultado de aumento da formação e reabsorção ósseas, com predomínio da última. Em graus mais elevados, a osteopenia é causada por redução no remodelamento ósseo, com predomínio da atividade reabsortiva. Em seguida, comparamos os efeitos do T3 e GC-1, um tireomimético seletivo pelo receptor b de T3 (TRb), no osso de camundongos fêmeas adultas. Na tíbia, o T3 reduziu a resistência, rigidez e resiliência, enquanto o GC-1 aumentou esses parâmetros e a Tb.Th, o que mostra que o GC-1 melhora a qualidade óssea. Considerando-se a seletividade do GC-1 pelo TRb, esses achados sugerem que o TRb medeia predominantemente ações positivas do T3 no osso. / Adult rats were treated with 2.5, 5, 10, 20 and 40x the physiological dose of triiodothyronine (T3) for 10 weeks. There was a dose-dependent reduction in bone mass, trabecular volume and thickness (Tb.Th), and cortical thickness. Up to 10xT3, there was an increase in the bone formation rate (BFR). Higher doses of T3 decreased BFR and bone resorption. These data show that, up to a certain degree of thyrotoxicosis, osteopenia is the result of an increase in bone formation and resorption, with a prevalence of resorption. In more severe thyrotoxicosis, the osteopenia is caused by a reduction in bone remodeling, with a predominance of bone resorption. Then, we compared the effects of T3 and GC-1, a thyromimetic that is selective for T3 receptor b (TRb), on bone of adult female mice. T3 treatment decreased tibial resistance, stiffness and resilience, while GC-1 increase these parameters and Tb.Th, showing that GC-1 improves bone quality. Considering the selectiveness of GC-1 for TRb, these findings suggest that TRb mediates mainly positive actions of T3 in the bone.

One indication of increasing fragility of bone is the accumulation of microscopic cracks, or microdamage, within the bone matrix. Microdamage accumulates in bone of the elderly, when changes in bone material properties and matrix architecture coupled with a decrease in bone repair mechanisms compromise bone integrity. To preserve bone mass and reduce fracture risk, therapeutics such as alendronate are prescribed which increase bone volume fraction by decreasing the rate of bone turnover. However, concerns over adverse effects of prolonged turnover suppression have been reinforced by findings of increased microdamage density with alendronate use. Microdamage formation is not always pathologic, but extensive accumulation of damage can be an indicator of reduced bone quality. The work in this thesis explores the hypothesis that microdamage in bone of lower quality will form more easily and progress more extensively than in bone of higher quality. Microdamage initiation stresses and strains were obtained for trabecular bone from older females, older males, and younger females to determine whether thresholds for damage initiation were lower in older females. Results suggest that the stress threshold for damage initiation in older females may indeed be lower compared with younger females, and that normalized strain thresholds for severe damage formation in older males may be decreased compared with older females. Damage propagation was evaluated as a function of age and sex to determine whether damage in older women progressed more extensively than in younger women or men. Results suggest that bone from older individuals had decreased resistance to crack propagation evidenced by an increased number of severely damaged trabeculae which expanded in area under cyclic loading; however no sex differences were uncovered. Finally, the stress/strain thresholds for damage initiation were investigated in alendronate-treated bone, and results indicate that a decreased stress threshold was needed to initiate damage formation of a linear and severe morphology after one year of treatment. After three years of treatment, however, micromechanical properties recovered, perhaps due to increased matrix mineralization which increased tissue level stiffness.

The study objectives of this thesis were to evaluate the effects of delayed feeding and specific aspects of the Programmed Nutrition (PN) feeding strategy (Alltech, Inc.) on growth performance, carcass characteristics, and skeletal characteristics of commercial broiler chicks through market age, as well as investigate the effects of breed and the PN feeding strategy on early growth and development. When commercial broiler chicks were fed reduced nutrient diets, delayed feeding decreased early growth performance and carcass yield (P<0.05), whereas post-hatch PN conditioning for 72 hours improved early growth performance and alleviated the negative effects of delayed feeding on carcass yield (P<0.05). Through market age, delayed feeding improved Gain: Feed (P<0.05), while PN had the opposite effect. Interactive effects and main effects of delayed feeding and PN were observed for tissue mineral concentration (P<0.05). PN lowered bone ash % (P<0.05) and increased meat oxidation of broiler chicks during storage (P<0.05). PN also had negative effects on early growth performance and bone breaking strength (P<0.05) of various meat-type breeds, but especially for non-commercial, moderate-growing or fast-growing breeds. In conclusion, PN may be suitable for commercial broiler chicks that experience delayed feeding and are fed reduced nutrient diets.