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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Effect of diet modification on human fecal mutagenic activity

Bell, Penelope Anne January 1982 (has links)
Dietary factors have been implicated in the etiology of colon cancer. The salient components of high-risk diets are thought to be high intakes of meat, especially beef, and fat, especially animal fat, and low intakes of fiber. Low-risk diets are thought to be high in fiber, and low in meat and animal fat. The present study examines the effects of short-term consumption of diets hypothesized to increase or decrease the risk for colon cancer on mutagenic activity of feces. Whether the fecal mutagens responsible for the mutagenic activity observed in the study are directly involved in the etiology of colon cancer is not known. However, most known mutagens are potentially carcinogenic, and fecal mutagenic activity may be an indicator of risk for colon cancer. Six healthy adult subjects consumed the following diets in sequence a baseline diet for one week, a low-risk lacto-ovo vegetarian, high fiber diet for two weeks, and a high-risk, high meat, low fiber diet for two weeks. Quantitative daily food intake records were kept, and daily bowel habits were recorded. Fecal samples were collected at the end of each diet period. Analyses were performed of the diets for food and nutrient intake, and of feces for percent dry weight and pH. Mutagenic activity of the fecal samples was assayed using the fluctuation test for mutagens. The subjects' habitual diets, although omnivorous, were found to closely resemble a low-risk diet pattern. Analysis of the vegetarian and high meat diets confirmed that the subjects had consumed foods which respectively represented the components of high-risk and low-risk diets. The overall fecal mutagenic activity obtained with samples on the high meat diet was higher than with the vegetarian or baseline diets using Salmonella typhimurium TA 98 and TA 100. The trend towards higher mutagenicity on the high meat diet over the vegetarian diet was consistent for all six subjects using TA 100, and for five of the six using TA 98. The vegetarian and baseline diets resulted in similar overall mutagenic activity. Analysis of the fecal sample parameters using the Kruskal-Wallis one-way analysis of variance showed no significant differences among fecal samples from the three diet periods with respect to wet weight, dry weight, percent dry weight, pH or number of daily bowel movements. However, a sign-test analysis showed a significant trend (p<0.05) towards fewer bowel movements on the high meat diet than on the vegetarian diet. There were significant differences among subjects for all of the fecal sample parameters (p<0.01 or p<0.001). Spearman rank correlations were significantly positive between mutagenic activities using bacterial strains Salmonella typhimurium TA 98 and TA 100 for the baseline diet (p<0.01) and the vegetarian diet (p<0.05). There were also significant positive correlations (p<0.001) between pH and fecal mutagenicity on the high meat' diet using tester strain TA 100, and between wet weight and dry weight. The results of this study indicate that the overall mutagenic activity of human feces can be increased over a period of two weeks by the consumption of a diet high in meat and low in fiber, which is considered to be a high-risk diet for colon cancer. / Land and Food Systems, Faculty of / Graduate
112

Mutagens in feces of vegetarians and non-vegetarians

Bergstrom, Danielle Cantin January 1982 (has links)
Mutagens in feces have been suggested to be an indicator for risk of colon cancer. Groups consuming vegetarian diets are known to have lower mortality from colon cancer. The purpose of this study was to assess mutagenic activity in feces of persons habitually consuming vegetarian or non-vegetarian diets and to try to identify dietary factors or other health habits which contributed to fecal mutagenicity. Eleven strict vegetarians, six ovo-lacto vegetarians and twelve non-vegetarians, all from the Greater Vancouver area, participated in this study. Data on certain demographic variables and health habits, as well as dietary intake (food frequency and food records), were taken. One fecal sample was collected from each subject for the study. Aqueous extracts of the feces were prepared and analyzed for mutagens using the fluctuation test with Salmonella typhimurium TA100 and TA98. Levels of mutagenicity on each organism were then statistically correlated with frequency of consumption of food groups, nutrient intake, demographic data and health habits. Ovo-lacto vegetarians and strict vegetarians, as groups, had significantly lower levels of fecal mutagens than non-vegetarians in the TA100 assay. With TA98, only the strict vegetarians had lower levels of mutagens compared to the non-vegetarians. The presence of several different mutagenic compounds was indicated. Significant negative correlations were found with mutagenicity on TA98 for all subjects with the following dietary variables: fruits and juices, fiber and iron. Similar negative correlations were found for total carbohydrate and Southgate fiber intakes and mutagenicity on TA100. Within the group of non-vegetarians, there were negative correlations with mutagenicity on TA98 and total protein and with mutagenicity on TA100 and calcium. With the demographic variables and health habits, no clear pattern emerged to indicate factors which would predict lowered mutagenicity for all subjects. It is concluded that vegetarians have lower levels of fecal mutagenicity and that several dietary factors are likely to contribute to this phenomenon. / Land and Food Systems, Faculty of / Graduate
113

Comparative Analysis of Survival and Decay of Fecal Indicator Bacteria in Bovine Feces and Freshwater Microcosms

Tariq, Reem 01 May 2018 (has links) (PDF)
Agricultural runoff can carry FIB that can pollute surface waters through the soil matrix. This study was designed to inspect the impact of temperature and matrix on the survival of FIB. The FIB were routinely enumerated over an 18-day period from fecal samples and freshwater microcosms maintained at 4oC, 22oC, and 35oC. It was found that the FIB studied underwent a primary growth of up to 1-log10 to 3-log10, highlighting the weakness of conventional FIB as indicators of pathogen contamination. The concentrations of FIB in the water phase were found to be significantly greater than those observed in the fecal phase in all FIB and their associated survivals were found to be significantly different too. Similarly, temperature was also found to be a significant factor for the survival of FIB. While the differences in the survival were significant, there was a slight variation in the patterns regarding the differences.
114

Caracterização molecular de isolados de Giardia spp. provinientes de amostras fecais de origem humana do Hospital Universitário - USP - São Paulo, pela análise de fragmentos do gene codificador da beta-giardina (bg). / Molecullar charaterization of Giardia spp. from human faecal samples of Hospital Universitário USP São Paulo, by analisys of fragments from code gene da beta-giardina (bg).

Santos, Valdir Azevedo dos 13 December 2011 (has links)
A giardíase é uma doença entérica de alta prevalência particularmente nos países em desenvolvimento. Diferentes espécies foram descritas em função de seus hospedeiros. A G. duodenalis é a espécie que parasito não só o homem, mas também animais domésticos e silvestres. Recentemente, com a aplicação de técnicas moleculares, foi possível identificar sete diferentes agrupamentos sendo que cada um deles tem predileção por determinadas espécies de hospedeiro. Essa discriminação não é possível por meio da microscopia. A identificação do(s) agrupamento(s) presente(s) na população de determinada região pode ser de grande importância na elaboração de políticas de saúde pública já que revela o perfil de transmissão desse protozoário. Este estudo teve por objetivos verificar o grau de positividade de enteroparasitos, a contribuição de cada um deles nesse índice e o genótipo dos cistos de G. duodenalis presentes em amostras de fezes de indivíduos atendidos no Hospital Universitário da Universidade de São Paulo. Foram analisadas 6717 amostras com positividade para algum enteroparasito de 12,5%, sendo S.stercoralis e G. duodenais respectivamente o helminto e protozoário patogênico mais frequentes. A maioria dos casos de G. duodenalis genotipada era dos agrupamentos AII e B. / Giardiasis is a very prevalent enteric disease occurring mainly in developing countries. Different species have been described concerning their hosts. G. duodenalis parasites not only men but also domestic and wild animals. Recently molecular techniques have been used to identify seven different assemblages which parasites specific hosts. The microscopic analysis do not allows that discrimination. It can be useful to know the assemblage profile of specific population in order to provide some important information to built public health politicies once it reveals the transmition of the protozoan The aim of this study was to verify the enteroparasites infection degree, the individual contribution of each one in this picture and to genotyping G. duodenalis cysts from human faecal samples of individuals from University Hospital from Universty of São Paulo. So, 6717 faecal samples were analysed and 12,5% were positive for some enteroparasite and S.stercoralis and G. duodenais were the helminth e pathogenic protozoan more frequently found. Most of the cases of G. duodenalis were from the assemblages AII and B.
115

Caracterização molecular de isolados de Giardia spp. provinientes de amostras fecais de origem humana do Hospital Universitário - USP - São Paulo, pela análise de fragmentos do gene codificador da beta-giardina (bg). / Molecullar charaterization of Giardia spp. from human faecal samples of Hospital Universitário USP São Paulo, by analisys of fragments from code gene da beta-giardina (bg).

Valdir Azevedo dos Santos 13 December 2011 (has links)
A giardíase é uma doença entérica de alta prevalência particularmente nos países em desenvolvimento. Diferentes espécies foram descritas em função de seus hospedeiros. A G. duodenalis é a espécie que parasito não só o homem, mas também animais domésticos e silvestres. Recentemente, com a aplicação de técnicas moleculares, foi possível identificar sete diferentes agrupamentos sendo que cada um deles tem predileção por determinadas espécies de hospedeiro. Essa discriminação não é possível por meio da microscopia. A identificação do(s) agrupamento(s) presente(s) na população de determinada região pode ser de grande importância na elaboração de políticas de saúde pública já que revela o perfil de transmissão desse protozoário. Este estudo teve por objetivos verificar o grau de positividade de enteroparasitos, a contribuição de cada um deles nesse índice e o genótipo dos cistos de G. duodenalis presentes em amostras de fezes de indivíduos atendidos no Hospital Universitário da Universidade de São Paulo. Foram analisadas 6717 amostras com positividade para algum enteroparasito de 12,5%, sendo S.stercoralis e G. duodenais respectivamente o helminto e protozoário patogênico mais frequentes. A maioria dos casos de G. duodenalis genotipada era dos agrupamentos AII e B. / Giardiasis is a very prevalent enteric disease occurring mainly in developing countries. Different species have been described concerning their hosts. G. duodenalis parasites not only men but also domestic and wild animals. Recently molecular techniques have been used to identify seven different assemblages which parasites specific hosts. The microscopic analysis do not allows that discrimination. It can be useful to know the assemblage profile of specific population in order to provide some important information to built public health politicies once it reveals the transmition of the protozoan The aim of this study was to verify the enteroparasites infection degree, the individual contribution of each one in this picture and to genotyping G. duodenalis cysts from human faecal samples of individuals from University Hospital from Universty of São Paulo. So, 6717 faecal samples were analysed and 12,5% were positive for some enteroparasite and S.stercoralis and G. duodenais were the helminth e pathogenic protozoan more frequently found. Most of the cases of G. duodenalis were from the assemblages AII and B.
116

The Relationship Between Microbiota, Diet, and Energy Production in the Alpaca

Carroll, Courtney 01 August 2017 (has links)
The alpaca is a small South American camelid (SAC) that is an important production animal in Peru, especially among the highly impoverished communities of the high Andes, and raised for its fiber and meat. Alpacas are highly reliant on the microbes within their digestive tracts to digest the plant material they consume; volatile fatty acids (VFAs) are released as a byproduct of this microbial fermentation and used as a major source of energy by the alpaca. To explore optimal parameters for alpaca microbiome analysis, performed 16S rRNA gene surveys on alpaca C1 and fecal samples that had been extracted using one of three different DNA extraction methods (PowerFecal® DNA Isolation Kit (MO BIO); ZR Fecal DNA MiniPrep™ (Zymo); and a non-commercial extraction method called salting out) and amplified using one of two different polymerase enzyme mixes (AccuPrime™ Pfx SuperMix and 5 PRIME HotMasterMix). We found that choice of polymerase enzyme had a profound effect on the recovered microbiome, with the majority of 5 PRIME-amplified fecal samples failing to amplify. Extraction method had an effect on the recovered microbiome of fecal samples (but not C1 samples), with samples extracted using the MO BIO kit and the salting out method recovering different communities. The Zymo extraction kit returned microbial communities comparable to each of the other extraction methods. These results suggested that the AccuPrime enzyme and either the MO BIO or Zymo kits were optimal for alpaca gut microbiome analysis. We also performed two 16S rRNA gene surveys, the first from alpacas fed either a grass hay (GH) or alfalfa hay (AH) diet, and the second a C1 survey of alpacas fed two-week periods of mixed grass hay plus one of four supplements. We discovered body site and diet effects on the microbiota of alpacas fed either the GH or AH diet, with samples grouping by general body site (C1, small intestine, and distal intestine) and diet. However, we found no significant effect on the C1 microbiome of alpacas administered grain supplements. To study how energy extraction related to the microbiome, we correlated OTUs from GH/AH-fed alpaca with C1 VFA abundances. We discovered no significant correlations, and a 16S survey of low body condition (LBC) and good body condition (GBC) alpacas showed no difference in C1 microbial communities. We concluded that the microbiota of the alpaca digestive tract follow trends seen in microbiome studies of ruminants, but found no evidence of a relationship between body condition, energy extraction, and the C1 microbiome in alpacas.
117

ニホンザルの洞窟利用と化石化過程 (予案)

Senokuchi, Yoshitaka, Abe, Yuji, Kashiwagi, Kenji, 瀬之口, 祥孝, 阿部, 勇治, 柏木, 健司 03 1900 (has links)
名古屋大学年代測定総合研究センターシンポジウム報告
118

Early detection of colorectal cancer /

Olsson, Louise, January 2004 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.
119

Comparação de técnicas coproparasitológicas para o diagnóstico de protozoários e helmintos intestinais de importância médica

Ribeiro, Steveen Rios 18 March 2011 (has links)
Made available in DSpace on 2016-12-23T13:56:08Z (GMT). No. of bitstreams: 1 Dissertacao de Steveen Rios Ribeiro.pdf: 4201771 bytes, checksum: 56acf4462c81abd472caf4c84eb8dd80 (MD5) Previous issue date: 2011-03-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Introduction. The diagnosis of intestinal parasites can be accomplished by different techniques of parasitological stool examinations (EPF), each with advantages and disadvantages according to the parasite to be identified. Aims. The aim of the present study was to compare traditional techniques of EPF (Spontaneous Sedimentation in Tube, Kato-Katz and Baermann-Moraes) with more sophisticated techniques (stool culture, detection of coproantigen and PCR) and two commercially available kits in Brazil (Paratest® and TF-Test ®). Material and Methods. Faecal samples from 160 individuals, a total of 356 samples, were analyzed by traditional techniques of EPF (Spontaneous Sedimentation in Tube, Kato-Katz and Baermann-Moraes), culture of fresh faeces and sediment of feces, detection of coproantigen, PCR for detection and differentiation of the complex Entamoeba histolytica/Entamoeba dispar and two commercially available kits in Brazil (Paratest® and TF-Test®). Results. The technique of Spontaneous Sedimentation in Tube had better sensitivity (80.43% of occurrences) for the diagnosis of eggs and larvae of helminths in feces. The Kato-Katz was better for identification of eggs of S. mansoni (100% of cases). The method of Baermann-Moraes found larvae of Strongyloides stercoralis detected similarly to spontaneous sedimentation. For the diagnosis of G. lamblia, C. parvum and E. histolytica, kits for detection of coproantigen showed better sensitivity. The stool culture showed excellent results for identification of Blastocystis hominis. The PCR was able to identify and differentiate the amoebas of the complex E. histolytica/ E. dispar. Both commercial kits showed lower sensitivity than the spontaneous sedimentation for the diagnosis of helminths, but Paratest® was the technique that has shown better sensitivity for protozoa (66.66% of cases). Conclusion. For the diagnosis of helminths, the Spontaneous Sedimentation Method in Tube showed better results, except for detection of eggs of S. mansoni, best detected by Kato-Katz. For the diagnosis of G. lamblia, E. histolytica and Cryptosporidium parvum, kits for detection of coproantigen were better. However, the kit for the diagnosis of E. histolytica does not detect the species E. dispar, best identified by the ABSTRACT PCR. The commercial kits (Paratest® and TF-Test ®), while facilitating the collection and preservation of the sample, have lower sensitivity than the Spontaneous Sedimentation method in Tube / O diagnóstico de parasitoses intestinais pode ser realizado por diferentes técnicas de Exame Parasitológico de Fezes (EPF), cada uma com vantagens e desvantagens de acordo com o parasito a ser identificado. Objetivos. Comparar técnicas tradicionais de EPF (Sedimentação Espontânea em Tubo, Kato-Katz e Baermann-Moraes) com técnicas mais sofisticadas (cultura de fezes, detecção de coproantígenos e PCR) e dois kits comerciais disponíveis no Brasil (Paratest® e TF-Test®). Material e Métodos. Amostras de fezes de 160 indivíduos, totalizando 356 amostras, foram analisadas por técnicas tradicionais de EPF (Sedimentação Espontânea em Tubo, Kato-Katz e Baermann-Moraes), cultura de fezes frescas e de sedimento de fezes, técnicas para detecção de coproantígenos nas fezes, PCR para detecção e diferenciação de Entamoeba do complexo histolytica/dispar e dois kits comerciais disponíveis no Brasil (Paratest® e TF-Test®). Resultados. A técnica de Sedimentação Espontânea em Tubo demonstrou melhor sensibilidade (80,43% das o corrências) para o diagnóstico de ovos e larvas de helmintos nas fezes. O Kato-Katz foi melhor para identificação de ovos do S. mansoni (100% das ocorrências). Já o método de Baermann-Moraes detectou larvas de Strongyloides stercoralis de modo semelhante à sedimentação espontânea. Para o diagnóstico de G. lamblia, C. parvum e E. histolytica, os kits de coproantígenos demonstraram melhor sensibilidade. A cultura de fezes mostrou excelentes resultados para identificação de Blastocystis hominis. O PCR conseguiu identificar e diferenciar as amebas do complexo E. histolytica/E. dispar. Os dois kits comerciais apresentaram sensibilidade mais baixa do que a Sedimentação Espontânea em Tubo para o diagnóstico de helmintos, mas o Paratest® foi a técnica que demonstrou melhor sensibilidade para protozoários (66,66% das ocorrências). Conclusão. Para o diagnóstico de helmintos o método de Sedimentação Espontânea em Tubo foi o que mostrou melhor resultado, exceto para detecção de ovos de S. mansoni, melhor detectados pelo Kato-Katz. Os kits de detecção de coproantígenos foram melhores para diagnóstico de G. lamblia, Cryptosporidium parvum e E. histolytica. Entretanto, o kit para diagnóstico de E. histolytica não detecta a espécie E. dispar, melhor identificada pelo PCR. Os kits comerciais (Paratest® RESUMO e TF-Test®), apesar de facilitarem a coleta e conservação da amostra, têm menor sensibilidade do que a Sedimentação Espontânea em Tubo
120

Período de coleta de urina e de fezes para avaliação da excreção de creatinina, produção microbiana e digestibilidade aparente dos nutrientes em Nelore / Period of urine and feces collection for evaluation of creatinine excretion, microbial production and nutrients apparent digestibility in Nelore bovines

Barbosa, Analívia Martins 02 March 2005 (has links)
Made available in DSpace on 2015-03-26T13:46:45Z (GMT). No. of bitstreams: 1 texto completo.pdf: 246842 bytes, checksum: f7b7371c8cb299837b636e055567a1b8 (MD5) Previous issue date: 2005-03-02 / This trial was carried out to evaluate the effect of periods of urine and feces collection on urinary excretion of creatinine, urea and purine derivatives, absorbed purine, microbial nitrogen compounds production (Nmic), apparent digestibility of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF) and nonfiber carbohydrates (CNF) and total digestible nutrients contents (TDN) of Nelore bovines four categories (heifers, steers, bulls and lactating cows) fed 25 or 50% concentrate, total dry matter basis. The plasma N-urea concentrations (NUP) were evaluated and the Nmic obtained in urine spot samples was compared with that of total collection. The experiment was divided in two experimental periods of 28 days each, when the feces and urine total collection were performed at 22nd and 28th day of each experimental period. Feces were colleted directly from the floor after excretion and the urine was obtained using catheters in females and funnels in males. A 25% concentrate-based diet was fed to the animals in the first period and a 50% concentrate-based diet in the second one, all of them with 12% CP. Sixteen Nelore bovines, under feedlot, housed in individual pens, were assigned to a completely randomized design, in a split plot scheme, where the treatments were represented by the plots (2 x 4 factorial scheme), with two levels of concentrate (25 or 50%) and four Nelore categories, and the split plots were represented by the urine collections. The comparisons for digestibility evaluation were made by regression analyses, that were performed considering 4 days of feces collection of each period. The equations were obtained by comparing the nutrients digestibility referent to one (24h), two (48h) or three days (72h) compared to four days (96h of collection). Comparison with six days of total feces collection, using equations (second experimental period [50% concentrate]) was considered reference (144h total feces collection). No interaction (P>0.05) among concentrate levels, Nelore categories and collection days for the urinary volume, the creatinine excretion and Nmic production was observed. Urinary volume was not affected (P>0.05) by the concentrate levels and collection days, but significant effect (P<0.05) was observed for cows. Creatinine excretion was not affected (P>0.05) by treatments and collection days, considering average of 27.1 mg/kg0.75. Absorbed purines and microbial nitrogen compounds production were also not influenced (P>005) by the treatments and collection days. Nmic production estimated by the urinary spot collection differed (P>0.05) neither from that obtained by total collection total, nor among the concentrate levels and Nelore categories. No significant difference (P>0.05) was observed for any evaluated digestibility and TDN contents during the total feces collection period. The results suggest that the coefficients of variation decresed as the period of collection days increased. Considering the results of creatinine excretion and of microbial protein production, it was concluded that a 24-h period is enough for researchs with Nelore, independently of the category, and that urinary spot sample collection can be used to estimate microbial protein production in all Nelore bovines (heifers, steers, bulls and lactating cows). Total feces collection from 1 to 6 days to evaluate nutrients apparent digestibility are precise, but better results could be obtained by increasing the collection period. / O presente trabalho foi conduzido com o objetivo de avaliar o efeito da duração do período de coletas de urina e de fezes sobre a excreção urinária de creatinina, de uréia e de derivados de purinas, as purinas absorvidas, a produção de compostos nitrogenados microbianos (Nmic), as digestibilidades aparentes da matéria seca (MS), matéria orgânica (MO), proteína bruta (PB), extrato etéreo (EE), fibra em detergente neutro (FDN) e de carboidratos não-fibrosos (CNF) e os teores de nutrientes digestíveis totais (NDT) em Nelores de quatro categorias (novilhas, machos castrados, machos inteiros e vacas em lactação) alimentados com 25 ou 50% de concentrado na base da matéria seca total das dietas. Avaliou-se ainda as concentrações de N-uréia plasmática (NUP) e comparou-se também a produção de Nmic obtida em amostras spot de urina com aquela da coleta total. O experimento foi conduzido em dois períodos experimentais com duração de 28 dias cada, sendo as coletas totais de urina e de fezes efetuadas do 22o ao 28o dias de cada período experimental. As fezes foram retiradas do piso imediatamente após excreção e a urina obtida com sondas em fêmeas e funis nos machos. Utilizou-se dieta com 25% de concentrado no primeiro período e com 50% no segundo experimental. Todas as dietas continham aproximadamente 12% de PB. Utilizaram-se 16 animais da raça Nelore, mantidos em confinamento, alojados em baias individuais, distribuídos em delineamento inteiramente casualizado, em esquema de parcelas subdivididas, tendo nas parcelas os tratamentos em esquema fatorial 2 x 4, sendo dois níveis de concentrado (25 ou 50%) e quatro categorias de Nelores e nas subparcelas os seis dias de coletas de urina. Já para a avaliação das digestibilidades, as comparações foram feitas através de análises de regressão, que foram efetuadas considerando quatro dias de coletas de fezes em cada período, sendo as equações obtidas sempre comparando as digestibilidades dos nutrientes referentes a um dia (24 h), 2 dias (48 h) ou 3 dias (72 h) em relação aos 4 dias (96 h de coleta). Foram feitas também comparações através de equações, utilizando os seis dias de coleta total de fezes, referentes ao segundo período experimental (50% de concentrado), sendo nesse caso utilizado como referência os seis dias de coleta total (144 h de coleta total de fezes). Não houve interação (P>0,05) entre níveis de concentrado, categorias de Nelore e dias de coleta para o volume urinário, a excreção de creatinina e a produção de Nmic. O volume urinário não foi influenciado (P>0,05) pelos níveis de concentrado e dias de coleta, contudo foi significativamente maior (P<0,05) para as vacas. A excreção de creatinina não foi afetada (P>0,05) pelos tratamentos e dias de coletas, observando-se média de 27,1 mg/kg0,75. As purinas absorvidas e a produção de compostos nitrogenados microbianos também não foram influenciadas (P>0,05) pelos tratamentos e dias de coleta. A produção de Nmic estimada através de amostra spot de urina não diferiu (P>0,05) daquela obtida pela coleta total, nem entre os níveis de concentrados e categorias de Nelore. Não houve diferença significativa (P>0,05) para nenhuma das digestibilidades avaliadas e também para os teores de NDT entre os dias de coleta total de fezes, contudo, observou-se que os coeficientes de variação diminuíram à medida que se aumentou o número de dias de coleta. Concluiu-se considerando as respostas obtidas para excreção de creatinina e a produção de proteína microbiana, que um período de coletas de urina de 24 horas é suficiente para trabalhos com Nelores, independente de serem novilhas, machos castrados ou inteiros e vacas em lactação e que a coleta de amostra spot de urina também pode ser utilizada para estimar a produção de proteína microbiana em novilhas, machos inteiros ou castrados e vacas lactantes da raça Nelore. Concluiu-se também que para avaliar a digestibilidade aparente dos nutrientes, coletas totais de fezes feitas durante um a seis dias são exatas. Contudo, a precisão é melhorada com o aumento dos dias de coleta.

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