Anatomia foliar, acúmulo de liteira e avaliação econômica do desempenho animal em capim-Tanzânia adubado com nitrogênio ou consorciado com estilosantes Campo Grande

• Autor(a) principal: Iwamoto, Bruno Shigueo
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/1493
• topic: Capim-Tanzânia; Fertilizante nitrogenado - Avaliação econômica; Bovinos - Ganho de peso; Desempenho animal - Faturamento; Ciências Agrárias; Zootecnia

The experiment was conducted in the Northwestern region of Paraná, state of Brazil, in Santo Inácio city, in order to evaluate the accumulation of herbage mass, accumulation of dead material forage, nutrient from litter, animal production and leaf anatomy rearing system on Tanzania grass pasture (Panicum maximum Jacq. Cv. Tanzania-1) fertilized with nitrogen or intercropped with Estilosantes Campo Grande (Stylosanthes spp) (ECG) from October 2010 to June 2011. It was performed an economic evaluation of this experiment and the previous periods (2008/9 and 2009/10) which are managed and submitted under the same treatments. It was used an experimental design in blocks with split plots with three replications having as main treatments (plots): Estilosantes + Tanzania, Tanzania + 75 kg N ha-1; Tanzania + 150 kg N ha-1; Tanzania + 225 kg N ha-1, and the subplots the seasons: spring, summer and fall. The experimental area of 12 ha of pasture was divided into three paddocks containing 4 blocks per block (experimental units), for a total of 12 plots of one hectare. The nitrogen and potassium fertilization was split in three applications made to haul every 45 days. It was used as nitrogen source the ammonium nitrate and potassium chloride as potassium source. The phosphorus fertilization was done in a single application, using the superphosphate as a source of phosphorus. For pasture management, it was used the method of continuous stocking with variable stocking and monitored weekly by measuring height by 50 points at random in each experimental unit using bastion graduate (100 cm), having the pasture been maintained between 40-45 cm. The animals used were Nelore steers with an average initial weight of 230 kg BW. Three "testers" animals were used per paddock and regulators, which were placed or removed depending on the height of the pasture. In order to estimate the mass production and morphological composition, samples were collected at ground level, every 28 days. The evaluation of animal production wascarried out by weighing the animals every 28 days. The collections of litters for evaluation of forage losses were taken every 28 days through line transects. To assess the proportion of tissues leaf blades were collected every 28 days. The Tanzania grass intercropped with Estilosantes Campo Grande provided the lowest stocking rate, in which the treatment with 225 kg N allowed the greatest value. The consortium submitted similar accumulation of dead forage to the treatment with 75 kg N, in which the treatments with 150 and 225 kg of N showed the greatest senescence. However, provided higher nutrient concentrations in litter and increased nutrient cycling processes. The seasons affect the senescence forage pasture, where the autumn showed the highest presence of litter with the highest concentrations and contributions of nutrients. The consortium provided similar results to the daily accumulation of dry mass and weight gain when fertilized with 75 kg of N. Doses of 150 and 225 kg N allowed greater animal productivity by providing higher stocking rates and consequently increasing the weight gain. The highest doses evaluated (150 and 225 kg N) reduced the proportion of adaxial and abaxial epidermal tissue with sclerenchyma and mesophyll growth of the leaf blade of Tanzania grass. In vitro digestibility increased with the decrease in acid detergent fiber fractions of leaf sheath and stem in higher N rates (150 and 225 kg). The consortium has brought some benefits, but less significant when compared with the highest N rates evaluated in this experiment. Regardless of the treatments, the seasons of spring followed by summer demonstrated superiority in nutritive value and productivity of pastures during the study period. Net revenues obtained in the average of the three periods were profitable with: R$ 115.85, R$ 106.72, R$ 149.18 and R$ 314.53 ha-1 for Tanzania grass intercropped with ECG or fertilized with 75, 150 kg and 225 N, respectively. However, in the second and third period evaluated, the economic indices were similar for all treatments evaluated, in which the Tanzania grass in consortium with ECG proved to be an interesting alter native to the producer due to less need for disbursement. In this case, the IRR month was 2.8%, 2.6%, 2.6% and 3.0% for Tanzania grass intercropped with ECG or fertilized with 75 kg of 150 and 225 N, respectively. All being considered attractive for investment. The use of the consortium of grasses and legumes has the potential to improve livestock productivity and can bring many ecological and economic benefits that need to be increasingly well studied.