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Necrotic enteritis (NE) is a major enteric disease in commercial poultry and manifests itself in clinical and subclinical forms. Despite years of research, NE is still among the leading diseases with the greatest economic impact on poultry production. Subclinical forms lead to poor performance (reduced feed intake, weight gain and eventually higher feed conversion ratio) but usually occurs with low mortality rates. The use of antibiotic growth promoters (AGPs) is proving to be an effective tool in maintaining gut health and modifying gut microbiota, thus improving broiler performance and reducing NE. Removal of AGPs has led to an increase in NE occurrence, particularly the subclinical forms. The lack of alternative strategies to control NE is mainly due to limited insight into the relationship between NE pathogenesis, the host microbiome and its immune responses. Therefore, key to overcoming NE is to define the cellular and molecular mechanisms that are involved in the progression of the disease, especially with regard to mucosal immune responses and gut microbiome. Also, assessing the impact of these changes on gut cell metabolism and function is of great importance. This information would be a valuable guide to prevent the onset or alleviate the negative impact of NE on bird's health and performance. In a series of experiments conducted for this project, the effect of single or multi-strain probiotics as well as multi-component additives were tested during NE challenge in order to define the cellular and molecular mechanisms that are involved in the progression of the disease. Results of these experiments revealed that challenging broilers with a 'naturally occurring' NE led to differential expression of tight junction (TJ) proteins in the jejunum compared to non-challenged birds. Supplementation of certain additives reduced NE lesion scores, improved performance and increased mRNA abundance of claudin-3, a key epithelial TJ protein. Multi-strain probiotics and multi-component additives (including a symbiotic and a product containing probiotics, prebiotics and essential oils) were more effective than single-strain probiotics or prebiotics. The aforementioned additives were also more effective in modulating immune responses to NE, especially by decreasing the mRNA abundance of IFN-γ and IL-10 in the jejunum. Furthermore, supplementation of these additives led to an increase in the expression of nutrient transporters (SGLT-1) and regulators of energy metabolism (PGC-1α, mTOR and AMPK); thus, improving nutrients absorption and metabolism. Microbial profiling using 16S rRNA sequencing showed that supplementation of each specific additive led to a signature-like microbiome in the ileal scrapings of broilers. However, supplementation of multi-component additives (including a symbiotic and a product containing probiotics, prebiotics and essential oils) modified the ileal microbiome in association with lower NE lesion scores, better performance and modulated immune responses. These additives reduced the relative abundance of bacteria such as ASF356, Bacteroides, Clostridium sensu stricto 1, Faecalibaculum, Lachnospiraceae UCG-001, Muribaculum, Oscillibacter, Parabacteroides, Rikenellaceae RC9 gut group, Ruminococcaceae UCG-014, and Ruminiclostridium 9 and increased the relative abundance of Lactobacillus compared to NE challenged birds. Collectively, these data indicate that during a subclinical naturally occurring NE, the use of multi-strain probiotics or multi-component additives, compared to single-strain probiotics or prebiotics, would be a more promising strategy in alleviating the effect of this enteric disease. / Doctor of Philosophy / Necrotic enteritis, an enteric disease, is one of the major diseases that negatively impacts the poultry industry and producers' profitability. The growing ban on the use of antibiotics that were used to prevent this disease has increased the number of necrotic enteritis outbreaks worldwide. Having a better understanding of the cellular and molecular mechanisms that are involved in the onset of this disease is of crucial importance and could lead to finding more effective ways to control this disease without drugs. The gut is the site of digestion and absorption of nutrients so any damage would lead to poor bird performance. In a series of experiments conducted for this project, several combinations of beneficial bacteria and nutrient sources that help bacterial growth in the gut (prebiotics) improved gut health leading to better performance during the grow-out period (days 0-42) when birds reach market age. These supplements protected the gut lining and reduced damages due to necrotic enteritis with less severe lesions. Barrier function of the gut was also improved by supplementing the diet with combination of beneficial bacteria and nutrients that help their growth in the gut. There are special types of proteins (called tight junctions) that seal up the space between intestinal cells (enterocytes) and prevent pathogens in the gut lumen from entering the body, thus preventing inflammation and disease. This helps the body to use the absorbed nutrients for growth rather than spending energy to fight pathogens, which collectively results in better growth performance. Concurrent supplementation of beneficial bacteria plus nutrients that help their growth balanced the immune responses in the gut by increasing the copy number of cytokines. Cytokines are proteins that orchestrate immune responses that the host mounts against pathogens. Certain cytokines regulate such responses by preventing the immune system from overreacting and mounting unnecessary reactions, thus preserving energy and nutrients for growth while reducing inflammation. Nutrient uptake from the gut lumen is facilitated by nutrient transporter proteins that reside on intestinal cells (enterocytes). Birds concurrently supplemented with beneficial bacteria and nutrients that help their growth in the gut increased the abundance of these proteins, resulting in improved nutrient uptake and performance compared to the control birds. Co-supplementation of beneficial bacteria and nutrient sources that help their growth modified the type and number of bacteria that are present in the gut lumen. The modified bacterial community were able to produce metabolites such as butyrate and propionate, which are beneficial for the health and growth of the intestinal cells, thus improving the bird's health and its performance. Overall, compared to beneficial bacteria alone, co-supplementation of beneficial bacteria with the nutrients that help their growth in the gut significantly reduced intestinal lesions and improved performance of broiler chickens during the production period. Moreover, dietary addition of these supplements improved gut barrier function by regulating the gene expression of tight junction proteins and gut mucosal immune responses as well as modifying the bacterial community of the gut. Therefore, such combination supplements hold promise in controlling necrotic enteritis in poultry and sustain good overall performance that translates into higher profitability to producers.

Immediately post-hatch, broiler chicks are exposed to microbes that begin colonizing the gut, including environmental pathogens. One of the costliest enteric diseases in broiler production is necrotic enteritis (NE), caused by the ubiquitous opportunistic bacteria Clostridium perfringens (CP). With the worldwide reduction in antibiotic growth-promoters (AGPs), there is increased interest in natural alternatives to reduce disease and improve broiler health. The overall objective of the studies described herein was to apply probiotics or synbiotics to birds by in ovo application or orally before they leave the hatchery, then evaluate bird performance and various intestinal responses. Data were analyzed in JMP with LS Means to separate means with significance assigned at P ≤ 0.05 and trends at 0.05 < P ≤ 0.10. The first 21-day (D) study used 480 male Cobb 500 broilers randomly divided into one of four treatments using a 2x2 factorial design: a no-additive control (CTRL), a one-time oral application of synbiotic at the hatchery fed a basal diet (HS), an oral application of water at the hatchery with dietary synbiotics (DS), and a hatchery synbiotic plus dietary synbiotic (HSDS). Performance was measured on day-of-hatch (DOH), D3, D7, D14, and D21. mRNA abundance of various intestinal markers was measured at D7 and D21, including tight junction proteins ZO-1, ZO-2, and CLD-1; nutrient transporters SGLT1 and PepT1; and immune response markers TLR2, TLR4, and IL-10. HS lowered feed intake (FI) and feed conversion ratio (FCR) without lowering body weight (BW) from D14-21. There was greater abundance of PepT1 mRNA (P ≤ 0.1) and IL-10 mRNA (P ≤ 0.05) on D21 in HSDS. Second, a 21-day pilot study with 480 male and female Cobb 500 broilers was conducted to determine the optimum in ovo dosage level of a probiotic or synbiotic (PROB or SYNB) applied at embryonic day 18 (E18) with subsequent NE challenge using seven treatments: in ovo application of sterile water (CTRL), low (PROB-L or SYNB-L: 1x105 CFU), medium (PROB-M or SYNB-M: 1x106 CFU), or high (PROB-H or SYNB-H: 1x107 CFU) probiotic or synbiotic doses dissolved in sterile water. Performance measurements were taken on DOH, D4, D8, D14 and D21. On D8, NE lesion scores were not impacted by treatment. D8 ileal samples were taken for mRNA abundance of TLR4, IL-10, IL-1β, AvBD8, AvBD10, and AvBD13. SYNB-H had higher abundance of AvBD10 mRNA compared to CTRL (P ≤ 0.1), and higher IL-1β mRNA compared to SYNB-L (P ≤ 0.05). PROB-H and SYNB-H had better performance than the low and medium doses, but were not better than the CTRL. The high doses were chosen for subsequent studies. Third, a longer 42-day study using 1,630 Ross 708 male and female broilers was conducted consisting of the following six treatments. A negative control (NC): sterile water in ovo fed basal corn/soybean meal mash diet without NE challenge; antibiotic growth-promoter (AGP+): sterile water in ovo fed basal diet with virginiamycin (0.5 kg/MT) as an AGP with NE challenge; NC+: same as NC plus NE challenge; SI+: synbiotic in ovo fed the basal diet and NE challenged; SD+: sterile water in ovo fed basal diet supplemented with synbiotic (0.5 kg/MT feed) and NE challenged; and SID+: synbiotic in ovo fed basal diet with synbiotic (0.5 kg/MT feed) with NE challenge. Cumulatively, SID+ had lower FI and FCR than NC+, but no change in BW or BWG. The combination treatment (SID+) often had an additive effect compared to SD+ or SI+ alone on mRNA abundance and D7 cecal fatty acid profiles. SD+ and SID+ also had higher D42 lean:fat ratios compared to NC+. Last, a 42-day study was conducted using 1,630 male and female Ross 708 broilers and the in ovo application of probiotics and subsequent NE challenge with five treatments. NC: sterile water in ovo, fed basal corn/soybean meal mash diet without NE challenge; AGP+: sterile water in ovo, fed basal diet with virginiamycin (0.5 kg/MT of feed) as AGP with NE challenge; NC+: NC treatment, with NE challenge; PI+: probiotic in ovo, fed basal diet, with NE challenge; PD+: sterile water in ovo, fed basal diet supplemented with probiotic (1.3 kg/MT of feed), with NE challenge. The use of probiotics in this study had little effect on performance, lean:fat ratios, and cecal fatty acid profiles, but PD+ increased mRNA abundance of D14 TLR2, D14 TNF-α, and D42 LEAP2 in cecal tonsils compared to controls. PI+ increased mRNA abundance of D7 and D42 MUC2, D7 LEAP2, and D42 TNF-α in the ileum. PI+ increased mRNA abundance in the cecal tonsils of D7 TLR2 and D42 TNF-α. These studies yielded interesting results about probiotics and synbiotics during a NE challenge by evaluating performance, intestinal immune responses, and fatty acid profiles in the ceca of broilers. In conclusion, the probiotic in this study did not improve broiler health during a NE challenge, but synbiotic use in ovo and continuation in the feed showed improvement over in ovo or dietary application alone. Synbiotic improved FCR over a challenged control, and altered mRNA abundance in the small intestine. / Doctor of Philosophy / The poultry industry is one of the most popular animal protein sources worldwide. As with any livestock operation, industry goals include optimizing animal health and well-being, maximizing animal productivity, and producing quality products in the most cost effective manner. Improvements in genetics, nutrition, and management have increased productivity and cut costs. One important application was the low-level use of antibiotics in feed. These medications reduced the risk of disease outbreak in flocks, which led to healthier birds and improved growth rates. However, when global concern of antibiotic resistance in human medicine came to light, both the livestock industry and governing bodies implemented voluntary and mandatory reduction or elimination of antibiotics. Previously, these important antibiotics helped to control costly diseases. As they are removed, alternatives to antibiotics will be important in disease control and prevention. A major group of alternatives to antibiotics in poultry includes probiotics, prebiotics, and synbiotics. Probiotic bacteria are considered 'good bacteria' in the gut, and provide various health benefits to the host. Prebiotics are non-living substances that support the growth of healthy bacteria. A synbiotic is the combination of both probiotics and prebiotics in a single application method. The goal of this research project was to give probiotics or synbiotics to broiler chicks and evaluate their potential benefits and effects on bird performance and the immune response. Ideally, applying probiotic bacteria as early as possible might translate into early colonization of the gut with healthy bacteria. This included oral application of synbiotics at the hatchery, or by safely injecting them into part of the egg that is swallowed by the chick embryo before hatch. This egg application, or in ovo application, is a safe, effective, widely-practiced method of vaccinating chicks to jumpstart their defense against disease. By vaccinating them in ovo, they can start to prime the immune system before they even hatch. Applying probiotics in ovo may improve health after early gut colonization with beneficial microbes. Numerous studies on natural alternatives to antibiotics have been conducted, with varying results. Results of this research indicate that in ovo application of probiotics and synbiotics is safe. Birds that received probiotics in the feed often performed similar to those that received none. However, the in ovo use of synbiotics combined with the continued use in the feed after hatch improved efficiency in broilers during an intestinal disease challenge and improved various aspects of gut function. Overall, as antibiotics are phased out, using probiotics and synbiotics may improve poultry health, but continued research will help understand the optimum ways to use them.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Em função de sua disponibilidade no mercado e qualidade nutricional, derivados da soja são importantes fontes de proteína na alimentação animal. Apresentam perfil de aminoácidos semelhante ao de fontes animais, o que estimula seu uso como potencial substituto da farinha de peixe nas rações para aquicultura. No entanto, são deficientes em aminoácidos sulfurados e apresentam fatores antinutricionais que prejudicam o crescimento de peixes. O processamento da soja permite obter produtos mais refinados e altamente digestíveis, como concentrados proteicos (CPS), que têm elevado teor proteico e baixa quantidade de fatores antinutricionais, extraídos no processo de fabricação. Neste contexto, foi determinado o Coeficiente de Digestibilidade Aparente (CDA) do CPS em dietas para juvenis de duas espécies de Characidae autóctones: pacu (Piaractus mesopotamicus) e dourado (Salminus brasiliensis). Também foram avaliados os efeitos do uso deste ingrediente em níveis crescentes de substituição da farinha de peixe na dieta (ensaios com seis tratamentos e quatro repetições), com o objetivo de determinar o nível seguro de substituição sem prejudicar o ganho de peso. O pacu apresentou CDA para proteína (95,33 %) e energia (84,29 %) mais altos que o dourado (CDAproteína = 82,6 %; CDAenergia = 66,6 %), indicando maior plasticidade da espécie para o aproveitamento de fontes vegetais. Baseado em ensaios de desempenho, nas dietas para pacu foi possível substituir até 78,05 % da farinha de peixe das dietas experimentais, enquanto que para dourados, até 37,2%. Acima destes níveis, houve redução no crescimento. A substituição crescente da farinha de peixe pelo CPS exerceu efeito regulatório sobre a atividade de enzimas pancreáticas nos primeiros segmentos do intestino das duas espécies, mensurada através da atividade da protease inespecífica, lipase inespecífica e &alpha;-amilase. Também promoveu redução na altura das dobras intestinais quando a substituição foi total, detectada através da morfometria da parede intestinal do intestino anterior. Estes efeitos podem ser consequência da ação conjunta de fatores antinutricionais da soja, principalmente inibidores de enzimas, potencializados quando a farinha de peixe foi totalmente substituída pelo CPS; e da habilidade com a qual cada espécie digere / absorve os nutrientes. Com base nos resultados obtidos, foi possível concluir que o CPS pode ser utilizado em substituições parciais da farinha de peixe em dietas para peixes onívoros e carnívoros. / Because of market availability and nutritional quality, soybean and its by-products are important sources of protein for the animal feed industry. The amino acid profile of soy products is similar to that of animal sources, encouraging their use as surrogate protein source to fishmeal (FM) in aquafeeds. However, soy products and by-products are deficient in sulfur amino acids and contain anti-nutritional factors that hamper fish growth. Secondary processing of soybean meals yield more refined and highly digestible protein ingredients such as the soy protein concentrate (SPC), which have higher protein contents and lower concentration of anti-nutritional factors, partially extracted or inactivated during the manufacturing process. In such a context, this work determined SPC\'s Apparent Digestibility Coefficient (ADC) in diets for two juveniles neotropical, native Characins species: pacu (Piaractus mesopotamicus), and dourado (Salminus brasiliensis), and also studied the effects of replacing graded levels of FM by SPC (six treatment levels and four repetions) in the aim to determine the optimum substitution level for better growth. Pacu presented higher ADC for protein (95,33 %) and energy (84,29 %) than dourado (ADCprotein = 82,6 %; ADCenergy = 66,6 %), indicating the plasticity of the specie to utilize plant sources. Based on growth performance, for pacu it was possible to substitute until 78,05% of FM, whereas for dourado, until 37,20%. Above these levels, there were reduction on growth performance. The increasing replacement of FM by SPC had regulatory effect on the activity of pancreatic enzymes in the first segment of the intestine of both species, measured through enzymatic assays for unspecific protease, unspecific lipase and &alpha;-amylase. It also caused a reduction on intestinal fold height of proximal intestine. All of these effects can be attributed to soybean anti-nutritional factors, especially enzyme inhibitors, whose action was enhanced when FM was completely replaced by the SPC; and the specific ability of each specie to digest / absorb plant nutrients. It is safe to infer that SPC can only be used as partial replacement of FM in diets for omnivore and carnivore fish.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Zum Studium des prophylaktischen Einflusses ausgewählter antibiotischer Leistungsförderer [Avilamycin (10 ppm), Avoparcin (15 ppm), Virginiamycin (20 ppm)] und ionophorer Antikokzidia [Monensin (100 ppm), Narasin (70 ppm)] sowie des metaphylaktischen bzw. therapeutischen Einsatzes von Tylosin [Tylan 0,5 g/l H2O] auf das Auftreten und die Ausprägung der Clostridium (Cl.) perfringens-Enterotoxämie (CPE) wurden Untersuchungen an insgesamt 33 Versuchsgruppen mit 825 Broilerküken durchgeführt. Die Erkrankung konnte mittels intraduodenaler Inokulation einer Vollkultur Cl. perfringens Typ A (ATCC 3624) sicher reproduziert werden. Die Morbiditätsrate betrug in allen infizierten Gruppen 100 %. An klinischer Symptomatik zeigte sich hauptsächlich profuser wässriger Durchfall. Schwerere Störungen, Apathie und Anorexie, waren selten und in allen beobachteten Fällen vom schnellen Tod des betreffenden Tieres begleitet. Allgemein fiel auf, daß die infizierten und nicht medikamentierten Tiere schneller und länger erkrankten. Bei infizierten und unmedikamentierten Tieren ergab sich eine Mortalitätsrate von 16 bis 36 %, in den medikamentierten Gruppen maximal 8 %. Tylosin zeigte eine sehr gute metaphylaktischen bzw. therapeutische Wirkung. Die Lebendmasseentwicklung betrachtend, konnte Avoparcin unter den Leistungsförderern beste Ergebnisse erzielen. Ähnliche Resultate wurden in den Kombinationsgruppen [Avilamycin plus Monensin oder Narasin] bzw. mittels Narasin erreicht. In absteigender Reihenfolge zeigten Avilamycin, Virginiamycin und Monensin eine geringere leistungsfördernde Wirkung. Die Bestimmung fäkaler bzw. ileozäkaler Clostridienkonzentrationen lebender, respektive verendeter Hühner erbrachte nur wenige und relativ unbedeutende statistisch gesicherte Korrelationen zu anderen Ergebnissen. Es konnten keine Zusammenhänge zwischen Erregerzahl und Lebendmassezunahme, bzw. Todesursache, aufgedeckt werden. Die Resultate aus allen Versuchen zusammenfassend, müssen den Kombinationen von Avilamycin mit Narasin bzw. Monensin beste Effekte hinsichtlich einer positiven Beeinflussung CPE-bedingter Morbidität, Mortalität und Lebendmasseverluste bescheinigt werden. Tylosin war in der Lage, die Verlustzahlen durch CPE rasch zu senken. Für die Ausprägung kompensatorischer Effekte hinsichtlich der Lebendmasseverluste unter der Infektion muß mit einer größeren Zeitspanne gerechnet werden. Die Polyether und auch Avilamycin sind als Futtermittelzusatzstoffe für die europäische Geflügelhaltung zugelassen. Durch die ständige Kokzidiosebedrohung in den Hühnerbeständen kann auf einen prophylaktischen Einsatz antikokzidieller Futtermittelzusatzstoffe momentan nicht verzichtet werden. Es ist zu vermuten, daß es durch den simultanen Einsatz von Polyether und Leistungsförderer zu einer positiven Beeinflussung der schädigenden Wechselwirkungen von Kokzidien und Cl. perfringens im Darm kommt. Bei vorhandener Empfindlichkeit der Eimerien sollte dies sowohl die Bekämpfung von CPE als auch von Kokzidiosen begünstigen. Der positive Eindruck von Avoparcin spielt, bedingt durch das europaweite Verbot, momentan für die Praxis keine Rolle. Die Entwicklungstendenzen auf dem Sektor antibiotisch wirksamer Futtermittelzusatzstoffe, eng verknüpft mit der bakteriellen Resistenzproblematik, werden in der Arbeit ausführlich diskutiert. / Investigations with 825 chickens in 33 trials were performed in order to find out the prophylactic effect of selected antibiotic growth promoters [avilamycin (10 ppm), avoparcin (15 ppm) virginiamycin (20 ppm)] and polyether ionophore antibiotics [monensin (100 ppm), narasin (70 ppm)] on the incidence of Clostridium (Cl.) perfringens enterotoxemia (CPE) in chickens as well as the therapeutic resp. metaphylactic influence of tylosin [Tylan 0,5 g/l H20]. The enterotoxemia could be reproduced regularly by intraduodenal infection with high numbers of vegetative cells of Cl. perfringens type A (ATCC 3624). The morbidity rate always reached 100 %. In spite of a profuse and watery diarrhoea the chickens normally showed no further considerable disturbances of the general status. Apathy or anorexia were rather rare and immediately followed by Exitus letalis of the related chickens. It was striking that the infected and non-medicated broilers contracted the disease more quickly and for a longer time. The mortality rate among the infected and non-medicated animals was 16 to 36 %, among the medicated groups max. 8 %. Tylosin showed a considerable metaphylactic effect in decreasing CPE mortality. The avoparcin group showed the best weight gain among the growth promoters, comparable to the results by means of the combinations [avilamycin + monensin or narasin] or narasin only. Decreasingly avilamycin, virginiamycin and monensin were less successful. Analysing the faecal resp. ileocecal quantities of Cl. perfringens adduced only a few statistically guaranteed correlation with other results. There was no causal connection between numbers of Cl. perfringens and life weight development. It was impossible to discover a numerical threshold of germs responsible for the death of the chickens. Summarising all the results of the entire attempts the combinations of avilamycin and narasin resp. monensin were the most effective concerning the reduction of morbidity, mortality and life weight losses by CPE. By application of tylosin it was possible to stop the mortality rate quickly. But it needs more time to achieve reductions of the CPE related weight losses. The two polyethers and also avilamycin are still admitted in the European Union. Currently an abandonment of anticoccidial feed supplements seems to be impossible due to the present danger of coccidiosis in poultry. By means of monensin/narasin plus avilamycin the adverse health effects of interactions of both pathogens should be reduced. Presupposing susceptibility of the coccida this should be a notable contribution to a better controlling and to the prevention of CPE and coccidiosis, too.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / C. difficile toxin A (TxA) plays an important pathogenic role in antibiotic-induced diarrhea and pseudomembranous colitis, a condition characterized by intense mucosal inflammation and secretion. Agonist activity at A2A adenosine receptors (A2A ARs) attenuates inflammation and damage in many tissues. This study evaluated the effect of a new selective A2A AR agonist (4-{3-[6-amino-9-(5-cyclopropylcarbamoyl-3,4-dihydroxytetrahydrofuran-2-yl)-9H-purin-2-yl]prop-2-ynyl}piperidine-1-carboxylic acid methyl ester; ATL313) on TxA-induced enteritis in murine ileal loops. ATL313 (0.05-5 nM) and/or the A2A AR antagonist (ZM241385; 5 nM) or PBS were injected inside ileal loops immediately prior to challenge with TxA (1-10 mg/loop) or PBS. Intestinal fluid volume/length and weight/length ratios were calculated 3 h later. Ileal tissue samples were collected for measurement of myeloperoxidase (MPO) content, evaluation of ADA activity, for histopathology and apoptotic immunohistochemistry (ApopTagÃ) and for assessment of TNF-&#945; levels by ELISA. TxA (1-10 Âg/loop) significantly (p<0.05) increased volume/length and weight/length, reaching maximum values at 5Âg/loop dosage. ATL313 (5 nM) treatment significantly (p<0.05) reduced TxA-induced volume/length and weight/length, as well as prevented mucosal disruption and TxA-induced apoptosis. These protective effects were reversed by ZM241385 (5 nM), the A2A AR antagonist. ATL313 (5 nM) also reduced neutrophil infiltration, as measured by MPO content; reduced the toxin A-induced increase in ADA activity. Prior to the challenge with TxA, a systemic injection of fucoidin, but not PBS, also reduced tissue destruction and toxin A-induced increase in ADA activity. In conclusion, the A2A AR agonist ATL313 has a great antiinflammatory effect in TxA-induced mice enteritis, significantly reducing tissue destruction and ADA activity. In addition, our data suggested that TxA-induced increase in ADA activity and tissue damage in murine ileal loops are related to the neutrophil infiltration induced by this toxin. / A toxina A do Clostridium difficile (TxA) desempenha um importante papel na patogÃnese da diarrÃia induzida por antibiÃticos e na colite pseudomembranosa, uma condiÃÃo caracterizada por intensa secreÃÃo e inflamaÃÃo da mucosa. A estimulaÃÃo de receptores A2A da adenosina reduz a inflamaÃÃo e o dano tecidual. Neste estudo, avaliou-se o efeito de um novo agonista seletivo para receptores A2A da adenosina (metil Ãster do Ãcido 4-{3-[6-amino-9-(5-ciclopropilcarbamoil-3,4- dihidroxitetrahidrofuran-2-il)-9H-purin-2-il]prop-2-inil}piperidina-1-carboxÃlico; ATL313) na enterite induzida pela TxA em alÃas ileais de camundongos. O ATL313 (0,05-5 nM) e/ou o antagonista dos receptores A2A da adenosina (ZM241385; 5 nM) ou PBS foram injetados em alÃas ileais imediatamente antes da injeÃÃo de TxA (1-10 Âg/alÃa) ou PBS. As razÃes volume de secreÃÃo/comprimento da alÃa e peso/comprimento da alÃa foram calculadas 3h depois. Amostras de tecido foram coletadas para dosagem de atividade de mieloperoxidade (MPO), atividade de ADA, histopatologia, imunohistoquÃmica para apoptose (ApopTag_) e dosagem de TNF-a_ por ELISA. A injeÃÃo de TxA (1-10 Âg) nas alÃas ileais aumentou significativamente (p<0,05) as razÃes volume de secreÃÃo/comprimento da alÃa e peso/comprimento da alÃa com pico em 5Âg. O tratamento das alÃas com ATL313 (5 nM) reduziu significativamente (p<0,05) a secreÃÃo e o edema, preveniu a destruiÃÃo da mucosa e a apoptose induzidos por TxA. Tais efeitos protetores foram revertidos pelo antagonista dos receptores A2A de adenosina, o ZM241385 (5 nM). O tratamento com ATL313 (5 nM), reduziu ainda a infiltraÃÃo neutrofÃlica, avaliada pela dosagem de MPO, e reduziu o aumento da atividade de ADA induzidos pela TxA, bem como a dosagem de TNF-a no tecido das alÃas ileais. O prÃ-tratamento sistÃmico com fucoidina, mas nÃo com PBS, tambÃm reduziu o dano na mucosa e atividade de ADA no tecido das alÃas ileais tratadas com TxA. Assim, conclui-se que na enterite induzida pela TxA em camundongos, o agonista dos receptores A2A da adenosina (ATL313) possui um potente efeito antiinflamatÃrio, reduzindo consideravelmente a lesÃo tecidual e a atividade de ADA. Nossos resultados tambÃm indicam que o aumento da atividade de ADA e o dano tecidual induzido pela TxA em alÃa ileal de camundongos està relacionado com a infiltraÃÃo neutrofÃlica induzida por esta toxina.

Em função de sua disponibilidade no mercado e qualidade nutricional, derivados da soja são importantes fontes de proteína na alimentação animal. Apresentam perfil de aminoácidos semelhante ao de fontes animais, o que estimula seu uso como potencial substituto da farinha de peixe nas rações para aquicultura. No entanto, são deficientes em aminoácidos sulfurados e apresentam fatores antinutricionais que prejudicam o crescimento de peixes. O processamento da soja permite obter produtos mais refinados e altamente digestíveis, como concentrados proteicos (CPS), que têm elevado teor proteico e baixa quantidade de fatores antinutricionais, extraídos no processo de fabricação. Neste contexto, foi determinado o Coeficiente de Digestibilidade Aparente (CDA) do CPS em dietas para juvenis de duas espécies de Characidae autóctones: pacu (Piaractus mesopotamicus) e dourado (Salminus brasiliensis). Também foram avaliados os efeitos do uso deste ingrediente em níveis crescentes de substituição da farinha de peixe na dieta (ensaios com seis tratamentos e quatro repetições), com o objetivo de determinar o nível seguro de substituição sem prejudicar o ganho de peso. O pacu apresentou CDA para proteína (95,33 %) e energia (84,29 %) mais altos que o dourado (CDAproteína = 82,6 %; CDAenergia = 66,6 %), indicando maior plasticidade da espécie para o aproveitamento de fontes vegetais. Baseado em ensaios de desempenho, nas dietas para pacu foi possível substituir até 78,05 % da farinha de peixe das dietas experimentais, enquanto que para dourados, até 37,2%. Acima destes níveis, houve redução no crescimento. A substituição crescente da farinha de peixe pelo CPS exerceu efeito regulatório sobre a atividade de enzimas pancreáticas nos primeiros segmentos do intestino das duas espécies, mensurada através da atividade da protease inespecífica, lipase inespecífica e &alpha;-amilase. Também promoveu redução na altura das dobras intestinais quando a substituição foi total, detectada através da morfometria da parede intestinal do intestino anterior. Estes efeitos podem ser consequência da ação conjunta de fatores antinutricionais da soja, principalmente inibidores de enzimas, potencializados quando a farinha de peixe foi totalmente substituída pelo CPS; e da habilidade com a qual cada espécie digere / absorve os nutrientes. Com base nos resultados obtidos, foi possível concluir que o CPS pode ser utilizado em substituições parciais da farinha de peixe em dietas para peixes onívoros e carnívoros. / Because of market availability and nutritional quality, soybean and its by-products are important sources of protein for the animal feed industry. The amino acid profile of soy products is similar to that of animal sources, encouraging their use as surrogate protein source to fishmeal (FM) in aquafeeds. However, soy products and by-products are deficient in sulfur amino acids and contain anti-nutritional factors that hamper fish growth. Secondary processing of soybean meals yield more refined and highly digestible protein ingredients such as the soy protein concentrate (SPC), which have higher protein contents and lower concentration of anti-nutritional factors, partially extracted or inactivated during the manufacturing process. In such a context, this work determined SPC\'s Apparent Digestibility Coefficient (ADC) in diets for two juveniles neotropical, native Characins species: pacu (Piaractus mesopotamicus), and dourado (Salminus brasiliensis), and also studied the effects of replacing graded levels of FM by SPC (six treatment levels and four repetions) in the aim to determine the optimum substitution level for better growth. Pacu presented higher ADC for protein (95,33 %) and energy (84,29 %) than dourado (ADCprotein = 82,6 %; ADCenergy = 66,6 %), indicating the plasticity of the specie to utilize plant sources. Based on growth performance, for pacu it was possible to substitute until 78,05% of FM, whereas for dourado, until 37,20%. Above these levels, there were reduction on growth performance. The increasing replacement of FM by SPC had regulatory effect on the activity of pancreatic enzymes in the first segment of the intestine of both species, measured through enzymatic assays for unspecific protease, unspecific lipase and &alpha;-amylase. It also caused a reduction on intestinal fold height of proximal intestine. All of these effects can be attributed to soybean anti-nutritional factors, especially enzyme inhibitors, whose action was enhanced when FM was completely replaced by the SPC; and the specific ability of each specie to digest / absorb plant nutrients. It is safe to infer that SPC can only be used as partial replacement of FM in diets for omnivore and carnivore fish.