Hypomagnesemia in beef cattle

ABSTRACT: Hypomagnesemia is a major cause of death in grazing beef cows in countries of the Southern Hemisphere such as Argentina, Australia and New Zealand. Here we review the literature on hypomagnesemia in beef cattle and describe an outbreak in Uruguay. The disease occurred in late autumn, affecting 6 to 11-year-old Aberdeen Angus and Hereford x Aberdeen Angus lactating multiparous cows in good body condition, grazing on natural grasslands that had been improved by fertilization and sowing of seeds of ryegrass and oat. Approximately 40 out of 225 cows were affected and 24 (10.7%) died. A presumptive diagnosis of hypomagnesemia was established based on sudden death, acute neuromuscular clinical signs, epidemiological data, and the response to Mg administration. The diagnosis was confirmed by detecting low Mg concentrations in serum (0.47-0.57mmol/L), vitreous humor (0.47-0.80mmol/L), aqueous humor (0.66mmol/L) and cerebrospinal fluid (0.59mmol/L). The largest component of the diet corresponding to fast-growing and exuberant forages of ryegrass and oat had high concentrations of K (3.48%), N (4.38%) and P (0.94%), suggesting secondary hypomagnesemia. In addition, the K/(Ca+Mg) ratio was 2.38 in forages of ryegrass and oat (reference value: 2.2), and 0.15 in the soil (reference value: 0.09), which represent risk factors for hypomagnesemia. In conclusion, hypomagnesemia is an important cause of mortality in beef cattle grazing improved natural grasslands in Uruguay and it can be easily prevented by correct seasonal Mg supplementation.

RESUMO: A hipomagnesemia é uma das principais causas de morte em vacas de corte em pastagem em países do Hemisfério Sul, como Argentina, Austrália e Nova Zelândia. Aqui, revisamos a literatura sobre hipomagnesemia em bovinos de corte e descrevemos um surto no Uruguai. A doença ocorreu no final do outono, afetando vacas Aberdeen Angus e Aberdeen Angus x Hereford de 6-11 anos de idade em boas condições corporais, lactantes, multíparas e pastando em campos naturais que foram melhorados com fertilização e plantio de azevém e aveia. Aproximadamente 40 de 225 vacas foram afetadas e 24 (10,7%) morreram. O diagnóstico presuntivo de hipomagnesemia foi estabelecido com base na morte súbita, sinais clínicos neuromusculares agudos, dados epidemiológicos e a resposta à administração de Mg. O diagnóstico foi confirmado pela detecção de baixos níveis de Mg no soro (0,47-0,57mmol/L), humor vítreo (0,47-0,80mmol/L), humor aquoso (0,66mmol/L) e líquido cefalorraquidiano (0,59mmol/L). O componente mais importante da dieta correspondia a pastagens de azevém e aveia de rápido crescimento, as quais apresentaram altas concentrações de K (3,48%), N (4,38%) e P (0,94%), que sugerem hipomagnesemia secundária. Além disso, a relação K/(Ca+Mg) foi de 2,38 em forragens de azevém e aveia (valor de referência: 2,2) e 0,15 no solo (valor de referência: 0,09), que representam fatores de risco para hipomagnesemia. Em conclusão, a hipomagnesemia é uma causa importante de mortalidade em gado de corte em pastagens naturais melhoradas no Uruguai e pode ser facilmente prevenida pela correta suplementação sazonal de Mg.

Hypomagnesemia in beef cattle / Hipomagnesemia em bovinos de corte

Hypomagnesemia is a major cause of death in grazing beef cows in countries of the Southern Hemisphere such as Argentina, Australia and New Zealand. Here we review the literature on hypomagnesemia in beef cattle and describe an outbreak in Uruguay. The disease occurred in late autumn, affecting 6 to 11-year-old Aberdeen Angus and Hereford x Aberdeen Angus lactating multiparous cows in good body condition, grazing on natural grasslands that had been improved by fertilization and sowing of seeds of ryegrass and oat. Approximately 40 out of 225 cows were affected and 24 (10.7%) died. A presumptive diagnosis of hypomagnesemia was established based on sudden death, acute neuromuscular clinical signs, epidemiological data, and the response to Mg administration. The diagnosis was confirmed by detecting low Mg concentrations in serum (0.47-0.57mmol/L), vitreous humor (0.47-0.80mmol/L), aqueous humor (0.66mmol/L) and cerebrospinal fluid (0.59mmol/L). The largest component of the diet corresponding to fast-growing and exuberant forages of ryegrass and oat had high concentrations of K (3.48%), N (4.38%) and P (0.94%), suggesting secondary hypomagnesemia. In addition, the K/(Ca+Mg) ratio was 2.38 in forages of ryegrass and oat (reference value: 2.2), and 0.15 in the soil (reference value: 0.09), which represent risk factors for hypomagnesemia. In conclusion, hypomagnesemia is an important cause of mortality in beef cattle grazing improved natural grasslands in Uruguay and it can be easily prevented by correct seasonal Mg supplementation.(AU)

A hipomagnesemia é uma das principais causas de morte em vacas de corte em pastagem em países do Hemisfério Sul, como Argentina, Austrália e Nova Zelândia. Aqui, revisamos a literatura sobre hipomagnesemia em bovinos de corte e descrevemos um surto no Uruguai. A doença ocorreu no final do outono, afetando vacas Aberdeen Angus e Aberdeen Angus x Hereford de 6-11 anos de idade em boas condições corporais, lactantes, multíparas e pastando em campos naturais que foram melhorados com fertilização e plantio de azevém e aveia. Aproximadamente 40 de 225 vacas foram afetadas e 24 (10,7%) morreram. O diagnóstico presuntivo de hipomagnesemia foi estabelecido com base na morte súbita, sinais clínicos neuromusculares agudos, dados epidemiológicos e a resposta à administração de Mg. O diagnóstico foi confirmado pela detecção de baixos níveis de Mg no soro (0,47-0,57mmol/L), humor vítreo (0,47-0,80mmol/L), humor aquoso (0,66mmol/L) e líquido cefalorraquidiano (0,59mmol/L). O componente mais importante da dieta correspondia a pastagens de azevém e aveia de rápido crescimento, as quais apresentaram altas concentrações de K (3,48%), N (4,38%) e P (0,94%), que sugerem hipomagnesemia secundária. Além disso, a relação K/(Ca+Mg) foi de 2,38 em forragens de azevém e aveia (valor de referência: 2,2) e 0,15 no solo (valor de referência: 0,09), que representam fatores de risco para hipomagnesemia. Em conclusão, a hipomagnesemia é uma causa importante de mortalidade em gado de corte em pastagens naturais melhoradas no Uruguai e pode ser facilmente prevenida pela correta suplementação sazonal de Mg.(AU)

Efecto del componente arbóreo sobre la dinámica de crecimiento y calidad nutricional de una pradera mixta en trópico alto / Effect of tree component on the growth dynamics and nutritional quality of a mixed grassland in the high tropic

Resumen Los sistemas ganaderos se basan en el monocultivo de gramíneas. El pastoreo comúnmente no tiene en cuenta la fisiología de las especies, lo que afecta la persistencia y calidad del forraje. Los sistemas silvopastoriles favorecen la producción y calidad del forraje. Por eso es importante conocer la dinámica de crecimiento de la pastura para determinar el momento óptimo de pastoreo. Con base en esto, el objetivo de esta investigación fue evaluar el efecto de Acacia melanoxilum sobre la producción y calidad nutricional de una pradera mixta en trópico alto. La investigación se desarrolló en el Centro de Investigación y Capacitación "Santa María del Puyón", ubicado en Sopo, Colombia. Se evaluó una pradera de Cenchrus clandestinum y Lolium perenne, en pasturas en callejones se establecieron parcelas bajo y fuera de los árboles, y se evaluó el crecimiento (15, 30, 45 y 60 días) durante nueve meses. Luego se determinaron las propiedades fisicoquímicas del suelo, la altura sin disturbar del pasto, el número de hojas, el índice de área foliar y la producción y calidad de forraje. Después se utilizó un diseño al azar, y se realizó estadística descriptiva y análisis de varianza, mediante el programa Infostat® para el análisis de datos. Bajo los árboles se observó mayor pH, materia orgánica, minerales y capacidad de intercambio catiónico, mayor altura sin disturbar (p = 0,0001), diferencias en producción de forraje verde (p = 0,0128), composición botánica y mayor proteína cruda (p = 0,0061). Los árboles de A. melanoxilum favorecen el crecimiento y la calidad nutricional de praderas mixtas en trópico alto.

Abstract Livestock systems are based on the monoculture of grasses, grazing does not usually take into account the physiology of the species, this affects the persistence and quality of the forage. Silvopastoral systems favor forage production and quality, it is important to know the growth dynamics of the pasture to determine the optimal grazing moment. The objective of this work was to evaluate the effect of Acacia melanoxilum on the production and nutritional quality of a mixed meadow in the high tropics. The research was carried out at the "Santa María del Puyón" Research and Training Center, located in Sopo, Colombia. A meadow of Cenchrus clandestinum and Lolium perenne was evaluated, in alley pastures, plots were established under and outside the trees, the growth was evaluated (15, 30, 45 and 60 days) for nine months. The physicochemical properties of the soil, undisturbed height, number of leaves, leaf area index, production and quality of forage were determined. A random design was used, descriptive statistics and analysis of variance were performed. The Infostat® program was used for data analysis. Under the trees there is a higher ph, organic matter, minerals and cation exchange capacity, higher undisturbed height (p = 0.0001), differences in green forage production (p = 0.0128), botanical composition, and higher protein crude (p = 0.0061). A. Melanoxilum trees favor the growth and nutritional quality of mixed grasslands in the high tropics.

Effects of experimental lightgaps and topography on enrichment plantings in a central Amazonian secondary forest

Enrichment plantings into secondary forest are an important option in restoring species diversity and ecosystem services. However, little attention has been given to environmental requirements for species performance. This study evaluated the effects of lightgaps and topographic position on the growth and survival of four native tree species (Pouteria caimito, Garcinia macrophylla, Dipteryx odorata and Cynometra bauhiniaefolia) planted into a 26-year old secondary forest originating from abandoned pastures in the central Amazon Basin. Artificial lightgaps and control plots under closed canopy were uniformly distributed on plateaus and bottomlands near water bodies. Seedlings were planted randomly into the plots and monitored for 28 months. Seedling survival rate was high (93%) and did not differ among species. Overall, lightgaps produced a 38% increase in seedling height relative to the controls. Although the four species naturally occur in mature forest, two of the four grew significantly more in lightgaps than in closed canopy secondary forest. Overall, bottomlands facilitated greater seedling growth in height (38%) relative to plateaus, but only one species exhibited a significant increase. This study shows the importance of the environmental variability generated with canopy openings along the topographic gradient, suggesting that both the selection of species and microsite conditions of planting sites have to be considered important criteria in the recovery of degraded areas. (AU)

Almacenes de biomasa y carbono aéreo y radicular en pastizales de Urochloa decumbens y Paspalum notatum (Poaceae) en el sureste de México

Introducción: Debido a su extensión actual, la biomasa radicular de los pastizales tropicales es de vital importancia para el almacenamiento del carbono terrestre, pero su estimación ha sido principalmente indirecta y con un rango muy amplio de valores. Objetivo: Documentar a nivel nacional y mundial, y comparar, las existencias de carbono radicular extraídas en forma directa, de dos pastizales de origen y tipo de crecimiento distinto. Método: Se midió la biomasa y carbono total de dos pastizales con más de 40 años de uso, uno nativo de América y de crecimiento estolonífero (Paspalum notatum) y otro introducido de África y de crecimiento en macollos (Urochloa decumbens). El estudio se realizó entre agosto y octubre 2016. Se seleccionaron 3 parcelas de 1 600 m2 por pastizal, con 10 subcuadros (4 m2 c/u) en cada parcela, para determinar composición florística, biomasa y C aéreo. La biomasa y C radicular se estimaron mediante extracción directa en tres trincheras (1.50 m x 0.50 m x 1.0 m) por parcela. El contenido de carbono orgánico se determinó con el método por ignición a una temperatura promedio de 550 °C durante 3 horas. Para el análisis estadístico se usó un ANOVA de dos factores, en el que un factor fueron dos tratamientos (tipo de pastizal) y el otro factor fue la parte morfológica del pasto (aéreo y radicular). Resultados: La composición florística de los dos tipos de pastizal fue diferente debido a su historia de manejo. En promedio se estimó 28.25 MgC ha-1 total para la localidad. El pastizal nativo y de crecimiento estolonífero P. notatum produce casi tres veces más biomasa (42.5 MgC ha-1) que el introducido y de crecimiento en macollos U. decumbens (14 MgC ha-1) debido al almacén radicular (38.5 vs. 11.46 MgC ha-1). El 74.5 % del carbono en P. notatum se localizó en la parte radicular y el 25.5 % en la parte aérea, mientras que en U. decumbens fueron 56.5 y 43.5 %, respectivamente. Conclusión: P. notatum acumuló más biomasa y carbono total y radicular que U. decumbens. La mejor adaptación del pasto nativo, así como la morfología de su sistema radicular, pueden explicar esta diferencia. El 96 % de la biomasa y del C radicular se encuentra en los primeros 0.50 m de profundidad. Debido a la contribución de su porción radicular, los pastizales tropicales pueden constituir importantes reservorios de carbono terrestre, considerando su extensión hoy en día.

Introduction: Due to its current coverage, the root biomass of tropical pastures is of vital importance for the terrestrial carbon storage, but its estimation has been mainly indirect and with a very wide range of values. Objective: To document at national and global level as well as compare, the root carbon stocks extracted directly from two grasslands of different growth type and origin. Methods: The biomass and root carbon stocks were directly extracted from two tropical pastures with more than 40 yr of age. The biomass and total carbon, one native with stoloniferous growth (Paspalum notatum) and one introduced with growth in tillers (Urochloa decumbens) were measured. The study was conducted between August and October 2016. Three plots of 1 600 m2 each were selected per pasture, with 10 sub-squares (4 m2 each) in each plot to determine the floristic composition, aboveground biomass and C. The biomass and root C were estimated by hand in three trenches (1.50 m x 0.50 m x 1.0 m) per plot. The organic carbon content was determined with the ignition method at an average temperature of 550 °C for 3 hours. For the statistical analysis, a two-factor ANOVA was used, where one factor was the treatments that were the type of pasture (2) and the other factor was the section of the grass (above and belowground). Results: The floristic composition of the two types of pasture was different due to its management history. On average, 28.25 Mg ha-1 of total C was estimated for the locality. The native pasture of stoloniferous growth P. notatum yields almost three-fold more biomass (42.5 MgC ha-1) than the introduced with growth in tillers U. decumbens (14 MgC ha-1) due to the radicular storage (38.5 vs. 11.46 MgC ha-1). Seventy-four point five percent of the carbon in P. notatum was located in the radicular part and 25.5 % above-ground, while in U. decumbens 56.5 and 43.5 %, respectively. Conclusions: P. notatum accumulated more total and radicular biomass and carbon than U. decumbens. The best adaptation of the native grass as well as the morphology of its root system may explain this difference. Ninety six percent of the biomass and root C is found in the first 0.50 m depth. Due to the contribution of its radicular portion, tropical pastures can constitute important reservoirs of terrestrial carbon considering its extension nowadays.

Reservas de carbono del pasto Cenchrus clandestinus (Poaceae) en los sistemas de manejo tradicional y silvopastoril, en diferentes relieves

El aumento de las emisiones de Gases de Efecto Invernadero (GEI) derivadas de las actividades humanas, son consideradas el principal responsable del cambio climático actual y el sector ganadero es responsable del 18 % de las emisiones de GEI en CO2 equivalente. El pasto kikuyo puede optimizar tanto la captura como la fijación del carbono. El objetivo del trabajo fue identificar las existencias de carbono en el pasto kikuyo en sus diferentes compartimentos, biomasa aérea (BA) y biomasa radicular (BR), a 20 y 40 cm de profundidad del suelo, bajo los sistemas tradicional y silvopastoril en diferentes relieves. Se realizaron seis muestreos (M) sucesivos de acuerdo al sistema de pastoreo (tradicional y silvopastoril), la geoforma del terreno (flanco cóncavo (FCC), flanco convexo (FCX), flanco rectilíneo (FR) y relieve plano (RP)). Se muestrearon la biomasa aérea (BA) y de raíces (BR). El método estadístico utilizado fue un diseño en bloques incompletos aleatorizados, se evaluaron dos tratamientos (T) (T1: tradicional y T2: silvopastoril) con cuatro bloques (B) en cada uno (B1: FCC, B2: FCX, B3: FR, B4: RP). El trabajo se realizó entre junio 2016 y junio 2017 en San Pedro de los Milagros, Antioquia Colombia. Los resultados permitieron determinar que las raíces a 20 cm de profundidad, el colchón muerto y las hojas, fueron los compartimentos con mayores existencias de carbono (4.52, 3.58 y 1.9 ton de C ha-1 respectivamente). Se encontraron diferencias (P < 0.05) entre relieve plano y el relieve rectilíneo para la biomasa de hojas, y entre el relieve plano con los demás relieves evaluados para la variable raíces gruesas a 20 cm de profundidad. La biomasa producida por la planta es directamente proporcional al carbono incorporado. La biomasa radicular, tanto para raíces finas como gruesas, contribuye a capturar en promedio 2 820 y 655 kg ha-1 de carbono a 20 y 40 cm de profundidad respectivamente. El pasto kikuyo contribuye a mantener reservas de carbono en las praderas. Por la alta producción de biomasa radicular, de colchón y la alta capacidad de rebrote en condiciones adversas, se concluye que este pasto juega un papel importante en la disminución de GEI y la conservación de los suelos del trópico alto bajo sistemas de lechería especializada.

The increase of Greenhouse Gases (GHG) emissions derived from human activities are considered the main cause of current climate change and the livestock sector is responsible for 18 % of the GHG emissions in CO2 equivalent. Kikuyu grass can optimize both carbon capture and carbon fixation. The aim of this paper was to identify carbon stocks in the kikuyu grass in its different compartments, above-ground biomass (AB) and below-ground biomass (BB) at 20 and 40 cm soil depth, under the traditional and silvopastoral systems in different reliefs. Six successive samplings (M) were taken according to the grazing system (traditional and silvopastoral system), and the geoform of the terrain (concave flank (CCF), convex flank (CXF), rectilinear flank (RF) and flat relief (FR)). The above-ground biomass and below-ground biomass were sampled. The statistical method used was a design in incomplete randomized blocks, two treatments were evaluated (T) (T1: traditional system and T2: silvopastoral system) with four blocks (B) in each one (B1: CCF, B2: CXF, B3: RF, B4: FR). This experiment was done from June 2016 to June 2017 in San Pedro de los Milagros, Antioquia, Colombia. The results allowed to determine that the roots at 20 cm depth, the dead creeping stems, and the leaves were the compartments with the highest carbon stocks (4.52, 3.58 and 1.9 ton of C ha-1, respectively). Differences were found (P < 0.05) between flat and rectilinear relief for the biomass of leaves, and between the flat relief with the other reliefs evaluated for the variable thick roots at 20 cm depth. The biomass produced by the plant is directly proportional to the incorporated carbon. The root biomass, both fine and thick roots, contributes to capture on average 2 820 kg and 655 kg of carbon per hectare at of 20 and 40 cm depth respectively. Kikuyu grass contributes to keep carbon reserves in the grasslands. Due to the high production of below-ground biomass and creeping stems, and its high capacity of regrowth under adverse conditions, this grass plays an important role in the reduction of GHG and the conservation of high tropical soils under specialized dairy systems.

Nutrient absorption in Tithonia Diversifolia / Absorción de Nutrientes en Tithonia diversifolia / Absorção de nutrientes em Tithonia diversifolia

Abstract Tithonia diversifolia is a robust shrub that has high ecological plasticity and adaptability, high capacity of nutrient absorption and high nutrient contents. These characteristics make Tithonia diversifolia be considered as a multi-purpose plant, such as for animal feed, soil decontamination and soil restorer. Likewise, it is a plant with high ecological plasticity and adaptability. The study of the nutrient absorption and the fertilization represent an important advance in the development of productive systems focused on maximizing forage productivity, which guarantees the soil sustainability. Based on this, a split plot design was conducted to study the effects of different levels of fertilization. The results showed an impact of the elements and levels of fertilization on the nutrient absorption capacity, finding that the elements that were incorporated in the fertilization increase the foliar contents and the nutrient absorption in the plant.

Resumen Tithonia diversifolia es un arbusto robusto que tiene alta plasticidad ecológica y adaptabilidad, alta capacidad de absorción de nutrientes y alto contenido de nutrientes. Estas características hacen que Tithonia diversifolia sea considerada una planta multipropósito, tanto para alimento animal como para descontaminación y restauración del suelo. El estudio de la absorción de nutrientes y la fertilización representa un avance importante en el desarrollo de sistemas productivos enfocados en la maximización de la productividad de forraje, lo cual garantiza la sostenibilidad del suelo. Con base en esto, se llevó a cabo un diseño experimental de parcelas divididas con el fin de estudiar los efectos de diferentes niveles de fertilización. Los resultados mostraron un impacto de los elementos y los niveles de fertilización en la capacidad de absorción de nutrientes; se encontró que los elementos que fueron incorporados en la fertilización incrementan los contenidos foliares y la absorción de nutrientes en la planta.

Resumo Tithonia diversifolia é um arbusto robusto que tem alta plasticidade ecológica e adaptabilidade, alta capacidade de absorção de nutrientes e alto conteúdo de nutrientes. Estas características fazem com que Tithonia diversifolia seja considerada uma planta multipropósito, tanto para alimento animal como para descontaminação e restauração do solo. O estudo da absorção de nutrientes e da fertilização representa um avance importante no desenvolvimento de sistemas produtivos enfocados na otimizacao da produtividade de forragem, o que garante a sustentabilidade do solo. Baseado em esto, se realizou um desenho experimental de parcelas divididas com a finalidade de estudar os efeitos de diferentes níveis de fertilização. Os resultados mostraram um impacto dos elementos e dos níveis de fertilização na capacidade de absorção de nutrientes. Se encontrou que os elementos que foram incorporados na fertilização incrementam os conteúdos foliares e a absorção de nutrientes na planta.

COMPORTAMIENTO AGRONÓMICO Y NUTRICIONAL DE GENOTIPOS DE Brachiaria SPP. MANEJADOS CON FERTILIZACIÓN NITROGENADA, SOLOS Y ASOCIADOS CON Pueraria phaseoloides, EN CONDICIONES DE LA ALTILLANURA COLOMBIANA / AGRONOMIC AND NUTRITIONAL RESPONSE OF Brachiaria SPP. GENOTYPES MANAGED WITH NITROGEN FERTILIZATION ALONE AND IN ASSOCIATION WITH Pueraria phaseoloides IN CONDITIONS OF THE COLOMBIAN ALTILLANURA

RESUMEN La altillanura colombiana es una microrregión que tipifica un tipo de producción bovina extensiva que requiere el uso de gramíneas adaptadas que respondan a la fertilización nitrogenada para mejorar el rendimiento y la calidad nutricional de las praderas, a fin de intensificar los sistemas de producción ganaderos. El estudio se desarrolló en la sede Taluma de Corpoica, ubicada a 04°34'25" Oeste y 71°20'10" Norte en el municipio de Puerto López (Meta, Colombia), en condiciones de clima y suelo representativos de la altillanura colombiana. El objetivo del estudio fue determinar el comportamiento agronómico y nutricional de los genotipos de Brachiaria brizantha CIAT 16315, 16467, 26990, 26124, 6387 y el control Mulato II manejados con fertilización nitrogenada sola y asociada con la leguminosa Kudzú (Puerariaphaseoloides). Se utilizó un diseño de bloques completos al azar con arreglo en franjas divididas, en donde la parcela correspondió a la gramínea forrajera y la franja al nivel de fertilización nitrogenada (N46, N92 y P. phaseoloides + N46). Los genotipos fueron evaluados durante 90 días, tanto en época seca, como lluviosa. Las accesiones con mayor producción de biomasa (p < 0,001) fueron B. brizantha CIAT 16315 (2.040 kgMS.ha-1), B. brizantha CIAT 16467 (1.864 kg MS.ha-1) y B. brizantha CIAT 6387 (2.033 kgMS.ha-1). El tratamiento de la gramínea + N92 (kgN.ha-1) presentó valores significativamente (p < 0,001) superiores de PC (9,55%) y degradabilidad del forraje (65,7%), y los menores contenidos de materia seca (37,05%), FDN (61,97%) y FDA (30,55%) en relación con las gramíneas fertilizadas con 46 kgN.ha-1 y las gramíneas asociadas con Kudzú y fertilizadas con 46 kgN.ha-1. Por mayor contenido de PC (p < 0,001), se destacaron los materiales B. brizantha CIAT 16315 (8,34%) y CIAT 26124 (8,06%) que no presentaron diferencias significativas con el pasto Mulato II (8,18%). Los resultados demostraron la importancia de la fertilización nitrogenada para mejorar la producción y calidad nutricional de las praderas de B. brizantha.

ABSTRACT The Colombian altillanura is a microregion that typifies a extensive cattle production system which requires the use of adapted grasses responding to nitrogen fertilization to improve yield and nutritional quality grassland to intensify livestock production systems. The study was conducted at the Taluma station of CORPOICA, located at 04°34'25" West and 71°20'10" North in the town of Puerto López (Meta, Colombia), under conditions of climate and soil of the Colombian altillanura. The objective of this study was to determine the agronomic and nutritional behavior of genotypes of Brachiaria brizantha CIAT 16315, 16467, 26990, 26124, 6387 and Mulato II as control, handled single nitrogen fertilization and associated with the legume Kudzú (Pueraria phaseoloides). Design of randomized complete block arrangement in divided stripes, where the plot corresponded to the forage grass strip and the level of nitrogen fertilization was used (N46, N92, and N46 + P. phaseoloides). Accessions with greater biomass production (p < 0.001) were B. brizantha CIAT 16315 (2040 kgDM.ha-1), B. brizantha CIAT 16467 (1864 kgDM. ha-1) and B. brizantha CIAT 6387 (2033 kgDM.ha-1). Treatment grasses + N92 (kgN.ha-1) values had significantly (p <0.001) higher in CP (9.55%) and degradability of forage (65.7%) and lower dry matter content (37.05 %%), NDF (61.97%) and FDA (30.55%) compared with the response of grasses fertilized with 46 kgN.ha-1 and grasses associated with Kudzú and fertilized with 46 kgN.ha-1. For higher CP content (p <0.001), materials B. brizantha CIAT 16315 (8.34%) and CIAT 26124 (8.06%) which did not differ significantly with grazing Mulato II (8.18%). The results demonstrated the importance of nitrogen fertilization on the production and nutritional quality pastures B. brizantha.

Where is sugarcane cropping expanding in the brazilian cerrado, and why? A case study

ABSTRACT Sugarcane growing area in Brazil sharply expanded between 2000 and 2010 due to the increasing world demand for sugar and ethanol. Since this expansion of sugarcane is said to occur in areas covered by degraded pastures, it is likely not threatening the environment or food production. In order to verify this assumption, we investigate at farm and field levels which types of land use sugarcane cropping replaced between 2005 and 2010 and the reasons for farmers shifting or not shifting to sugarcane, as a case study in two counties in the state of Goiás. Within the studied period, sugarcane cropping expansion was related to large farms, lower risk perceived by farmers, and higher profitability compared with soybean and beef cattle-raising. For smallholders, particularly dairy farmers, the need to comply with the set-aside rules under Brazilian Forest Code (Código Florestal Brasileiro) made a shift to sugarcane less attractive, as it would have forced them to reduce farm cultivable area, with loss of incomes. From 30,408 ha under sugarcane surveyed, 45.7% had used to be pastures, 31% had previously been pastures rotated with soybean and maize, and 23.3% had been cropped exclusively with soybean or maize.

Seedling growth and survival of five tree species in secondary forests and adjacent pastures in the montane rain forests of Southern Costa Rica / Crecimiento y supervivencia de plántulas de cinco especies de árboles en bosques secundarios y pastizales adyacentes en un bosque lluvioso montano del sur de Costa Rica

Abstract:Successful forest restoration in tropical environments is limited by the paucity of studies on the initial establishment and early survival requirements of seedlings of most native tropical tree species under disturbed conditions. Here, we evaluated the initial growth responses and the regeneration potential of seedlings of five tree species native to Costa Rica (Hasseltia floribunda, Inga densiflora, Persea americana, Tapirira mexicana and Trichilia pittieri). Seedlings were grown in secondary forests and adjacent open pastures under contrasting conditions of light availability. We quantified seedling growth, survival and herbivory from August 2010 to August 2011 on a monthly basis, and measured differences in leaf mass per area (LMA) at the end of the experiment. We found significant variation in growth responses between the understory of secondary forests and pastures. Growth in height was highest in pastures across all species, with I. densiflora, P. americana and T. mexicana showing the most striking differences. In contrast, H. floribunda and T. pittieri did not show differences in diameter growth between environments. Except for T. mexicana, herbivory increased throughout the experiment in all the species. Herbivory increased faster in pastures for H. floribunda and T. pittieri and showed higher rates in the forest understory for I. densiflora and P. americana. Seedling survival showed significant differences for all species across environments. Survival of H. floribunda and I. densiflora was higher in secondary forests, whereas the other species showed higher survival in pastures. LMA showed higher values in the pastures across all species, showing that individuals exposed to high light conditions had great photosynthetic rate and great leaf construction capacity. Due to their rapid growth and high survival, I. densiflora and T. mexicana showed great potential to restore abandoned pastures and secondary forests. Increasing our knowledge on the response of seedlings under disturbed conditions in tropical ecosystems is critical for improving the restoration of altered environments by matching the ecological amplitude of native species with specific environmental conditions. Rev. Biol. Trop. 64 (4): 1565-1583. Epub 2016 December 01.

Resumen:La restauración exitosa del bosque en ambientes tropicales está limitada por la carencia de estudios sobre los requisitos de hábitat, el establecimiento inicial, y la sobrevivencia de las plántulas de la mayoría de las especies de árboles tropicales nativos. En este estudio, evaluamos las respuestas en el crecimiento inicial y el potencial de regeneración de las plántulas de cinco especies de árboles nativos de Costa Rica (Hasseltia floribunda, Inga densiflora, Persea americana, Tapirira mexicana y Trichilia pittieri). Sembramos las plántulas en bosques secundarios y en pastizales abiertos adyacentes con condiciones de luz contrastantes. Cuantificamos el crecimiento, la supervivencia y el daño por herbivoría de las plántulas de forma mensual entre agosto 2010 y agosto 2011, y medimos las diferencias en el la masa foliar por área de la hoja al final del experimento. Existió una variación significativa en el crecimiento de las plántulas expuestas a la sombra en los bosques secundarios y aquellas que crecieron en pastizales. El crecimiento en altura fue mayor en pastizales en todas las especies; I. densiflora, P. americana y T. mexicana mostraron la mayor diferencia entre ambientes. En con- traste, H. floribunda y T. pittieri no mostraron diferencias en el crecimiento del diámetro entre ambientes. Con la excepción de T. mexicana, todas las especies mostraron un aumento en herbivoría durante el estudio. En los pastizales, el incremento de la herbivoría fue más rápido en H. floribunda y T. pittieri, mientras que para I. densiflora y P. americana fue mayor en el bosque. La sobrevivencia de plántulas fue diferente entre ambientes para todas las especies. La sobrevivencia de H. floribunda e I. densiflora fue mayor en el bosque secundario, mientras que en las demás especies hubo mayor sobrevivencia de plántulas en los pastizales. La masa foliar por área fue mayor en las plántulas que crecieron en los pastizales que en bosque secundario para todas las especies, lo que sugiere que los individuos que crecieron en condiciones de alta incidencia de luz tuvieron mayor tasa fotosintética y mayor capacidad de construcción de la hoja. Debido al rápido crecimiento y alta supervivencia I. densiflora y T. mexicana tienen gran potencial para la restauración de bosques secundarios y pastizales abandonados. Generar información sobre la respuesta de plántulas creciendo en bosques secundarios y pastizales en regeneración es crítico para mejorar los procesos de restauración de ambientes alterados. La restauración de estos bosques depende de la correspondencia entre las condiciones específicas de hábitat y la plasticidad ecológica de las especies nativas.

Doses of phosphorus on initial development and forage production of cultivars of Panicum maximum / Doses de fósforo no desenvolvimento inicial e produção de forragem de cultivares de Panicum maximum

Phosphorus shortage in the Savanna is one of the main limiting factors for forage production and directly responsible for the degradation of pastures in this Brazilian region. Thus, the aim of this study was to evaluate the effect of increasing doses of P on the initial development and forage production of four cultivars of P. maximum. The experiment was conducted during the months of December 2010 to May 2011 at Universidade Estadual de Mato Grosso do Sul, Unit of Aquidauana-MS. It was used the completely randomized design in a factorial scheme 4x5, with four replications. The experimental unit consists of polyethylene pots with 5 L capacity arranged in countertop in greenhouse. The first factor consisted of four P. maximum cultivars (Massai, Mombaça, Áries and Atlas), while the second factor consists of five doses of phosphorus (0, 5, 10, 30 and 45 mg dm-3). It was evaluated the following morphometric traits: plant height, length and width of the leaf blade, number of tillers, dry mass of shoot and of roots at 60 DAS. The approximate dose of 25 mg dm-3 of phosphorus provided better initial development and forage production in all cultivars evaluated of Panicum maximum. Mombaça cultivar has better initial development and forage production about to the others.

A escassez de fósforo no Cerrado é um dos principais fatores limitantes para a produção de forragem e responsável diretamente pela degradação das pastagens nesta região brasileira. Assim, o objetivo deste trabalho foi avaliar o efeito de doses crescentes de P sobre o desenvolvimento inicial e produção de forragem de quatro cultivares de Panicum maximum. O experimento foi conduzido durante os meses de dezembro de 2010 a maio de 2011 na Universidade Estadual de Mato Grosso do Sul, Unidade Universitária de Aquidauana, MS. O delineamento experimental utilizado foi inteiramente casualizado, no esquema fatorial 4x5, com quatro repetições. A unidade experimental consistiu de potes de polietileno com capacidade de 5 L dispostos em bancadas na estufa. O primeiro fator foi composto por quatro cultivares de P. maximum (Massai, Mombaça, Áries e Atlas), enquanto o segundo fator consistiu de cinco doses de fósforo (0, 5, 10, 30 e 45 mg dm-3). Foram avaliados os seguintes caracteres morfométricos: altura de plantas, comprimento e largura da lâmina foliar, número de perfilhos, massa seca da parte aérea e das raízes aos 60 dias após a semeadura. A dose aproximada de 25 mg dm-3 de fósforo proporcionou melhor desenvolvimento inicial e produção de forragem em todas as cultivares de Panicum maximum avaliadas. A cultivar Mombaça apresentou melhor desenvolvimento inicial e produção de forragem em relação às demais.

CAMBIOS EN EL PAISAJE INDUCIDOS POR DINÁMICAS SOCIOECONÓMICAS: UN ESTUDIO DE CASO CARTOGRÁFICO EN UNA MICROCUENCA DEL NORTE DEL TOLIMA (1955 A 2010) / LANDSCAPE CHANGES INDUCED BY SOCIO-ECONOMIC DYNAMICS: MAPPING CASE STUDY IN A NORTHERN TOLIMA WATERSHED (1955 to 2010)

El análisis cartográfico de una zona, permite identificar cambios del paisaje y de su dinámica antrópica en un territorio; estos reflejan procesos sociales generados por la interacción hombre-naturaleza. Se realizó una revisión histórica y cartográfica de los cambios del paisaje en una zona del municipio del Líbano (Tolima). Este trabajo se desarrollo en el marco del proyecto de investigación titulado "Agroecosistemas y cultura en fincas de la ecorregión cafetera del Tolima: evolución y conflicto" financiado por la Oficina Central de Investigaciones de la Universidad del Tolima. El objetivo del estudio fue documentar los cambios en los usos del suelo en el territorio de la microcuenca La Tigrera, especialmente la evolución de los agroecosistemas de café y su influencia en la transformación del paisaje. Se revisó información secundaria como mapas temáticos, literatura especializada e información institucional del Comité de Cafeteros del Tolima y de Cortolima. Por otra parte, se analizaron fotos aéreas (escala aproximada 1:60.000) de los años 1955, 1965, 1988 y 2010. Estas se procesaron de forma análoga a través de fotointerpretación, para cuantificar las áreas de ocupación de los usos del suelo presentes en el área de estudio. Se usó un ambiente SIG para crear cartografía temática de usos del suelo, utilizando programas especializados como AutoCAD 2010, Global Mapper, gvSIG 1.10 y ArcGis 1.10, con los cuales se procesaron imágenes tipo raster a partir de la digitalización de las fotos aéreas. Los resultados sugieren transformaciones del paisaje y patrones de uso de la tierra como consecuencia de las decisiones de actores que están inmersos en sistemas socioeconómicos y biofísicos, caracterizados por una compleja red de interrelaciones que evolucionan en el tiempo. Es notoria la reducción del área de bosques para dar paso primero a la caficultura y luego a las pasturas. Se concluye que las relaciones espaciales y de uso del suelo en la ecorregión cafetera del Tolima, son una expresión particular de las relaciones socioeconómicas originadas por la caficultura, lo que marca un ámbito tradicional en las decisiones que se toman en la familia, pero influenciadas por fuerzas macroeconómicas.

The cartographic analysis of an area allows identification of the landscape changes and the anthropic dynamics in a territory; they reflect social processes generated by human-nature interaction. A historical and cartographic review of the landscape changes was carried out in an area of the Municipality of Líbano (Tolima). This work was developed within the framework of the research project "Agroecosystems and culture in farms of the coffee ecoregion of Tolima: revolution and conflict" financed by the Central Research Office at Universidad del Tolima. The aim of the study was to document changes in land use in the territory of La Tigrera watershed, especially the evolution of coffee agroecosystems and their influence on the transformation of thelandscape.Secondary information was reviewed including thematic maps, specialized literature and institutional information of the Tolima Coffee GrowersCommittee and Cortolima.On the other hand, aerial photographs (approximate scale 1: 60,000) for the years 1955, 1965, 1988 and 2010 were analyzed and processed using analogue photo interpretation to quantify areas of occupation of land use present in the study area. A GIS environment was used to create thematic mapping of land use, using specialized programs like AutoCAD 2010, Global Mapper, gvSIG 1.10 and ArcGIS 1.10 with which raster images were processed from digitization of aerial photos. The results suggest changes in the landscape and patterns of land use as a result of the decisions of actors involved in socio-economic and biophysical systems, characterized by a complex network of relationships that evolve over time. The reduction of forest areas to give way to coffee first and then to pasture is notorious. It is concluded that the spatial relationships and land use in the Tolima coffee eco-region are a particular expression of the socio-economic relations caused by the coffee industry, marking a traditional area in the decisions made within the family but influenced by macroeconomic forces.

Avifauna en sistemas silvopastoriles en el Corredor Biológico Mesoamericano, Tabasco, México / Avifauna in silvopastoral systems in the Mesoamerican Biological Corridor, Tabasco, México

Silvopastoral systems support local ecological and economical features as they enhance conservation of floral and faunal communities. As other animal communities, avifauna may be a good representative of habitat altera- tions, both as the species and functional levels. In order to attend the initiative of Mesoamerican Biological Corridor initiative (CBM) in the state of Tabasco, we studied the diversity of birds in two silvopastoral systems: scattered trees in pastures (ADP), and trees in boundary-hedgerows (AL). For this, we applied the fixed radius counting point method in three priority sites in Tabasco´s CBM during the dry and wet season of 2011, and a total of 56, 60 and 62 points were evaluated in Huimanguillo, Tenosique and Tacotalpa, respectively. We observed 2 084 individuals of 154 species (79-89% of expected diversity) and 36 bird families. We detected 92, 87 and 85 species in Huimanguillo, Tenosique and Tacotalpa, respectively, including 35 protected species, of which 23, 19 and 16 in each locality, respectively. All sites showed high diversity (H´≥3.20), low species dominance (D≥0.08) and high equitability (J≥0.77). Species composition showed differences between sites, being most similar Tacotalpa and Tenosique. Ten species were considered characteristic for sites. Although the silvopastoral system did contain protected species, the low diversity and the early successional character of the arboreal components were not attractive to frugivorous bird species. Diversification with native trees can improve the systems to create a complementary habitat and to increase landscape connectivity. The management of silvopastoral practices on cattle dominated landscapes in Tabasco could improve its ecological quality, and thus achieve the CBM´s objectives of biodiversity conservation combined with human economic activities.

Los sistemas silvopastoriles contienen rasgos ecológicos y económicos que contribuyen con la conservación de comunidades florísticas y faunísticas que en ellas se desarrollan. Entre otras comunidades faunísticas se encuentra la avifauna la cual es un grupo representativo de las alteraciones del habitat, tanto a nivel específico como grupo functional. Con el objetivo de atender la iniciativa de Corredor Biológico Mesoamericano en Tabasco, México, se analizó la diversidad de aves en dos sistemas silvopastoriles: árboles dispersos en potreros (ADP) y árboles en cercos o linderos (AL). Se aplicó el método de punto de conteo de radio fijo en tres sitios prioritarios del CBM de Tabasco, ubicados en los municipios: Huimanguillo, Tacotalpa y Tenosique. Los datos provienen de las estaciones seca y húmeda del 2011. Se registraron 2 084 aves de 154 especies (79-89% del esperado) y 36 familias. Se detectaron 92, 87 y 85 especies, incluyendo 35 protegidas, con 23, 19 y 16 en Huimanguillo, Tacotalpa y Tenosique, respectivamente. Todos los sitios mostraron alta diversidad (H’≥3.20), baja dominancia de especies (D≥0.08) y alta equidad (J≥0.77). La composición de especies mostró diferencias entre sitios, con mayor similitud entre Tacotalpa y Tenosique. Diez especies pueden considerarse características de los sitios. Aunque en los sistemas silvopastoriles se refugian aves protegidas, el componente arbóreo es poco diverso y corresponde a especies de sucesión secundaria temprana, lo que limita a las aves frugívoras y especialistas de bosque. Diversificar estos sistemas con árboles nativos puede mejorar estos hábitats complementarios e incrementar la conectividad del paisaje para cumplir con los objetivos del CBM en la conservación de la biodiversidad y provisión de bienes a las poblaciones humanas.

Virulence of entomopathogenic nematodes (Rhabditida: Steinernematidae, Heterorhabditidae) to spittlebug Mahanarva spectabilis (Hemiptera: Cercopidae) / Virulência de nematoides entomopatogênicos (Rhabditida: Steinernematidae, Heterorhabditidae) para cigarrinha-das-pastagens Mahanarva spectabilis (Hemiptera: Cercopidae)

The spittlebug can seriously limit the production of forage, and the use of chemical products to control insect pests is costly and can harm the environment. Thus, there is a need to reduce the reliance on chemical agents by developing new strategies. The virulence of nine strains of entomopathogenic nematodes (EPNs) to spittlebugs was investigated under laboratory and greenhouse conditions. Fourth/fifth-instar nymphs of Mahanarva spectabilis were exposed to EPNs in the laboratory and the most virulent strains were applied on the nymphs in the greenhouse at concentrations of 2,000 and 4,000 EPNs/mL. The efficacy of the pathogenic agent was confirmed by the dissection of dead hosts. All the tested strains were pathogenic to the M. spectabilis nymphs in laboratory, particularly Steinernema carpocapsae, S. feltiae, S. riobrave and Heterorhabditis amazonensis RSC1, each of which caused nymph mortality higher than 80%. The concentration did not influence the efficiency of the strains, and those selected in the laboratory had similar efficiency in the greenhouse, except for S. carpocapsae, which was not as effective as the others. Entomopathogenic nematodes can be included in integrated pest management programs to M. spectabilis.(AU)

A cigarrinha-das-pastagens pode causar sérias limitações na produção de forragens, e o uso de produtos químicos para o controle é caro, além de poder prejudicar o ambiente. Então, existe a necessidade de reduzir o uso de agentes químicos através do desenvolvimento de novas estratégias de controle dessa praga. A virulência de nove isolados de nematoides entomopatogênicos (NEPs) sobre a cigarrinha-das-pastagens foi avaliada em condições de laboratório e casa-de-vegetação. Ninfas de quarto/quinto ínstar de Mahanarva spectabilis foram expostas aos isolados de NEPs em laboratório, e os mais virulentos foram aplicados sobre as ninfas em casa-de-vegetação sob as concentrações de 2000 e 4000 JIs/mL. A eficácia do agente patogênico foi confirmada pela dissecação dos hospedeiros mortos. Todos os isolados testados foram patogênicos às ninfas da cigarrinha-das-pastagens em laboratório, particularmente Steinernema carpocapsae, S. feltiae, S. riobrave e Heterorhabditis amazonensis RSC1, cada um deles causando mortalidade maior que 80%. A concentração não influenciou a eficiência, exceto para S. carpocapsae, o qual não foi tão efetivo como os demais em casa-de-vegetação. Nematoides entomopatogênicos podem ser incluídos em programas de manejo integrado de M. spectabilis.(AU)

Impacto del uso del suelo agropecuario sobre macroinvertebrados acuáticos en pequeñas quebradas de la cuenca del río La Vieja (Valle del Cauca, Colombia)

Agricultural land use impacts on aquatic macroinvertebrates in small streams from La Vieja river (Valle del Cauca, Colombia). The expansion of the agricultural frontier in Colombia has exerted significant pressure on its aquatic ecosystems during the last few decades. In order to determine the impacts of different agricultural land uses on the biotic and abiotic characteristics of first and second order streams of La Vieja river watershed, we evaluated 21 streams located between 1 060 and 1 534 m asl in the municipalities of Alcalá, Ulloa, and Cartago (Valle del Cauca, Colombia). Seven streams were protected by native vegetation buffers, eight had influence of coffee and plantain crops, and six were influenced by cattle ranching. Habitat conditions, channel dimensions, water quality, and aquatic macroinvertebrates were studied in each stream. Streams draining cattle ranching areas had significantly higher dissolved solids, higher phosphorus, higher alkalinity, higher conductivity, and lower dissolved oxygen than those covered by cropland and forests. Coarse substrates and diversity of flow regimes were significantly higher in cropland and protected streams when compared to streams affected by cattle ranching, whereas the percent of silt and slow currents was significantly higher in the latter. A total of 26 777 macroinvertebrates belonging to 17 orders, 72 families and 95 genera were collected. The most abundant groups were Diptera 62.8%, (Chironomidae 49.6%, Ceratopogonidae 6.7%), Mollusca 18.8% (Hydrobiidae 7.2%, Sphaeriidae 9.6%) and Trichoptera 5.7% (Hydropsychidae 3.7%). The Ephemeroptera, Trichoptera, and Plecoptera orders, known for their low tolerance to habitat perturbation, had high abundance in cropland and forested streams, whereas Diptera and Mollusca were more abundant in those impacted by cattle ranching. Results indicate that streams draining forests and croplands have better physical and biological conditions than those draining pastures, and highlight the need to implement protective measures to restore the latter. Rev. Biol. Trop. 62 (Suppl. 2): 203-219. Epub 2014 April 01.

Con el fin de determinar el impacto del uso del suelo sobre las características bióticas y abióticas de quebradas en la cuenca del río La Vieja, se evaluaron 21 quebradas en los municipios de Alcalá, Ulloa y Cartago (Valle del Cauca). Siete quebradas estaban protegidas por franjas de vegetación ribereña, ocho tenían influencia agrícola y seis influencia ganadera. Se registraron las condiciones de protección y perturbación del hábitat, aspectos físicos del cauce, se tomaron muestras de agua para análisis fisicoquímico y bacteriológico, y se recolectaron macroinvertebrados acuáticos. En las quebradas con influencia ganadera los sólidos disueltos, la alcalinidad, conductividad y fósforo total fueron significativamente mayores, mientras que el oxígeno disuelto fue significativamente menor. Las quebradas agrícolas y protegidas presentaron más sustratos gruesos y más tipos de corriente. Se recolectaron 26 777 macroinvertebrados de 17 órdenes, 72 familias y 95 géneros. Los grupos con mayor abundancia relativa fueron Diptera 62.8%, (Chironomidae 49.6%, Ceratopogonidae 6.7%), Mollusca 18.8% (Hydrobiidae 7.2%, Sphaeriidae 9.6%) y Trichoptera 5.7% (Hydropsychidae 3.7%). Ephemeroptera, Trichoptera y Plecoptera, presentaron mayor abundancia en las quebradas protegidas y con influencia agrícola, mientras los dípteros y moluscos fueron más abundantes en las ganaderas. Las quebradas protegidas y agrícolas presentan mejores condiciones físicas y biológicas que las quebradas con influencia ganadera.

Análisis multiciiterio del estado de las pasturs de la hacienda Ganadera garcíía abajo en corinto (cauca, Colombia) / Multi-critera annalysis of grasses of the fam livestock garcia abajo in corrinto (cauca, Colombia)

La evaluación de pasturas utilizando criterios múltiples constituye una herramienta de importancia para la toma de decisiones en el manejo de sistemas ganaderos sostenibles. El objetivo fue construir un índice de estado con base en indicadores productivos y biológicos de los componentes herbáceo y leñoso para tipificar 50 potreros de una explotación ganadera de la Hacienda García Abajo, departamento del Cauca, Colombia. Se levantó información de nueve variables que describen factores incidentes en la producción (área de potreros, edad de la pastura, topografía, árboles y cobertura de dosel), la composición botánica (leguminosas, arvenses, especies de gramíneas) e indicadores de cantidad y calidad de las pasturas (biomasa forrajera y color). Siete de estas variables fueron medidas y calificadas con los uso de una herramienta multicriterio. Mediante estadística multivariada se realizó una tipología de potreros. El conglomerado C1 agrupa los 17 potreros con mayor tiempo de establecimiento, mientras C2 corresponde al de menor cantidad de potreros, los cuales son pasturas jóvenes. C3 agrupa el mayor número de potreros (25), los que a su vez tienen la mayor extensión promedio. C2 fue el conglomerado con mayor producción de biomasa y el que presentó menor porcentaje de vegetación espontánea. En conclusión, el análisis multicriterio para evaluar pasturas permite tomar decisiones y realizar juicios fundamentados sobre diferentes valoraciones, lo cual hace que el diagnóstico sea más acertado y mejor la formulación de soluciones con base en referentes endógenos, a fin de ir mejorando progresivamente el manejo de la finca.

Evaluation of pasture, based on a multicriteria approach, is an important issue for decision making in the design of sustainable farming systems. The aim was to build a state index, based on production and biological indicators of pasture in 50 paddocks of a farm estate Garcia Abajo, located on department of Cauca, Colombia. Nine variables describing incidents factors in production factors (area of pasture, pasture age, topography, trees and canopy cover), the botanical composition (legumes, weeds, grass species) and indicators of quantity and quality of pastures (forage biomass and color) was measured and ranked with the use of a multi-criteria tool. Using multivariate statistics, a typology of pastures was performed. The C1 cluster groups the 17 paddocks longer listing, while C2 corresponds to fewer paddocks, which are young pastures. C3 contains the largest number of pastures (25), which in turn have the largest area averages. C2 fuel conglomerate highest biomass production, and has the lowest percentage of spontaneous vegetation. In conclusion, the multi-criteria analysis to evaluate pastures allows the decision maker to make judgments based on different ratings, which makes diagnosis and formulating solutions, based on endogenous concerning more successful.

Andropogon grass consortium with stylo in two times: the forage response and sources of phosphorus rates / Consórcio de capim andropógon com estilos antes em dois momentos: resposta da forragem a níveis e fontes de fósforo

The use of legumes intercropped with forage in the Brazilian savannah (Cerrado) region is an alternative to reverse the process of pasture degradation. The natural phosphorus deficiency in this region and the high retention capacity of this nutrient in the soil are factors that directly affect the sustainability of the production system. The objective of this study was to evaluate the effect of a phosphate with medium solubility (Arad) compared to more soluble sources such as triple superphosphate and mono-ammonium phosphate, on the formation and maintenance of pastures of Andropogon gayanus with or without the introduction of Stylosantes guianensis in pasture already established in the Brazilian savannah. Two experiments were carried out under field conditions in an Oxisol using a randomized block design with split plots, plots with two sources of phosphorus (Arad and super-triple or MAP) and subplots with different levels of phosphorus. The study showed that andropogon grass, even though characterised as forage requiring low fertilization, responded to increased fertilization, especially with the use of more soluble sources of P at planting. From the second year on, with the introduction of Stylosantes guianensis, verified effects were seen on legumes in their efficiency of utilization of residual fertilization from the first year; however, this didn't affect legume dry matter production resulting from the P sources used for the andropogon grass. The mixed stands of andropogon grass and Stylosantes guianensis made it more advantageous to increase the P sources using phosphate fertilizer with lower solubility (Arad), when compared to MAP.

O uso de leguminosas consorciadas com gramíneas na região do Cerrado brasileiro é uma alternativa para reverter os processos de degradação das pastagens. Tanto a natural deficiência de fósforo nesta região como a alta capacidade de fixação deste nutriente ao solo são fatores que afetam diretamente a sustentabilidade do sistema produtivo. O objetivo deste estudo foi avaliar o efeito do fosfato natural de média solubilidade (Arad) comparada a fontes mais solúveis, na formação e manutenção de pastagens de Andropogon gayanus com introdução de Stylosantes guianensis na pastagem já estabelecida em região dos cerrados. Foram realizados dois experimentos em condições de campo sob um Latossolo Vermelho Amarelo usando o delineamento de blocos ao acaso com parcelas subdivididas, tendo nas parcelas duas fontes de fósforo (Arad e super triplo ou MAP) e nas subparcelas diferentes níveis de fósforo. O estudo mostrou que o andropógon mesmo sendo caracterizado como capim de baixa exigência em fertilidade responde ao aumento da adubação fosfatada, principalmente com o uso de fontes mais solúveis de P no plantio. A partir do segundo ano, com a introdução de Stylosantes guianensis verificou-se efeito da leguminosa na eficiência de aproveitamento do residual da adubação do primeiro ano, contudo, a leguminosa não influenciou a produção de matéria seca decorrente das fontes de P empregadas para o capim andropógon. O plantio consorciado de Stylosantes guianensis e capim andropógon, tornou mais vantajoso o aumento da adubação fosfatada com fontes de P de solubilidade menor (Arad), quando comparado ao MAP.

Physiological and bromatological aspects of Brachiariahumidicola / Aspectos fisiológicos y bromatológicos de Brachiaria humidicola / Aspectos fisiológicos e bromatológicos de Brachiaria humidicola

Brachiaria humidicola was brought to Colombia in order to improve forage production and poor acid soils wherethere was no fodder adapted to these conditions in which this species could be an excellent alternative. However,work to compile aspects and qualitative physiological characteristics are scarce, for this reason, a brief review botanyand morphophysiological of this species also present results of various studies that show the values of quality foragesuch as content protein, neutral detergent fiber (NDF) and acid detergent fiber (FDA), in vitro digestibility of dry matter and lignin content among others. The review took into account the behavior of Brachiaria in environments of special interest such as: soil, nutrients and water.

Brachiaria humidicola, fue traída a Colombia con el propósito de mejorar la producción de forraje en suelos ácidos y pobres donde no se contaba con forrajes adaptados a estas condiciones, en las cuales esta especie pudiera ser una excelente alternativa. Sin embargo, trabajos que compilen aspectos relacionados con sus características fisiológicas y bromatológicas son escasos; por tal motivo se realizó una breve revisión botánica y morfofisiologíca de estaespecie, además se presentan resultados de diversas investigaciones que muestran valores de calidad de este forraje tales como contenido proteico, fibra en detergente neutra (FDN) y fibra en detergente acida (FDA), digestibilidad in vitro de la materia seca y contenido de lignina entre otros. En la revisión se tuvo en cuenta el comportamiento de Brachiaria en ambientes de especial interés como son: suelos, nutrientes y agua.

Brachiaria humidicola, foi trazida para a Colômbia com um propósito de melhorar a produção de forragem emsolos ácidos e pobres onde não se contava com forragens adaptadas a estas condições, nas quais esta espécie pudesse ser uma excelente alternativa. Contudo, trabalhos que juntem aspectos relacionados com as suas característicasfisiológicas e bromatológicas são escassos; por tal motivo foi realizada uma breve revisão botânica e morfofisiológicadesta espécie, ademais são dados resultados de diversas pesquisas que mostram valores de qualidade desta forragem tais como conteúdo proteico, fibra em detergente neutra (FDN) e fibra em detergente acida (FDA), digestibilidade in vitro da matéria seca e conteúdo de lignina entre outros. Na revisão foi tido em conta o comportamento de Brachiariaem ambientes de interesse especial como: solos, nutrientes e água.

Nutritional value of forage species from the Central Highlands Region of Mexico at different stages of maturity / Valor nutricional de espécies forrageiras nativas da Região Central Montanhosa do México em diferentes estádios de maturidade

This paper has two objectives, the first is to determine the chemical composition, gas production parameters and the gas release kinetics, at different stages of maturity, of three grasses and a legume commonly found in long established pastures in Mexico central highland plateau. The second is to combine the gas release kinetics analysis and the GP fitted to a mathematical model in order to improve the biological understanding of the fermentation kinetics obtained from the GP technique. Representative samples of Pennisetum clandestinum (kikuyu grass), Sporobolus indicus (mouse tail), Eleocharis dombeyana (reed), Trifolium amabile (Aztec clover) plus a composite sample were collected in the growing season (July, September and November 2003) and analysed using an in vitro gas production (GP) technique. The accumulated GP was fitted to the model described in PALMER et al. (2005). Significant differences (P<0.001) were observed among species and periods for chemical composition, organic matter and neutral detergent fibre digestibility. Significant differences (P<0.05) were observed regarding fermentation parameters and gas release kinetic, with T. amabile and P. clandestinum being the species with the highest fermentability, whereas S. indicus and E. dombeyana were poorly fermented. P. clandestinum and T. amabile showed higher nutritive value than S. indicus and E. dombeyana. Composite samples were influenced by the chemical and fermentation characteristics of all species. It was concluded that the use of gas release kinetics analysis was useful for differentiating the fermentation kinetic of the soluble and insoluble fraction in the grasses and legume. Therefore by performing both approaches, the gas release kinetics analysis and the GP fitted to a mathematical model, gave a better description of the fermentation kinetic of grasses and the legume was achieved when only one approach had been used.

O uso da análise de cinética de produção de gases, em conjunto com a análise de prova de curva e as propriedades químicas da forragem permitem uma melhor descrição das características nutritivas das forragens. Objetivou-se estudar a composição nutritiva e características de fermentação de ruminal de três gramíneas, uma leguminosa e uma mistura composta de pastagens do Planalto Montanhoso Central do México. As amostras representativas de Pennisetum clandestinum (kikuyu grama), Sporobolus indicus (rabo de rato), Eleocharis dombeyana (cana), Trifolium amabile (trevo asteca) mais uma amostra composta foram coletadas durante os meses de Julho, Setembro e Novembro de 2003. Foi utilizada a técnica de produção de gás in vitro (GP). Os perfis de GP foram ajustados ao modelo descrito por PALMER et al. (2005). As diferenças (P<0.001) foram observadas entre espécies e períodos quanto à composição química, matéria orgânica e digestibilidade da fibra em detergente neutro. As diferenças (P<0.05) dos parâmetros de fermentação e cinética de produção de gases mostraram T. amabile e P. clandestinum com fermentação mais intensa, ao passo que S. indicus e E. dombeyana tiveram fermentação limitada. Concluiu-se que a combinação da análise de cinética de produção de gases e o perfil de GP ajustado ao modelo matemático ajudou a descrever as características nutritivas das gramíneas, da leguminosa e da amostra composta de forma mais acurada do que quando um dos métodos foi utilizado de forma isolada.

Variação espacial do teor de matéria orgânica do solo e produção de gramínea em pastagens de capim-marandu / Spatial variation of the content of soil organic matter and production of pasture grass marandu

O objetivo deste estudo foi quantificar e descrever a variabilidade espacial, visando o mapeamento das características agronômicas da gramínea e do teor de matéria orgânica do solo (MOS) em pastagens de Brachiaria brizantha cv. Marandu cultivadas em Neossolo Quartzarênico Órtico típico com diferentes níveis de degradação. As coletas das plantas e do solo foram realizadas em malha de amostragem regular com distâncias de 5 x 5 m em área de 900 m². A produção de massa seca de folhas verdes (MSFV), colmo (MSC), material morto (MSMM), massa seca total (MST) e o teor de MOS das pastagens foram submetidos às analises de estatística descritiva, à comparação de média pelo teste de Tukey ao nível de 5% de significância, ao estudo geoestatístico e interpolação por krigagem ordinária. A variabilidade espacial da produção de MSFV, MSC, MSMM e MST e a MOS foram observadas dentro e entre as áreas de pastagens de capim-Marandu com nível baixo, médio e alto de degradação. A grade de 5 x 5 m é adequada para quantificar e descrever a variabilidade espacial bem como mapear as características agronômicas de pastagens de capim-Marandu com nível de degradação baixo e alto. O teor de MOS em todos os níveis de degradação da pastagem apresentou variabilidade espacial definida permitindo assim seu mapeamento. Já em área com nível médio de degradação a grade de 5 x 5 m é pouco eficiente para para quantificar, descrever e mapear a variabilidade espacial das variáveis MSC e MST devido aos baixos coeficientes de determinação e altas somas do quadrado dos resíduos além da ausência de dependência espacial para a MSMM.

The aim of this study was to quantify and describe the spatial variability, with a view to mapping of the agronomic properties of the grass and organic matter content of soil in Brachiaria brizantha grass cultivar Marandu grown in Typic Quartzipsamment with different level of degradation. The collections of plants and soil were carried out in regular grid with distances of 5 versus 5 m area of 900 m². The dry mass of green leaves (MSFV), stem (MSC), dry matter (MSMM) and total dry mass (MST) and the content of soil organic matter (MOS) of pasture were analyzed for descriptive statistics, comparison of average by Tukey at 5% significance, geostatistical analyses and interpolation by ordinary kriging. Spatial heterogeneity of production MSFV, MSC, MSMM, MST and MOS were observed within and between areas of Marandu grass with low grade, middle and high degradation. The grid of 5 versus 5 m is adequate to quantify, describe and map of spatial variability of agronomic properties and the content of pasture grass MOS level of degradation with low and high. The MOS content in all levels of degradation of pasture was defined spatial variability thus allowing its mapping. Already in the area with the average level of degradation of the grid 5 x 5 m is ineffective for to quantify, describe and map the spatial variability of variables MSC and MST because of low coefficients of determination and large sums of squared residuals and the absence of spatial dependence for MSMM