Production Potential of South America Grasslands

Grasslands exist all over the world under a wide range of climates, soil types, topography conditions and seasonality. The South America grasslands cover a wide range of ecosystems and vegetaion types, going from desert areas to steppes, subhumid temperate, subtropical and tropical savannas embodying also portions of the tropical rain forest environment, and represent one of the Earth’s largest expanses of natural rangelands (Oesterheld et al., 1992). They represent developed ecosystems requiring acquaintance to accept sound agronomic and ecological activities. The diversity of vegetation determined by the latitudes 6oN, down to the southern most tip of the continent at 55o 58’ S originated a spectrum of users and uses without knowledge of its potential, imposing pressures upon the natural resources, seeking more profit, and jeopardizing its sustainability, since it encompasses a wide range of contrasting situations and conflicts in resource use (Deregibus, 2000)

Dynamic of Native Pasture Influenced by Deferment of Grazing and Fertilization

Native pastures of southern Brazil cover 12 million ha and are the main forage feed resource for most domestic livestock. However, their heavy and continuous use has reduced standing biomass and the presence of good forage species, reducing animal performance and jeopardizing the ecosystem sustainability. An alternative for better use of these pastures and their preservation is grazing deferment that allow natural reseeding. The objective of this research was evaluate native pasture dynamic after six years of grazing deferments (GD) periods and soil fertilization effects by point-quadrat method every season. All pasture components were affected by GD, with prostrate grasses increasing their frequency (P \u3c 0.05) under continuous grazing while periods of rest encouraged erect plants. Fertilization improved pasture condition by reducing frequencies of no forage species, litter and bare soil, and increasing frequencies and dry matter contribution of good ones like native legumes, especially Desmodium incanum

Composição botânica de uma pastagem nativa melhorada submetida a diferentes sistemas de pastejo.

Este estudo teve por objetivo comparar a estrutura botânica de um campo nativo melhorado submetido à diferentes sistemas de pastejo, buscando assim obter subsídios para a proposição de alternativas de manejo que impliquem em uma exploração pecuária mais racional e rentável

Estrutura do dossel em pastagens de capim-marandu submetidas a quatro ofertas de lâminas foliares.

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Herbage Allowance and Nitrogen Fertilization Effects on Morphological Characteristics of \u3ci\u3ePaspalum notatum\u3c/i\u3e Flügge

The grazing study was conducted at the Estação Experimental Agronomica – UFRGS, 30o S, on a native pasture, to evaluate the leaf area index and structural morphological traits of bahiagrass (Paspalum notatum Fl.), within the requirements of a Central Composite Rotatable experimental design, providing for equal precision, with two blocks, encompassing two factors at five levels each, namely: Herbage Allowance (HA) = 4.0; 5.5; 9.0; 12.5 and 14.0 kg green dry matter per 100 kg liveweight per day (% LW), in association with Nitrogen (N) fertilization levels of 0; 30; 100; 170 and 200 kg ha-1 as urea, The leaf length and leaf area index (LAI) were increased as HA and N levels increased. The tiller density was increased at higher HA where the N contribution showed to be more effective. More lenient grazing also increased leaf life span and leaf lamina length, while N promoted canopy density and reduced leaf life span and number of leaves per tiller. The higher LAI values developed were accomplished by reduced tiller densities that supported small number of leaves per tiller, with increased leaf sizes

Sheep Performance in Italian Ryegrass Swards at Contrasting Sward Heights

The objective of this study was to assess the effect of Italian ryegrass (Lolium multiflorum Lam.) sward height on lamb performance. The experiment was carried out at the Research Station of UFRGS, Eldorado do Sul, Brazil. Yearling no-castrated male lambs were assessed in terms of individual animal performance and gain per hectare. The experiment was carried out in a randomised block design with three replications of four treatments: 5, 10, 15 and 20 cm of sward surface height (SSH), which were maintained using continuous variable stocking, and monitored by a sward stick. Samples of 0.25 m2 were cut to ground level to estimate herbage and leaf lamina mass. Live weight gain per area and per animal increased in a quadratic pattern. The best animal production was found in a sward of approximately 15 cm high

Brazilian Native Species as Potential New Sources of Natural Antioxidant and Antimicrobial Agents

The antioxidant and antimicrobial activities of extracts of 12 plant species growing in Brazil were determined. Antimicrobial activity against 12 food-related bacterial species was studied using the disc-diffusion, MIC, and MBC methods. Campomanesia eugenioides extract was the most active against the tested Gram-positive bacteria, whereas Parapiptadenia rigida bark extract presented the highest activity against the evaluated Gram-negative bacteria (MIC and MBC of 0.075 and 0.62 mg ml−1, respectively, against Pseudomonas aeruginosa). Those two extracts also presented high phenolic content and high DPPH and ABTS radical scavenging ability. C. eugenioides extract presented high Fe2+ chelating capacity. The results of the present study demonstrate that, among the evaluated extracts, P. rigida bark and C. eugenioides, both Brazilian native species, presented the highest potential of application as natural antimicrobial and antioxidant agents

Microspore embryogenesis: assignment of genes to embryo formation and green vs. albino plant production

Plant microspores can be reprogrammed from their normal pollen development to an embryogenic route in a process termed microspore embryogenesis or androgenesis. Stress treatment has a critical role in this process, inducing the dedifferentiation of microspores and conditioning the following androgenic response. In this study, we have used three barley doubled haploid lines with similar genetic background but different androgenic response. The Barley1 GeneChip was used for transcriptome comparison of these lines after mannitol stress treatment, allowing the identification of 213 differentially expressed genes. Most of these genes belong to the functional categories “cell rescue, defense, and virulence”; “metabolism”; “transcription”; and “transport”. These genes were grouped into clusters according to their expression profiles among lines. A principal component analysis allowed us to associate specific gene expression clusters to phenotypic variables. Genes associated with the ability of microspores to divide and form embryos were mainly involved in changes in the structure and function of membranes, efficient use of available energy sources, and cell fate. Genes related to stress response, transcription and translation regulation, and degradation of pollen-specific proteins were associated with green plant production, while expression of genes related to plastid development was associated with albino plant regeneration