NTRODUCTION: Colonic bacteria produce short-chain fatty acids (SCFAs) by fermentation of dietary carbohydrates and fiber. The production of SCFAs is greatest in proximal colon where propulsion is likely to be highly dependent on chemical/nutrient stimuli. Unabsorbed SCFAs entering the distal colon are likely to modify peristalsis initiated by fecal pellet-induced distension. AIM: To determine the effect of individual SCFAs on propulsive contractions in guinea pig proximal colon and on pellet propulsion in distal colon. METHODS: Proximal colon was excised, cannulated and placed in Krebs buffer in an organ bath. After equilibration, the colon was distended with 1ml of Krebs buffer alone or containing sodium salts of acetate, butyrate, or propionate at 10-100mM. Motility was video recorded, spatiotemporal maps generated, and the number of full-length propulsive contractions during a 5 min period was determined. The distal colon was removed from guinea pig and placed in an organ bath containing Krebs buffer. Following equilibration, video-tracking software was used to measure the velocity of propulsion of a clay pellet placed in the orad end of a segment. Krebs buffer alone or containing individual SCFAs at 30mM was perfused caudad to the pellet at 0.1 ml/min. RESULTS: The basal rate of propulsive contractions in Krebs buffer was 2.9 ± 0.7 per 5 min. Butyrate and propionate had concentration-dependent and opposing effects on propulsive contractions; acetate had no effect. Butyrate significantly increased propulsive contractions (maximal increase of 207% (p ≤ 0.05) at 30 mM) whereas propionate abolished propulsive contractions (91-100% inhibition at 10-30mM). Control Krebs buffer containing 10- 100mM NaCl had no effect. The mean rate of pellet propulsion during perfusion of Krebs buffer alone was 1.5 ± 0.2 mm/sec. Addition of sodium butyrate (30 mM) to the perfusate increased the velocity of pellet propulsion by 40 ± 4% (p<0.05) whereas addition of 30mM sodium propionate decreased velocity of pellet propulsion by 75 ± 8%. Acetate had no significant effect in either proximal or distal colon. Mixtures of SCFAs showed a general decrease in overall motility. CONCLUSION: SCFAs have differential effects on propulsive contractions in the proximal and distal colon of the guinea pig, with butyrate being excitatory and propionate being inhibitory. These studies suggest that the movement of feces in the colon depends not only on distension but the chemical (i.e. dietary) composition of the feces.

High fibre diets are associated with reduced risk of type 2 diabetes mellitus (T2DM). This may be due to short-chain-fatty-acids (SCFA) influencing insulin resistance and secretion via changes in free-fatty-acids (FFA) and specific gut hormones. We aimed to determine the postprandial effects of inulin, a fermentable, soluble fibre in healthy subjects. Twelve fasted subjects were studied for 6 hours after either 80g high fructose corn syrup (HFCS), 56g HFCS plus 24g inulin, or 56g HFCS drinks using a randomized, cross-over design. SCFA were higher after inulin beginning at 4 hours. FFA were lower 4 hours after inulin than 56gHFCS. GLP-1 was higher 30 minutes after inulin than 56 and 80HFCS, while ghrelin was lower from 4-6 hours after inulin. The results support the hypothesis that inulin and SCFA generated from colonic fermentation of dietary fibre may improve insulin resistance and secretion via modulation of FFA and specific gut hormones.

High fibre diets are associated with reduced risk of type 2 diabetes mellitus (T2DM). This may be due to short-chain-fatty-acids (SCFA) influencing insulin resistance and secretion via changes in free-fatty-acids (FFA) and specific gut hormones. We aimed to determine the postprandial effects of inulin, a fermentable, soluble fibre in healthy subjects. Twelve fasted subjects were studied for 6 hours after either 80g high fructose corn syrup (HFCS), 56g HFCS plus 24g inulin, or 56g HFCS drinks using a randomized, cross-over design. SCFA were higher after inulin beginning at 4 hours. FFA were lower 4 hours after inulin than 56gHFCS. GLP-1 was higher 30 minutes after inulin than 56 and 80HFCS, while ghrelin was lower from 4-6 hours after inulin. The results support the hypothesis that inulin and SCFA generated from colonic fermentation of dietary fibre may improve insulin resistance and secretion via modulation of FFA and specific gut hormones.

Short-chain fatty acids are the major by-products of bacterial fermentation of undigested dietary fibers in human large intestine. SCFAs, mostly propionate and butyrate, inhibit proliferation and induce apoptosis in colon cancer cells, but clinical trials had mixed results regarding the anti-tumor activities of SCFAs. Herein we demonstrate that propionate and butyrate induced autophagy in human colon cancer cells to dampen apoptosis whereas inhibition of autophagy potentiated SCFA induced apoptosis. Colon cancer cells, after propionate treatment, exhibited extensive characteristics of autophagic proteolysis: increased LC3-I to LC3-II conversion, acidic vesicular organelle development and reduced p62/SQSTM1 expression. Propionate-induced autophagy was associated with decreased mTOR activity and enhanced AMP kinase activity. The elevated AMPKα phosphorylation was associated with cellular ATP depletion and overproduction of reactive oxygen species due to mitochondrial dysfunction involving the induction of MPT and loss of Δψ. In this context, mitochondria biogenesis was initiated to recover cellular energy homeostasis. Importantly, when autophagy was prevented either pharmacologically ii (3-MA or chloroquine) or genetically (knockdown of ATG5 or ATG7), the colon cancer cells became sensitized toward propionate induced apoptosis through activation of caspase 7 and its downstream effector caspase-3. The observations indicate that propionatetriggered autophagy serves as an adaptive strategy for retarding mitochondria-mediated apoptotic cell death, whereas application of an autophagy inhibitor (Chloroquine) is expected to enhance the therapeutic efficacy of SCFAs in inducing colon tumor cell apoptosis.

Introduction: The role of short-chain fatty acids (SCFAs) in colonic motility is controversial. Germ free (GF) mice are unable to produce SCFAs and serve as a model to study how their absence affects colonic motility. GF transit is slower than controls and colonization of these mice improves gastrointestinal (GI) transit and serotonin (5-HT) levels. Our aim was to determine the role SCFAs play in improving transit, and whether this is dependent on mucosal 5-HT signaling. Methods: Motility was assessed in GF mice via spatiotemporal mapping with intraluminal perfusion of either PBS or SCFA cocktail. Outflow from the colon was recorded to quantify propulsive contractions. Motility was then assessed in TPH1-KO mice with PBS, butyrate and then propionate. GPR43 and 5-HT staining was performed in control and GF colons. Mice were then given chow diet or high sugar diet (HSD) and motility was recorded. Fecal pellets were taken at baseline and just prior to motility experiments and SCFA levels were measured with mass spectrometry. Results: GF mice exhibit significantly lower proportion of propulsive contractions, lower volume of outflow per contraction and slower velocity of contractions compared to controls. SCFAs changed the motility patterns to that of the controls in all parameters. Butyrate administration significantly increased the proportion of propulsive contractions in controls, yet failed to in TPH1 KO mice. Propionate significantly inhibited propulsive contractions in both mice. HSD-fed mice were not different from chow-fed mice in any parameter. No SCFA was significantly reduced, but the change in butyrate concentration was significantly associated with LDC frequency. Conclusions: Our results reveal significant abnormalities in the propulsive nature of colon motor patterns in GF mice, explaining the decreased transit time in in vivo studies. We show that butyrate, not propionate, activates propulsive motility and that this requires mucosal 5-HT, possibly released by ECs. / Thesis / Master of Science (MSc)

A utilização de volumoso em dietas de bovinos em terminação é importante para estimular a ingestão de energia, manter a saúde ruminal e diminuir distúrbios digestivos. A literatura é carente de informação, especialmente nas condições tropicais e em especial com animais zebuínos em relação à níveis e fontes de volumosos e seus efeitos no comportamento ingestivo, saúde e metabolismo ruminal de bovinos em terminação. Os objetivos desse experimento foram avaliar teores de FDN de feno (FDNf) de baixa qualidade, em dietas contendo alto teor de concentrado, quanto ao consumo, digestibilidade dos nutrientes, comportamento ingestivo e parâmetros ruminais de bovinos confinados. Foram utilizados cinco bovinos machos, castrados, da raça Nelore (PC inicial 337,0&#177;10,0kg) distribuídos em um delineamento em quadrado latino 5x5. Cada período experimental foi composto por 20 dias, sendo os 15 primeiros dias destinados à adaptação dos animais e os cinco dias restantes, às colheitas. As dietas experimentais foram formuladas para serem isoproteicas e conterem 4,5; 8,0; 11,5 e 15,0% de FDNf (% na MS) de baixa qualidade e 64,7, 60,7, 56,6, 52,5% de milho moído e 14,5, 14,3, 14,0, 13,8% de casca de soja. O quinto tratamento foi constituído por 18,5% de FDNf e 20,9% de casca de soja. Todos os tratamentos foram inclusos na análise de regressão e polinômios ortogonais (linear e quadrático) foram utilizados para avaliar o efeito de concentrações de FDNf para os quatro primeiros tratamentos. Foi realizado um contraste entre o quarto e o quinto tratamento. O aumento do teor de FDNf nas dietas ocasionou efeito quadrático (p < 0,1) para IMS, NDT e MO. Os consumos de CNF, CHOT, PB e EE não foram afetados pelos tratamentos (p > 0,1). As concentrações de NDT (p < 0,01), as digestibilidades aparentes totais da MS (p < 0,01), MO (p < 0,01), FDN (p= 0,05), CHOT (p < 0,01) e da PB (p = 0,06) foram reduzidas linearmente com o aumento do teor de FDNf na dieta. As digestibilidades aparentes totais de CNF (P = 0,70) e EE (P = 0,86) não foram afetadas pelos tratamentos. As concentrações de EM, ELm e de ELg foram reduzidas (p<0,01) de forma linear com a inclusão de FDNf nas dietas. A inclusão de FDNf nas dietas aumentou de forma quadrática (p<0,05) o tempo de ingestão, ruminação e mastigação dos animais. Por kg de MS, houve aumento linear no tempo ingestão (p<0,05), ruminação (p<0,01) e mastigação (p<0,01). Por kg de FDNf houve aumento linear no tempo de ruminação (p<0,1) e de mastigação (P,0,05). Aumentar o teor de FDNf nas dietas proporcionou aumento linear (p<0,05) no pH e no teor de N-NH3 ruminal do animais. Também houve aumento linear na proporção molar de acetato (p< 0,01), isobutirato (p = 0,10) e na relação C2:C3 (p< 0,05). A inclusão de 18,5% de FDNf e 20,9% de CS (% na MS) na dieta ocasionou aumento (p < 0,05) nos consumos de MS, NDT, MO e FDN, ELm (p<0,1) e ELg (p<0,1). Aumentar a inclusão de FDNf para 18% e CS para 20,9% na dieta aumentou a digestibilidade aparente total da FDN (p<0,1). A inclusão de 18,5% de FDNf e 20,9% de CS na dieta ocasionou aumento no tempo, expresso em min dia-1, de ingestão (p< 0,05) e mastigação (p< 0,05). Aumentar o teor de FDNf e CS na dieta ocasionou aumento na proporção molar de acetato (p<0,1) e aumento na relação C2:C3 (p< 0,05). A manipulação do teor de FDNf da dieta permite alterar a ingestão de energia, o comportamento ingestivo, a eficiência fermentativa no rúmen de animais confinados. / Roughage is included in beef cattle finishing diets to increase feed and energy intakes, while maintaining rumen health and reducing digestive disorders. The available literature is scarce regarding to the effects of levels of roughage in finishing diets for Zebu cattle on ingestive behavior and rumen parameters. The objectives of this experiment were to evaluate the effects of levels of NDF from hay of low quality in finishing diets containing high levels of concentrate on consumption, digestibility of nutrients, ingestive behavior and rumen parameters of zebu cattle. Five Nellore steers (337,0&#177;10,0kg IBW) were used in a 5x5 Latin-square design. Each experimental period lasted 20 days, the first 15 days were used for adaptation and the last 5 days for collection. The experimental diets were formulated to be isoprotein with 4,5; 8,0; 11,5 or 15,0% of NDF (% in DM) from low quality hay (rNDF) and 64.7, 60.7, 56.6, 52.5% ground corn and 14.5, 14.3, 14.0, 13.8% soybean hulls. The fifth treatment consisted of 18.5% of hay NDF and 20.9% of soybean hulls. All treatments were submitted to the regression analysis and orthogonal polynomials (linear and quadratic) were used to evaluate the effect of roughage NDF concentrations for the first four treatments. A contrast was used to compare the fourth and the fifth treatments. The increase of rNDF level in the diet caused a quadratic response (P < 0,1) on intakes of DM, OM and TDN (p<0.01), while the intakes of NFC, TCHO, CP and EE were not affected by treatments (p>0.1). The diets TDN (p<0.01) and the total tract apparent digestibilities of DM, (p<0.01), OM (p< 0.01), NDF (P=0.05), TCHO (p< 0.01) and CP (P = 0.06) decreased linearly as low quality hay NDF was included in the diets. The total tract apparent digestibilities of NFC (P = 0,70) and EE (P = 0,86) were not affected by treatments. The diet concentrations of ME, NEm and NEg, decreased linearly (p<0,01) as roughage NDF level increased in the diets. Inclusion of roughage NDF in the diets caused a quadratic increase (p<0.05) in ingestion time, rumination time and mastication time (minutes per day). When ingestive behavior was expressed per kg of DM there was a linear increase in ingestion time (p<0,05), rumination time (p<0,01) and mastication time (p<0,01). When ingestive behavior was expressed per kg of roughage NDF there was a linear increase in rumination time (p<0.1) and mastication time (p<0.05). Inclusion of roughage NDF in the diets caused a linear increase (p<0.05) in rumen pH (p<0.05), in rumen N-NH3 (p<0.05), in the molar proportions of acetate (p< 0,01) and isobutirate (p< 0,1), and in the rumen C2:C3 ratio (p< 0,05). The diet containing 18.5% of roughage NDF and 20.9% of soybean hulls (% of DM) increased the consumptions of DM (p<0.05), TDN (p<0,05), OM (p<0.05), NDF (p<0.05), NEm (p<0,1) and NEg (p<0,1) compared with the containing 15% of roughage NDF and 13.8% soybean hulls. Increasing roughage NDF to 18.5% and soybean hulls to 20.9% in the diet increased the total apparent digestibility of NDF (p<0,1), and ingestion (p<0.05) and chewing (p<0.05) times expressed in min.day-1. Increasing roughage NDF and soybean hulls in the diet increased the molar proportion of acetate (p< 0.1) and the C2:C3 ratio (P < 0,05). The manipulation of the roughage NDF content of finishing diets allows to manipulate energy intake, ingestive behavior and efficiency of rumen fermentation of Zebu cattle.

No presente trabalho estudou-se o metabolismo ruminal e a fermentação com produção de gases e de metano avaliadas pela técnica de ex-situ (micro-rúmen) em duas espécies de ruminantes domésticos, o bovino e o bubalino, visando contribuir com a importante área da nutrição de ruminantes na geração de dados para realização de uma alimentação mais eficiente e econômica desses animais. Para tanto, o trabalho está apresentado em forma de capítulos com uma Introdução sobre o tema, uma revisão da literatura e o Capítulo 3 redigido na forma de um artigo científico para futura publicação. Na revisão da literatura (Capítulo 2) são apresentadas discussões sobre os principais trabalhos publicados em literatura especializada em importantes aspectos, subdivididos nos seguintes tópicos: Diferenças fisiológicas no processo digestivo entre bovinos e bubalinos; a proteína na nutrição de ruminantes; a uréia como fonte proteica; fermentação ruminal e seus produtos e fatores que influenciam a fermentação ruminal. Ressalta-se, porém, que há escassez de trabalhos publicados comparando as duas espécies de ruminantes nessa área, especialmente com o uso de uréia em dietas. Como os ruminantes possuem a capacidade de transformar fonte de nitrogênio não proteico em proteína de alto valor biológico há necessidade de explorar essa vantagem da espécie para diminuir os custos de produção sem afetar a produção desses animais. Há vantagens e desvantagens do uso da uréia na alimentação animal, mas é necessário elucidar as diferenças que existem nas duas espécies quando utilizamos essa fonte de nitrogênio. Neste estudo foi possível caracterizar o perfil da fermentação ruminal das duas espécies estudadas. A produção de metano pelos ruminantes é apontada como fator contribuidor para o efeito estufa, e neste trabalho avaliamos esses parâmetros tanto de metabolismo como de fermentação existentes nessas espécies e a influência da uréia nesses sistemas. A utilização de uréia em uma dieta com 50% de volumoso promoveu maior consumo de matéria seca e extrato etéreo e maior produção de ácido propiônico com menos relação acético:propiônico, não influenciando nos coeficientes de digestibilidade dos nutrientes, na dinâmica ruminal e no pH em relação às dietas com 50% de volumoso sem uréia e com 80% de volumoso com uréia. Além disso, essa última dieta promoveu redução da produção de metano em relação à dieta contendo 50% de volumoso e 50% de concentrado com nitrogênio proteico com farelo de soja, modulando de forma a evidenciar sua importância na nutrição de ruminantes, com redução de custos de produção e dos efeitos deletérios causados pelo gás metano ao meio ambiente. / We have studied the ruminal metabolism fermentation with gas production and methane measured by ex-situ technique (micro-rumen) in two species of domestic ruminants, cattle and buffaloes to contribute to the important area of ruminant nutrition in order to become more efficient and economical feeding of these animals. To this end, the work is presented in the form of chapters with an introduction on the topic, a literature review and Chapter 3 written as a scientific paper for future publication. In the literature review (Chapter 2) discussions of important papers published in specialized literature is divided into the following topics: cattle vs buffaloes - physiological differences; protein in ruminant nutrition; urea as the protein source; ruminal fermentation and its products; factors that influence the rumen fermentation,. It is noteworthy, however, that there is scarcity of studies comparing the two ruminant species in this area, especially with the use of urea in diets. As ruminants have the ability to transform source of non-protein nitrogen in protein of high biological value there is need to explore this kind of advantage to reduce production costs without affecting the total production. There are advantages and disadvantages of the use of urea in animal feed, but it is necessary to elucidate the differences between the two animal species when using this source of nitrogen. In this study it was possible to characterize the profile of ruminal fermentation of both species. Methane production by ruminants is implicated as contributing factor to the greenhouse effect, and in this paper we have evaluated these parameters as fermentation metabolism in buffalo and cattle and the influence of urea on feeding systems. The use of urea in a diet with 50% forage promoted greater dry matter and fat intake and increased propionic acid production with less acetic:propionic ratio, but no influence was observed in the digestibility of nutrients, ruminal pH and rumen dynamics when compared to diets with 50% forage without urea and 80% of forage with urea. Moreover, this latest diet promoted reduction of methane production in relation to the diet containing 50% forage and 50% concentrate without urea, modulating in order to highlight its importance in ruminant nutrition, reducing costs production and the damaging effects to the environment by emission of methane gas.

Quatro experimentos foram realizados para estudar o desempenho, produção de metano e metabolismo ruminal em ovinos alimentados com dietas contendo nitrato de cálcio (NC). Experimento 1: Cinquenta borregas foram utilizadas, em delineamento em blocos completos casualizados, para avaliar o desempenho, as características de carcaça e a produção de CH4. As dietas continham teores crescentes (0, 1, 2, 3 ou 4% na MS) de NC. Houve efeito quadrático para consumo de MS, peso final, ganho médio diário e eficiência alimentar. O aumento do consumo de NC promoveu redução da produção de CH4. O peso ao abate, peso da carcaça quente e fria e espessura da parede corporal reduziram linearmente. Houve efeito quadrático para a espessura de gordura, área de olho de lombo e para a luminosidade. A inclusão de NC reduz a produção de metano, no entanto, em teores a partir de 2%, reduz o consumo, o ganho médio diário e a eficiência alimentar. Em teores de até 4% de NC não alterou os valores de NaNO3 e NaNO2 na carne fresca. Experimento 2: Cinco ovinos canulados no rúmen, distribuídos em delineamento em quadrado latino, foram utilizados para avaliar o metabolismo ruminal, digestibilidade e balanço de N. As dietas continham teores crescentes (0, 1, 2, 3 ou 4% na MS) de NC encapsulado. Houve efeito quadrático para o consumo de MS, consumo de água/kg MS e N retido. Houve efeito linear crescente para a digestibilidade da MO, da FDN e da PB. Houve efeito linear decrescente para o N fecal. Houve efeito quadrático para a concentração de AGCC total e para a proporção molar de ácido valérico. Houve efeito linear crescente para a proporção de ácido acético, butírico e isobutírico. Houve efeito quadrático para o N-NH3 e aumento linear para o pH ruminal. O NC encapsulado até teores de 4% para ovinos aumenta a digestibilidade dos nutrientes e da fibra insolúvel em detergente neutro, o pH ruminal e a proporção de ácido acético em relação a concentração de AGCC. No entanto o consumo é reduzido quando o NCE é adicionado em teores de 4%. Experimentos 3 e 4: foram realizados em delineamento em blocos completos casualizados para avaliar dietas contendo diferentes fontes de nitrogênio: farelo de soja (controle), ureia, nitrato de cálcio encapsulado (NCE) e nitrato de cálcio não encapsulado (NCNE). Em ambos os experimentos analisou-se os contrastes: controle vs nitrogênio nãoproteico (ureia, NCE e NCNE), ureia vs nitrato de cálcio (NCE e NCNE) e NCE vs NCNE. No experimento 3 foram utilizados 44 cordeiros para determinar os efeitos de diferentes fontes de nitrogênio nas características de desempenho e de carcaça. O peso final, o ganho médio diário e a eficiência alimentar foram maiores no controle em relação ao NNP. No experimento 4 foram utilizados 20 ovinos machos castrados, canulados no rúmen, para avaliar o metabolismo ruminal e a digestibilidade dos nutrientes. A digestibilidade da FDN foi maior nas dietas contendo NNP em relação à dieta controle. O pH ruminal foi maior nas dietas com NNP em relação ao controle; e maior no NC em relação a dieta com ureia. O ácido acético foi maior nas dietas com NC em relação a dieta com ureia. O ácido propiônico foi maior com NNP comparados à dieta controle e menor nas dietas com NC comparada à dieta com ureia. A relação acetato: propionato foi maior no NC em relação à ureia. A inclusão de 2% do íon nitrato, tanto na forma de NCE como NCNE para ovinos, permite que o desempenho e características de carcaça sejam similares a dieta com inclusão de 1,1% de ureia. O NC influencia no aumento da digestibilidade da fibra em detergente neutro, do pH ruminal, da proporção de acetato em relação a concentração de AGCC total e da relação Ac:Pr. / Four experiments were conducted to study the performance, methane production and ruminal metabolism in sheep fed diets containing calcium nitrate (CN). Experiment 1: Fifty ewe lambs were used, in a randomized complete block design, to determine the performance, carcass characteristics and methane production. Diets contained increasing levels (0, 1, 2, 3 or 4%, DM basis) of CN. There was a quadratic effect on dry matter intake, final body weight, average daily gain and feed efficiency. Increased CN intake promoted reduction in methane production. Slaughter weight, hot carcass weight and chilled carcass weight reduced linearly. There were a quadratic effect on the fat thickness, rib eye area and for brightness. Increased CN reduces the production of methane, however, in amounts from 2% reduces intake, average daily gain and feed efficiency. In amounts of up to 4% did not change NaNO3 and NaNO2 in fresh meat. Experiment 2: Five sheep, cannulated in the rumen, distributed in a Latin Square design, were used to determine ruminal metabolism and digestibility. There was a quadratic effect for DM intake, water intake/kg DM and N retained. There was a linear increase for the digestibility of OM, NDF and CP, while fecal N decreased linearly. There was a quadratic effect on the concentration of the total SCFA and the molar proportion of valeric acid. There was a linear effect on the proportion of acetic acid, butyric acid and isobutyric acid. There was a quadratic effect for N-NH3 while ruminal pH increased linearly. The encapsulated CN up to 4% in sheep increases the digestibility of the nutrients and insoluble in neutral detergent fiber, ruminal pH and the proportion of acetic acid relative concentration of SCFA. However intake is reduced when the encapsulated CN is added at 4%. Experiments 3 and 4: were conducted in a randomized complete block design to evaluate diets containing different nitrogen sources: soybean meal (control), urea, encapsulated calcium nitrate (ECN) and nonencapsulated calcium nitrate (NECN). In both experiments were analyzed the following contrasts: control vs non-protein nitrogen (urea, ECN and NECN), urea vs calcium nitrate (ECN and NECN) and ECN vs NECN. In Experiment 3, 44 ram lambs were used to determine the effects of different nitrogen sources on performance and carcass traits. The final weight, average daily gain and feed efficiency were greater in the control diet compared to the NPN. In the experiment 4, 20 wethers, cannulated in the rumen, were used to assess the rumen metabolism and diets digestibility. The NDF digestibility was greater in diets containing NPN compared to the control. The ruminal pH was higher in the NPN diets compared to the control; and greater in the diets with NC than those with urea. The acetic acid was higher in diets with CN than the urea diet. The propionic acid was higher in the NPN diets compared to the control and lower in CN compared to the urea diet. The acetate: propionate ratio was higher for diets with CN compared to the urea diet. CN influences the increased digestibility of neutral detergent fiber, ruminal pH, the proportion of acetate relative to the total SCFA concentration and the relationship Ac: Pr.

No presente trabalho estudou-se o metabolismo ruminal e a fermentação com produção de gases e de metano avaliadas pela técnica de ex-situ (micro-rúmen) em duas espécies de ruminantes domésticos, o bovino e o bubalino, visando contribuir com a importante área da nutrição de ruminantes na geração de dados para realização de uma alimentação mais eficiente e econômica desses animais. Para tanto, o trabalho está apresentado em forma de capítulos com uma Introdução sobre o tema, uma revisão da literatura e o Capítulo 3 redigido na forma de um artigo científico para futura publicação. Na revisão da literatura (Capítulo 2) são apresentadas discussões sobre os principais trabalhos publicados em literatura especializada em importantes aspectos, subdivididos nos seguintes tópicos: Diferenças fisiológicas no processo digestivo entre bovinos e bubalinos; a proteína na nutrição de ruminantes; a uréia como fonte proteica; fermentação ruminal e seus produtos e fatores que influenciam a fermentação ruminal. Ressalta-se, porém, que há escassez de trabalhos publicados comparando as duas espécies de ruminantes nessa área, especialmente com o uso de uréia em dietas. Como os ruminantes possuem a capacidade de transformar fonte de nitrogênio não proteico em proteína de alto valor biológico há necessidade de explorar essa vantagem da espécie para diminuir os custos de produção sem afetar a produção desses animais. Há vantagens e desvantagens do uso da uréia na alimentação animal, mas é necessário elucidar as diferenças que existem nas duas espécies quando utilizamos essa fonte de nitrogênio. Neste estudo foi possível caracterizar o perfil da fermentação ruminal das duas espécies estudadas. A produção de metano pelos ruminantes é apontada como fator contribuidor para o efeito estufa, e neste trabalho avaliamos esses parâmetros tanto de metabolismo como de fermentação existentes nessas espécies e a influência da uréia nesses sistemas. A utilização de uréia em uma dieta com 50% de volumoso promoveu maior consumo de matéria seca e extrato etéreo e maior produção de ácido propiônico com menos relação acético:propiônico, não influenciando nos coeficientes de digestibilidade dos nutrientes, na dinâmica ruminal e no pH em relação às dietas com 50% de volumoso sem uréia e com 80% de volumoso com uréia. Além disso, essa última dieta promoveu redução da produção de metano em relação à dieta contendo 50% de volumoso e 50% de concentrado com nitrogênio proteico com farelo de soja, modulando de forma a evidenciar sua importância na nutrição de ruminantes, com redução de custos de produção e dos efeitos deletérios causados pelo gás metano ao meio ambiente. / We have studied the ruminal metabolism fermentation with gas production and methane measured by ex-situ technique (micro-rumen) in two species of domestic ruminants, cattle and buffaloes to contribute to the important area of ruminant nutrition in order to become more efficient and economical feeding of these animals. To this end, the work is presented in the form of chapters with an introduction on the topic, a literature review and Chapter 3 written as a scientific paper for future publication. In the literature review (Chapter 2) discussions of important papers published in specialized literature is divided into the following topics: cattle vs buffaloes - physiological differences; protein in ruminant nutrition; urea as the protein source; ruminal fermentation and its products; factors that influence the rumen fermentation,. It is noteworthy, however, that there is scarcity of studies comparing the two ruminant species in this area, especially with the use of urea in diets. As ruminants have the ability to transform source of non-protein nitrogen in protein of high biological value there is need to explore this kind of advantage to reduce production costs without affecting the total production. There are advantages and disadvantages of the use of urea in animal feed, but it is necessary to elucidate the differences between the two animal species when using this source of nitrogen. In this study it was possible to characterize the profile of ruminal fermentation of both species. Methane production by ruminants is implicated as contributing factor to the greenhouse effect, and in this paper we have evaluated these parameters as fermentation metabolism in buffalo and cattle and the influence of urea on feeding systems. The use of urea in a diet with 50% forage promoted greater dry matter and fat intake and increased propionic acid production with less acetic:propionic ratio, but no influence was observed in the digestibility of nutrients, ruminal pH and rumen dynamics when compared to diets with 50% forage without urea and 80% of forage with urea. Moreover, this latest diet promoted reduction of methane production in relation to the diet containing 50% forage and 50% concentrate without urea, modulating in order to highlight its importance in ruminant nutrition, reducing costs production and the damaging effects to the environment by emission of methane gas.

Ruminal acidosis is a persisting digestive disorder in modern ruminant production; however, the susceptibility of cows to ruminal acidosis differs among cows fed a common diet. The overall objective of this research was to evaluate factors affecting the susceptibility of cows to ruminal acidosis. This research demonstrated that feeding sucrose in replacement for corn grain to Holstein cows in early lactation does not increase the risk for ruminal acidosis and may actually increase ruminal pH. However, regardless of dietary treatment, cows in early lactation were at risk for ruminal acidosis. In Study 2, diets differing in the forage-to-concentrate ratio were fed to Holstein cows to evaluate changes in the in vivo rate of short-chain fatty acid absorption (SCFA) and the expression of genes coding for transporters and enzymes involved in the absorption and metabolism of SCFA in ruminal tissue. Contrary to the hypothesis, the fractional rate of absorption and expression of genes involved in SCFA absorption and metabolism were not affected by the forage-to-concentrate ratio. Considerable variation among individual cows for the severity of ruminal acidosis was detected for cows on the diet containing the low forage-to-concentrate ratio. To determine the cause of this variation, a ruminal pH measurement system was developed to accurately and precisely measure ruminal pH in non-cannulated small ruminants. Sheep were then subjected to a ruminal acidosis challenge model in vivo, and the absorption of acetate and butyrate across the isolated ruminal epithelia was measured in vitro in Ussing chambers. The results of this study demonstrated that differences in the severity of ruminal pH depression among animals could largely iv be accounted for by differences in the absorptive capability of the ruminal epithelium. In summary, although ruminal acidosis is a common digestive disorder in dairy production systems, variation in the susceptibility to ruminal acidosis is common. The cause for much of this variation is due to differences in the absorptive capacity of the ruminal epithelia. / Animal Science