Características morfogênicas e estruturais dos pastos e desempenho de novilhos em capim-braquiária sob diferentes alturas

• Ano de defesa: 2009
• Autor(a) principal: Faria, Dawson José Guimarães
• Orientador(a): Fonseca, Dilermando Miranda da
• Banca de defesa: Veloso, Cristina Mattos , Gomide, Carlos Augusto de Miranda
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Zootecnia
• Departamento: Genética e Melhoramento de Animais Domésticos; Nutrição e Alimentação Animal; Pastagens e Forragicul
• País: BR
• Palavras-chave em Português: Ecofisiologia; Lotação contínua; Morfogênese
• Palavras-chave em Inglês: Ecophysiology; Continuous stocking; Morphogenesis
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PASTAGEM E FORRAGICULTURA
• Link de acesso: http://locus.ufv.br/handle/123456789/1741

The experiment was conducted in the Forage Crops Sector of Federal University of Viçosa-MG, in a sward of Brachiaria decumbens Stapf. Growing Basilisk, evaluating the production of Forage Crops, morphogenic and structural characteristics of the sward, animal performance and pattern of defoliation by steers on signal grass in four sward heights, aiming to find the best height management of this species, under continuous stocking. The experiments consisted of sward heights (10, 20, 30 or 40 cm) in a completely randomized design with two replications. The experimental period was from January 09th, 2006 to June 30th, 2007, totaling 537 days of evaluation. The sward system adopted was continuous stocking with variable stocking rate, keeping two animals per paddock during the test period with addition and removal of animals to maintain balance on sward heights. Crossbred steers were used, with 236.9 kg and Nellore x Red Angus crossed with 193.9 kg of average initial body weight in 2006 and 2007, respectively. For the morphogenic and structural characteristics of the sward, defoliation pattern, morphological composition, availability of dry grass, dry and green grass, stem, leaf blade and dead material the experimental period was divided into the following seasons of the year: summer (January to March) and autumn (April to June) in the years of 2006 and 2007, winter (July to September) and spring (October to December) of 2006 only. The animal performance was evaluated in two seasons, Water 1 (January to May, 2006) and Waters 2 (October, 2006 to April, 2007). The sward height influenced the rate of stem stretching in intact linear and positive stage. The greatest heights showed higher stem stretching being under grazing, with smaller values compared to the intact stem. The stretching of the intact blades increased linearly with the height of the sward. However the grazing blades had cubic response during summer 1 and positive linear during spring and summer 2, depending on the height of grasses. There was a higher rate of intact blade stretching compared to the grazing blades. The rate of leaf emergence responded linear and negatively to the heights of the grasses, while the phytochrome and the duration of life of the leaf showed linear and positive response. The height of grasses influenced the total number of alive leaves, with linear decreasing response in the summer of 2006, linear increasing during winter and cubic in the fall of 2007. For the number of alive grazing leaves was observed negative linear response in both summers and cubic effect in the spring, depending on the height of grasses. The number of intact leaves had a quadratic response in the autumn 1 and cubic during spring and summer 2 depending on the heights sward. The blade final length increased linearly with the height of grasses. The rate of senescence of the intact and grazing blades increased with the height of grasses, with lower values for the last ones. For the relationship between blade and stem, the effect was negative linear depending on the height of sward for all seasons of the year, except in the winter and summer 2, seasons in which it was observed a quadratic effect. It was observed that the heights of grasses imposed linear negative effect compared to the number of basal tillers during summers, autumn 1, winter and spring. For the number of aero tillers, the effect was linear negative in summer 1; linear positive in autumn 1, without effect in the winter and autumn 2, quadratic in the spring and cubic during summer 2 depending on the sward heights. The total number of alive tillers was changed depending on the height of grasses, displaying quadratic effect during autumn 1 and spring, lack of effect during winter and autumn 2 and linear during summers. During autumn 1, the point of maximum was estimated at 20.77 cm with 1451.6581 tillers and during spring 19.49021 at 1515.0331 cm tillers. The total dry grass availability, dry and green materials and dry stems increased linearly with the height of grasses. The availability of dry leaves blade showed different responses depending on the height of grasses in the seasons, increasing linearly in the spring, summer 2 and autumn 2 with quadratic response in summer 1 and autumn 1 and cubic during winter. There was increased availability of dry and dead material with the heights of the grasses at all times evaluated, except in summer 2. There was, for the forage density, a linear and decreasing effect on the height of grasses. The increase in the sward heights promoted increasing and linear effect upon the percentage of stems during summers and autumns and cubic during spring. For the leaf blade percentage the effect was linear positive during summers and autumns and cubic during winter according to the increase of the height of grasses. There was a linear effect upon the percentage of dead material, decreasing for the summers and increasing during winter depending on the height of grasses. Regarding the intensity of defoliation of expanded blades, there was positive linear effect of the height of grasses in the autumn 1 and Summer 2 only. For the intensity of blade defoliation spreading, there was positive linear effect depending on the height of grasses during summers, autumn 1 and spring. There is greater intensity of spreading blade defoliation than expanded blades at all times of the swards. For the range expanded blade defoliation there was linear increase from lower to higher sward height. It was observed just the grass height s effect upon the range of defoliation of expanding blades during summer 2. It was found that the growing leaves are grazing more frequently than the expanded ones. The average daily gain of the animals did not differ between the heights of grasses, with the average value of 784 and 606 g.animal.day-1, in the first and second period of waters respectively. The consumption of forage was influenced by grass height, in a cubic way for water 1 and linear for water 2. There was cubic response of stocking rate compared to the sward heights during the two periods of evaluation. The productivity per area was influenced by the height of grasses, in a quadratic way, in the first and second season of water. The morphogenic and structural characteristics, morphological composition of the sward, availability of dry material of blade leaves, of stem and dead material, density of forage are influenced by sward height. The defoliation caused lower values of stretching of stems and grazing blades. The height of grasses influenced the stocking rate, consumption of forage and productivity per area, but not the weight gain of steers. The heights of grasses guide management actions for the production system. B. decumbens sward, in continuous stocking, with sward height of approximately 16 cm offered greater stocking rates, while heights of 18 and 20 cm had greater productivity per area.