Miguel Marques Gontijo Neto

Consumo e tempo diário de pastejo por novilhos Nelore em pastagem de capim-tanzânia sob diferentes ofertas de forragem

This work aimed to evaluate the effects of forage allowances on canopy changes, the grazing time and forage intake by steers grazing tanzaniagrass (Panicum maximum Jacq.) pasture. The four levels of herbage allowance (HA) (kg of leaf blade /100 kg animal live weight/day, %) were: 6.1 ± 0.59; 11.1 ± 0.77; 18.0 ± 1.24 and 23.9 ± 1.15%. Eight Nelore animals averaging 229.0 and 249.5 kg grazed each paddock in the first and second sampling periods, respectively. A completely randomized block design was used. Grazing time, leaf dry matter availability, leaf:stem ratio and canopy height were highly correlated with forage intake and can be used to develop prediction models of forage intake and performance of the grazing animal. Studies on intake and grazing animal performance in relation to forage allowances should consider the pasture structural traits for data interpretation and comparison. Tanzaniagrass forage allowances induced changes in the pasture structural characteristics and had quadratic effect on the daily grazing time and on the forage intake by Nelore steers. Shortest grazing time and highest forage intake were observed on pasture with herbage allowance of about 22.5 kg leaf blade/100 kg BW, which corresponded to a post-grazing mass of 4323.2 kg/ha dry matter, 2887.6 kg/ha dry green matter and average canopy height of 64 cm.

Produção de gramíneas do gênero Brachiaria sob níveis de sombreamento

O trabalho foi realizado com o objetivo de avaliar a producao de B. decumbens cv. Basilisk e B. brizantha, cultivares Marandu e Xaraes, sob diferentes niveis de sombreamento. Utilizou-se delineamento em blocos casualizados com esquema de parcelas subdivididas, considerando os niveis de sombreamento (0, 50, 70%) como parcela e as especies ou cultivares como subparcelas. Sementes das gramineas foram postas a germinar em bandejas e transplantadas (tres plântulas por vaso). Foram realizados quatro cortes em cada subparcela. Antes de cada corte, mediram-se a altura de planta e a area foliar de quatro folhas em cada planta e quantificou-se o numero de perfilhos vivos por vaso. Apos a colheita, as plantas foram separadas em lâmina, colmo + bainha e material morto para determinacao da producao de materia seca. Para producao de materia seca total, calcularam-se a producao media em cada um os cortes e a producao total. No ultimo corte, avaliou-se a massa seca de raizes. As interacoes significativas foram desdobradas adequadamente. O fator qualitativo foi submetido a comparacao de medias pelo teste Tukey e o quantitativo a analise de regressao linear. A excecao da producao media em quatro cortes e da producao de colmos e de material morto, observou-se interacao significativa para todas as outras variaveis. Independentemente do nivel de sombreamento, o cultivar Xaraes destacou-se positivamente na maioria das caracteristicas analisadas, enquanto, no nivel de 50% de sombreamento, o capim-braquiaria apresentou maior produtividade, em porcentagem de producao a pleno sol. Na avaliacao da porcentagem de folhas, destacou-se o capim-xaraes, seguido do capim-marandu. Independentemente da forrageira, o nivel de sombreamento teve efeito direto sobre o numero de perfilhos/planta, a producao de MS do sistema radicular, a area foliar e o valor SPAD.

Sobrevivência e crescimento inicial em campo de espécies florestais nativas do Brasil Central indicadas para sistemas silvipastoris

This work aimed to evaluate the rate of survival and the initial development of eleven native tree species established in existing pastures of Brachiaria brizantha at the Beef Cattle Center (Campo Grande, MS). The soil is a dystrophic clay Dark- Red Latosoil. The seedlings were planted in 16 rows, with 10 m between rows and 4 m between plants in a row. It was used a completely randomized design with four replicates. Each row contained at least one seedling of all the trees evaluated. A repeat was composed of four rows. The Tukey test (P=0,05) showed significant differences between the survival means, indicating that the seedling container and ecological succession groups (pioneer, early secondary, late secondary and climax) affected the results. The highest survival rates were found for the ipe (Tabebuia impetiginosa), caroba (Jacaranda cuspidifolia) and aroeira (Myracrodruon urundeuva). The highest rates of relative growth (P=0,05) in 12 months were observed for chico-magro (Guazuma ulmifolia), caroba (J. cuspidifolia) and canafistula (Peltophorum dubium). The growth rates of the pioneer species were higher (P=0,05) than the more advanced ecological groups in the successional scale (late secondary and climax). The differences increased over the time and during rainy season (P=0,05). The results indicated the use of three species to be established in the existing pasture of the Cerrado (savannahs), considering the increments in height, stem diameter and survival rate: chico-magro (G. ulmifolia), caroba (J. decurrens) and canafistula (Peltophorum dubium). The three species belong to the initial successional group.

Híbridos de sorgo (Sorghum bicolor (L.) Moench) cultivados sob níveis crescentes de adubação: características agronômicas, carboidratos solúveis e estruturais da planta

The agronomic characteristics, neutral detergent fiber (NDF), acid detergent fiber (ADF) and total soluble and structural carbohydrates contents of five hybrid sorghum (AG-2002, AG-2005E, AGX-212, AGX-213 e AGX-215), cultivated under different fertilization levels, were evaluated. A randomized blocks design, in a 5 x 4 factorial scheme, with four replicates, was used. The qualitative factors means were analyzed by means of Tukey test at 5 and 1% of probability. The evaluated hybrids showed different proportions of stem (29.01 to 53.38%), leaves (16.70 to 22.64%) and panicle (29.91 to 52.43%), where stem and panicle were highly correlated with height, 0.79** and -0,82**, respectively. Dry matter content of whole plant was strongly affected by stem and panicle proportion, where the panicle showed higher DM contents (48.79 to 56,80%) and stem, the smaller (18.86 to 22.54%). The increase in the fertilization levels provided increment in the panicle production, that decreased stem+leaves/panicle proportions and increased panicle proportion and DM content of whole plant. The total soluble carbohydrates contents, in dry matter basis, varied among evaluated hybrids (12.24 to 19.80%) and increased as the fertilization levels increased. The evaluated hybrids showed significant differences among the NDF (57.38 to 62.30), ADF (25.29 to 31.56%), hemicellulose (28.56 to 33.87%), cellulose (19.20 to 24.34%) and lignin (6.04 a 6.51%) contents. The NDF and hemicellulose contents decreased as the fertilization levels increased.