Abstract Oxides (Al2O3, SiO2, TiO2, ZrO2, Y2O3, CeO2, MgO) are among the most used reinforcements for Aluminum Matrix Composites (AMC); while the combination of Al with Si, Cu and/or Mg excels among the alloying systems used as matrices. Some works in literature study the effects of the reinforcements and the alloying elements on the composites manufacturing, microstructure and mechanical properties. Nevertheless, it is necessary a recompilation of the interactions oxide reinforcement-alloyed matrix, including the reciprocal effects between them. Our search revealed that not only reactions occur at the interfacial regions, but also other phenomena depending on the reinforcement characteristics and the matrix composition, which affect mechanical properties. These phenomena include modifications in the matrix microstructure and its precipitation process, diffusion of elements through the interfaces, change in the reinforcement wettability by the liquid metal, loss of alloying elements, and deterioration of the reinforcement. This work presents the occurrence of these phenomena for Al matrices with different contents of Si, Cu and Mg reinforced with the most used oxides. Its novelty lies in exploring these combinations of conditions, which could serve as a benchmark study and help for a better understanding and selection of the matrix-reinforcement system.

Resumo O potencial biotecnológico das microalgas tem sido alvo de uma série de pesquisas que visam utilizar seu potencial para produzir macromoléculas de alto valor agregado. Uma especial atenção tem sido dada à produção de biocombustíveis, como biohidrogênio, biodiesel e bioetanol, a partir de lipídios e carboidratos de microalgas. A bioprospecção e a identificação precisa de microalgas são importantes na busca de linhagens com melhor desempenho em termos de produção de biomassa e lipídios. Metodologias que combinam morfologia e técnicas moleculares permitem uma identificação mais precisa das espécies. Assim, este trabalho teve como objetivo identificar a nova cepa LGMM0013 coletada na Represa do Iraí, localizado no estado do Paraná, Brasil e avaliar a produção de biomassa, carboidratos e lipídios. Com base na morfologia e na árvore filogenética obtida com sequências ITS (“Internal Transcribed Spacer”), a cepa LGMM0013 foi identificada como Desmodesmus abundans. D. abundans acumulou 1500 mg L-1 de biomassa seca após 22 dias de crescimento em condições autotróficas, 50% superior a Tetradesmus obliquus (LGMM0001) (Scenedesmaceae-Chlorophyceae), uma cepa cultivada frequentemente em fotobiorreatores para produção de biomassa no NPDEAS, na Universidade Federal do Paraná (UFPR) para a produção de biomassa. Na análise da biomassa de D. abundans LGMM0013 constatou-se acúmulo de 673,39 mg L-1 de carboidratos, 130% maior que T. obliquus (LGMM0001). A produção de lipídios foi de 259,7 mg L-1, equivalente à de T. obliquus. A privação de nitrogênio aumentou a produção de biomassa e carboidratos em D. abundans LGMM0013, indicando uma maior capacidade de produção de biomassa desta cepa.

Abstract The biotechnological potential of microalgae has been the target of a range of research aimed at using its potential to produce macromolecules with high added value. Particular focus has been given to biofuels' production, such as biohydrogen, biodiesel, and bioethanol from lipids and carbohydrates extracted from microalgal biomass. Bioprospecting and accurate identification of microalgae from the environment are important in the search for strains with better performance. Methodologies that combine morphology and molecular techniques allow more precise knowledge of species. Thereby, this work aimed to identify the new strain LGMM0013 collected at Iraí Reservoir, located in Paraná state, Brazil, and to evaluate the production of biomass, carbohydrates, and lipids from this new microalgal strain. Based on morphology and phylogenetic tree from internal transcribed spacer (ITS), strain LGMM0013 was identified as Desmodesmus abundans. D. abundans accumulated 1500 mg L-1 of dried biomass after 22 days of cultivation in autotrophic conditions, 50% higher than Tetradesmus obliquus (LGMM0001) (Scenedesmaceae-Chlorophyceae), usually grown in photobioreactors located at NPDEAS at the Federal University of Paraná (UFPR) to produce biomass. Analysis of the D. abundans biomass from showed an accumulation of 673.39 mg L-1 of carbohydrates, 130% higher than T. obliquus (LGMM0001). Lipid production was 259.7 mg L-1, equivalent to that of T. obliquus. Nitrogen deprivation increased the production of biomass and carbohydrates in D. abundans LGMM0013, indicating this new strain greater biomass production capacity.

Abstract The objective of the work was to determine the incidence of the sampling depth on the carbon and nitrogen content in soils of the municipality of Zona Bananera of the department of Magdalena (Colombia). Data analysis was performed with statistical software Infostat v.2008 and R v.3.5.2, using multivariate analysis of variance, Pearson's correlation analysis, and descriptive statistics of each variable. The results show significant differences (p<0,05) between the depth groups for the selected variables, with lower contents found at depth 2. In addition, there is a significant contribution of the variables to the statistical differences between the groups, except for ammonium and nitrate. Correlation is evident between the variables C oxidizable/MO, NO3 -/NO2 -, and NH4 +/C oxidizable/MO. The results obtained showed low Pearson correlation coefficients. It is concluded that the variables C oxidizable and MO are firmly related, while the others present a non-linear relationship.

Resumen El objetivo del trabajo fue determinar la incidencia de la profundidad de muestreo sobre el contenido de carbono y nitrógeno en suelos del municipio de Zona Bananera del departamento del Magdalena (Colombia). El análisis de los datos se realizó con software estadístico Infostat v.2008 y R v.3.5.2, empleando análisis de varianza multivariado, análisis de correlación de Pearson y estadística descriptiva de cada variable. Los resultados muestran diferencias significativas (p<0,05) entre los grupos de profundidad para las variables seleccionadas encontrándose contenidos menores en la profundidad 2. Además, existe una contribución significativa de las variables a las diferencias estadísticas entre los grupos, exceptuando el amonio y el nitrato. Se evidencia correlación entre las variables C oxidable/MO, NO3 -/NO2 -, y NH4 +/C oxidable/MO. Los resultados obtenidos mostraron coeficientes de correlación de Pearson bajos. Se concluye que las variables C oxidable y MO están fuertemente relacionadas, mientras que las demás presentan una relación no lineal.

SUMMARY: The aim of the study was to determine the number and anatomical configuration of roots and root canals of maxillary first and second premolars using cone-beam computed tomography scans. n273 CBCT scans were evaluated, obtaining a sample of 592 maxillary premolars. Root number and root canal anatomy were categorized using Ahmed´s classification. Data was analyzed using Pearson’s Chi-squared test. Two roots were present on 157 first premolars, one root in 132 premolars and three roots in 17. Second premolars presented one root in 266 samples and two roots in 20; no second premolars presented three roots. Eight different configurations were found; the most frequent was 2MP B1 P1 in first premolars (51,3 %) and 1MP1 (63.6 %) in second premolars. The most frequent morphology found in maxillary premolars in Chilean population was two and three roots. The analysis of internal anatomy using CBCT revealed a highly variable distribution of root canals, generally of low to medium complexity, similar to what is found in other ethnic groups.

RESUMEN: El objetivo de este estudio fue determinar el número y la configuración de raíces y canales radiculares de primeros y segundos premolares maxilares utilizado tomografía computacional de haz cónico. 273 TCHC fueron evaluados, obtenido una muestra de 592 premolares maxilares. El número de raíces y la anatomía de los canales radiculares fueron categorizados utilizando la clasificación de Ahmed. Los datos fueron analizados con la prueba Chi- Cuadrado de Pearson. Dos raíces fueron observadas en 157 primeros presentaron una raíz en 266 muestras y dos raíces en 20; no se encontraron tres raíces en segundos premolares. Ocho diferentes configuraciones fueron encontradas; siendo la más frecuente 2MP B1 P1 en primeros premolares (51,3 %) y 1MP1 (63,6 %) en segundos premolares. La morfología radicular más frecuentemente encontrada en premolares de población Chilena fue de dos y tres raíces. El análisis de la anatomía interna usando TCHC mostró una gran variabilidad de en la distribución de los canales radiculares. Generalmente de mediana y baja complejidad como los encontrados en otros grupos etnicos.

Background: Chronic limb ischemia can lead to high rates of limb loss and mortality. Open surgery is the gold standard for treatment of distal disease. Endovascular surgery should have less complications with similar outcomes. Aim: To report a cohort of patients with distal arterial disease treated with endovascular surgery at our institution. Material and Methods: Review of angioplasty records of patients undergoing distal lower extremity endovascular procedures between 2016 and 2019. Demographics, comorbidities, form of presentation, type of intervention, perioperative complications, and length of stay were analyzed. The primary outcomes were wound healing, reinterventions and freedom from major amputation. Secondary outcomes were overall survival and amputation-free survival. Results: Forty-eight limbs of 41 patients with a mean age 75 years (78% males) were treated. Ninety-three percent had hypertension, 88% diabetes, 30% chronic kidney disease. 73% presented with major wounds. Plain balloon and drug coated balloon angioplasties were carried out in 65 and 31% of procedures respectively, with no difference in results. In 46% of the cases, only chronic total occlusions were treated. Wound healing was achieved in 85% of procedures and 90% of patients were free from amputation at one year of follow up. Complications were observed in 18% of procedures, perioperative mortality was 2% and one-year survival was 76%. Conclusions: Endovascular therapy achieves high rates of wound healing and freedom from amputation with low perioperative mortality and moderate complication rates.

Resumen En este artículo se presenta los resultados de tres metodologías diferentes en las que se aplicó una simulación Monte Carlo para estimar el valor de π: el método de comparación de áreas, el método propuesto por Buffon y la extensión de Laplace al método de Buffon. Se estudió con detalle el resultado no determinista de las simulaciones y se demostró que cumplen con los teoremas fundamentales de la probabilidad. Los tres casos se desarrollaron en un lenguaje de programación de alto nivel: Python, junto con la librería Numpy que le otorga una performance optimizada.

Abstract This article presents the result of three dierent methodologies that estimate the π value using the Monte Carlo’s simulation: the comparative area’s method, the method proposed by Buffon and the Laplace’s extension. The three cases were developed in Python - a high level language and Numpy library which give it an optimized performance. The non-deterministic result of the simulations was studied in detail and it was shown that they comply with the fundamental theorems of probability.

Resumen 18. La calidad de la leche cruda de las ovejas es un factor muy importante a tener en cuenta cuando se escogen las mejores hembras para los sistemas productivos ovinos, porque el rango de crecimiento de los corderos está altamente relacionado con ello. El objetivo de este trabajo fue determinar las características fisicoquímicas de la leche cruda de ovejas de raza Dorper a través de los días en lactancia. Los parámetros evaluados fueron: porcentaje de grasa, proteína, lactosa, sólidos totales, sólidos no grasos y punto de congelación expresado en grados centígrados. Los animales fueron organizados en tres grupos de acuerdo a sus días en lactancia (3-20 días, 21-40 días y 41-60 días, con 40 ovejas por grupo). El análisis de la leche fue realizado usando un MilkoScan- Mars®. El recuento de células somáticas fue efectuado con un equipo Portacheck para cabras. Se realizó un ANOVA para determinar las diferencias estadísticas entre los grupos para cada parámetro (p<0,05). No hubo diferencias estadísticas para grasa, sólidos no grasos y sólidos totales; los otros parámetros tuvieron diferencias estadísticas. Los mejores resultados fueron grasa: 8.09% (grupo 2), proteína: 5.45% (grupo 1), lactosa: 5.22% (grupo 2), sólidos no grasos: 11.13% (grupo 1), sólidos totales: 19.17% (grupo 2), punto de congelación -0.5836°C (grupo 1) y recuento de células somáticas: 75.3 x 1000 cel./ml (grupo 2). Los resultados de las características fisicoquímicas de la leche cruda de ovejas Dorper fueron mejores comparados con otras razas (lecheras o cárnicas).

Abstract 14. The quality of raw milk is a key factor to consider when selecting the best females for sheep production systems because the lamb growth rate is highly correlated with this. The objective of this work was to determine the physicochemical characteristics of raw milk from Dorper sheep across sixty days of lactation. Parameters evaluated were percentage of fat, protein, lactose, total solids, non-fatty solids and freezing point expressed in degrees centigrade. Animals were randomly assigned to three groups according to days of lactation, as follows: 3-20 days, 21-40 days and 41-60 days (40 ewes each). Milk analysis was performed using MilkoScan Mars. Somatic cell count was performed with a SCC Portacheck equipment for goats. ANOVA was performed to determine statistical differences among the groups for each parameter (p<0.05). There were no statistical differences for fat, non-fat solids, and total solids; the other parameters have statistical differences. The best results were fat: 8.09% (group 2), protein: 5.45% (group 1), lactose: 5.22% (group 2), non- fatty solids: 11.13% (group 1), total solids: 19.17% (group 2), freezing point -0.5836°C (group 1) and SCC 75.3 x 1000 cells/ml (group 2). The physicochemical characteristics of Dorper’s raw milk were better than other breeds, including dairy and meat breeds.

Abstract Non-destructive evaluation of multilayer media represents an electromagnetic inverse problem, usually solved with analysis techniques in the time and frequency domains. The time- domain analysis technique depends directly on the accurate detection of reflected peaks measured by ground-penetrating radar (GPR), which limits this technique when the reflected pulses overlap with each other or the transmitted signal. Therefore, this paper presents a new practical methodology to obtain the antenna design requirements (operating frequency and temporal response) that avoid overlapping reflected pulses. The major finding is that the proposed methodology enables the production of specific antennas for the analyzed homogeneous and low-loss dielectric multilayer problem, serving as a practical guide for GPR antenna design. A typical pavement example is analyzed to apply the methodology, and, as a result, an ultra-wideband (UWB) directive antenna with tolerable dispersion is obtained according to the design specifications. Finally, the antenna simulations were compared and validated with measurements.

ABSTRACT In order to evaluate the effect of taro (Colocasia esculenta (L.) Schott) meal on the productive performance and morphometry of the gastrointestinal tract of fattening pigs, 16 castrated male animals as a result of an alternate crossbreeding of Largewhite x Duroc x Pietrain were used, with an initial liveweight of 69 kg. They were distributed into two equal groups of eight pigs and each pig constituted an experimental unit. Two treatments were evaluated: a control diet T0 (corn and protein concentrate of pigs) and T40 (substitution of corn in 40% for taro tuber meal), according to a completely randomized design, and an analysis of variance was also carried out. Daily food intake (DFI), daily weight gain (DWG), food conversion (FC), final weight (FW), carcass yield (CY) and dorsal fat (DF) were determined. In addition, the GIT, stomach, small intestine, large intestine, caecum and liver of the animals were weighed and measured. There was no effect (P> 0.05) for the DFI, DWG, FC, CY and DF. Likewise, there was no effect (P> 0.05) for the weight of the GIT, stomach, small intestine, large intestine, caecum and liver. There were also no differences (P> 0.05) for the elongation of the GIT, small intestine, large intestine and cecum. Under the conditions of this study, the use of taro tuber meal as a partial substitution of corn in the diet is feasible, since it does not have a negative influence on the indicators of productive performance nor on the morphometry of the gastrointestinal organs of fattening pigs.

RESUMEN Para evaluar el efecto de la harina de taro (Colocasia esculenta (L.) Schott) en el comportamiento productivo y morfometría del tracto gastrointestinal de cerdos en ceba, se utilizaron 16 animales machos castrados producto del cruzamiento alterno de las razas Largewhite x Duroc x Pietrain, con un peso vivo inicial de 69 kg. Se distribuyeron en dos grupos iguales de ocho cerdos y cada cerdo constituyó una unidad experimental. Se evaluaron dos tratamientos: una dieta control T0 (maíz y concentrado proteico de cerdos) y T40 (sustitución del maíz en 40% por harina de tubérculos de taro), según diseño completamente aleatorizado y se realizó análisis de varianza. Se determinó el consumo diario de alimento (CDA), ganancia diaria de peso (GDP), conversión alimentaria (CA), peso final (PF), rendimiento de la canal (RC) y grasa dorsal (GD). Además, se efectuó el pesaje y medición del TGI, estómago, intestino delgado, intestino grueso, ciego e hígado de los animales. No se encontró efecto (P>0.05) para el CDA, GDP, CA, RC y GD. No existió efecto (P>0.05) para el peso del TGI, estómago, intestino delgado, intestino grueso, ciego e hígado. Tampoco hubo diferencias (P>0.05) para la elongación del TGI, intestino delgado, intestino grueso y ciego. En las condiciones de este estudio es viable el uso de la harina de tubérculos de taro en sustitución parcial del maíz en la dieta, por no hallar influencia negativa en los indicadores de comportamiento productivo ni en la morfometría de los órganos gastrointestinales de cerdos en ceba.

Recovery of motor function after central nervous system (CNS) injury is dependent on the regeneration capacity of the nervous system, which is a multifactorial process influenced, among other things, by the role of neuromodulators such as serotonin. The neurotransmitter serotonin can promote neuronal regeneration but there are also reports of it causing restriction, so it is important to clarify these divergent findings in order to understand the direct scope and side effects of potential pharmacological treatments. We evaluated the effect of serotonin on the extent of neuritic outgrowth and morphology of three different neuronal types in the leech Haementeria officinalis during their regeneration in vitro: Retzius interneurons (Rz), annulus erector (AE) motoneurons, and anterolateral number 1 (AL1) CNS neurons. Neurons were isolated and cultured in L15 medium, with or without serotonin. Growth parameters were registered and quantified, and observed differences were analyzed. The addition of serotonin was found to induce AL1 neurons to increase their average growth dramatically by 8.3-fold (P=0.02; n=5), and to have no clear effect on AE motoneurons (P=0.44; n=5). For Rz interneurons, which normally do not regenerate their neurites, the addition of concanavaline-A causes substantial growth, which serotonin was found to inhibit on average by 98% (P=0.02; n=5). The number of primary neurites and their branches were also affected. These results reveal that depending on the neuronal type, serotonin can promote, inhibit, or have no effect on neuronal regeneration. This suggests that after CNS injury, non-specific pharmacological treatments affecting serotonin may have different effects on different neuronal populations.

ABSTRACT. The present research was carried out at the Abai City, Department of Caazapá, with the main objective of determining the healing time between the new preputial ostium and the pexia of the penis to the abdominal wall in teaser bulls. Eight bovine animals, halfbreed, aged 18-24 months, with an average weight of 200 and 300 kg, were studied. The cattle were divided into two groups randomly, undergoing general anesthesia and corresponding surgeries: new preputial ostium and pexia of the penis to the abdominal wall. The results showed that the healing time was lower in the animals submitted to the surgery of the penis pexia to the abdominal wall, with statistically significant differences (p<0.05).

RESUMEN. El presente trabajo de investigación se llevó a cabo en la un Establecimiento de la Ciudad de Abai, Departamento de Caazapá, con el objetivo de determinar el tiempo de cicatrización entre las técnicas de nuevo ostio prepucial y la pexia del pene a la pared abdominal en toros detectores de celo. Fueron utilizados 8 animales de la especie bovina, mestizos, de 18 a 24 meses de edad, con peso promedio entre 250 a 300 kg, que divididos al azar en dos grupos, sometidos a anestesia general y cirugías correspondientes de nuevo ostio prepucial y pexia del pene a la pared abdominal. Los resultados demostraron que el tiempo de cicatrización fue menor en los animales sometidos a la cirugía de la pexia del pene a la pared abdominal, encontrándose diferencias estadísticamente significativas (p<0,05).

Abstract This study analyzed the impact of coaching as a strategy for training sales personnel in the hotel industry in Mexico. The aim was to offer quality services and marketing by improving the training and education of sales personnel, providing strategies that integrate the emotional dimension in human development to provide a high-quality service at a fair price. The research methodology consisted of a quasi-experimental study using a descriptive-comparative design, with a sample of 30 participants who comprised the experimental and control groups. The technique of stratified probability sampling was used, considering the functions of the personnel, the characteristics of the hotel and the geographic area where they are located. Two questionnaires were used as research instruments: one with sociodemographic indicators and the other based on indicators that measure the impact of coaching on work performance as well as an interview script. The results were obtained by comparing the obtained frequencies according to the variables established with and without coaching. These results showed the positive relationship of sales executives who underwent the coaching course and the characteristics and objectives that the managers asked of those in charge of this area in their hotels. One important conclusion is that the training must include human development as the foundation for performing daily work, always accompanied by a good leader who aids in personal and professional development in a comprehensive way.

Resumen En el presente estudio se analizó el impacto del coaching como estrategia formativa del personal encargado de las ventas en la industria hotelera en México. El objetivo fue brindar servicios de calidad y comercialización a través del mejoramiento de la formación y capacitación del personal responsable de las ventas, brindando estrategias que integren la dimensión emocional en el desarrollo humano para proporcionar un servicio de calidad a un precio justo. La metodología de investigación consistió en un estudio cuasi-experimental empleando un diseño descriptivo-comparativo, con una muestra de 30 participantes quienes conformaron los grupos control y experimental. Se utilizó la técnica de muestreo probabilístico estratificado, considerando las funciones del personal, las características del hotel y la zona geográfica en donde se encuentran. Como instrumentos de investigación se utilizaron dos cuestionarios, uno con indicadores sociodemográficos y otro basado en indicadores que miden el impacto del coaching en el desempeño laboral, así como un guion de entrevista. Los resultados se obtuvieron a partir de la comparación entre las frecuencias obtenidas, de acuerdo a las variables establecidas con y sin coaching. Estos resultados mostraron la relación positiva de los ejecutivos de ventas que recibieron curso de coaching con las características y objetivos que los gerentes solicitaron a los responsables de esta área en sus hoteles. Una importante conclusión es que la capacitación debe incluir el desarrollo humano como base para realizar su trabajo diario, siempre acompañado de un buen líder que le ayude a desarrollarse personal y profesionalmente de manera integral.

The development of white spot lesions (WSLS) is a significant risk associated with orthodontic treatment when oral hygiene is poor. Fixed orthodontic appliances transform procedures of conventional oral hygiene more difficult and increase the number of sites plaque retention. While prevalence values vary, the data are sufficient to consider the demineralization as a important problem, making prevention during treatment one of the major clinical challenges. The purpose of this paper is review to date the available literature regarding the etiology, prevention and treatment of white spots associated with orthodontic treatment with dental braces.

El desarrollo de lesiones de mancha blanca (WSLs) es un riesgo significativo asociado con el tratamiento de ortodoncia cuando la higiene oral es deficiente. Aparatos de ortodoncia fijos transforman los procedimientos de higiene oral convencionales más difíciles y aumentan el número de sitios de retención de placa. Si bien los valores de prevalencia son variados, los datos son suficientes para considerar la desmineralización como un problema importante, haciendo de la prevención durante el tratamiento uno de los mayores desafíos clínicos. El propósito de este trabajo es realizar una revisión actualizada de la literatura disponible respecto a la etiología, prevención y tratamiento de manchas blancas asociadas al tratamiento de ortodoncia con aparatología fija.

Aunque la robótica ha avanzado hasta el punto de ser relativamente accesible con proyectos de bajo costo, aún cabe la necesidad de crear modelos que representen fielmente el comportamiento físico de un robot creando una plataforma completamente virtual. Esto nos permite, por un lado, probar algoritmos de comportamiento o de inteligencia artificial y, por otro lado, encontrar probables problemas en el diseño físico. El presente trabajo propone el modelado cinemático y la simulación de un robot móvil autónomo, particularmente de un robot omni-direccional con ruedas. Se plantea la metodología para la construcción del modelo cinemático así como su implementación utilizando diversas herramientas. El resultado es un modelo que representa a un robot móvil omni-direccional triangular con ruedas, que fue probado utilizando un modelo tridimensional importado de 3D Studio®, y utilizando Matlab® para la simulación del modelo. También se implementa el mismo modelo utilizando una herramienta dedicada a la simulación de robots, que ofrece un ambiente muy completo de simulación. El ambiente de simulación ofrece un comportamiento muy cercano al real y refleja las características cinemáticas del robot.

Although robotics has progressed to the extent that it has become relatively accessible with low-cost projects, there is still a need to create models that accurately represent the physical behavior of a robot. Creating a completely virtual platform allows us to test behavior algorithms such as those implemented using artificial intelligence, and additionally, it enables us to find potential problems in the physical design of the robot. The present work describes a methodology for the construction of a kinematic model and a simulation of the autonomous robot, specifically of an omni-directional wheeled robot. This paper presents the kinematic model development and its implementation using several tools. The result is a model that follows the kinematics of a triangular omni-directional mobile wheeled robot, which is then tested by using a 3D model imported from 3D Studio® and Matlab® for the simulation. The environment used for the experiment is very close to the real environment and reflects the kinematic characteristics of the robot.

In vitro methane production was determined in mixtures of grasses and legumes of Colombian highlands were evaluated using the gas production technique. Samples of two grasses, ryegrass (Lolium perenne) and kikuyu (Pennisetum clandestinum), and two legumes, white clover (Trifolium repens) and big trefoil (Lotus uliginosus), from two different paddocks were harvested. The treatments were mixtures of kikuyu and lotus, kikuyu and white clover, ryegrass and lotus and ryegrass and clover in three different grass: legumes ratio (90:10, 70:30 and 50:50). The methane concentration in the gas was determined by gas chromatography. Methane production per unit of degraded dry matter decreased 14 % (p<0.05) when the proportions of legume increased associated with kikuyu. However, no differences were observed when legumes were mixed with ryegrass. When proportion of lotus, a tanniferous legume, increased total methane production decreased independently of grass suggesting an effect in methanogenic population.

Se determinó la producción de metano in vitro para mezclas de gramíneas: leguminosas del trópico alto colombiano, utilizando la técnica de producción de gas. En dos lotes diferentes, se recogieron muestras de dos gramíneas, ryegrass (Lolium perenne) y kikuyo (Pennisetum clandestinum), y dos leguminosas, trébol blanco (Trifolium repens) y lotus grande (Lotus uliginosus). Se evaluaron cuatro mezclas de las gramíneas y las leguminosas: kikuyo y lotus, kikuyo y trébol blanco, ryegrass y lotus y ryegrass y trébol en tres proporciones diferentes de gramínea: leguminosa (90:10, 70:30 y 50:50). La concentración de metano en el gas se determinó por cromatografía de gases. Al aumentar las proporciones de leguminosas en la mezcla con el kikuyo, la producción de metano por unidad de materia seca degradada disminuyó hasta un 14 % (p<0,05). Sin embargo, no se observaron diferencias cuando se mezclaron con el ryegrass. Para el lotus, una leguminosa tanífera, al aumentar su proporción en la mezcla se disminuyó la producción total de metano (p<0,05) y su proporción en el gas independientemente de la gramínea base sugiriendo un efecto del lotus sobre las poblaciones metanogénicas.