-Morphogenetic and structural characteristics of the native grasses of the Pampa Biome Andropogon lateralis, Aristida laevis, Axonopus affinis, Erianthus angustifolius, Paspalum notatum, Paspalum plicatulum, Piptochaetium montevidense and Sorghastrum pellitum were evaluated as to the effect of nitrogen (N) fertilization (zero and 100 kg N/ha). The experimental design was of randomized blocks with three replicates in a 8 × 2 (native grasses × N) factorial arrangement. Accumulated thermal sums of 350 and 700 degree days determined the interval between cuts for prostrate and caespitose growth habit species, respectively. Species considered of resource conservation (A. laevis, E. angustifolius, P. plicatulum and S. pellitum) had the highest leaf elongation rate when they received N. For leaf appearance rate, phyllochron, leaf senescence rate, leaf lifespan, number of green leaves and final length of leaf blades, there was difference between the evaluated species.
-The experiment was carried out to evaluate forage intake, performance and ingestive behavior of beef heifers. Productive, structural and chemical characteristics of the pasture were also evaluated. The experimental design was completely randomized in a 3 × 2 factorial arrangement, with three pasture systems (Alexandergrass [Urochloa plantaginea Link.] with and without supplement to heifers and Coastcross [Cynodon dactylon (L.) Pers.]) and two phenological stages: vegetative and flowering. The grazing method was put-and-take stocking. Grazing, ruminating and idle activities, feeding stations, displacement patterns, bite mass and bite rate were evaluated. The forage intake was estimated using chromic oxide as an indicator of fecal output. The heifers modified the use of feeding stations and displacement patterns between phenological stages and pasture systems. Heifers consumed more forage in the vegetative stage (2.81% of body weight in dry matter) than in the flowering stage (1.92% of body weight in dry matter). Average daily gain, body condition and stocking rate were similar for heifers in the evaluated systems. Beef heifers receiving protein supplement on Alexandergrass pasture consumed more forage than heifers fed Coastcross exclusively. Regardless of the species, no difference was observed when the heifers were exclusively on pasture. Pasture systems on Alexandergrass or Coastcross provide suitable nutrient intake for heifers to be mated at 18 months of age.
Foi avaliado o efeito de diferentes frequências de suplementação sobre o uso da pastagem (fluxo de tecido foliar, intensidade e frequência de desfolhação) em papuã (Urochloa plantaginea (Link) Hitch). As bezerras de corte permaneceram exclusivamente em pastejo ou receberam grão inteiro de aveia durante sete ou cinco dias por semana (de segunda à sexta feira). A quantidade semanal de suplemento foi similar nas duas frequências. O delineamento experimental foi inteiramente casualizado, com medidas repetidas no tempo, três tratamentos e duas repetições de área. Os fluxos de tecidos, a frequência e intensidade de desfolhação são similares quando as bezerras permanecem exclusivamente em pastejo ou recebem grão de aveia em diferentes frequências.
ABSTRACT:The determination of biomass flows can assist on improving pasture fertilization techniques, contributing to identify the best management methods and, in relation the use of fertilizers. Nitrogen deficiency in pastures can reduce forage production. On the other hand, there is an environmental concern on nitrogen (N) losses when this nutrient is used in excess and this concern guides the search for new grazing systems that optimize its use. Leaf biomass flow, intensity and frequency of defoliation were evaluated in Alexandergrass (Urochloa plantaginea (Link) Hitch) fertilized with Zero, 100, 200 or 300 kg/ha nitrogen (N) as urea. The grazing method was put and take stocking in order to keep the forage mass at 3,000 kg/ha DM. The experimental animals were Angus heifers with an initial age of 15 months and body weight of 241.5±5 kg. The experimental design was completely randomized following a repeated measure arrangement, with four treatments and variable number of experimental units. The highest growth of leaf blades was achieved with 100 kg/ha N. Senescence and intake flows and defoliation intensity were similar among the N levels used. The frequency of return to the same tiller (days) was influenced by N levels and evaluation periods. Our findings recommend the use of 100 kg/ha N in Alexandergrass pasture.
ABSTRACT. Morphogenetic, structural variables and leaf biomass flows of Italian ryegrass (Lolium multiflorum Lam.) were evaluated under two stocking rates: 'Low' and 'High'. These rates were determined by heifers exclusively on pasture or on pasture and supplemented with corn grain. The experimental design was completely randomized following a repeated measure arrangement, two stocking rates, two and four replications of area for the stocking rates 'low' and 'high', respectively. The morphogenetic variables, the number of green leaves and tiller density were similar in both stocking rates. Leaf senescence rate was higher with low stocking rate. Heifers grazed with similar intensity and frequency in both stocking rates. The increase by 33.6% in the stocking rate caused by the use of supplement does not change the leaf biomass flow of Italian ryegrass, but alters its potential efficiency of use near the reproductive stage of the plant.
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