Although belonging to the same species, different Brachiaria brizantha varieties used for pasture vary significantly in their morphological structure. Therefore, this study starts from the central hypothesis that the defoliation dynamics during the period of occupation by animals in pastures formed by Brachiaria brizantha under rotational stocking varies among cultivars during the year. The experimental design used was randomized blocks with three treatments and three repetitions, with the cultivars consisting of Brachiaria brizantha cv. Xaraés, BRS Paiaguás, and Ecótipo B4. The defoliation patterns during the grazing periods were estimated using the marked tiller technique. Despite alterations in the tiller and forage mass components in the wet and dry seasons, no variations were observed in the tiller defoliation dynamics and the respective structural components. In the wet season, the area grazed only once was greater for BRS Paiaguás compared to the other two cultivars, but the other areas representing the grazing horizons were equally exploited among the grass varieties during the year. Therefore, based on the defoliation dynamics of pastures in Brazil’s tropical climate, it is possible to suggest that pastures formed by grasses with different structures and growth habits can be submitted to similar management strategies without impairing the forage canopy exploitation by the animals.
The present work aims to evaluate the morphological and structural characteristics of Brachiaria brizantha cultivars in the system of grazing in the intermittent stocking. The experiment was conducted at EMBRAPA -Beef Cattle. The experimental delineation used was a randomized block with three treatments and three repetitions. The treatments were constituted by grasses of the same species (Brachiaria brizantha) composed by cv. Xaraé s, BRS Paiaguá s, and the ecotype B4. On the heights of post-grazing, it was observed an interaction between seasons of the year and cultivars. It was observed that the leaf appearance rate (LAR) was higher in the cv. BRS Paiaguá s, in relation to the other pastures. The leaf elongation rate (LER) was higher in perforations of the ecotype B4. In the winter, it was registered the lowest values of leaf area index (LAI), LAR, and LER, and, as a consequence, impact in a higher leaf life duration. Although there were some structural variations between tropical climate pastures, it was possible to verify that the phenotypic plasticity of these pastures presented the same behavior, once it suffered a higher influence of abiotic factors. Therefore, all the pastures of B. brizantha converged to the same LAI indicating high phenotypic plasticity.
A hipótese testada foi que pastos de clima tropical da mesma espécie, porém com hábitos de crescimento distintos, apresentariam oscilações na plasticidade fenotípica ao longo do ano. Assim, o presente trabalho visa avaliar as características morfológicas e estruturais de cultivares de Brachiaria brizantha em sistema de pastejo em lotação intermitente. O experimento foi conduzido Empresa Brasileira de Pesquisa Agropecuária -Centro Nacional de Pesquisa em Gado de Corte. O delineamento experimental utilizado foi de blocos casualizados com três tratamentos e três repetições, totalizando nove unidades experimentais (piquetes). Cada piquete foi constituído de uma área de 1,5 hectares igualmente subdividida em seis subunidades (réplicas) em método de pastejo lotação intermitente. Os tratamentos foram constituídos por gramíneas da mesma espécie (Brachiaria brizantha) compostas pela Brachiaria brizantha cv. Xaraés, BRS Paiaguás e o ecótipo B4. Utilizou-se os dados de morfogênese e estrutura para estimar as primeira e segunda variáveis canônicas, bem como os coeficientes canônicos padronizados. Os coeficientes canônicos padronizados da primeira variável canônica mostraram que filocrono e duração de vida de folha são as variáveis que mais interferem sobre a primeira variável canônica. A primeira variável canônica explica 95% da variação no fluxo de tecidos, além disso, é possível observar uma distribuição diferenciada no fluxo de tecidos entre os pastos estudados. Diante disso, em manejos baseados em lotação intermitente recomenda-se que para a diversificação de espécies em ambientes pastoris, a cultivar Xaraés seja utilizada como principal recurso forrageiro no período das águas e a BRS Paiaguás seja utilizada de forma estratégica no período seco. A plasticidade fenotípica dos pastos B. brizantha pode ser elucidados pela duração de vida de folha e filocrono. Palavras -chave: morfogênese; pastejo; plasticidade fenotípica. Multivariate approach of tissue flow in pastures of Brachiaria brizantha
The hypothesis tested was that pastures of the genus Brachiaria, but with variations in forage canopy architecture (canopy height, leaf area index and tiller population density), would not present oscillations in the variables related to primary production and to nutritive value, under similar soil and climate conditions, and under the same management system. Thus, the present work intends to evaluate the different cultivars of Brachiaria brizantha, observing the dissimilarity of the variables related to forage biomass and nutritive value. The experiment was conducted by Embrapa beef cattle. The design was completely randomized blocks with three replicates. The treatments were three ecotypes of Brachiaria brizantha, B4, BRS Paiaguás and Xaraés. The grazing method used was the intermittent variable stocking rate. The data of forage canopy height (FCH), tiller population density (TPD) and leaf area index (LAI) were submitted to analysis of variance. Estimates of the first and second canonical variables, as well as standardized canonical coefficients were performed. It was noticed oscillations at the FCH between the grasses, in which, pastures of ecotype B4 present the highest height in relation to the other B. brizantha. BRS Paiaguás presents the highest TPD. The standard canonical coefficients of the first canonical variable showed that neutral detergent fiber (NDF) and lignin are the variables that most affect the first canonical variable, positively and negatively. This indicates that these are the variables that most interfere in the differentiation of characteristics related to the nutritive value of B. brizantha grasses. The first canonical variable explains 80.5% of the B. brizantha pasture variation, in addition, it is possible to observe a differentiated distribution among the pastures studied. The B. brizantha pastures present variations in forage canopy architecture, which end up impacted by the canopy lignin concentration.
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