No description available.

Three experiments were carried out to investigate dietary and genetic factors influencing the n-3 polyunsaturated fatty acid content of sheepmeat. In the first experiment, four isoenergetic and iso-nitrogenous diets, based on dried grass with similar fat levels (60 g/kg OM) from different sources; Megalac (control), linseed (a-linolenic acid, CI8:3n-3), fish oil (eicosapentaenoic, C20:5n-3 and docosahexaenoic, C22:6n-3 acids) and linseed plus fish oil were fed to four rumen and duodenal cannulated sheep in a 4x4 Latin square design. Biohydrogenation of C 18:3n-3 was, 80-92 % in all diets, while that of C20:5n-3 and C22:6n-3 was 58-74 %. Dietary n-3 PUFA decreased microbial efficiency (p < 0.05) measured using the total purine technique as a microbial marker, whilst fish oil depressed fibre digestion in the rumen (p < 0.01). In experiment two, the same four diets were randomly allocated to 72 lambs from three breeds; Suffolk, Soayand Friesland blocked on live weight. Muscle fatty acid content was 2.4-2.8 % of tissue weight. Compared to the control diet, linseed doubled the quantity of CI8:3n-3 in muscle and increased levels of C20:5n-3 and C22:6n-3 by 0.5 (p < 0.001). Fish oil alone increased C20:5n-3 and C22:6n-3 by 3-4 times (p < 0.001), whilst the mixed diet resulted in n-3 PUFA levels intermediate between the linseed and fish oil diets. Soay lambs deposited more PUF A on the control diet than Suffolk or Friesland lambs (p < 0.05). In the third experiment three iso-energetic and iso-nitrogenous diets, with different fat sources, Megalac or formaldehyde treated linseed (protected) with or without fish oil, and with two levels of vitamin E 100 (low) and 500 (high) mg/kg OM were randomly allocated to 96 lambs from two breeds; Suffolk and Scottish Blackface blocked on live weight. Muscle fatty acid content was 2.3-3.1 % of tissue weight but was lower in control fed lambs (p3 mg/kg muscle) in all lambs fed any of the diets. Overall, dietary modifications were more effective than genetic factors in increasing the n-3 PUF A in sheepmeat.

Hydrolysis of dietary lipids to free fatty acids (FFA) is a prerequisite for ruminal biohydrogenation, a bacterially mediated process that extensively saturates unsaturated FFAs thus limiting the absorption and ultimate assimilation of these healthy nutrients into ruminant produced foods. Three experiments were conducted to learn how to better enrich, isolate and study lipolytic bacteria from the rumen while providing further characterization of four prominent lipase-producing bacteria that are known to be major contributors of lipolysis in the rumen. In experiment one the effects of various physical treatments on ruminal lipase activity were investigated by comparing incubation positions, glass bead levels, transfer techniques and combinations of headspace gasses. Based on results from this experiment an incubation system was established as a standard for subsequent studies for culturing and transferring mixed and pure cultures of ruminal bacteria. In experiment two the effect of glycerol on lipolysis by Anaerovibrio lipolyticus 5S, Butyrivibrio fibrisolvens 49, Propionibacterium avidum, and Propionibacterium acnes was examined. Two levels of glycerol were examined on lipase activity and results showed that glycerol inhibited rates of FFA accumulation at both levels. In addition the mechanism behind glycerol inhibition was also examined by culturing and assaying activity of the four bacteria to determine if glycerol inhibition is a result of equilibrium displacement or lipase gene expression inhibition. Results indicated that higher and constitutively expressed lipase activity of A. lipolyticus 5S and P. avidum probably contribute more to lipolysis in ruminants than P. acnes and B. fibrisolvens 49. In the case of P. acnes and B. fibrisolvens 49 cells, results suggest that lipase gene expression is down-regulated in these bacteria. Experiment three was conducted to further characterize the lipase activity of the four different bacteria by growing them with four different energy substrates and measuring enzyme activity at early logarithmic and stationary phase. Results from this study showed that diets containing a high content of oleic acid and linolenic acid promoted higher rates of lipolysis in the rumen. In accordance with findings in experiment two these results support that P. avidum may contribute to a higher amount of lipolysis than previously considered.

No description available.

Este trabalho teve o objetivo de avaliar o uso de monensina, levedura e a interação destes aditivos no metabolismo digestivo e desempenho de animais Nelores. Foram realizados dois experimentos. Experimento 1. Foram utilizados quatro novilhos Nelores com cânulas no rúmen e no duodeno para avaliar a degradabilidade, digestibilidade, biohidrogenação, microrganismos ruminais e emissão de metano quando fornecidos monensina e/ou levedura na dieta contendo óleo de girassol em experimento quadrado latino e arranjo fatorial 2x2. Os tratamentos consistiram em com e sem levedura e com e sem monensina. A levedura utilizada foi a Sacharomyces cerevisiae cepa 1026. As variáveis estudadas foram degradabilidade in situ, digestibilidade in vivo avaliada pelo método de indicador interno FDNi, pH, nitrogênio amoniacal e ácidos graxos de cadeia curta do rúmen, protozoários ciliados, biohidrogenação ruminal, e estimativa do número das bactérias Anaerovibrio lipolyica, Butyrivibrio fibrisolvens e Megasphaera elsdenii, por PCR em tempo real. Experimento 2. Foi realizado ensaio para avaliar o desempenho e características de carcaça e carne de touros Nelores utilizando os aditivos supracitados. Foram utilizados cinquenta e dois touros Nelores com aproximadamente 233kg em delineamento em blocos ao acaso. O fornecimento de monensina reduziu o número de protozoários ciliados no rúmen, aumentou a eficiêcia alimentar e a porcentagem de C18:1 trans10-11 e de C18:2 t11c15 na carne. O uso de levedura aumentou a degradabilidade efetiva da MS, o NDT da dieta, os protozoários ciliados, o pH ruminal, a expressão relativa da bactéria B. fibrisolvens, a ingestão de MS dos animais confinados, os ácidos graxos insaturados no conteúdo duodenal e os ácidos graxos saturados na carne, e reduziu a eficiência alimentar, os ácidos graxos saturados no conteúdo duodenal e os ácidos graxos insaturados na carne. Houve interação para a digestibilidade da FDN, ingestão de matéria seca por quilo de peso metabólico, espessura de gordura subcutânea, e ácidos graxos insaturados na carne. O uso de monensina em dieta com óleo foi eficiente para melhora na conversão alimentar. A utilização de cultura de levedura mesmo em dieta com óleo favoreceu os microrganismos ruminais e a energia da dieta. / This work had the objective of evaluate the use of monensin, yeast and the interaction of these additives on Nellore digestive metabolism and performance. It were conducted two trials. Experiment 1. It were utilized four Nellore steers with rumen and duodenum cannulas to evaluate the diet degradability, digestibility, biohydrogenation, rumen microrganisms and methane emission when supplied monensin and/or yeast on the diet with sunflower oil in a latin square desing and a 2x2 fatorial arranjement.The treatments were with and without yeast and with and without monensin. The yeast utilized was the Sacharomyces cerevisiae 1026 strain. The variables studied were in situ degradability, in vivo digestibility evaluated by indicator method NDFi, pH, ammonia nitrogen and rumen short chain fatty acid, ciliate protozoa, biohydrogenation, and estimative of bactéria Anaerovibrio lipolyica, Butyrivibrio fibrisolvens e Megasphaera elsdenii, by real time PCR. Experiment 2. A trial was realized to evaluate the performance and carcass and meat characteristics of Nellore steers utilizing the additives above. It were utilized fifthty two Nellore bulls with 233kg live weight average in a random blocks design. The monensin supplied decreased the protozoa number, the relative efficiency of B. fibrosolvens, increased feed efficiency and the percentage of C18:1 trans10-11 and C18:2 t11c15 in the meat. The use of yeast increased the effective degradability of DM, the TDN, ciliate protozoa, rumen pH, DM intake, unsaturated fatty acid on the duodenal content, and the saturated fatty acid in the meat, and decreased the feed efficiency, saturated fatty acid on the duodenum content and the unsaturated fatty acid of the meat. There were interaction effect to NDF digestibility, dry matter intake per kg of metabolic weight, fat thickness, and unsaturated fatty acid in the meat. The use of monensin was efficient to get the feed efficiency better. The utilization of yeast culture, even in a oil diet, was favorable to rumen microorganisms and the diet energy.

Made available in DSpace on 2014-06-11T19:32:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-24Bitstream added on 2014-06-13T21:05:23Z : No. of bitstreams: 1 freitasjunior_je_dr_jabo.pdf: 667541 bytes, checksum: 50527f5d0b0b3899e3c394c774df1bb2 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O objetivo deste estudo foi avaliar a biohidrogenação ruminal e o fluxo intestinal de ácidos graxos em vacas leiteiras suplementadas com diferentes fontes de gordura dietética. Foram utilizadas 8 vacas da raça Holandesa no terço médio de lactação (80 ± 20 dias em lactação; média ± DP) canuladas no rúmen e abomaso (580 ± 20 kg de peso corporal; media ± DP), agrupadas em dois quadrados latinos 4 x 4 balanceados, alimentadas com as seguintes dietas: 1) Controle (C), dieta a base de milho e farelo de soja; 2) Óleo de soja refinado (OS); 3) Grão de soja in natura (GS); e 4) sais de cálcio de ácidos graxos insaturados (SCAG). A produção de leite e o consumo de matéria seca foram mensurados diariamente durante todo o período experimental. As amostras utilizadas para análise da composição e o perfil de ácidos graxos do leite foram coletadas de dois dias alternados, sendo provenientes das duas ordenhas diárias. As amostras de sangue para análise dos metabólitos sanguíneos foram coletadas em tubos vacuolizados por punção da veia e/ou artéria coccígea e em tubos com EDTA para análise do perfil de acidos graxos. Para avaliação da fermentação ruminal as amostras de líquido ruminal foram coletadas nos tempos zero (antes da alimentação), e 2, 4, 6, 8, 10 e 12 horas após alimentação matinal. A digestibilidade foi determinada por meio da utilização do indicador externo óxido crômico. O indicador FDNi foi utilizado para estimativa do fluxo abomasal de matéria seca. Foram utilizados dois modelos para calcular a biohidrogenação ruminal: Modelo A) calculado pela taxa de desaparecimento entre o consumido e o fluxo abomasal; Modelo B): calculado por meio da dinâmica ruminal, taxa fracional de desaparecimento ruminal, e fluxo abomasal. Não houve efeito das fontes de gordura sobre o consumo e a digestibilidade aparente total da...(Resumo completo, clicar acesso eletrônico abai / The aim of this study was to evaluate the ruminal biohydrogenation and intestinal flow of fatty acids in dairy cows supplemented with different sources of dietary fat. Eight Holstein cows in the mid lactation (80 ± 20 day in milk; mean SD) cannulated in the rumen and abomasum (580 ± 20 kg of weight; mean ± SD) with milk yield of 25 kg/d were assigned randomly into two 4 x 4 Latin squares, fed the following diets: 1) control (C); 2) refined soybean oil (SO); 3) whole soybean raw (WS) and 4) calcium salts of unsaturated fatty acids (CSFA). Milk yield and dry matter intake were measured daily throughout the experimental period. The samples used for analysis of composition and fatty acid profile of the milk were collected from two alternate days, and from the two daily milkings. Blood samples for analysis of blood metabolites were collected in tubes vacuolated by vein puncture and/or coccygeal artery and were collected in tubes with EDTA to obtain the plasma. To evaluation of the rumen fermentation ruminal fluid samples were collected at time zero (before feeding), and 2, 4, 6, 8, 10 and 12 hours after morning feeding. The digestibility was determined by using the external marker chromic oxide. The marker NDFi was used to determine the abomase flow from the dry matter. Two models were used to calculate the rate biohydrogenation: Model A): calculated by disappearance rate using abomasal fatty acids flow, and fatty acids intake and; Model B): calculated by ruminal turnover, fractional passage rate and fractional biohydrogenation rate and ruminal pool for each fatty acid. There was no effect of fat sources on intake and total apparent digestibility of the dry matter and nutrients and on yield and milk composition, microbial protein synthesis, fatty acid profile of milk and blood. The balances of nitrogen and energy were also not... (Complete abstract click electronic access below)

Doctor of Philosophy / Department of Animal Sciences and Industry / J. S. Drouillard / The main goal of this dissertation was to evaluate different methods to protect polyunsaturated fatty acids (PUFA) against biohydrogenation by ruminal microorganisms. The first chapter is a review of literature pertaining to fat and fatty acid metabolism by ruminants and why these fats are relevant in human nutrition. The second chapter discusses effects of supplementing high concentrations of dietary copper to feedlot cattle to assess impact on PUFA profiles in tissues. Two levels of copper (10 or 100 mg/kg) were supplemented to diets with or without flaxseed during the finishing period for beef heifers. Added copper did not affect performance (P > 0.15). Final body weights were similar for cattle fed with or without flaxseed (P > 0.05), but cattle fed diets with flaxseed consumed less feed (P < 0.05), and therefore were more efficient (P < 0.01). Carcass traits were unaffected by treatment. Feeding elevated levels of copper did not appreciably alter proportions of PUFA in plasma, but plasma concentrations of omega-3 fatty acids were greater for heifers fed flaxseed (P < 0.05). Chapter 3 describes the evaluation of 3 novel methods to protect PUFA from microbial biohydrogenation activity within the rumen, including a) coextrusion of flaxseed with molasses; b) mixing with soybean meal followed by induction of a non-enzymatic browning reaction; and c) encapsulation of ground flaxseed within a matrix consisting of dolomitic lime hydrate (L-Flaxseed). The resulting products were evaluated using in vitro methods to estimate resistance to biohydrogenation or in 12- to 14-d feeding studies in which plasma concentrations of [alpha]-linolenic acid (ALA) were measured. Our processing strategies a) and b) did not improve efficiency of omega-3 fatty acid utilization (P > 0.1). The in situ study of L-flaxseed revealed a 2-fold increase in resistance of ALA to ruminal biohydrogenation, and the concentration in plasma after 14 d on feed was more than 4 times that observed in cattle fed ground flaxseed, suggesting the dolomitic lime hydrate was effective as a protective matrix. Chapter 4 evaluated performance, carcass traits, and meat quality of finishing beef heifers in response to feeding diets containing L-Flaxseed. Animals were blocked by weight, randomly assigned to individual pens, and pens to 6 dietary treatments: Control (high concentrate finishing diet), ground flaxseed fed at 3 or 6% of diet DM, L-Flaxseed fed at 2, 4, or 6%. Concentration of ALA in meat increased linearly in response to the level of flaxseed fed (P < 0.05); Moreover, transfer of dietary ALA to tissues increased by 47% when flaxseed was encapsulated within the dolomitic lime matrix. Cattle that were fed diets with 4 or 6% L-Flaxseed consumed less feed than other treatments (P < 0.05), which adversely affected feedlot performance and carcass traits.

Made available in DSpace on 2015-03-26T13:54:44Z (GMT). No. of bitstreams: 1 texto completo.pdf: 621378 bytes, checksum: 21392034a1465e351e40062319308703 (MD5) Previous issue date: 2008-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study aimed to evaluate the effects of lipid sources with different degrees of fatty acid saturation on the intake, digestibility, nitrogen balance, nutrient flow, microbial production and efficiency, ruminal characteristics, fatty acid (FA) profile in omasal digesta (flow), and ruminal biohydrogenation. Eight rumen fistulated goats that were neither pregnant nor lactating, distributed in a double 4 x 4 Latin square design, were used. Four diets were used, one of them was the control diet (CD) and the other tree were supplemented with different sources of lipids: soy oil (SO), palm kernel oil (PKO), canola oil (CO). Supplementation with 2.3% of oil in dry matter (DM) of total diet did not influence the intakes of DM, energy and nutrients, except the ethereal extract (EE), with higher intake effects for the supplemented diets. The total apparent digestibility of dry matter and nutrients did not show any effects due to the different oil sources, although CO had shown a reduction in the ruminal digestibility of DM, organic matter (OM), neutral detergent fiber (NDF), crude protein (CP), EE and total carbohydrates (TC). Nitrogen balance efficiency was not higher by using the lipid sources. DM and nutrient flow differed among the evaluated diets. The highest flow of all studied variables (g.d-1) was found when CO was used, being similar only to PKO values for NDF and TC. Reduced values for ammoniacal nitrogen concentration were found when PKO was used. It was not found variations among the diets for pH evaluation and transit kinetics. When the lipid profile of omasum was performed, high percentages of vaccenic acid (C18:1 tans- 11) was found for the diet supplemented with SO. Such diet also showed a better efficiency on the conversion of some FA s into C18:1 trans-11 in the rumen. Soy oil may be used as a supplement on dairy goat diet, associated with the ruminal pH reduction by using higher rates of concentrate in relation to the forage on the diet, as a strategy to increase excretion of conjugated linoleic acid (CLA) in milk without compromising nutrient digestibility, microbial efficiency and conditions of the ruminal environment. / Objetivou-se com este estudo, avaliar o efeito do uso de fontes lipídicas apresentando diferentes graus de saturação de ácidos graxos (AG) sobre o consumo, a digestibilidade, o balanço de nitrogênio, o fluxo de nutrientes, a produção e a eficiência microbiana, as características ruminais, e o perfil de AG da digesta omasal (fluxo). Utilizou-se 8 cabras fistuladas no rúmen, não-gestantes e não-lactantes, distribuídas em um delineamento em quadrado latino 4 x 4, duplicado. Foram utilizadas 4 dietas, sendo uma dieta controle (DC) e três suplementadas com diferentes fontes de lipídios: óleo de soja (OS), óleo de palmiste (OP), óleo de canola (OC). A suplementação com óleo em 2,3% na MS da dieta total não influenciou o consumo de matéria seca (MS), de energia e nutrientes, exceto de extrato etéreo (EE), com maior consumo para as suplementadas. A digestibilidade aparente total da MS e nutrientes não sofreram efeito das diferentes fontes, embora o tratamento com óleo de canola tenha promovido redução na digestibilidade ruminal da MS, da matéria orgânica (MO), da fibra em detergente neutro (FDN), da proteína bruta (PB), do EE e dos caboidratos totais (CT). O balanço de nitrogênio foi mais eficiente sem a inclusão das fontes lipídicas. Os fluxos de MS e de nutrientes, diferiram entre as rações avaliadas, sendo que o maior fluxo de todas essas variáveis (g.d-1) foi observado quando utilizada a dieta óleo de canola, assemelhando-se apenas com a óleo de palmiste nos valores de FDN e CT. Valores reduzidos para a concentração de nitrogênio amoniacal foram obtidos com o uso da ração OP. Na avaliação do pH e da cinética de trânsito não foram verificados variações entre dietas. No omaso, foi observado elevados teores de ácido trans-vacênico (C18:1 tans-11) quando utilizado a dieta OS. Na análise de eficiência de conversão de alguns AGs em C18:1 trans-11 no rúmen, verificou-se que a dieta OS também apresentou superioridade em relação às demais, sugerindo maior produção de ácido linoléico conjugado (CLA). Conclui-se que o óleo de soja pode ser suplementado na dieta de cabras leiteiras, associado à redução do pH ruminal, com o uso de maior proporção de concentrado na dieta, como estratégia para aumentar a excreção de CLA no leite, sem comprometer a digestibilidade dos nutrientes, a eficiencia microbiana e as condições do meio ruminal.

Orientador: Mauro Dal Secco de Oliveira / Banca: Jane Maria Bertocco Ezequiel / Banca: Atushi Sugohara / Banca: Arlindo Saran Netto / Banca: Marcos Veiga dos Santos / Resumo: O objetivo deste estudo foi avaliar a biohidrogenação ruminal e o fluxo intestinal de ácidos graxos em vacas leiteiras suplementadas com diferentes fontes de gordura dietética. Foram utilizadas 8 vacas da raça Holandesa no terço médio de lactação (80 ± 20 dias em lactação; média ± DP) canuladas no rúmen e abomaso (580 ± 20 kg de peso corporal; media ± DP), agrupadas em dois quadrados latinos 4 x 4 balanceados, alimentadas com as seguintes dietas: 1) Controle (C), dieta a base de milho e farelo de soja; 2) Óleo de soja refinado (OS); 3) Grão de soja in natura (GS); e 4) sais de cálcio de ácidos graxos insaturados (SCAG). A produção de leite e o consumo de matéria seca foram mensurados diariamente durante todo o período experimental. As amostras utilizadas para análise da composição e o perfil de ácidos graxos do leite foram coletadas de dois dias alternados, sendo provenientes das duas ordenhas diárias. As amostras de sangue para análise dos metabólitos sanguíneos foram coletadas em tubos vacuolizados por punção da veia e/ou artéria coccígea e em tubos com EDTA para análise do perfil de acidos graxos. Para avaliação da fermentação ruminal as amostras de líquido ruminal foram coletadas nos tempos zero (antes da alimentação), e 2, 4, 6, 8, 10 e 12 horas após alimentação matinal. A digestibilidade foi determinada por meio da utilização do indicador externo óxido crômico. O indicador FDNi foi utilizado para estimativa do fluxo abomasal de matéria seca. Foram utilizados dois modelos para calcular a biohidrogenação ruminal: Modelo A) calculado pela taxa de desaparecimento entre o consumido e o fluxo abomasal; Modelo B): calculado por meio da dinâmica ruminal, taxa fracional de desaparecimento ruminal, e fluxo abomasal. Não houve efeito das fontes de gordura sobre o consumo e a digestibilidade aparente total da ... (Resumo completo, clicar acesso eletrônico abai / Abstract: The aim of this study was to evaluate the ruminal biohydrogenation and intestinal flow of fatty acids in dairy cows supplemented with different sources of dietary fat. Eight Holstein cows in the mid lactation (80 ± 20 day in milk; mean SD) cannulated in the rumen and abomasum (580 ± 20 kg of weight; mean ± SD) with milk yield of 25 kg/d were assigned randomly into two 4 x 4 Latin squares, fed the following diets: 1) control (C); 2) refined soybean oil (SO); 3) whole soybean raw (WS) and 4) calcium salts of unsaturated fatty acids (CSFA). Milk yield and dry matter intake were measured daily throughout the experimental period. The samples used for analysis of composition and fatty acid profile of the milk were collected from two alternate days, and from the two daily milkings. Blood samples for analysis of blood metabolites were collected in tubes vacuolated by vein puncture and/or coccygeal artery and were collected in tubes with EDTA to obtain the plasma. To evaluation of the rumen fermentation ruminal fluid samples were collected at time zero (before feeding), and 2, 4, 6, 8, 10 and 12 hours after morning feeding. The digestibility was determined by using the external marker chromic oxide. The marker NDFi was used to determine the abomase flow from the dry matter. Two models were used to calculate the rate biohydrogenation: Model A): calculated by disappearance rate using abomasal fatty acids flow, and fatty acids intake and; Model B): calculated by ruminal turnover, fractional passage rate and fractional biohydrogenation rate and ruminal pool for each fatty acid. There was no effect of fat sources on intake and total apparent digestibility of the dry matter and nutrients and on yield and milk composition, microbial protein synthesis, fatty acid profile of milk and blood. The balances of nitrogen and energy were also not... (Complete abstract click electronic access below) / Doutor

Este trabalho teve o objetivo de avaliar o uso de monensina, levedura e a interação destes aditivos no metabolismo digestivo e desempenho de animais Nelores. Foram realizados dois experimentos. Experimento 1. Foram utilizados quatro novilhos Nelores com cânulas no rúmen e no duodeno para avaliar a degradabilidade, digestibilidade, biohidrogenação, microrganismos ruminais e emissão de metano quando fornecidos monensina e/ou levedura na dieta contendo óleo de girassol em experimento quadrado latino e arranjo fatorial 2x2. Os tratamentos consistiram em com e sem levedura e com e sem monensina. A levedura utilizada foi a Sacharomyces cerevisiae cepa 1026. As variáveis estudadas foram degradabilidade in situ, digestibilidade in vivo avaliada pelo método de indicador interno FDNi, pH, nitrogênio amoniacal e ácidos graxos de cadeia curta do rúmen, protozoários ciliados, biohidrogenação ruminal, e estimativa do número das bactérias Anaerovibrio lipolyica, Butyrivibrio fibrisolvens e Megasphaera elsdenii, por PCR em tempo real. Experimento 2. Foi realizado ensaio para avaliar o desempenho e características de carcaça e carne de touros Nelores utilizando os aditivos supracitados. Foram utilizados cinquenta e dois touros Nelores com aproximadamente 233kg em delineamento em blocos ao acaso. O fornecimento de monensina reduziu o número de protozoários ciliados no rúmen, aumentou a eficiêcia alimentar e a porcentagem de C18:1 trans10-11 e de C18:2 t11c15 na carne. O uso de levedura aumentou a degradabilidade efetiva da MS, o NDT da dieta, os protozoários ciliados, o pH ruminal, a expressão relativa da bactéria B. fibrisolvens, a ingestão de MS dos animais confinados, os ácidos graxos insaturados no conteúdo duodenal e os ácidos graxos saturados na carne, e reduziu a eficiência alimentar, os ácidos graxos saturados no conteúdo duodenal e os ácidos graxos insaturados na carne. Houve interação para a digestibilidade da FDN, ingestão de matéria seca por quilo de peso metabólico, espessura de gordura subcutânea, e ácidos graxos insaturados na carne. O uso de monensina em dieta com óleo foi eficiente para melhora na conversão alimentar. A utilização de cultura de levedura mesmo em dieta com óleo favoreceu os microrganismos ruminais e a energia da dieta. / This work had the objective of evaluate the use of monensin, yeast and the interaction of these additives on Nellore digestive metabolism and performance. It were conducted two trials. Experiment 1. It were utilized four Nellore steers with rumen and duodenum cannulas to evaluate the diet degradability, digestibility, biohydrogenation, rumen microrganisms and methane emission when supplied monensin and/or yeast on the diet with sunflower oil in a latin square desing and a 2x2 fatorial arranjement.The treatments were with and without yeast and with and without monensin. The yeast utilized was the Sacharomyces cerevisiae 1026 strain. The variables studied were in situ degradability, in vivo digestibility evaluated by indicator method NDFi, pH, ammonia nitrogen and rumen short chain fatty acid, ciliate protozoa, biohydrogenation, and estimative of bactéria Anaerovibrio lipolyica, Butyrivibrio fibrisolvens e Megasphaera elsdenii, by real time PCR. Experiment 2. A trial was realized to evaluate the performance and carcass and meat characteristics of Nellore steers utilizing the additives above. It were utilized fifthty two Nellore bulls with 233kg live weight average in a random blocks design. The monensin supplied decreased the protozoa number, the relative efficiency of B. fibrosolvens, increased feed efficiency and the percentage of C18:1 trans10-11 and C18:2 t11c15 in the meat. The use of yeast increased the effective degradability of DM, the TDN, ciliate protozoa, rumen pH, DM intake, unsaturated fatty acid on the duodenal content, and the saturated fatty acid in the meat, and decreased the feed efficiency, saturated fatty acid on the duodenum content and the unsaturated fatty acid of the meat. There were interaction effect to NDF digestibility, dry matter intake per kg of metabolic weight, fat thickness, and unsaturated fatty acid in the meat. The use of monensin was efficient to get the feed efficiency better. The utilization of yeast culture, even in a oil diet, was favorable to rumen microorganisms and the diet energy.