\u3cem\u3eIn Situ\u3c/em\u3e Digestibility of \u3cem\u3eGliricidia sepium\u3c/em\u3e Combined with \u3cem\u3eBrachiaria decumbens\u3c/em\u3e in a Silvopastoral System

Silvopastoral system (SPS) are characterized by a combination of trees, pasture and herbivores animals, in the same physical area, in order to obtain diversified products. A promising legume tree that has been studied and used in SPS in tropical areas is gliricidia [Gliricidia sepium (Jacq.) Steud]. Advantages of gliricidia use in SPS include N inputs via biological fixation, improvement of soil properties, nutrient cycling and also a source of feed to grazing animals (Cubillos-Hinojosa et al., 2011). Gliricidia has high crude protein concentration in its leaves, which complements the usual N-poor diet of ruminants grazing warm-season grasses. The introduction of gliricidia in SPS faces a problem due to the low initial acceptability by cattle, being necessary an adaptation period in order to cattle reach satisfactory intake levels (Carvalho Filho et al., 1997). In general, the quality of the forages can be predicted by accessing their nutritive value, represented by the chemical composition and digestibility of the forage constituents (Van Soest, 1994). The digestibility of dry matter in forages consumed in a SPS can be influenced by the forage species used, by grass/legume combinations, and by the proportion that each forage species takes in the diet of the ruminants. This study evaluated in situ digestibility of gliricidia in increasing levels of inclusion in the diet composed by sabi grass (Brachiaria decumbens, Stapf) in a silvopastoral system

Relationship between Field Measurements in Three \u3cem\u3eBrachiaria\u3c/em\u3e Species with Leaf Area Index and Light Interception by Indirect Methods

Brachiaria species play a strategic role in ruminant production systems in Brazil, covering an estimated pasture area of approximately 90 million hectares (Karia et al., 2006), however, these pastures are subject to different degrees of degradation due to inadequate management. In pasture management, field measurements such as canopy height, for example, are used by managers as a tool to establish parameters for the optimal point to cut the forage and for the post-grazing residue, in order to maximize production by harvesting at maximum of herbage mass accumulation, and to avoid problems associated to overgrazing, by setting ideal post-grazing height for forage regrowth. The use of the variables light interception (LI) and leaf area index (LAI) has been recommended as a tool for pasture management, based on the theory that, when the canopy reaches a light interception of 95%, the forage is near its maximum growth rate, which is called critical LAI (Brougham, 1956). The residual LAI refers to the leaf area of the post-grazed stubble. Residual LAI is used to establish the minimum leaf area necessary to ensure an efficient pasture regrowth (Lemos et al., 2014). Light interception and the LAI are difficult to measure at the farm level, due to the high cost of the equipment and technical feasibility of the process. The objective of this study was to evaluate the relationship between LI and LAI measured by two different equipment, with canopy height and soil cover in three species of Brachiaria

Canopy Height and Its Relationship with Leaf Area Index and Light Interception of Tropical Grasses

Photosynthetic tissues, mainly green leaves, are the major component of forage growth and development. The amount of these tissues in a forage plant is influenced directly by the cutting management, which is based on cutting frequency and stubble height. It is usual to recommend as a management practice to cut (or graze) the forage whenever it reaches a given stubble height. Brougham (1956) stated that, when the forage canopy is intercepting 95% of the photosynthetic active radiation, this is the critical leaf area index (LAI), which means the forage is near its maximum growth rate without shading itself. There is also the optimum LAI, where the forage reaches the maximum point of mass accumulation, indicating time to start grazing or cut. Generally the critical and optimum LAI have close values, but they are not necessarily the same (Brown and Blaser, 1968). This trial evaluated the relationship among canopy height, leaf area index, and light interception in ten different tropical grasses

Valor nutritivo de gramíneas forrageiras exóticas sob incidência de espécies espontâneas no agreste de Pernambuco

Na produção pecuária das áreas semiáridas do Nordeste predomina a utilização da vegetação nativa como base da alimentação dos animais, porém, em geral, as pastagens dessa região apresentam baixa capacidade de suporte. Com a necessidade de intensificação dos sistemas de produção animal sob pastejo, há uma demanda natural pela substituição de determinadas forrageiras nativas de baixo potencial forrageiro, por espécies com maior potencial produtivo e superior qualidade nutricional. Neste sentido, o plantio de espécies forrageiras exóticas têm sido estimulado na região semiárida do Nordeste. Este estudo avaliou o valor nutritivo do pasto e a composição botânica em pastagens de quatro gramíneas forrageiras exóticas promissoras para região semiárida do Agreste de Pernambuco: capim-corrente (Urochloa mosambicensis Hackel Dandy), capim-buffel (Cenchrus ciliaris L.); capim-pangolão (Digitaria pentzii Stent) e Panicum maximum Jacq. (genótipo espontâneo na região). Os tratamentos foram avaliados em ciclos de pastejo e em períodos de diferimento. No estudo sobre a diversidade botânica nas pastagens, estas foram avaliadas quanto à flutuação da massa de forragem e massa de espécies espontâneas, além da composição botânica das espécies espontâneas, ao longo de uma estação de pastejo. De maneira geral, as gramíneas apresentaram tendência a declinar a massa forragem ao longo dos ciclos de pastejo, e as espécies espontâneas tenderam a aumentar sua massa nas pastagens de capim-buffel. O capim-corrente aparentou ter uma habilidade de suprimir espécies espontâneas mesmo em condições que apresentava reduzida massa de forragem. As pastagens de gramíneas exóticas na região do Agreste aparentam ser bastante afetadas por espécies de porte arbustivo, principalmente as pertencentes à família Malvaceae. A espécie Sidastrum paniculatum (L.) Fryxell demonstrou ser uma invasora potencial para as pastagens da região. Em amostras do pasto obtidas por meio de pastejo simulado foram analisados os teores de matéria seca (MS), proteína bruta (PB), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), lignina e Digestibilidade in vitro da MS (DIVMS). Os teores de FDN, FDA e lignina tenderam a variar substancialmente entre as espécies, quando estas estiveram submetidas ao pastejo. O capim-buffel apresentou, tanto durante o pastejo como no diferimento, baixos coeficientes de DIVMS (44,79 e 50,17%, respectivamente) e maiores percentuais de FDN (68,55%) e lignina (3,74%) durante o pastejo, sendo a espécie com valor nutritivo mais baixo entre as avaliadas. O capim-pangolão destacou-se qualitativamente pelos baixos teores de FDN (54,3%) e pela alta DIVMS (64,2%) durante o pastejo. Entre as gramíneas forrageiras avaliadas, os capins pangolão e P.maximum demonstraram potencial em termos de valor nutritivo para serem utilizados nos sistemas de produção animal sob pastejo na região do Agreste de Pernambuco.In the livestock production of semiarid areas from Northeast-Brazil predominates the use of native vegetation of the region as the base of animal nutrition, in general the native pastures of this region have low carrying capacity. With the intensification of animal production systems, there is a natural demand for replacement of native forages with low potential for species with higher yield and superior nutritional quality. Cultivation of exotic grass species have been stimulated in the semiarid region of the Northeast. This study evaluated botanic composition of the pasture and the nutritive value of four promising exotic grasses to semiarid region of Agreste of Pernambuco: sabi grass (Urochloa mosambicensis Hackel Dandy), buffel grass (Cenchrus ciliaris L.); pangola grass (Digitaria pentzii Stent) and Panicum maximum Jacq. (spontaneous genotype in the region). The treatments were evaluated in grazing cycles. In the study of the botanical diversity, the pastures were assessed for their susceptibility to occurrence of weed species by mass comparison, and by the fluctuation of their botanical composition during a grazing season. In general, the grasses decline their forage mass over the grazing cycles, weed species tended to increase their mass in buffel grass pasture. The sabi grass appears to have an ability to suppress weeds even when this grass had low forage mass. The pastures of exotic grasses in the Agreste region were strongly affected by shrub weeds, especially those belonging to the Malvaceae family. The specie Sidastrum paniculatum (L.) Fryxell proved to be a potential weed to the pastures of this region. In pasture samples obtained by simulated grazing were analyzed: dry matter (DM), crude protein (CP); neutral detergent fiber (NDF), acid detergent fiber (ADF); lignin and in vitro digestibility of DM (IVDMD). Among the chemical characteristics analyzed NDF, ADF and lignin tended to vary substantially among species when they were under grazing. Buffel grass presented during the grazing and deferment, low coefficients of IVDMD (44.79 and 50.17%, respectively) and higher NDF percentage (68.55%) and lignin (3.74%) during the grazing period, was the specie with lowest nutritional value among evaluated species. Pangola grass stood out qualitatively by low NDF (54.3%) and high IVDMD (64.2%) during the grazing period. Among the grasses evaluated, pangola grass and P.maximum demonstrated potential in a nutritional perspective, for being used in animal production systems in the Agreste region of Pernambuco.Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNP

Prediction of the nutritional value of grass species in the semiarid region by repeatability analysis

<div><p>Abstract: The objective of this work was to estimate the repeatability (r) and the number of samples required to measure the nutritional value of four warm-season forage grasses growing in a semiarid region. The grasses evaluated were Urochloa mosambicensis, Cenchrus ciliaris, Digitaria pentzii, and Megathyrsus maximus. Evaluations occurred under two forage management conditions: stockpiling and grazing. Hand-plucked forage samples were analyzed for dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, and in vitro DM digestibility (IVDMD). Four methods were used to estimate r and the number of samples required: analysis of variance, method of principal components based on the covariance (PCCOV) and the correlation (PCCOR) matrices, and structural analysis (EVCOR). Species were compared by the probability of the difference using the t-test. The method PCCOV presents the highest coefficient of repeatability and, therefore, a lower number of samples required. Lignin is the trait that have the highest number of samples required. In terms of qualitative traits, D. pentzii and M. maximus show the best forage qualities among the species evaluated.</p></div

Nitrogen, phosphorus, and potassium cycling in pasture ecosystems

Inadequate management practices are the main factors that can cause pasture degradation, and one of the key factors is to understand the nutrient cycling in pasture ecosystems. This review aimed to describe the cycling processes of important nutrients in pasture ecosystems (nitrogen, phosphorus, and potassium), analyzing the interactions of soil-plant-animal components. The use of forage legume species intercropped with grasses is a strategy to increase the nitrogen content in the soil, minimizing costs with nitrogen fertilization in pastures. Manure and plant residues are great organic sources of phosphorus and potassium but are also fundamental for supplying microminerals. Nitrogen losses in pastures are mainly caused by leaching, runoff, and volatilization. The addition of phosphorus to the soil must be performed carefully, as there is an increase in phosphorus losses with increasing accumulation in the soil. Phosphorus is often returned to the soil far from where it was used, so the stock transfer represents a loss in pasture ecosystems that can account for approximately 5% of the inputs of phosphate fertilizers. Potassium losses mostly occur by leaching and runoff. Improving management practices is essential for balanced nutrient cycling in pasture ecosystems