Productive traits and nutritional value of Urochloa ruziziensis submitted to different planting densities and defoliation intensities

ABSTRACT The aim of this study was to evaluate the forage mass and accumulation and nutritional value of cultivars Kennedy and BRS Integra (Urochloa ruziziensis), subjected to two planting densities (15 and 30 plants/m2) and three stubble height (15, 30 and 40 cm). The experimental design was a randomized block, in a 2x2x3 factorial, with three replications. The experimental period comprised two agrostological years. Plants managed under lower stubble height (15cm), showed lower leaf:stem ratio and higher canopy heights at harvest, based on the light interception of 95%. The highest forage mass was observed to cultivar BRS Integra under lower planting density (15 plants/m2). The two cultivars showed high nutritive value, without influence of studied factors. In general, the cultivars were similar for most variables studied. Planting with 15 plants/m2 and moderate defoliation (30cm residue) resulted in higher forage accumulation, especially in the second year after planting. These targets are suggested for the management of U. ruziziensis cultivars

The growth dynamics in Brachiaria species according to nitrogen dose and shade

It was studied the effects of shading (0, 36 and 54%) and of four nitrogen doses (0, 50, 100 and 150 mg N/dm³ of soil) on the morphogenetic traits and on the tillering of grasses of Brachiaria genus (B. decumbens, B. ruziziensis and B. brizantha cv. Marandu and cv. Xaraes), cultivated in pots with 5 kg substrate. It was used a complete random design, in a 3 × 4 × 4 factorial scheme with three replications. Nitrogen promoted increase in leaf appearance rate and in average leaf blade length, whereas shading increased stem elongation rate. Leaf elongation rate and tillering varied with the interaction among shading percentages and nitrogen doses. Shading increased response efficiency of leaf elongation rate to nitrogen doses, but reduced for tillering, evidencing priority existing tillering growth in detriment to appearance of new tillers when there is light restriction for the plants. Phenotypic adjustments, in response to light reduction, indicate that the studied grasses present tolerance to moderate shading.Estudaram-se os efeitos do sombreamento (0, 36 e 54%) e de doses de nitrogênio (0, 50, 100 e 150 mg/dm³ de solo) nas características morfogênicas e no perfilhamento de gramíneas do gênero Brachiaria (B. decumbens, B. ruziziensis e B. brizantha cvs. Marandu e Xaraes) cultivadas em vasos com capacidade para 5 kg de substrato. Adotou-se o delineamento inteiramente casualizado, em esquema fatorial 3 × 4 × 4 com três repetições. O nitrogênio promoveu aumento na taxa de aparecimento de folhas e no comprimento médio das lâminas foliares, enquanto o sombreamento aumentou a taxa de alongamento do colmo. A taxa de alongamento de folhas e o perfilhamento variaram com a interação entre as percentagens de sombra e as doses de nitrogênio. O sombreamento aumentou a eficiência de resposta da taxa de alongamento de folhas às doses de nitrogênio, mas reduziu para o perfilhamento, evidenciando prioridade no crescimento de perfilhos existentes em detrimento do surgimento de novos perfilhos quando há restrição de luminosidade para as plantas. Os ajustes fenotípicos, em resposta à diminuição de luz, indicam que as forrageiras estudadas apresentam tolerância ao sombreamento moderado

Canopy characteristics and behavior of Nellore heifers in Brachiaria brizantha pastures under different grazing heights at a continuous stocking rate

The objective of this study was to evaluate the Brachiaria brizantha cv. Marandu canopy structure maintained at different grazing heights under a continuous stocking rate and with a dietary supplementation strategy for the animals during the rainy season. This study also intended to observe the relationships of these variables with the grazing behaviors of the heifers. The effects of three canopy heights (15, 25 and 35 cm) were evaluated in association with three types of supplements: one mineral and two protein/energy supplements, the first with a high rumen degradable protein and energy and the others with a low ratio. Both the protein/energy supplements were provided at 0.3% of body weight/day. The experimental design was completely randomized, with two replications and repeated measures, and took place during the period from January to April 2008. The supplementation strategies did not affect any variable related to the canopy structure. Total and green herbage masses and the ratio of green/dead material increased with canopy height. The leaf/stem ratio was higher in the lowest canopy height: 15 cm. Changes in the canopy structure caused variations in the grazing behavior of the animals. Animals maintained in the 15-cm-tall pasture grazed for a longer time, increasing the time for each meal, but the number of meals was lower than that of the animals grazing within the 35-cm-tall pasture. The grazing time of animals receiving the energy/protein supplement was lower only in the period of the day during which it was supplied. Canopy structure is affected by sward height, and changes animal behavior. Supplementation does not affect the canopy structure of the pastures with similar heights