Calcitriol [1α,25(OH)2D3], the hormonally active form of vitamin D3 (D3) is produced in both renal and extrarenal tissues. Our findings demonstrate that physiological doses of UVB radiation at 300 nm induce the conversion of 7-dehydrocholesterol (7-DHC) via preD3 and D3 into calcitriol in the pmol range in epidermal keratinocytes. The hydroxylation of photosynthesized D3 to calcitriol is strongly suppressed by ketoconazole, a known inhibitor of cytochrome P450 mixed function oxidases. The UVB-induced formation of calcitriol in human skin is demonstrable in vivo by the microdialysis technique. These results suggest that human skin is an autonomous source of hormonally active calcitriol. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

In MCF-7 breast tumor cells, ionizing radiation promoted autophagy that was cytoprotective; pharmacological or genetic interference with autophagy induced by radiation resulted in growth suppression and/or cell killing (primarily by apoptosis). The hormonally active form of vitamin D, 1,25D3, also promoted autophagy in irradiated MCF-7 cells, sensitized the cells to radiation and suppressed the proliferative recovery that occurs after radiation alone. 1,25D3 also enhanced radiosensitivity and promoted autophagy in MCF7 cells that overexpress Her-2/neu as well as in p53 mutant Hs578t breast tumor cells. In contrast, 1,25D3 failed to alter radiosensitivity or promote autophagy in the BT474 breast tumor cell line with low-level expression of the vitamin D receptor. Enhancement of MCF-7 cell sensitivity to radiation by 1,25D3 was not attenuated by either a pharmacological or genetic block to autophagy; this was due largely to the promotion of apoptosis via the suppression of protective autophagy that occurs in response to radiation alone. Moreover, pharmacological blockade of autophagy did not sensitize noncancerous MCF10a cells to radiation; conversely, 4T1 mouse mammary tumors were highly sensitive to pharmacological inhibition of autophagy, suggesting selective radiosensitization against cancer cell lines. The current studies are consistent with the premise that while autophagy mediates a cytoprotective function in irradiated breast tumor cells, promotion of autophagy can also confer radiosensitivity by vitamin D (1,25D3). In addition, this work highlights the technical challenge of establishing the potential cytotoxic function of autophagy in an experimental system where the cytoprotective function may be concurrently expressed.

Master of Science / Department of Animal Sciences and Industry / Jim Nelssen / Seven experiments using a total of 3,251 preweaned pigs, nursery pigs, and sows were used to determine the effects of: 1) supplemental vitamin D[subscript]3 on suckling and nursery pig growth, and maternal performance, and 2) high sulfate water, dietary zeolite and humic substance on nursery pig performance. Also, a web-based survey was developed to question pork producers and advisors of the swine industry on their knowledge of feed efficiency. Experiment 1 tested an oral dose of either; none, 40,000 or 80,000 IU vitamin D[subscript]3 given to pigs 24 to 48 h after farrowing. No differences in growth performance or bone mineralization were observed, but vitamin D[subscript]3 supplementation increased serum 25(OH)D[subscript]3 on d 10, 20, and 30, but returned to control values by d 52. Experiments 2 and 3 evaluated an oral dose of vitamin D[subscript]3 to pigs just before weaning, as well as added D[subscript]3 in nursery diets and in drinking water. There were no effects on growth performance; however, serum 25(OH)D[subscript]3 increased with all sources of vitamin D[subscript]3 supplementation. Experiment 4 evaluated if pigs had a preference to 1 of 3 dietary concentrations of vitamin D[subscript]3. Pigs ate less feed from diets containing very high levels of vitamin D[subscript]3 compared to commonly supplemented levels. Experiment 5 evaluated 3 levels of vitamin D[subscript]3 in sow diets. There were no effects on sow productivity, subsequent pig performance, or piglet bone ash content. However, increasing vitamin D[subscript]3 increased sow serum 25(OH)D[subscript]3, milk vitamin D, and pig serum 25(OH)D[subscript]3. Experiment 6 and 7 evaluated the effects of dietary zeolite and humic substances in nursery pigs drinking high sulfate water. Ultimately, pigs drinking high sulfate water had increased fecal moisture content and decreased growth performance, and feed additives evaluated were ineffective in ameliorating these negative effects. Finally, data collected from the feed efficiency survey suggest that there are knowledge gaps about practices that effect feed efficiency. Results from this survey will help extension educators better target specific industry segments with current information and provide more specific areas of future research where lack of information has been identified.

A indústria de alimentos está constantemente desenvolvendo produtos que fornecem, além de nutrientes, benefícios adicionais à saúde, tais como os enriquecidos com vitaminas. A vitamina D3 (colecalciferol) é sintetizada na pele durante a exposição da luz solar, controla a homeostase de cálcio e fósforo, metabolismo ósseo, pressão arterial e reabsorção renal de cálcio. O processo de microencapsulação vem sendo bastante aplicado em alimentos e um dos objetivos principais é o controle da liberação do agente ativo no momento e local desejado. A tecnologia de spray chilling é interessante para a microencapsulação de vitaminas lipossolúveis. O objetivo deste trabalho foi microencapsular vitamina D3, utilizando o método de spray chilling para a produção das micropartículas lipídicas sólidas (MLS). Para produção das MLS utilizou-se gordura vegetal com ponto de fusão em torno de 48 °C como carreador. Três tratamentos foram estabelecidos: sem aditivos (T1), com adição de 1% de cera de abelha (T2) e com 1% de lecitina de soja (T3). As micropartículas foram caracterizadas quanto à morfologia por microscopia eletrônica de varredura, tamanho médio por difração a laser, espectroscopia no infravermelho por transformada de Fourier (FTIR) e foi analisada a estabilidade da vitamina D3 durante o armazenamento a 10 e 25 °C, por meio de quantificações periódicas em cromatografia líquida de alta eficiência (CLAE). As micropartículas obtidas foram esféricas, semelhantes morfologicamente e com distribuição monocaudal de partículas. O tamanho médio das partículas variou em função dos seus ingredientes, sendo que as micropartículas produzidas apenas com vitamina e gordura foram menores em relação às demais (83,0% < 100 &micro;m). A espectroscopia na região do infravermelho (FTIR) demonstrou que não ocorreu interação entre os ingredientes. A estabilidade da vitamina D3 encapsulada foi satisfatória ao longo de 65 dias com valores superiores a 87% para os três tratamentos e a temperatura apresentou influência na estabilidade. As MLS produzidas com cera apresentaram melhores resultados de estabilidade de vitamina D3 com valores de 90,18 ± 2,23 % após 65 dias de estocagem. Esses resultados são promissores e demostram a viabilidade da técnica de spray chilling na produção de MLS carregadas de vitamina D3, possibilitando uma futura aplicação em alimentos. / The food industry is constantly developing products that provide, in addition to nutrients, additional health benefits such as enriched food with vitamins. Vitamin D3 (cholecalciferol), which is synthesized in the skin during exposure of sunlight, controls the homeostasis of calcium and phosphorus, bone metabolism, blood pressure and renal reabsorption of calcium. The microencapsulation process has been widely applied in food and is a key objective to control the release of active agents at specific time and desired location. The spray chilling technology is interesting for microencapsulation of fat-soluble vitamins. The objective of this work was microencapsulating vitamin D3 using the spray chilling method for the production of solid lipid microparticles (SLM). For the production of the SLM it was used vegetable fat with melting point around at 48 °C as a carrier. Three treatments were established: no additives (T1), 1% of beeswax (T2), and 1% soybean lecithin (T3). The morphology of microparticles was characterized by scanning electron microscopy, laser diffraction (average size) and Fourier transform infrared spectroscopy (FTIR). Additionally, vitamin D3 stability was examined during storage at 10 and 25 °C, through periodic measurements by High-performance liquid chromatography (HLPC). The microparticles obtained were spherical with similar morphology and unimodal size distribution. The average particle size varied according to composition wherein microparticles produced with vitamin and fat were lower than other (83.0% of particles smaller than 100 &micro;m). Spectroscopy in the infrared (FTIR) showed that there was no interaction between the components. The stability of vitamin D3 encapsulated was satisfactory over 65 days with values greater than 87% for the three treatments and temperature have any influence on the stability. The SLM produced with wax showed better stability for vitamin D3 with values of 90.18 ± 2.23% after 65 days of storage. These results are promising and demonstrate the feasibility of spray chilling technique in the production of SLM loaded with vitamin D3, allowing future application in foods.

Sufficient vitamin D is important for overall health. However, cutaneous production of vitamin D is limited by season and little vitamin D naturally occurs in food. Therefore, vitamin D supplementation is necessary. Vitamin D is available in pharmacies as vitamin D2 and vitamin D3, and can also be obtained by irradiating mushrooms to produce vitamin D2. Types of vitamin D supplementation were tested to compare their ability to increase vitamin D status and their effect on broad gene expression in human white blood cells. 2000 IU of vitamin D2, vitamin D3 or vitamin D2 in irradiated mushroom powder were given to subjects daily for twelve weeks. A placebo mushroom powder group was included in the second half of the study. To determine the effect of different supplementation on vitamin D status, whole blood was obtained weekly and serum was assayed for 25(OH)D2 and 25(OH)D3. Change in total 25(OH)D was determined from baseline to twelve weeks; 25(OH)D levels in the placebo mushroom powder group did not change significantly at 1.8 ± 1.8 ng/ml (9.6 ± 9.6%), the mushroom D2 group increased by 10.9 ± 10.2 ng/ml (53.2 ± 49.8%), the supplemental D2 group increased by 11.8 ± 7.4 ng/ml (60.2 ± 37.8%) and the supplemental D3 group increased by 21.7 ± 8.9 ng/ml (114.2 ± 46.8%). As expected, the total active form of vitamin D (1,25-dihydroxyvitamin D) showed no change in all groups because of its tight regulation. To determine the potential influence of vitamin D supplementation on differential gene expression in the immune system, white blood cells were isolated from whole blood samples taken before and after supplementation. RNA was extracted, and microarray assays were performed. Gene Set Enrichment Analysis was completed to determine strongly influenced pathways. However, due to the numerous variables between halves of the study, gene expression data was treated as separate studies. Even so, pathways involving RNA activation and degradation were significant between mushroom powder and mushroom D2 supplementation in both halves of the study, indicating the influence of compounds in mushrooms on RNA metabolism pathways. Supplemental vitamin D2 affected gene expression, though only two pathways showed significant change. Supplemental vitamin D3 was found to influence pathways involved in replication, transcription, and translation in both halves of the study. In conclusion, mushrooms powder, mushroom vitamin D2, supplemental vitamin D2, and supplemental vitamin D3 all influence differential gene expression in human white blood cells.

Bone formation and remodeling require continuous generation of osteoprogenitors from bone marrow stromal cells (MSC), which are regulated by local growth factors and hormones with putative roles in mesenchymal proliferation and differentiation. Hepatocyte growth factor (HGF) and its receptor c-Met are widely expressed in MSC and are thought to play a key role in the interactions between cells. 1,25-dihydroxyvitamin D (1,25OHD) is the most active metabolite of vitamin D. 1,25OHD binds to its nuclear/membrane vitamin D receptor (VDR) and generates appropriate biological responses. The purpose of this study was to investigate the regulation of proliferation and differentiation by HGF in human bone marrow-derived stromal cells (hMSC). We examined the impact of HGF on hMSC cell-cycle regulation and the combination effects of HGF and 1,25OHD on hMSC osteogenic differentiation to enhance our knowledge of hMSC regulation. hMSC isolated from bone marrow were plated and grown in DMEM supplemented with 3% FBS incubated at 37C with 5% CO2 in air. HGF treatment of hMSCs reduced the rate of cell proliferation and this result was not due to apoptosis or cell senescence. Real-time RT-PCR and Western blot analysis showed increased gene and protein expression of the cell-cycle inhibitors p53, p21, and p27 after HGF treatment. These results appear to be specific because HGF did not significantly alter the gene expression level of other cell-cycle mediators such as RB, cyclin D1, CDK2, CDK4, or CDK6. Transfection of siRNA specific for cMet, the HGF receptor, eliminated the HGF anti-proliferation effect. cMet siRNA also eliminated the increase in p53, p21, and p27, further supporting a role for these cell-cycle inhibitors in HGF¡¯s regulation of hMSC. These results suggest that treatment of hMSC with HGF slows cell proliferation by increasing the expression of p53, p21, and p27. The reduced rate of cell proliferation did not appear to be due to cell differentiation, because treatment of hMSC with HGF alone did not induce cell differentiation. However, HGF in combination with a known osteogenic differentiation activator, 1,25OHD, significantly increased cell maturation/differentiation compared to 1,25D alone, as indicated by an increase in osteocalcin mRNA (a marker for osteogenic differentiation). Whereas HGF had no effect on 1,25OHD synthesis per se, HGF did induce 1,26OHD receptor (VDR) gene expression. HGF up-regulated the expression of the p63 gene, a member of the p53 family. Knocking down the p63 gene reduced the HGF effect on VDR expression and eliminated the HGF-induced up-regulation of the osteogenic differentiation markers osteopontin (OPN) and bone sialoprotein (BSP). Moreover, the ChIP assay shows that p63 was able to bind to the VDR promoter, possibly explaining the mechanism of p63-mediated VDR up-regulation. These results indicate that HGF can also induce hMSC osteogenic differentiation when combined with 1,25OHD by up-regulating 1,25OHD receptor VDR expression.

Background: The interest of vitamin D has increased in the last years. That is because there is so many possible positive effects of vitamin D and also because many individuals has vitamin D deficiency. Modern man spends much time indoors which leads to lower levels of vitamin D. People who have emigrated from a sunny climate to a Nordic climate often gets a deficiency due to a more pigmented skin which requires a larger amount of UVB to get an adequate synthesis of vitamin D. Aim: The aim with this study is to compare and evaluate how similar the instrument mini VIDAS measures 25(OH)D total against the current existing method cobas e 602. A discussion about if 25(OH)D total has a place in primary health care is included in the study. Method: The comparison was based on 39 samples. The samples was analyzed on cobas e 602 and mini VIDAS. A precision test was performed. External controls from DEQAS was also included in the study. The results have been presented with simple linear regression analysis, mean value, SD and CV. Results: The comparison between cobas e 602 and mini VIDAS gave a coefficient of determination of 81,34 %. mini VIDAS was closest to the external controls target values. Conclusion: There is no obvious conclusions about if mini VIDAS fulfills the requirement to be introduced to primary health care. The coefficient of determination of 81,34 % should be at least 95 %. However is mini VIDAS closer to the external controls target values then cobas e 602. There is factors that implies that 25(OH)D total has a place in primary health care with regards to demand, use and because many individuals has vitamin D deficiency. The instrument is also user-friendly to a primary health care laboratory. / Bakgrund: Intresset för vitamin D har ökat de senare åren. Det beror dels på att det finns många eventuella positiva effekter av vitamin D och dels på att många individer har brist på vitamin D. Nutidens människa spenderar mycket tid inomhus vilket leder till lägre nivåer av vitamin D. Personer som har utvandrat från ett soligt klimat till nordiskt klimat får ofta brist på grund av en mer pigmenterad hud som behöver större mängd UVB för att få en adekvat syntes av vitamin D. Syfte: Syftet med den här studien är att jämföra och utvärdera hur lika det patientnära instrumentet mini VIDAS mäter 25(OH)D total mot befintlig metod cobas e 602. Diskussion om analysen 25(OH)D total har en plats i primärvården ingår även i studien. Metod: Jämförelsen baserades på 39 st prover. Proven analyserades på cobas e 602 och mini VIDAS. Ett precisionsförsök gjordes. Externkontroller från DEQAS inkluderades även i studien. Resultaten har presenterats genom enkel linjär regressionsanalys, medelvärde, SD och CV. Resultat: Jämförelsen mellan cobas e 602 och mini VIDAS gav en förklaringsgrad på 81,43 %. mini VIDAS var närmst externkontrollernas målvärden. Slutsats: Det går inte att dra självklara slutsatser ifall mini VIDAS uppfyller kraven att införas i primärvården. Förklaringsgraden som är på 81,43 % bör vara minst 95 %. Däremot överensstämmer mini VIDAS med externkontrollerna bättre än cobas e 602. Det finns faktorer som tyder på att analysen 25(OH)D har en plats i primärvården med avseende på efterfrågan, användningsområde och antal individer med brist. Instrumentet är dessutom användarvänligt för ett primärvårdslaboratorium.

7-Dehydrocholesterol (7-DHC) is the substrate of 7-dehydrocholesterol reductase (DHCR7) in the cholesterol synthesis pathway. Keratinocytes in human skin possess the enzymes necessary for cholesterol synthesis but are also responsible for vitamin D3 synthesis from 7-DHC by exposure to UVB irradiation. It has been well established that DHCR7 is regulated by the SREBP pathway in the regulation of cholesterol synthesis, but little is known about the regulation of DHCR7 by the vitamin D pathway. In this study, the regulation of DHCR7 activity by vitamin D was explored. Treatment of adult human epidermal keratinocyte (HEKa) cells with vitamin D3 resulted in a rapid decrease in DHCR7 activity which was not due to changes in the amount of enzyme present. This suppression of activity was observed only in HEKa cells, a primary cell line cultured from normal human skin, and not in an immortalized skin cell line (HaCaT cells) nor in two liver-derived hepatoma cell lines. Because vitamin D3 treatment of HEKa cells did not change the content of lanosterol nor 7-DHC, these results suggest that vitamin D3 rapidly down-regulates the entire cholesterolgenesis pathway, presumably at a very early step in the pathway. 25-Hydroxyvitamin D3, the first metabolite and circulating form of vitamin D3, had a lesser effect on DHCR7 activity, while 1,25-dihydroxyvitamin D3, the activated form of the vitamin, had no effect on DHCR7, indicating that the vitamin D receptor is not involved. The decrease in DHCR7 activity was due neither to the dephosphorylation of the enzyme, an established mechanism of inactivation, nor to direct inhibition by vitamin D3. Vitamin D3 markedly inhibited proliferation and induced differentiation of HEKa cells, suggesting a possible role for hedgehog signaling in the decrease in DHCR7 activity.

Epidemiological evidence from season of birth and migrant studies has led to the proposal that developmental vitamin D3 (DVD) deficiency may be a risk factor for schizophrenia. Concurrently, there has been recent intense interest in vitamin D3 as a modifying factor in the development of immune responses. However, the effects of DVD deficiency on immune function remains unknown. Thus, a model of DVD deficiency has been developed in Sprague-Dawley rats. Briefly, female rats were maintained on a vitamin D3 deficient diet prior to and during gestation. At birth dams were returned to a vitamin D3 replete diet. Post-weaning their offspring, the DVD-deficient rats, were maintained on a vitamin D3 replete diet. Therefore, this model represents a transient, prenatal vitamin D3 deficiency. A number of structural and cellular changes have been described in the DVD-deficient rat brain, including ventriculomegaly, decreased growth factor expression, and increased rates of mitosis. These changes are correlated with altered adult behaviour in the DVD-deficient rat, including a locomotor sensitivity to novelty. This thesis will focus on extending these findings and characterising immune function in the DVD-deficient rat. Vitamin D3 can affect cellular differentiation and is anti-proliferative and pro-apoptotic in many tissues including the brain. The effect of DVD deficiency on brain development has been restricted to neuronal cells in vivo and in vitro. However, the effect of this exposure on glial cell maturation and phenotype was unknown. The experiments reported in this thesis demonstrated that primary cortical glial cell cultures from DVD-deficient rat neonates displayed a similar phenotype and maturational status compared with cells from control rats. Learning and memory was examined in this model by exploring the phenomenon of latent inhibition. DVD-deficient rats displayed normal latent inhibition, however, they exhibited a subtle performance acquisition deficit during the early stages of the conditioned avoidance learning task. Extended handling and pre-exposure were able to ameliorate this deficit, though with this treatment normal latent inhibition was also abolished in both control and DVD-deficient rats. Ultrasonic vocalization and nociceptive threshold testing confirmed that alterations in peripheral sensation could not explain this performance acquisition deficit. The results suggested that anxiety or attentional mechanisms may have contributed to this rate of learning deficit. Finally, as vitamin D3 is a powerful immunoregulator, there is the potential for a transient DVD deficiency to induce a persistent alteration in the development and function of the immune system. This hypothesis was supported by findings that showed DVD deficiency resulted in a primed immune system, as indicated by an enlarged spleen, thymus and peripheral lymph tissue as well as increased pro-inflammatory cytokine production in response to an in vitro stimulation. However, these findings did not lead to an alteration in cell mediated immune response in vivo. The results from the research reported in this thesis indicate that a transient, prenatal vitamin D3 deficiency had a subtle yet significant effect on the immune system and behaviour of the adult rat. These findings add further weight to the body of evidence that link prenatal vitamin D3 status to various adverse health outcomes. The DVD-deficient rat model is an integral step in understanding prenatal vitamin D3 deficiency as a potential environment risk factor in the development of immune and psychiatric disorders.

Submitted by Jordan (jordanbiblio@gmail.com) on 2017-02-20T16:55:45Z No. of bitstreams: 1 DISS_2015_Laura Caroline Almeida Branco Drosghic.pdf: 1024901 bytes, checksum: 769c0ac66d67204071d5db39a72654cd (MD5) / Made available in DSpace on 2017-02-20T16:55:45Z (GMT). No. of bitstreams: 1 DISS_2015_Laura Caroline Almeida Branco Drosghic.pdf: 1024901 bytes, checksum: 769c0ac66d67204071d5db39a72654cd (MD5) Previous issue date: 2015-03-30 / CAPES / A produção de aves sempre buscou maximizar a eficiência produtiva de frangos de corte, mas associadas a essas melhorias surgiram características indesejadas. Os transtornos ósseos são ocasionados pela rápida deposição de tecido animal, ao mesmo tempo em que o desenvolvimento ósseo continuou com crescimento normal. Isso fez com que houvesse prejuízo à capacidade de deslocamento, ao bem estar e, consequentemente ao desenvolvimento destas. Surgiram inúmeros programas nutricionais como uso da vitamina D e seus metabólitos que participam na regulação da homeostase de cálcio e fósforo por um mecanismo que aumenta a captação intestinal destes, diminuindo as perdas renais e estimulando a reabsorção óssea. O presente estudo teve como objetivo utilizar a Solanum glaucophyllum como fonte suplementar de 1,25-dihidroxicolecalciferol nas características ósseas de frangos de corte. Para tal, foram desenvolvidos dois ensaios. No ensaio 1 utilizando frango de corte fêmea e no 2 frango de corte macho. Avaliou-se a utilização suplementar de Solanum glaucophyllum como fonte de vitamina D3 ativa. Foram utilizados um total de 1.296 frangos de corte da marca comercial Cobb® em delineamento em blocos ao acaso com 6 tratamentos e 6 repetições com 18 aves por unidade experimental. Os tratamentos consistiram na suplementação de 0,0; 0,5; 1,0; 1,5; 2,0 e 2,5 μg de vitamina D3 ativa/kg de ração. Aos 21 e 35 dias de idade as aves foram pesadas e um frango por repetição com peso médio do lote foi abatido para se obter os tibiotarsos. As variáveis analisadas foram os pesos in natura, seco e desengordurado, comprimento, diâmetros, resistência óssea, índice Seedor, teores de proteínas colagenosas e não colagenosas, minerais e cinzas. No ensaio 1, aos 35 dias de idade, a composição orgânica e mineral dos ossos (peso in natura, proteínas não colagenosas, cinzas) foi afetada pelo fornecimento suplementar de 2,5 μg de vitamina D3 na forma de 1,25(OH)2D3. Já no ensaio 2 as características ósseas foram afetadas pela suplementação de vitamina D3 ativa nas rações. Recomenda-se até 1,5 μg de vitamina D3 ativa nas rações para frangos de corte machos de 8 a 35 dias de idade. / Poultry farming has always aimed to maximize production efficiency in broilers, but unwanted characteristics came together with these improvements. Bone disorders are caused by rapid deposition of animal tissue, while the bone development continues its normal growth. This meant the movement capacity was damaged, as the welfare and consequently the development of these birds. Several nutritional programs have been emerged, such as the use of vitamin D and its metabolites involved in regulating calcium and phosphorous homeostasis by a mechanism which enhances their intestinal uptake, reducing renal losses and stimulating bone resorption. With the present study, it was aimed to use Solanum glaucophyllum as a supplementary source of 1,25-dihydroxycholecalciferol in bone characteristics of broiler chickens. To this end, two assays were conducted. In the assay 1, they were used female broilers, and in the assay 2, male broilers. It was evaluated the additional use of Solanum glaucophyllum as a source of active vitamin D3. A total of 1,296 broiler chickens of Cobb® trademark were used in a randomized block design, with 6 treatments and 6 repetitions with 18 birds. The treatments consisted of supplementation of 0.0; 0.5; 1.0; 1.5; 2.0 and 2.5 μg of active vitamin D3 / kg of feed. At 21 and 35 days of age, the birds were weighed and one chicken by repetition, representing the average weight of the lot, was slaughtered in order to get the tibia tarsus. The analyzed variables included fresh, dry and degreased weights, length, diameter, bone resistance, Seedor index, collagenous and non-collagenous protein contents, minerals and ashes. In the assay 1, at 35 days of age , the organic and mineral composition of the bones ( fresh weight, non- collagenous proteins and ashes) were affected by the additional provision of 2.5 μg of vitamin D3 in the 1,25 (OH ) 2D3 form. In the assay 2, bone characteristics were affected by active vitamin D3 supplementation in the diet. It is recommended the provision of 1.5 μg of active vitamin D3 in feed for broilers from 8 to 35 days old.