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El objetivo del estudio fue relacionar los estilos de aprendizaje (EA) y hábitos de estudios (HE) con el rendimiento académico (RA) de los estudiantes de propedéutico de la Universidad Autónoma Chapingo. Para obtener la información se utilizaron dos instrumentos, el cuestionario de Honey-Alonso de estilos de aprendizaje (CHAEA) y el cuestionario de hábitos y técnicas de estudio (CHTE). El muestreo consideró a 142 estudiantes de propedéutico, de los que se obtuvieron las calificaciones de sus materias cursadas. Las respuestas del cuestionario sobre los HE y de los EA se analizaron mediante la prueba de Kruskal-Wallis y se evaluó la correlación entre las diferentes escalas. Durante el primer semestre, quienes manifestaron tener hábitos moderados tuvieron la menor calificación (77), y los de buenos y excelentes hábitos tuvieron similar calificación (81.5-81.7). Durante el primer semestre los estudiantes con muy altos EA tuvieron la menor calificación (79). En los estudiantes con EA activo no se observó correlación con las calificaciones. Se concluye que la correlación de los hábitos de estudio y los estilos de aprendizaje con el rendimiento académico en estudiantes de propedéutico de la Universidad Autónoma Chapingo fue muy baja y en muchos casos no existió significancia.

Objective: To analyze the occurrence of the reproductive seasonality and its relation to the time of the year, feeding, race, and social environment of sheep in the municipality of Singuilucan, Hidalgo, Mexico. Design/methodology/approach: Forty-one surveys with sheep breeders were carried out. The data obtained was subject to a logistic regression analysis, in order to analyze the degree to which the said variables intervene on the occurrence or absence of seasonal anestrus periods in ewes. The environment in which they are developed and the traditional handling of production units must be taken into account. Results: Seasonal anestrus periods have been recorded in 95.1% of the production units; such variables as seasons of the year, feeding type, race, and social environment have a significant influence (P

The objective was to assess grazing as an element of profitability and competitiveness of a small-scale sheep production system (SSSPS) in central Mexico and compare its economic performance by means of an analysis of scenarios. A questionnaire was applied to 66 sheep farmers on technical variables, flock management, economic and social aspects. Two scenarios were analyzed to assess the contribution of grazing on profitability and competitiveness. The first analysis was when grazing was the feed base, and secondly, costs of opportunity and economic impacts were studied under the assumption that sheep do not graze and total feed has to be bought from feed vendors. In order to determine the differences between the farmers with the highest and lowest profitability indexes, a four-stratum stratification was made (stratum 1, between 6 and 35 sheep; stratum 2, 36 to 70 sheep, stratum 3 = 71 - 105 sheep; and stratum 4, 106 to 140 sheep). Quantitative variables (technical management, flock management and social aspects) were evaluated with analysis of variance, while qualitative variables were analyzed by means of a Kruskal-Wallis test. Production cost analysis and profitability index were assessed with the Policy Analysis Matrix. Differences were found between strata, farmers with more than 70 sheep have the best profitability indices and the least vulnerability before the non-grazing scenario. Grazing had a positive effect reducing the cost of production and increasing competitiveness in the four strata assessed. However, farmers with higher technical level, specialized breeds and larger flocks (strata 3 and 4) have higher economic profits.

The objective was to assess grazing as an element of profitability and competitiveness of a small-scale lamb fattening production system in central México and compare its economic performance by means of an analysis of scenarios. Two scenarios were analysed to assess the contribution of grazing on profitability and competitiveness. The first analysis was when grazing was the feed base, and secondly, costs of opportunity and economic impacts were studied under the assumption that sheep do not graze, and total feed has to be bought from external suppliers. The economic effect of grazing on the profitability was analysed by means of the Policy Analysis Matrix. Differences were found between strata; farmers with more than 70 sheep have the best profitability indices and the least vulnerability under the non-grazing scenario. Grazing had a positive effect reducing the cost of production and increasing competitiveness in the four strata assessed. However, farmers with higher technical level, specialised breeds and larger flocks (strata 3 and 4) have higher economic profits. The conclusion was that the profitability in fattening sheep is linked to taking advantage of grazing. However, to keep and improve the current financial performance, there is a need for the adoption of strategies for an integral improvement of the system and the adoption of better grazing management to further reduce production costs.

La creciente demanda de alimentos en areas urbanas genera cada vez mayor cantidad de desperdicios organicos, incluyendo residuos vegetales. El manejo de estos residuos vegetales causa emisiones de gases efecto invernadero (GEI) por su recoleccion, transporte, y deposito en vertederos. Para identificar su potencial de GEI, en un mercado de alimentos se recolectaron residuos de hojas de lechuga (LS), de col (BOV), de coliflor (BOB), de maiz (HZM), de espinaca (SO) y de nopal (OF), se fermentaron in vitro usando liquido ruminal como inoculo y se compararon con heno de avena (AS), heno de alfalfa (AH) y ensilado de maiz (EZM), forrajes utilizados con frecuencia en la alimentacion de rumiantes. Las variables fueron degradacion in vitro de la materia seca (DIVMS), pH, cinetica de produccion de gas y concentracion de metano (CH 4 ). La fermentacion se realizo durante 96 h a 39 oC y las muestras de gas para medir la concentracion de CH 4 se tomaron a 9, 12, 24, 34 y 48 h de incubacion. La DIVMS de LS, BOV, BOB, HZM y OF fue 12.8 % mayor a AS, AH y EZM. Entre las 9 y 12 h de incubacion la emision de CH 4 a partir de BOV, BOB and HZM fue 44.8 % superior a los tres forrajes. La principal conclusion es que estos residuos vegetales son degradados adecuadamente por los microorganismos ruminales y, por lo tanto, se pueden usar para la produccion de biogas en areas urbanas para disminuir su deposito en vertederos.

This article combines a Policy Analysis Matrix with a sensitivity and poverty line analysis with the objective of evaluating the economic contribution of comparative advantages to the private profitability and competitiveness of small-scale dairy systems. For 1 year, socioeconomic data were collected from 82 farms selected from four strata via statistical sampling. Two scenarios were established to determine the quantitative contribution of comparative advantages: (1) a simulated scenario, which accounted for the cost of purchasing the total food and the opportunity cost of the family labour force (FLF), and (2) an actual production scenario, which accounted for the cost of producing food and eliminating the payment of the FLF and included other income. The E3 and E4 producers were the most profitable and competitive in the simulated scenario and actual production scenario. Of the four scales evaluated, the E2 and E1 producers were the most efficient in taking advantage of the economic contribution provided by the comparative advantages in their own production of food and employment of the FLF, in addition to accounting for other income, a condition that increased their profitability by 171 and 144% and competitiveness by 346 and 273%, respectively. The poverty results indicated that only E3 and E4 producers were non-vulnerable in the simulated scenario and actual production scenario. The purchase of food was the comparative advantage with the greatest sensitivity to cost increases in the two scenarios analysed, which exacerbated the effect on the E1 and E2 producers.

International audience; No abstract

Heat stress and a high metabolic rate of broilers increase the production of reactive oxygen species, which must be removed by antioxidants to prevent oxidative stress. Selenium (Se) is a potent antioxidant as it is a structural part of glutathione peroxidase (GPx). Dietary supplementation of Se can help reduce the oxidative stress caused by heat-stress conditions. The aim was to evaluate the effect of Se supplementation on the performance and antioxidant status of broilers under heat stress, by using a meta-analysis approach, and to quantify the contribution to heterogeneity of the explanatory variables through a meta-regression procedure. A database of 74 trials was created from 56 published studies that met the following inclusion criteria: papers that reported a measure of effect size, sample size, measure of variability and random procedure. The response variables were GPx and malondialdehyde concentrations, DM intake, average daily gain, and feed conversion rate. Broiler line, Se source, and dosage, heat-stress level, days of experimentation, sample source (blood, liver or meat) and basal Se concentration were considered to be explanatory variables. All statistical analyses were performed in R software, by using the ‘meta’ and ‘Metafor’ packages for meta-analysis and meta-regression respectively. High concentrations of GPx were found in Se-supplemented broilers (>1.76; P = 0.001), in comparison to control groups. However, when the random model was applied to GPx studies, it showed high heterogeneity (I2 = 95.4%), which was reduced (I2 = 61.5) when heat-stress temperature, Se source and its dosage and tissue sample were included as covariates in the meta-regression analysis. The highest standard mean difference of GPx was founded in studies that reported supplementation with inorganic Se sources (2.92), in comparison to supplementation with organic and nano-Se sources (1.66 and 1.44 respectively). The standard mean differences of malondialdehyde and feed conversion rate were significantly lower (

Accounting and mathematical modeling methods were combined to analyze the cost structure and economic optimization of small-scale dairy production systems in the present study. Information on the technical, economic, and production characteristics of 72 farms was obtained over a two-year period. Four strata of farms were defined using a random stratified sampling design with proportional allocation. To evaluate production costs, two accounting methods were used: (1) the activity-based budgeting (AB) method, which counted the actual cost of feed cultivation and family labor (FL) as a percentage of total feed and labor costs for each stratum, and (2) the standard accounting (SA) method, which estimated production costs according to the cost of purchasing 100% of feed and hiring 100% of labor. Based on the results of the AB method, four scenarios were developed and adapted to a mixed integer linear programming model to predict the percentage of feed cultivation and FL that maximizes economic benefits. The base scenario evaluated the actual percentages of feed cultivation and FL employed by each farm category, and scenarios I, II, and III simulated the purchase of feed and hire of labor at 20%, 50%, and 100%, respectively. The results showed that 100% dependence on the purchase of feed and hire of labor increases the daily production cost by 20% compared to the base scenario in the four evaluated strata. The mathematical model indicated that the production of less than 90% of feed and use of less than 80% family labor significantly decrease the income in each analyzed stratum. Accordingly, production under the simulated conditions of scenarios I, II, and III is economically and financially non-viable.

ResumenSe analizó contablemente la evolución y desempeño de las estrategias productivas, económicas y comerciales utilizadas por productores lecheros de pequeña escala en la zona periurbana de Texcoco, México. Para tal motivo, los datos económicos y productivos fueron obtenidos de 1023 lactancias en el periodo 2000–2012. Se utilizó la metodología general de costos para establecer las estructuras contables de los sistemas de producción y la metodología financiera de reajustabilidad de valores mediante la construcción de deflactores usando la variación del Índice Nacional de Precios al Consumidor. Se presenta evidencia que entre los periodos analizados el grupo de productores, ubicado en el estrato I, definió como estrategias una nula participación de mano de obra eventual y contratada, así como la independencia en la compra de insumos (ya que este estrato produce 90% de sus insumos); el estrato II disminuyó tres de los cuatro principales rubros del costo total de producción (alimentación, medicamentos y servicio reproductivo) e incrementó la utilidad promedio por litro de leche ($2.00) con estrategias comerciales de venta; el estrato III definió como estrategias el aumento de productividad (59%), la disminución en costo (29%) del principal insumo (alimento) en la dieta y el aprovechamiento de la escala productiva para obtener la mayor entrada de ingresos por unidad productiva.AbstractAn accounting analysis was performed on the evolution and performance of productive, economic and marketing strategies implemented by small-scale dairy farmers in the peri-urban area of Texcoco, Mexico. Economic and production records for 1 023 lactation were obtained in two periods, 2000 and 2012. The general cost methodology was used to establish the accounting structures of these production systems, and the re-adjustment of values financial methodology through calculating deflated values based on data from the Mexican National Index of Consumer Prices. Evidence is presented that farmers in Stratum I defined as strategies not hiring temporary or permanent labour, as well as independence in the purchase of inputs (this Stratum produces 90% of its inputs). Stratum II reduced 3 of the main 4 items of the total production cost (feeding, medicines and breeding) and increased the mean profit per litre of milk ($ 2.00 MXN) through selling strategies. Stratum III defined as their strategies increased productivity (59%), a reduction in the cost (29%) of the main input (feed) and taking advantage of their productive scale to obtain a higher receipt of revenues for the farm.

Latin America systematic breakdown processes are being approached by a myriad of researchers coming from different places of the region, users of a complex diversity of epistemological frameworks. This allows the observation of common interests: social, economic, political, cultural and environmental vulnerability processes. This work purpose is to develop a conceptual map, from the papers presented in the 9th ALASRU Congress (Mexico City, 2014), through social network analysis, in order to synthetize the reticular construction in Latin America of development and sociology discourse and group it at a “glocal” level, per region, institution and researcher. This was done by analyzing two types of co-occurrences: words from a given text and actor per words. This allowed to restructure (in semantic terms) every and each abstract presented in the Congress, regarding their concepts and grammatical connectors, which generated a casual grid for each paper discourse.

Se analizó contablemente la evolución y desempeño de las estrategias productivas, económicas y comerciales utilizadas por productores lecheros de pequeña escala en la zona periurbana de Texcoco, México. Para tal motivo, los datos económicos y productivos fueron obtenidos de 1 023 lactancias en el periodo 2000-2012. Se utilizó la metodología general de costos para establecer las estructuras contables de los sistemas de producción y la metodología financiera de reajustabilidad de valores mediante la construcción de deflactores usando la variación del Índice Nacional de Precios al Consumidor. Se presenta evidencia que entre los periodos analizados el grupo de productores, ubicado en el estrato I, definió como estrategias una nula participación de mano de obra eventual y contratada, así como la independencia en la compra de insumos (ya que este estrato produce 90% de sus insumos); el estrato II disminuyó tres de los cuatro principales rubros del costo total de producción (alimentación, medicamentos y servicio reproductivo) e incrementó la utilidad promedio por litro de leche ($2.00) con estrategias comerciales de venta; el estrato III definió como estrategias el aumento de productividad (59%), la disminución en costo (29%) del principal insumo (alimento) en la dieta y el aprovechamiento de la escala productiva para obtener la mayor entrada de ingresos por unidad productiva.