Adair José Regazzi

Respostas morfogênicas e estruturais de Panicum maximum cv. Mombaça sob diferentes níveis de adubação nitrogenada e alturas de corte

The morphogenetic and structural characteristics of Panicum maximum cv. Mombaca were evaluated in response to different levels of nitrogen supply and cutting regimes. The study was conducted in a glasshouse with natural conditions of light and temperature. Treatments corresponded to four levels of nitrogen supply (0, 50, 100 and 200 mg/dm3) and three cutting heights (5, 10 and 20 cm). The morphogenetic evaluations included leaf appearance and elongation rate, phyllochron and leaf lifespan. The structural measurements were: number of leaves, number of tillers and leaf lamina length of fully expanded leaves. The morphogenetic responses were affected by nitrogen supply during regrowth, highlighting the importance of that nutrient for manipulating sward structure. All variables responded positively to nitrogen supply, except phyllochron. Cutting height had a significant effect on leaf lifespan, leaf lamina length of fully expanded leaves and number of green leaves per tiller. Leaf appearance and elongation rate per tiller were increased in 133 and 104%, respectively, by nitrogen supply. The relationship between both group of variables was determinant for the characterization of the main vegetative changes on plants. The responses observed on morphogenetic characteristics comprise an efficient attribute to manipulate canopy structure, allowing improved allocation of productive resources to growth and developmental processes.

Características morfogênicas e estruturais na rebrotação da Brachiaria brizantha cv. marandu submetida a três doses de nitrogênio

Um experimento foi disposto no delineamento em blocos casualizados, sob o esquema fatorial 3x8, tres dose de N (0, 20 e 40 mg dm-3 semana-1 de N) e oito tempos de rebrotacao (0, 2, 4, 8, 16, 24, 32 e 48 dias apos o corte de uniformizacao), em vasos, em casa-de-vegetacao, com tres repeticoes para cada tratamento, para avaliar as caracteristicas morfogenicas (taxa de aparecimento foliar [TApF] e taxa de alongamento foliar [TAlF]) e estruturais (comprimento medio de folhas [CMF], numero de folhas vivas perfilho-1 [NFVP], peso medio de perfilho [PMP] e densidade de perfilhos [DP]) da Brachiaria brizantha cv. Marandu. A TApF foi afetada significativamente com o aumento da dose de N. Plantas que receberam 40 mg dm-3 semana-1 de N apresentaram filocronos bem inferiores (6,99 dias folhas-1) aos encontrados na testemunha (12,20 dias folhas-1). A TAlF tambem foi bem sensivel a aplicacao de N, elevando-se significativamente com o aumento do suprimento de N, em torno de 185,24 e 264,32%, respectivamente, para as plantas que receberam 20 e 40 mg dm-3 semana-1 de N. O CMF sofreu efeito significativamente positivo com o aumento da dose de N. Tanto a dose de N quanto o tempo de rebrotacao tiveram efeito significativamente positivo sobre o NFVP e o PMP. Apesar do maior NFV, plantas que receberam doses de N tiveram maior perda por senescencia. Os fatores quantitativos estudados tambem tiveram efeito significativamente positivo sobre a DP.

Avaliação de Três Cultivares de Panicum maximum Jacq. sob Pastejo: Composição Química e Digestibilidade da Forragem

A study was conducted to evaluate three cultivars of Panicum maximum Jacq. under rotational grazing for the nutritive value,where the estimates of crude protein, neutral detergent fiber, acid detergent fiber, lignin, cellulose, silica, and in vitro digestibility of the organic material were performed in samples of leaves and stems. Additional nitrogen was applied in cv. Tanzania at the end of the rainny season. Samples were taken in June, September, and October 1998 and in March 1999. Some differences among treatments were observed. In general, cv. Massai showed a lower nutritive value with lower crude protein and digestibility, and higher neutral detergent fiber, acid detergent fiber, and lignin, either in samples of leaves or in stems. Therefore, its utilization as a forage option should be based on other agronomic characteristics. The cv. Mombaca exhibited higher concentrations of silica and its nutritive value was not affected by nitrogen fertilization at the end of the rainny season, except for an increase in the percentage of crude protein and a reduction in the amount of lignin and silica in March. The nutritive value of the stems was inferior to the leaves. The nutritive value was highest in all treatments at the beginning of the rainny period.

Morphogenetic characteristics and forage accumulation of Tanzania grass (Panicum maximum Jacq.) in two post-graze stubbles

This trial was conducted at National Beef Cattle Research Center of Brazilian Agricultural Research Corporation (Embrapa Beef Cattle), to evaluate the morphogenetic characteristics of leaves and tiller, green dry matter yield and growth index of Tanzaniagrass in two post-graze stubbles (high post-graze stubble (HPS) ¾3.6 t of DM/ha and low post-graze stubble (LPS) ¾ 2.3 t of DM/ha) until 35 days after grazing. The experimental design was a complete randomized block, with treatments assigned to a split plot design, with three replicates. Differences between post-graze stubble (PS) in the tiller dynamics only occurred to new basal tiller. The appearance of new basal tillers and new aerial tillers linearly decreased during the days after grazing. There was no difference between the post-graze stubble and the new and remaining tillers for the leaf elongation rate and leaf senescence. On the other hand, the leaf duration of elongation was lower in the low PS and the new tillers, producing leaves with lower fully length. There was interaction in the leaf appearance rate between PS and kind of tillers, with a higher one for low PS in the remaining and new tiller. There was no difference among the post-graze stubbles for green dry matter yield, with mean values of 61.4 and 47.9 kg/ha.day, for low and high PS, respectively. There was also no difference between high and low PS for the relative growth rate and leaf area index (LAI). However, the LAI increased, as a function of to the days after grazing.

Análise de critérios de qualidade da madeira de eucalipto para produção de celulose kraft

Seventy five Eucalyptus wood clones obtained from different geographic regions in Brazil were used for this study. Based on statistical analysis it was demonstrated that an active alkali charge and also wood lignin and extractive contents presented a significant effect on pulping yield. Wood specific gravity did not present a significant effect on pulping yield but affected wood consumption for pulp production (m3wood/ ton pulp). Wood specific gravity, lignin content and extractive content were recommended as criteria to establish wood quality prior to pulping characteristics determination.

Aspectos quantitativos do processo de reciclagem de nutrientes pelas fezes de bovinos sob pastejo em pastagem de Brachiaria decumbens na Zona da Mata de Minas Gerais

The experiment was carried out at the experimental station of EMBRAPA/National Dairy Research, at Coronel Pacheco, in the Zona da Mata region of Minas Gerais, to evaluate the qualitative aspects of the nutrients recycling through the feces of grazing bovines. A 110 square meter plot was located in a previous established pasture of Brachiaria decumbens. There were significant differences on the nitrogen and magnesium concentrations of forage, for 10 weeks, apparently reflecting amounts in the forage. There were no variation of the other nutrients in the forage and feces. The average frequency defecation was of 9.84 defecations/animal per day and the average weight of the feces at each defecation was of 200.5 g dry matter. It was verified, by means of some data estimates, that the nutrients recycling in the feces, so 93.28% N, 76.68% P, 1.99% K, 72.93% Ca and 62.54% Mg, that was ingested by the animal returned to the pasture as feces, the same as 18.09% N, 35.46% P, 5.47% K, 30.26% Ca and 15.43% Mg, available as primary production, returned to the pasture through feces.

Uso de modelos de regressão aleatória para descrever a variação genética da produção de leite na raça Holandesa

Data comprising 68,523 test day milk yield of 8,536 cows of the Holstein breed, calving from 1996 to 2001, were used to compare random regression models, for estimating variance components. Test day records (TD) were analyzed as multiple traits, considering each TD as a different trait. The test day records were analyzed as longitudinal traits by different random regression models regarding the function used to describe the trajectory of the lactation curve of the animals. The Wilminks exponential function, the Ali and Schaeffer logarithmic function and the Legendre orthogonal polynomials of second and fourth order were used. The comparisons among the models were based on the following criteria: estimates of variance components of the multiple-trait model and random regressions models, values of residual variance and values of the logarithms of the likelihood functions. The heritability estimates obtained using the multiple-trait model varied from 0.110 to 0.244, for the random regression models the values ranged from 0.127 to 0.301, being the largest estimates observed in the models with larger number of parameters. The random regression models which used the Legendre polynomials was the model which better described the genetic variation of the milk yield.

Testes para verificar a igualdade de parâmetros e a identidade de modelos de regressão não-linear em dados de experimento com delineamento em blocos casualizados

Considerou-se o ajustamento de equacoes de regressao nao-linear e o teste da razao de verossimilhanca, com aproximacoes pelas estatisticas qui-quadrado e F, para testar as hipoteses de igualdade de qualquer subconjunto de parâmetros e de identidade dos modelos para dados com repeticoes provenientes de experimento com delineamento em blocos completos casualizados. Concluiu-se que as duas aproximacoes podem ser utilizadas, mas a aproximacao pela estatistica F deve ser preferida, principalmente para pequenas amostras.

Avaliação de características de qualidade da carne de suínos por meio de componentes principais

Data from 326 animals of a F2 swine population were used to select traits related to meat quality by principal components analysis. The following traits were considered: pH at 45 minutes post mortem (pH45), pH at 24 hours post mortem (pHu), drip loss (DL), cooking loss (CL), total loss (TL), intramuscular fat (IMF), objective tenderness (OT), lightness (L), redness (a) and yellowness (b). Variation lower than 0.7 (eigenvalue lower than 0.7) indicated four traits, which were significantly correlated to the other traits, to be discarded. These results suggest the use of pH45, pHu, L, a, IMF and CL as swine meat quality traits in future experiments.

Eficiência da seleção univariada direta e indireta e de índices de seleção em Eucalyptus grandis

This study used data from six experiments with half-sib families of Eucalyptus grandis, carried out at six localities, to evaluate the following traits: circumference at breast height (CAP), plant height (ALT), rust incidence (FER), canker incidence (CAN) and number of normal trees per plot (NAR). The direct and indirect selection methodologies were compared with the selection indices (classic and Pesek and Baker method) using all the traits. Neither selection method yielded the expected distribution of genetic gains. Both the classic and Pesek and Bakers indices produced a more suitable distribution of expected genetic gains.