Luciana Gerdes

Avaliação de características de valor nutritivo das gramíneas forrageiras Marandu, Setária e Tanzânia nas estações do ano

Foi realizado um experimento de campo, em blocos completos ao acaso, em esquema de parcelas subdivididas, com 12 repeticoes, com o objetivo de comparar os teores de proteina bruta (PB), fibra em detergente neutro (FDN) e digestibilidade in vitro da materia seca (DIVMS), da planta inteira e suas fracoes lâmina e haste do Marandu (Brachiaria brizantha Stapf. cv. Marandu), da setaria (Setaria sphacelata [Schum.] Moss var. sericea [Stapf.] cv. Kazungula) e do Tanzânia (Panicum maximum Jacq. cv. Tanzânia-1), em cortes aos 35 dias de crescimento, nas estacoes de primavera (21/11 a 25/12/97), verao (29/12/97 a 02/02/98), outono (13/04 a 18/05/98) e inverno (28/05/98 a 01/07/98). As parcelas foram representadas pelas gramineas forrageiras e as subparcelas, pelas estacoes do ano. Marandu e Tanzânia nao diferiram quanto aos teores de PB e DIVMS. A Setaria apresentou teores de PB mais elevados que o Marandu, no outono e no inverno, porem menor DIVMS que este, nas quatro estacoes. Tanzânia e Setaria nao diferiram quanto aos seus teores de PB e DIVMS, nas quatro estacoes. Os teores de FDN foram maiores no Tanzânia, mas nao diferiram entre Marandu e Setaria. O mais alto valor nutritivo, considerando-se maiores teores de proteina e DIVMS e menores teores de FDN, foram observados no outono, independentemente da especie forrageira.

Ganho de peso e produtividade animal em capim‑marandu sob pastejo rotativo e adubação nitrogenada

The objective of this work was to assess management targets for marandu palisade grass (Urochloa brizantha cv. Marandu) subjected to rotational stocking and to nitrogen fertilization rates, from January 2009 to April 2010. Treatments consisted of a combination of two grazing frequencies (pre-grazing heights of 25 and 35 cm) and two levels of nitrogen application (50 and 200 kg ha-1 per year). in a completely randomized block design, in a 2x2 factorial arrangement, with four replicates. The established post-grazing height was 15 cm. Greater values of daily weight gain per animal per day (0.629 and 0.511 kg day-1), weight gain per hectare (886 and 674 kg ha-1), and stocking rate (3.13 and 2.85 AU ha-1) were found for pre-grazing height of 25 cm. The application of 200 kg ha-1 of N increased the percentage of leaves in post-grazing forage mass, forage accumulation rate, stocking rate, as well as weight gain per hectare. The best grazing strategy corresponds to the pre-grazing height of 25 cm, regardless of the nitrogen application.

Avaliação de características agronômicas e morfológicas das gramíneas forrageiras Marandu, Setária e Tanzânia aos 35 dias de crescimento nas estações do ano

A field plot experiment was conducted in the Instituto de Zootecnia, Nova Odessa-SP, in a split plot design with 12 replicates, to compare, in the grasses marandu (Brachiaria brizantha Stapf. cv. Marandu), setaria (Setaria sphacelata cv. Kazungula) and tanzania (Panicum maximum cv. Tanzania-1): dry matter yield, dry matter percentage, sward height, leaf blade percentage, apical meristem height, in cuts at 35 days of growth, in the spring (21/11 to 25/12/97), summer (29/12/97 to 02/02/98), fall (13/04 to 18/05/98) and winter (28/05 to 01/07/98) seasons. The plots were the grasses and the split-plots the year seasons. Tanzania always showed high leaf blade percentage and low apical meristem height and presented the highest dry matter yield during fall season, and in the spring and winter, its dry matter yield did not differ from the other grasses, that were alike in the four seasons. The Setaria grass showed the smallest dry matter percentage in the four seasons, and the smallest leaf blade percentage, during spring and summer, which can limit its intake by the animals.

Características do dossel forrageiro e acúmulo de forragem em pastagem irrigada de capim-aruana exclusivo ou sobre-semeado com uma mistura de espécies forrageiras de inverno

Three winter forage species: black oat (Avena strigosa Schreb. cv. Common), italian ryegrass (Lolium multiflorum Lam. cv. Common) and white clover (Trifolium repens L. cv. Zapican) were introduced in a pasture of aruanagrass (Panicum maximum Jacq. cv. Aruana), grazed by sheep in an intensive production system (irrigation, fertilization and rotational stocking) with the objective of increasing the forage supply during the dry winter period. From 04-14-00 to 01-18-01 and 06-07-01 to 02-22-02, in six grazing periods, the pre-grazing forage mass, botanical composition and leaf blades percentage were evaluated in the six regrowth periods, as well as forage accumulation (FA). A completely randomized block design with replication within blocks was used. The treatments were: 1) grass alone and 2) the grass oversown with the mixture of winter forages. The oversown pasture had a greater total forage mass than the control in the second period as well as in the overall mean of the six periods of first year. The black oat made higher contribution in the second period while italian ryegrass contribution was higher in the third period. Higher FA was observed in the oversown pasture compared to the pure aruanagrass pasture, in the second, fifth and in the mean of the six regrowth periods. Total forage mass did not differ between treatments in the second year. The black oat contribution was higher in the first period while that of italian ryegrass was higher in the third period. The FA was similar in the two pasture systems. Fertilized and irrigated aruanagrass pasture, oversown with winter annual forages, out-yielded pure aruanagrass pasture during the dry winter period.

Composição química e digestibilidade da massa de forragem em pastagem irrigada de capim-aruana exclusivo ou sobre-semeado com mistura de aveia preta e azevém

Uma mistura de duas especies forrageiras de inverno: aveia preta (Avena strigosa Schreb cv. Comum) e azevem anual (Lolium multiflorum Lam. cv. Comum) foi sobre-semeada em uma pastagem de capim-aruana (Panicum maximum Jacq. cv. Aruana), utilizada com ovinos em sistema intensivo de producao (irrigacao, adubacao e lotacao rotacionada), com o objetivo de melhorar o valor nutritivo da forragem no periodo critico do ano. Nos doi anos (primeiro ano: 14/04/00 a 18/01/01 e segundo ano: 07/06/01 a 22/02/02), foram avaliadas a composicao quimica e digestibilidade da forragem, antes da entrada dos animais (pre-pastejo) nas pastagens, em seis periodos de pastejo. O delineamento experimental foi de blocos completos casualizados (quatro), com duas repeticoes dentro do bloco e dois tratamentos: 1) capim-aruana exclusivo e 2) capim-aruana sobre-semeado. Para as amostras do total da forragem pre-pastejo e dos componentes (aruana, aveia preta e azevem), avaliaram-se os teores de proteina bruta (PB), de fibra em detergente neutro (FDN), de fibra em detergente acido (FDA) e de lignina e a digestibilidade in vitro da materia seca. No primeiro ano, a PB da forragem de capim-aruana exclusivo foi maior que a do sobre-semeado no terceiro periodo de pastejo e semelhante nos demais. FDN, FDA e lignina da forragem no tratamento exclusivo foram mais elevadas que no tratamento sobre-semeado, na media dos seis periodos. A digestibilidade da forragem foi semelhante nos dois tratamentos, em todos os periodos de avaliacao. No segundo ano, o teor de PB da massa total de forragem da pastagem de capim-aruana exclusivo foi maior que o da pastagem sobre-semeada, no quarto periodo, porem semelhante nos demais e na media dos seis periodos. Os teores de FDN, FDA e lignina e a DIVMS da massa total de forragem foram semelhantes nas duas pastagens na media e ao longo dos seis periodos, exceto para FDN no segundo periodo. Pastos com capim-aruana sob adubacao nitrogenada, irrigacao e manejo adequados apresentaram composicao quimica e digestibilidade semelhantes as de pastos do capim sobre-semeados com aveia preta e azevem.

Influence of nitrogen on the production characteristics of ruzi grass

Understanding the action of the nitrogen (N) in grasses can aid in pasture management and increase the efficiency of this nutrient. The objective of this study was to determine the influence of N rates and of the available N from the previous crop on Brachiaria ruziziensis cv. Comum. The experiment was conducted in a greenhouse. The treatments were arranged in a 2×4 factorial design and were distributed according to a fully randomized block design with four replications. Two N rates (0 and 15 mg dm-3) were applied at grass planting and four N rates were applied as topdressing after the first cutting (0, 15, 30 and 45 mg dm-3). The grass was cut twice above-ground. The comparison between N rates applied at planting was made using F test, and the degrees of freedom of the N rates applied as topdressing were broken down into orthogonal polynomials. The N rate of 15 mg dm-3 applied at planting the ruzi grass promoted increases in the numbers of leaves and shoot dry matter production. During the second growth, N rates (15, 30 and 45 mg dm-3) applied as topdressing increased the number of leaves and the shoot dry matter production. The available N from the previous crop (soybean) was sufficient for the initial tillering of the ruzi grass. This study showed that the correct management of N fertilization is necessary for ruzi grass when grown after a previous crop (soybean). Key words: Available nitrogen, forage plants, management of nitrogen, residual nitrogen.