RESUMO: Biocidas e/ou antibióticos em concentrações sub-inibitórias podem promover o desenvolvimento de resistência adaptativa ou mesmo resistência cruzada nos micro-organismos. Entretanto, estudos destas respostas após o tratamento com a prata são escassos na literatura. Compostos a base de prata, incluindo as nanopartículas de prata (Ag-NPs), podem ser uma alternativa na prevenção e/ou tratamento de mastite bovina. Assim, este trabalho objetivou determinar o efeito de doses sub-inibitórias de Ag-NPs e dos íons Ag+ provenientes do nitrato de prata (AgNO3) sobre isolados de Staphylococcus aureus e de Escherichia coli, provenientes de leite de vacas com mastite. As Ag-NPs foram sintetizadas por redução química utilizando AgNO3 e citrato de sódio e a Concentração Mínima Inibitória (CMI) das Ag-NPs e íons Ag+ nos patógenos da mastite foi determinada. Os isolados foram expostos a concentrações sub-inibitórias de Ag-NPs ou de AgNO3 por 10 dias consecutivos para verificar o desenvolvimento de resistência adaptativa à prata pela mudança no valor da CMI, e de resistência cruzada com antibióticos pela mudança no perfil de sensibilidade em relação ao controle. AgNO3 apresentou-se mais efetivo contra todos os isolados. Não foi verificada alteração no valor da CMI nem do perfil de sensibilidade aos antibióticos, indicando que não houve seleção de resistência adaptativa à prata e de resistência cruzada aos antibióticos pelos micro-organismos estudados. O uso potencial da prata apresentado nos resultados é favorável à continuidade dos estudos objetivando a elaboração de terapias à base de prata para o tratamento da mastite bovina.

ABSTRACT: Biocides and/or antibiotics used in subinhibitory concentrations can promote the development of adaptive resistance or even cross-resistance in microorganisms. However, studies on these responses following silver treatments are scarce in the literature. Silver-based compounds, including silver nanoparticles (Ag-NPs), can be an alternative in the prevention and treatment of bovine mastitis. Thus, this research evaluated the effect of subinhibitory dosages of Ag-NPs and Ag+ ions from silver nitrate (AgNO3) on Staphylococcus aureus and Escherichia coli isolated from milk of cows with mastitis. Ag-NPs were synthesized by chemical reduction using AgNO3 and sodium citrate and the minimum inhibitory concentration (MIC) of Ag-NPs and Ag+ ions on the mastitis pathogens were determined. Isolates were exposed to subinhibitory concentrations of Ag-NPs or AgNO3 for 10 consecutive days to verify the development of adaptive resistance evaluated by changes in the MIC values. The development of cross-resistance with antibiotics was also studied, being verified by comparing the sensitivity profile of treated cells with non-treated cells. AgNO3 was more effective against all isolates. There was no change in the MIC values or in the antibiotic sensitivity profile for both bacteria following consecutive exposure to subinhibitory dosages of Ag-NPs or AgNO3, indicating that silver was not able to select adaptive resistance or cross resistance to the tested antibiotics. The potential of silver presented by these results is favorable to the continuity of studies aiming to elaborate silver-based therapies for the treatment of bovine mastitis.

ABSTRACT The objective of the present study was to compare the effects of corn processing on performance and intestinal parameters of weanling piglets. To accomplish our goal, 42 piglets (21 days-old, 7.18±1.0 kg body weight) were randomly allocated (seven pens/treatment; three pigs/pen) to one of two treatments: ground corn – corn ground through a hammer mill with a 1.0-mm screen after being ground by a hammer mill with a 3.0-mm screen, and extruded corn – corn was wet extruded after being ground by a hammer mill with a 2.0-mm screen and, after extrusion, it was ground by a hammer mill with a 1.0-mm screen. In both methods, corn from the same batch was used. Results were considered statistically significant when P<0.05 and a tendency when P<0.10. Analyses were performed using the GLIMMIX procedure of SAS. Pigs fed ground or extruded corn diet had similar growth performance. Duodenum and jejunum of pigs fed extruded corn had greater villus height compared with those of pigs fed ground corn. Crypt depth was not influenced by corn processing. Duodenum and jejunum of pigs fed extruded corn had greater villus:crypt ratio compared with those of pigs fed ground corn. In the duodenum, the expression of zonula occludens-1 (ZO-1) was greater, and the expression of Occludin-1 tended to be greater in pigs fed the extruded corn diets. There was no effect of corn processing on ZO-1 and Occludin-1 expression in the jejunum, nor TGF-β1 expression in duodenum and jejunum. There was no effect of the type of corn processing on colonic total bacteria or Enterobacteriaceae and Lactobacillus abundance. Piglets fed diets with ground corn or extruded corn have similar growth performance. However, piglets fed diets with extruded corn present improved intestinal morphology and tight junction protein expression compared with those fed ground corn.

The objective of this research was to evaluate the effect of whey fermented by Enterococus faecium in consortium with Veilonella parvula in vitro on ruminal microorganisms in different substrates, with or without monensin. The first experiment was carried out in a completely randomized design, in a 6 × 3 factorial arrangement (six substrates × three whey levels) with two replicates. In experiment two, a 2 × 3 × 4 factorial arrangement (with and without monensin, three foods and four levels of fermented whey) was used, in a randomized design with four replicates, totaling 24 treatments. There was no interaction among the wheys and the substrates in the variable for pectin, starch, and carboxymethyl cellulose. There was a greater growth of amylolytic and pectinolytic microorganisms and a lower growth of proteolytic and cellulolytic microorganisms. A significant effect of optical density was found in the media without substrate and that containing trypticase and glucose due to the addition of fermented whey. There was interaction for the pH at 24 hours among whey, food and monensin. For ammonia at 24 hours there was effect for food, whey and monensin, and interaction among factors. For microbial protein at 24 hours, there was effect for food, whey, monensin and no interaction among sources of variation. The use of whey fermented by bacteria Enterococcus faeciumand Veilonella parvula improves microbial protein synthesis by ruminal bacteria in media containing different energy sources. The combination of fermented whey and monensin shows variable results in relation to microbial growth.

The objective of this study was to evaluate the fermentation profile, chemical composition and microbial population and losses in the silages of signalgrass and Mombasa grass fertilized with the following levels of nitrogen (N): 0, 30, 60 and 90 kg/ha. The grasses were harvested at 70 days of regrowth, chopped and then ensiled in laboratory silos that had 20 kg of capacity and a snap-top cover and were fitted with Bunsen valves. Before ensiling, samples of the plants were used for the isolation and identification of lactic acid bacteria (LAB) in epiphytic microbiota. The design adopted was a 4 × 2 factorial arrangement, with four doses of N and two forage species, in a completely randomized design, with four replicates. The predominant species of LAB was Lactobacillus fermentum. The interaction between the N dose and forage species affected the dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and water soluble carbohydrates (WSC) of the silages. The pH values and gas losses were influenced only by the forage species, with higher values for the Mombasa grass. For the ammonia (NH3-N) levels and effluent losses, there was an effect of the interaction between the forage species and N doses, and the highest values of NH3-N and effluent losses were found in the Mombasa grass silage fertilized with 60 kg N/ha. Nitrogen fertilization reduces the levels of DM and WSC in the silages and also increases the levels of CP, NH3-N and effluent losses.

Two experiments were carried out to evaluate the effect of supplementation with different nitrogenous compounds on the activities of carboxymethil cellulase (CMCase) and glutamate dehydrogenase (GDH). In the first experiment, four treatments were evaluated in vitro: cellulose, cellulose with casein, cellulose with urea, and cellulose with casamino acids. After 6, 12 and 24 hours of incubation, CMCase and GDH activity, pH, and concentrations of ammonia nitrogen (AN) and microbial protein were measured. In the three incubation periods, the concentration of AN was higher when urea was used as a supplemental source of nitrogen. The activity of CMCase was higher with the addition of urea and casamino acids when compared with the control and the casein treatment. Supplementation with casamino acids provided higher GDH activity when compared with the control at 6 hours of incubation. At 12 hours of incubation, the GHD activity was also stimulated by casein. At 24 hours, there was no difference in GHD activity among treatments. In the second experiment, three rumen-fistulated bulls were used for in situ evaluation. Animals were fed Tifton hay (Cynodon sp.) ad libitum. The treatments consisted of control (no supplementation), supplementation with non-protein nitrogenous compounds (urea and ammonium sulphate, 9:1) and supplementation with protein (albumin). In treatments with nitrogenous compound supplementation, 1 g of crude protein/kg of body weight was supplied. The experiment was conducted in a 3 × 3 Latin square design. The measurements were performed at 6, 12 and 24 hours after supplementation. No difference in GDH activity was observed among treatments. The control treatment showed higher CMCase activity when compared with the treatments containing supplemental sources of nitrogen. However, urea supplementation provided higher CMCase activity compared to albumin.

The objective of this study was to evaluate the whey fermented by Enterococcus faecium in consortium with Veilonella parvula on the in vitro growth of ruminal bacteria and as a supplement in the cattle diet. In the in vitro experiment, a randomized design, with the following combinations was used: ruminal bacteria; ruminal bacteria and inactive whey; ruminal bacteria and active whey; and active whey. In the in vivo experiment, five fistulated Zebu Holstein-Zebu crossbred heifers were distributed in a 5 × 5 Latin square. Supplements were formulated without the addition of whey, with the addition of two levels of unfermented whey (2.5 and 5 L/day) or two levels of fermented whey (2.5 and 5 L/day). A positive effect of the whey fermentation was detected on the consumption of dry matter, organic matter, crude protein, ether extract, non-fiber carbohydrates and neutral detergent fiber, corrected for ash and protein in kg/day. No effects of whey were observed on the pH and concentration of rumen ammonia nitrogen, serum concentration of urea and glucose, urinary excretion of urea or nutrient digestibility, except for the total digestible nutrients. Supplementation with whey improved the apparent nitrogen balance, but supplementation with fermented whey decreased the intestinal flow of microbial nitrogen and microbial synthesis efficiency in relation to the unfermented whey. The whey fermentation process does not optimize the physiological responses of heifers supplemented with 2.5 and 5.0 L of whey.

Objetivou-se com este trabalho avaliar o efeito de níveis de ácido láctico e do ácido propiônico sobre a fermentação de microrganismos ruminais in vitro. No experimento 1, os níveis, em um total de 12, foram os seguintes: adição de 0 (controle 1), 50, 100, 150, 200 e 250 mM de ácido láctico e 0 (controle 2), 50, 100, 150, 200, 250 mM de ácido propiônico, respectivamente, aos tubos de incubação, que continham inóculo ruminal, glicose e meio de cultura sintético, com duas repetições para cada combinação. No Experimento 2, as combinações, em um total de 4, foram os seguintes: presença de 12 e 24 mM de ácido propiônico e 0 mg glicose, respectivamente; presença 12 e 24 mM de ácido propiônico e 40 mg glicose, respectivamente, aos tubos de incubação que continham inóculo ruminal, com ou sem glicose e meio de cultura sintético com duas repetições cada. Não houve efeito na velocidade específica de crescimento dos microrganismos ruminais na presença de ácido láctico ou propiônico. Entretanto, quando nos meios havia concentrações maiores desses ácidos, houve maior fase lag no crescimento dos microrganismos. A concentração de 24 mM de ácido propiônico inibiu a produção de ácido acético e ácido butírico em meio com glicose. Apesar de não ser usado como fonte de energia pelos microrganismos ruminais, o ácido propiônico afeta seu metabolismo. Os ácidos láctico e propiônico, em concentrações elevadas, inibem o crescimento de determinados microrganismos ruminais.

The objective of this work was to evaluate the effect of the levels of lactic and propionic acids on in vitro fermentation of ruminal microorganisms. In experiment 1, the levels, in a total of 12 were the following: addition of 0 (control 1), 50, 100, 150, 200 and 250 mM of lactic acid and 0 (control 2), 50, 100, 150, 200 and 250 mM of propionic acid, respectively, in incubation flasks, which contained ruminal inoculum, glucose and synthetic culture medium, with two repetitions for each combination. In experiment 2, the combinations, in a total of 4, were the following: presence of 12 and 24 mM of propionic acid and 0 mg of glucose, respectively; presence of 12 and 24 mM of propionic acid and 40 mg of glucose, respectively, to the incubation flasks which contained ruminal inoculum, with or without glucose and in synthetic culture medium with two repetitions each. There was no effect on the specific growth velocity of ruminal microorganisms in the presence of lactic acid or propionic acid. However, when there were greater concentrations of these acids in the media, there was a longer lag phase in the microorganism phase. Acid propionic at the concentration of 24 mM inhibited the production of acid acetic and butyric acid in a media with glucose. Despite of not being used as a source of energy by the ruminal microorganisms, propionic acid affects their metabolism. Lactic and propionic acids inhibit growth of some ruminal microorganisms at elevated concentrations.

Objetivou-se avaliar o efeito da suplementação proteica e/ou com carboidratos sobre a degradação ruminal da fibra em detergente neutro (FDN) de forragem tropical de alta qualidade. No experimento, foi simulada a suplementação de bovinos em terminação sob pastejo durante o período chuvoso (70% de forragem e 30% de concentrado, com base na matéria seca). Como forragem basal utilizou-se amostra de capim-elefante (Pennisetum purpureum Schum.) cortado aos 21 dias de rebrotação. O concentrado utilizado no tratamento-base foi formulado de forma a apresentar 30% de proteína bruta, com amido como componente energético e caseína como componente proteico. Os tratamentos foram construídos mediante o não-fornecimento das fontes proteica e/ou energética do suplemento e substituição total do amido por pectina. Desta forma, avaliaram-se seis tratamentos (1. forragem; 2. forragem + amido; 3. forragem + pectina; 4. forragem + caseína; 5. forragem + caseína + amido; e 6. forragem + caseína + pectina) em ambiente ruminal simulado por incubação in vitro em diversos tempos de incubação: 0, 3, 6, 9, 12, 24, 36, 48, 72 e 96 horas. O procedimento de incubação foi repetido cinco vezes, perfazendo o total de cinco avaliações por tempo de incubação para cada tratamento. Os resíduos de incubação foram avaliados quanto ao teor de FDN e interpretados por intermédio de modelo não-linear logístico. A suplementação isolada com amido ou pectina reduziu em 9,9 e 8,4% a taxa de degradação da FDN potencialmente degradável (FDNpd). Efeitos similares foram verificados com a suplementação exclusivamente proteica, com redução de 19,1% sobre a taxa de degradação da FDNpd. A suplementação conjunta com proteína e carboidratos promove redução dos efeitos deletérios da suplementação isolada com esses compostos.

The objective was to evaluate the effect of protein and (or) carbohydrate supplementation on the rumen degradation of neutral detergent fiber (NDF) from high-quality tropical forage. The experiment simulated the supplementation of finishing cattle under grazing during the rainy season (70:30 forage to concentrate ratio, as dry matter basis). Samples of elephant grass (Pennisetum purpureum Schum.) cut after 21 days regrowth were used as basal forage. The concentrate used was formulated to contain 30% crude protein, using starch as the energetic source and casein as the protein source. The treatments were established by omission of the protein and/or energy source and replacement of starch by pectin. Thus, six treatments were evaluated: 1. Forage, 2. Forage plus Starch, 3. Forage plus Pectin, 4.Forage plus Casein, 5. Forage plus Casein plus Starch and 6. Forage plus Casein plus Pectin. The treatments were evaluated under rumen environment, simulated by in vitro incubation, where the experimental diets were submitted to different incubation periods: 0, 3, 6, 9, 12, 24, 36, 48, 72, and 96 hours. The incubation procedure was repeated five times so that five evaluations within each incubation time were made for each treatment. The incubation residues were evaluated according to their NDF contents and interpreted using a non-linear logistic model. It was observed that the exclusive supplementation with starch or pectin depressed 9.9 and 8.4% the degradation rate of potentially degradable NDF. A similar effect was observed with exclusive supplementation with protein, where a decrease of 19.1% on the degradation rate of potentially degradable NDF was observed. As carbohydrates and protein were supplemented together, a decrease in negative effect on NDF degradation was observed.

Objetivou-se avaliar o efeito da infusão ruminal de ácido propiônico (APR) associado a dietas em mistura completa com duas relações volumoso:concentrado (RVC), 80:20 e 60:40 (% da MS), para novilhos. Foram utilizados quatro novilhos mestiços, Holandês × Zebu, com idade média de 7 meses e 160 kg de peso vivo, distribuídos em delineamento experimental quadrado latino. As dietas foram isoprotéicas e os animais alimentados à vontade, na forma de ração em mistura completa. O ácido propiônico foi produzido por fermentação do soro de leite reconstituído, pelo consórcio das bactérias Enterococcus sp. e Veillonella sp. Diariamente e junto ao fornecimento dos alimentos sólidos, infundiram-se no rúmen 2 L do composto contendo ácido propiônico. Não houve interação APR × RVC para os consumos de nutrientes, exceto nutrientes digestíveis totais (NDT). Os consumos de matéria orgânica (MO), proteína bruta (PB), extrato etéreo (EE), fibra em detergente neutro (FDN) e NDT foram influenciados pela relação volumoso:concentrado utilizada. Não houve interação APR × RVC para as digestibilidades totais de MS, MO, PB, EE, FDN e CT. Todavia, as digestibilidades de MS, MO, EE e CT foram influenciadas pela relação volumoso:concentrado. Não houve interação APR × RVC para as concentrações médias de N-NH3 e pH do líquido ruminal, no entanto, a APR propiciou efeito sobre o pH medido 4 horas após a alimentação. Não se observou interação ou efeito dos fatores principais sobre as concentrações de ácidos graxos voláteis no líquido ruminal, ou níveis de glicose e o nitrogênio uréico sérico.

This study aimed to evaluate the effect of intraruminal infusion of propionic acid (RPA) associated to two (80:20 and 60:40) forage:concentrate ratios (FCR), for young bulls. Four Holstein × Zebu crossbred young bulls with average age of 7 months and 160 kg of body weight (BW) were distributed to a 4 × 4 Latin square design. A total mixed ration, isonitrogenous diets, was ad libitum fed to animals. The propionic acid was obtained by fermentation of reconstituted milk whey by the consortium of bacteria Enterococcus sp. and Veillonella sp.. Daily and along with the supply of solid feeds, 2 L of the compound containing propionic acid were intrainfused in the rumen. There was no RPA × FCR interaction for the intake of nutrients, except for total digestible nutrients (TDN). The organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF) and TDN intakes were influenced by the FCR. There was no RPA × FCR interaction on the total digestibility of DM, OM, CP, EE, NDF and TC. However, the digestibility of DM, OM, EE and CT were influenced by the FCR. There was no RPA × FCR interaction for the mean N-NH3 concentration and pH of the rumen fluid; however, RPA provided effect on the pH measured 4 hours after meal. There was no interaction or effect of the main factors on volatile fatty acids concentrations in the rumen fluid, or on glucose levels and serum urea nitrogen.

Objetivou-se avaliar o efeito da suplementação protéica e/ou com carboidratos sobre a degradação ruminal da fibra em detergente neutro (FDN) de forragem de baixa qualidade. Simulou-se a suplementação de bovinos em terminação, sob pastejo em Brachiaria decumbens de baixa qualidade, durante o período seco (70% de forragem e 30% de concentrado, com base na matéria seca). O concentrado referente ao tratamento base foi formulado de forma a apresentar 30% de proteína bruta, utilizando-se amido, como componente energético, e caseína, como componente protéico. Os tratamentos foram construídos a partir da omissão do fornecimento das fontes protéica e/ou energética do suplemento, associando-se, ainda, a substituição total do amido por pectina. Desta forma, seis foram os tratamentos avaliados: 1. forragem; 2. forragem + amido; 3. forragem + pectina; 4. forragem + caseína; 5. forragem + caseína + amido; e 6. forragem + caseína + pectina. Os tratamentos foram avaliados em ambiente ruminal simulado por incubação in vitro e submetidos a diferentes tempos de incubação: 0, 3, 6, 9, 12, 24, 36, 48, 72 e 96 horas. O procedimento de incubação foi repetido quatro vezes, perfazendo-se o total de quatro avaliações por tempo de incubação para cada tratamento. Os resíduos de incubação foram avaliados quanto ao teor de FDN e interpretados por intermédio de modelo não-linear logístico. Observou-se que a taxa de degradação da FDN potencialmente degradável (FDNpd) foi ampliada em cerca de 46% com a suplementação com caseína, resultando em incrementos de 14,6% sobre a fração efetivamente degradada. Observou-se efeito de menor amplitude com a inclusão ou alteração da fonte de carboidrato suplementar. A suplementação com amido causou redução na taxa de degradação da FDNpd, ao passo que a suplementação com pectina não afetou este parâmetro em comparação à ausência de carboidratos. Na presença de caseína, a suplementação com amido elevou o tempo de latência discreta para a degradação da FDN.

The effect of the protein and (or) carbohydrates supplementation on the rumen degradation of neutral detergent fiber (NDF) from low quality forage was evaluated. The experiment simulated the supplementation of finishing cattle grazing low quality Brachiaria decumbens pasture during dry season (70:30 forage to concentrate ration, %DM). The concentrate referring to the basal treatment was formulated to contain 30% CP, using starch as the energetic source and casein as the protein source. The treatments were established by omission of protein and (or) carbohydrates sources, associated with substitution of starch by pectin. In that way, six treatments were evaluated: 1. Forage, 2. Forage plus Starch, 3. Forage plus Pectin, 4.Forage plus Casein, 5. Forage plus casein plus starch and 6. Forage plus casein plus pectin. The treatments were evaluated under rumen environment, simulated by in vitro incubation, where the experimental diets were submitted to different incubation periods: 0, 3, 6, 9, 12, 24, 36, 48, 72, and 96 hours. The incubation procedure was repeated four times in a way that four evaluations within each incubation time were done for each treatment. The incubation residues were evaluated according to its contents of NDF and interpreted using a non-linear logistic model. It was observed that the degradation rate of potentially degradable NDF (pdNDF) was increased almost 46% with casein supplementation, resulting in an increment of 14.6% on the effective degraded fraction. A minor effect was observed with the inclusion or substitution of the supplemental carbohydrate source. The starch supplementation resulted in reduction on pdNDF degradation rate, whereas the supplementation with pectin did not affected this parameter, when compared to no carbohydrate supplementation. In the presence of casein, the starch supplementation raised the discrete lag time for NDF degradation.

Foram estudados os efeitos in vitro dos inibidores monensina e própolis sobre a fermentação ruminal de aminoácidos. Utilizou-se líquido ruminal de um novilho em pastejo, acrescentado de solução de tripticase, em três tratamentos (controle, monensina e própolis). Na 1ª fase do experimento, foram feitas transferências diárias de inóculos para novos tubos com os mesmos tratamentos até o 10º dia e, no 11º dia, iniciou a 2ª fase, efetuando-se as combinações dos tratamentos da 1ª fase (C, M, P), no total de nove, com transferência diária e incubação por mais nove dias. Do 1º ao 10º dia de incubação (1ª fase), o ionóforo e a própolis não aumentaram significativamente a produção de amônia em comparação ao controle. A própolis foi mais eficiente em dimiuir a produção de amônia que a monensina na 1ª fase e ainda reduziu a produção de amônia e a atividade específica de produção de amônia (AEPA) na 2ª fase, independentemente do tratamento aplicado na 1ª fase. Quando os inibidores estavam ausentes na 1ª fase, a monensina foi tão eficiente quanto a própolis na 2ª fase. Verificou-se que, ao remover os inibidores na 2ª fase no tratamento monesina, houve aumento significativo na produção de amônia, mas este efeito não foi detectado no tratamento com própolis, que manteve amônia em baixas concentrações.

The objective of this trial was to study the in vitro effects of monensin and propolis on ruminal fermentation of amino acids. Ruminal fluid was collected from a steer grazing tropical pasture and after addition of casein hydrolysate was used in the incubations. Treatments consisted of: control-C; monensin-M; and propolis-P. In the first phase of the study, inocula were transferred daily into new tubes until day 10; on the 11th day of incubation, tubes from each of the treatments were used to inoculate three new tubes (C, M, P) yielding nine combinations that were also transferred daily and incubated for nine days (second phase). From day one to day 10 of incubation (first phase), addition of ionophore and propolis prevented increase in ammonia production compared to the control. Propolis was more efficient in decreasing ammonia production than monensin in the first phase and it was also able to decrease ammonia production and specific activity of ammonia production (SAAP) in the second phase regardless of the first phase treatments; monensin was as efficient as propolis, in the second phase, when the inhibitors were absent in the first phase. It was observed a significant increase in ammonia production with monensin by removing the inhibitors in the second phase