Valéria Pacheco Batista Euclides

Intervalo hídrico ótimo na avaliação de sistemas de pastejo contínuo e rotacionado

Soil physical quality in continuous and short-duration rotational cattle grazing systems was evaluated using the Least Limiting Water Range (LLWR) approach. Soil samples were collected on an experimental site at the Embrapa - Beef Cattle Research Center (Campo Grande, MS, Brazil). The studied soil was a Typic Acrudox. Four sampling sites were selected: two under a short-duration continuous grazing system and two under intensive short-duration rotational grazing system. Thirty soil cores were collected in each site under the continuous grazing system, planted with Brachiaria decumbens cv. Basilisk grass. One of the continuous grazing sites had received biannual fertilization (Cc) while the other had not been fertilized (Cs). Thirty soil cores were also collected in each site under the intensive rotational grazing system, planted with Panicum maximum cv. Tanzania grass. In the intensive rotational grazing system the two sites differed in relation to the post-graze residue level left. In one site (R1) it varied from 2.0 to 2.5 t total dry matter (TDM) ha-1 and in the other R2 it varied from 3.0 to 3.5 t TDM ha-1. The cores were subjected to a soil water suction gradient, and then used for soil bulk density (Db), soil resistance to penetration (SR), volumetric water content (qv), and LLWR determinations. The intensive short-duration rotational grazing system presented the worse physical soil conditions for plant growth, as evaluated by the LLWR. The highest Db and the lowest LLWR were found in R1, which could be a consequence of the heavier stocking rates used on this site.

Consumo voluntário de forragem de três cultivares de Panicum maximum sob pastejo

Os objetivos deste trabalho foram estimar o consumo de materia seca de animais pastejando tres cultivares de Panicum maximum e relaciona-lo com ganho de peso, tempo de pastejo (TP) e algumas caracteristicas quimicas e estruturais do pasto. O delineamento experimental foi o de blocos casualizados com tres tratamentos e tres repeticoes. O consumo voluntario de materia seca (CVMS) foi estimado em quatro ocasioes (maio, setembro, novembro e fevereiro). Para calcular a producao de fezes, foi usado o oxido cromico como marcador externo. Foram estimados a digestibilidade in situ da materia seca e o tempo de pastejo, respectivamente, por intermedio de extrusas e tacografos. Foram estimadas as disponibilidades da forragem e dos componentes da planta. Apesar de os CVMS pelos animais terem sido semelhantes entre as cultivares, foram observadas maiores diferencas nos ganhos de peso, para os animais pastejando o capim Tanzânia, seguidos daqueles pastejando os capins Coloniao e Tobiata. Diferencas tambem foram observadas entre as cultivares para TP, que foi menor para os animais em pasto de Tobiata, quando comparados aos que pastejaram as outras duas cultivares. O aumento no TP observado durante o periodo da seca nao foi suficiente para impedir queda no consumo de forragem neste periodo. O CVMS foi correlacionado (r2 = 0,77) com ganho diario de peso. As caracteristicas estruturais das pastagens, disponibilidade de folhas e relacao material verde:material morto, influenciaram mais o CVMS, ganho de peso diario e TP que os valores nutritivos das mesmas.

Desempenho de novilhos F1s Angus-Nelore em pastagens de Brachiaria decumbens submetidos a diferentes regimes alimentares

O objetivo deste experimento foi avaliar as eficiencias biologica e economica de sistemas de alimentacao, durante os periodos criticos, como alternativa de reducao da idade de abate de bovinos recriados em pastagens de Brachiaria decumbens. Sessenta bezerros F1s Angus-Nelore desmamados foram distribuidos nos seguintes tratamentos: A) sem suplementacao; B) suplementacao somente no primeiro periodo seco; C) suplementacao apenas na segunda seca; D) suplementacao nos dois periodos secos; e E) suplementacao no primeiro periodo seco e confinamento no segundo. Os suplementos utilizados foram racoes comerciais fornecidas diariamente em quantidades equivalentes a 0,8 e 0,9% do peso vivo, nas primeira e segunda secas, respectivamente. O confinamento durou 100 dias e os novilhos receberam, ad libitum, uma racao contendo 40% de feno de Brachiaria decumbens e 60% de concentrado. O periodo experimental foi da desmama ate o abate (460 kg). Durante o primeiro periodo seco, os animais suplementados apresentaram maiores ganhos de peso diario (GPD) que os nao suplementados, 460 e 70 g, respectivamente. Durante o segundo periodo seco, os animais confinados apresentaram maiores GPD (1.285 g), seguidos dos suplementados em pasto (580 g), enquanto os nao suplementados perderam peso (-180 g). Houve aumento na capacidade de suporte dos pastos, onde os animais receberam suplementacao, em 24 e 30%, durante os primeiro e segundo periodos secos, respectivamente. Os animais que passaram por restricao alimentar no segundo periodo seco apresentaram ganho compensatorio, quando cessou a restricao, mas esse nao foi suficiente para que os animais atingissem pesos de abate a mesma idade dos suplementados. As idades de abate foram 30,1; 28,0; 26,6; 24,2; e 22,0 meses, respectivamente, para os tratamentos A, B, C, D e E. Tambem foi apresentada a avaliacao economica.

Brazilian scientific progress in pasture research during the first decade of XXI century

This paper aims to discuss the scientific progress obtained in the past ten years in genetics and plant breeding, soil fertility and plant nutrition and the importance of target sward conditions for planning, controlling and recommending management grazing of tropical grasses. In addition, progress in crop-livestock integration systems and management alternatives for mitigation of greenhouse gas emission by beef cattle production systems, two very important areas related to sustainable production systems, will also be discussed.

Valor nutritivo da forragem e produção animal em pastagens de Brachiaria brizantha

The objectives of this work were to evaluate animal production and its relationship with pasture characteristics of Brachiaria brizantha cultivars Marandu, Xaraes and Piata. The experiment had a randomized complete block design, with three treatments and two replicates. Two-ha paddocks were divided into two and submitted to alternated grazing, with 28 days of grazing and 28 days of rest. Three tester steers were kept in each paddock; additional steers were placed in each paddock by the put and take technique, to assure post grazing residues of about 3 Mg ha-1 of dry matter. The pastures were sampled monthly to estimate the nutritive value of the forage. The animals were weighted, and the stocking rate was adjusted twice a week. Despite the lower average daily gain (ADG), in the cv. Xaraes pasture, the stocking rate was greater, which resulted in greater productivity, in comparison with cvs. Marandu and Piata. The pasture with cv. Piata had the highest ADG. These results indicate that cvs. Xaraes and Piata are new alternatives for Cerrado pastures. The choice of the forage cultivar should fit the animal and production system targets.

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.

Ingestive behaviour, herbage intake and grazing efficiency of beef cattle steers on Tanzania guineagrass subjected to rotational stocking managements

The objective of this experiment was to evaluate the ingestive behaviour, herbage intake and grazing efficiency of beef cattle steers grazing on Panicum maximum Jacq. cv. Tanzania subjected to different rotational stocking intensities. Treatments corresponded to two post-grazing conditions (residues of 25 and 50 cm) associated with a pre-grazing condition of 95% sward canopy light interception during regrowth (LI). The grazing time increased linearly with the duration of the occupation period (475 to 630 minutes/day). On paddocks grazed down to a residue of 25 cm, the bite rate increased linearly along the occupation period, with an average of 42.5 bites/minute. On paddocks grazed down to a residue of 50 cm, the bite rate was stable and equal to 39 bites/minute. There was no difference in herbage intake between grazing intensities. However, grazing at 25 cm residue resulted in greater herbage removal (68.0 vs. 45.6%) and greater grazing efficiency (90.4 vs. 49.8%) than grazing at 50 cm residue. Post-grazing residues of Tanzania guineagrass under rotational stocking management may be set at either 25 or 50 cm, since the herbage intake was not affected within this grazing intensity range. However, herbage removal and grazing efficiency were reduced with the 50 cm post-grazing height and grazing time increased with long occupation periods.

Desempenho animal, produção de forragem e características estruturais dos capins marandu e xaraés submetidos a intensidades de pastejo

The objectives were to evaluate the forage yield, the structural characteristics, the herbage intake, the grazing behavior and beef cattle performance in the palisadegrass cvs. Marandu and Xaraes pastures submitted to three grazing intensities. The experiment was carried out at Embrapa Gado de Corte. The experimental period was from October 2005 to June 2006. The area was of 8 ha, divided in 12 paddocks of 0.67 ha. Two cultivars of palisadegrass, Marandu and Xaraes, and three grazing intensities, 15, 30, and 45 cm of sward height were evaluated. The experimental design was randomized block in a split plot arrangement and two replications. The main plot was constituted by cultivars and the subplot by the grazing intensities. The grazing was continuously stocking with variable stocking rate. Each paddock was grazed by three steers and regulating animals were utilized to adjust the sward heights. The sward heights were monitored twice per week. The grass was sampled each 28 days to estimate the herbage yield, herbage accumulation rate, pasture structural characteristics, and nutritive value. Animals were weighed each 28 days. The dry matter intake was estimated in the summer and the autumn, and the grazing behavior in the summer. Herbage accumulation and average daily gain decreased as the grazing intensities increased for both palisadegrass cvs. Xaraes and Marandu. The forage intake for the animals in xaraes grass pasture was limited by the variation in the sward structure. Based on the sward structural characteristics, forage intake and the productivity, these grasses require differentiated management. Marandu grass must be managed between 25 and 40 cm of height and xaraes grass at 40 cm.

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.

Características morfogênicas e estruturais e produção de forragem do capim-marandu submetido a intensidades e freqüências de desfolhação

This trial was carried out to evaluate the influence of defoliation intensities (10 and 20 cm stubble height) and defoliation frequencies (three cut intervals based on the appearance of 5, 7 and 9 leaves/tiller after each defoliation event) on the morphogenetic and structural traits, tillering and herbage production of Brachiaria brizantha cv Marandu swards. Treatments were allocated to experimental units according to a completely randomized design, in a 2 x 3 factorial arrangement, with three replications, in a total of 18 experimental units. Two cuts were performed in the most frequent treatment and one cut for the remaining treatments. Greater defoliation intensity resulted in greater leaf tissue turn over and, when combined to greater defoliation frequencies resulted in younger tillers, which grew up in an environment with lesser light competition. Cutting intensity at 20 cm favored tiller transition from vegetative to reproductive stage, resulting in greater contribution of pseudo stem and dead material to the herbage mass. If frequent defoliation is used, the 10 cm stubble height is the recommended intensity. If less frequent defoliation is used, the 10 cm stubble height may decrease herbage yield, mainly when using the seven leaves frequency. Greater defoliation frequencies showed greater sward renovation, with greater leaf elongation and leaf appearance rates, greater leaf blade length and lesser pseudo-stem accumulation and elongation. Although greater herbage production was obtained at the 20 cm cutting height and 7 leaves frequency, considering all evaluated traits, more frequent cuts promoted greater tissue turn over with high herbage production characterized by its high amount of leaves and less amount of pseudo stem and dead material, allowing for higher herbage production efficiency.