ABSTRACT The objective was to examine the effect of two short-term protein-energy supplementation (STPES) strategies at the rearing phase on the performance of Nellore calves grazing on Mombaça or Marandu grasses. The experiment used 72 calves (7-mo old, 229±3.0 kg body weight [BW]) allotted in a completely randomized block design to four treatments in a 2 × 2 factorial arrangement: two forage cultivars (Panicum maximum cv. Mombaça vs. Brachiaria brizantha cv. Marandu) and two STPES (WEAN – STPES immediately after weaning vs. TRAN – STPES in the transition of dry-rainy). The WEAN animals received 1 kg day−1 (n = 36) of a protein-energy supplement, whereas TRAN animals were subjected to STPES at 2 g/kg BW day−1 (n = 36), both for 53 days. Every 28 days, calves were weighed to measure performance, and pastures were sampled to evaluate productive and structural traits. Growth performance was analyzed considering a completely randomized block design with a 2 × 2 arrangement of treatment, whereas forage responses included repeated measures. Marandu had a higher forage mass (3,586 kg) than Mombaça (2,890 kg), but there was no difference in forage mass in each cultivar between preconditioning periods. The nutritional composition of Marandu and Mombaça cultivars did not differ and had similar results of in vitro fermentation variables. Stocking rate was higher for WEAN, in the Mombaça pastures. The STPES at weaning on Marandu provided greater gains per area. When applied in the period following the weaning and coinciding with the dry season, the STPES improves the performance of newly weaned calves kept on Marandu and Mombaça grasses.

RESUMO: O objetivo foi avaliar os efeitos das doses anuais de 100 e 200 kg ha-1 de nitrogênio (N) sobre as características morfogênicas e estruturais do capim-ipyporã, em lotação intermitente durante as estações do ano. O delineamento experimental foi em blocos ao acaso, com dois tratamentos e três repetições de área. Os pastos de capim-ipyporã foram submetidos ao pastejo por bovinos de corte. Foram avaliadas as características morfogênicas e estruturais do dossel forrageiro por meio da técnica de perfilhos marcados. Também foi avaliado o acúmulo de forragem e a densidade populacional de perfilhos (DPP). Foi observada interação significativa (P < 0,05) das doses de N e estações do ano para o período de descanso (PD), duração de vida das folhas (DVF), filocrono, taxa de alongamento de colmos (TAlC) e comprimento final das folhas (CFF). Durante o inverno, o PD foi menor (40 vs 50 dias) nos pastos adubados com 200 kg ha-1 de N. Em contra partida, no inverno, os pastos adubados com 100 kg ha-1 de N apresentaram maiores valores para DVF, filocrono e TAlC, e menores para o CFF. Não foi observado efeito isolado de doses de N (P > 0,05) para as taxas de acúmulo de forragem; de aparecimento, alongamento e de senescência de folhas, relação folha:colmo e para a DPP. No entanto, o efeito das estações foi significativo para estas variáveis, com os maiores valores observados durante a primavera e verão. O uso de 200 kg ha-1 de N para pastos de capim-ipyporã promove redução da estacionalidade de produção da forrageira.

ABSTRACT: This study examined the effects of annual nitrogen (N) rates of 100 and 200 kg ha-1 on the morphogenetic and structural traits of Ipyporã grass (Brachiaria brizantha × Brachiaria ruziziensis) under intermittent grazing during the seasons of the year. The experiment was laid out in a randomized-block design with two treatments and three area replicates. Ipyporã grass pastures were grazed by beef cattle. Morphogenetic and structural traits of the forage canopy were evaluated using the marked-tiller technique. Forage accumulation and tiller density (TD) were also evaluated. Significant interaction effects (P < 0.05) between N rates and seasons were observed for the rest period, leaf lifespan (LLS), phyllochron, stem elongation rate (SER) and final leaf length (FLL). During winter, the rest period was shorter (40 vs. 50 days) in the pastures fertilized with 200 kg ha-1 N. Conversely, in winter, the pastures fertilized with 100 kg ha-1 N showed higher LLS, SER and phyllochron values, but lower FLL values. There was no isolated effect of N rates (P > 0.05) on forage accumulation rate; leaf appearance, elongation or senescence rates; leaf:stem ratio; or TD. However, the effect of seasons was significant for these variables, with the highest values occurring during spring and summer. The use of 200 kg ha-1 N in Ipyporã grass pastures reduces the seasonality of forage production.

Resumen Este trabajo tuvo como objetivo evaluar los efectos de tres dosis de nitrógeno (N) en las características morfogénicas y estructurales, la masa (MR) y la distribución de las raíces en el perfil del suelo, y la resistencia del suelo a la penetración de las pasturas de guinea Mombasa manejados con pastoreo rotacional. El diseño experimental utilizó bloques al azar con tres dosis de N (100, 200 y 300 kg ha-1) y tres repeticiones. El criterio para interrumpir el rebrote de los pastos fue la altura de 80 a 90 cm del dosel (90-95 % de intercepción de luz por el dosel). Los animales fueron retirados de los potreros cuando el dosel alcanzó el 50 % de la altura prepastoreo. Se evaluó la masa y acumulación del forraje, las características morfogénicas y estructurales del dosel, la MR y distribución en el perfil del suelo, y la resistencia del suelo a la penetración. En pastos fertilizados con 200 y 300 kg ha-1 de N, se observó la mayor aparición foliar (0.090 hojas macollo-1 día-1 y 0.081 hojas macollo-1 día-1), tasas de alargamiento (2.82 y 2.61 cm macollo-1 d-1) y mayor acumulación diaria de forraje (113.8 y 106.6 kg ha-1d-1). El uso de 300 kg ha-1 de N promovió una mayor resistencia del suelo a la penetración a 10 cm de profundidad en el pospastoreo (3.3 MPa). No se observó ningún efecto de las dosis de N en la MR (P>0.05). Por lo tanto, el control de la altura antes y después del pastoreo de los animales en los potreros ayudó a mantener la estructura del pasto y evitar el proceso de compactación del suelo. De acuerdo con los resultados, se concluye que 200 y 300 kg ha-1 de fertilización con N es una estrategia para intensificar los pastos.

Abstract This work aimed to evaluate the effects of three nitrogen (N) doses on the morphogenic and structural characteristics, root mass (RM) and distribution in the soil profile, and penetration soil resistance of Mombasa guineagrass pastures managed with rotational stocking. The experimental design used randomized blocks with three N doses (100, 200, and 300 kg ha-1) and three replicates. The criterion for interrupting the pastures’ regrowth was the height of 80 to 90 cm of the canopy (90-95 % of light interception by the canopy). The animals were removed from the paddocks when the canopy reached 50 % of the pre-grazing height. Forage mass and accumulation, canopy morphogenic and structural characteristics, RM and distribution in the soil profile, and soil resistance to penetration were evaluated. In pastures fertilized with 200 and 300 kg ha-1 of N, the highest leaf appearance (0.090 and 0.081 leaves-1 tiller-1 d-1), elongation rates (2.82 and 2.61 cm tiller-1 d-1) and highest daily forage accumulation (113.8 and 106.6 kg ha-1d-1) were observed. Using 300 kg ha-1 of N promoted greater soil resistance to penetration at 10 cm of depth in the post-grazing (3.3 MPa). No effect of N doses was observed for RM (P>0.05). The pre- and post-grazing height control of animals in the paddocks therefore helped to maintain the pasture structure and avoid the soil compaction process. According to the results, it is concluded that 200 and 300 kg ha-1 of N fertilization is a strategy for intensifying pastures.

ABSTRACT The objective of this two-year study was to evaluate live weight gain per animal and per area and their relationships with the characteristics of BRS Ipyporã (Brachiaria ruziziensis × Brachiaria brizantha) and Marandu (Brachiaria brizantha) pastures. A completely randomized block design was used with two treatments and four replicates. The grazing method was rotational stocking, with variable stocking rate. Stocking rate was adjusted twice a week during the grazing period (six or seven days) and post-grazing canopy height target of 15 cm. Animals were weighed every 28 days. Pastures were evaluated pre-grazing to estimate forage accumulation rate, forage mass (FM), leaf (LP) and stem (SP) percentages, and nutritive value. In the post-grazing, FM, LP, and SP were evaluated. Marandu palisadegrass pastures had greater FAR, pre-grazing FM, and hence, a greater SR when compared with BRS Ipyporã. However, compared with Marandu, BRS Ipyporã showed greater LP, leaf:stem ratio, crude protein, and in vitro organic matter digestibility, resulting in greater individual live weight gain. The lesser stocking rate in Ipyporã pastures was compensated, providing a greater individual live weight gain of steers, resulting in a similar live weight gain per area for the two cultivars. Thus, BRS Ipyporã is a good alternative for the diversification of pastures in the Cerrado region.

RESUMO: O objetivo deste trabalho foi comparar as características estruturais, morfológicas e bromatológicas da forragem e o desempenho de bovinos de corte, da raça Caracu (200±9kg de peso inicial), suplementados com mistura mineral múltipla (0,25% do peso corporal) em pastos diferidos de Brachiaria brizantha , cv. 'Marandu', e Brachiaria decumbens , cv. 'Basilisk', sob pastejo contínuo. Após o rebaixamento dos pastos a 10cm de altura, realizado em março de 2014 por meio de pastejo, ambas as espécies foram vedadas e diferidas por 126 dias. O período experimental foi de julho a outubro de 2014, e as avaliações das características do pasto e as pesagens dos animais foram realizadas a cada 28 dias. A maior massa de forragem foi registrada em pastos de 'Marandu'. A maior porcentagem de folhas e a menor de material morto foram observadas para a 'Basilisk'. Os maiores teores de proteína bruta (8,1 vs 7,0 ± 0,2%), digestibilidade in vitro da matéria orgânica (57,7 vs 53, 9 ± 0,4%), os menores teores de fibra em detergente neutro (69,2 vs 72,7 ± 0,4%) e, consequentemente, o maior ganho médio diário (680 vs 530 ± 0,04g animal-1) foram registrados para a cv. 'Basilisk'. O diferimento de pastagens de 'Marandu' ou 'Basilisk' associado à suplementação com mistura mineral múltipla figura como alternativa de manejo para recria de bovinos de corte durante o período seco. Para a duração do período de vedação utilizada, pastos de B. decumbens são mais indicados para alcançar o maior desempenho animal.

ABSTRACT: The objective of this study was to compare structural, morphological and bromatological characteristics of forage as well as performance of Caracu beef cattle (200 ± 9 kg of initial body weight) supplemented with a multi-mineral mixture (0.25% of body weight) on deferred pastures of Brachiaria brizantha 'Marandu' and Brachiaria decumbens 'Basilisk' under continuous grazing. After the pasture was grazed to 10 cm of height, in March 2014, both grasses were left to rest and subjected to a 126-day deferment period. The experimental period lasted from July to October 2014; the sward characteristics and the animal's weight were evaluated every 28 days. The highest forage mass was recorded in 'Marandu' grass, whereas the highest leaves percentage and lowest dead material percentage were observed in 'Basilisk' pastures. Similarly, the highest crude protein content (8.1 vs. 7.0 ± 0.2%), in vitro organic matter digestibility (57.7 vs. 53.9 ± 0.4%), lowest neutral detergent fiber content (69.2 vs. 72.7 ± 0.4%), and; consequently, the highest average daily gain (680 vs. 530 ± 0.04g animal-1) were recorded for 'Basilisk' pastures. 'Marandu' and 'Basilisk' deferment was associated with a multi-mineral mixture supplementation as a management alternative for rearing beef cattle during the drought periods. Because of the duration of the pasture recovery period in this study, B. decumbens pastures were more likely to achieve the highest animal performance.

Resumo: O objetivo deste trabalho foi avaliar o acúmulo de forragem e o valor nutritivo do híbrido de Urochloa 'BRS RB331 Ipyporã' (Urochloa brizantha x Urochloa ruziziensis) submetido à pastejo intermitente. Os tratamentos corresponderam às combinações entre as condições de pré-pastejo, interceptação de 95% da luz incidente e máxima interceptação de luz, e as de pós-pastejo, 10 e 15 cm de altura de resíduo, em delineamento de blocos ao acaso, em arranjo fatorial 2x2, com quatro repetições. Pastos manejados com 95% de interceptação da luz apresentaram maior taxa de acúmulo de forragem, proporção de folhas, relação folha:colmo, teor de proteína bruta e densidade populacional de perfilhos basilares (DPPb), em comparação àqueles manejados com máxima interceptação da luz. Pastos manejados com 15 cm de altura do resíduo apresentaram maior DPPb do que os manejados com 10 cm e apresentaram pequena variação de DPPb entre as estações do ano avaliadas, independentemente do tratamento. Pastos do híbrido interespecífico de Urochloa 'BRS RB331 Ipyporã' apresentam maior acúmulo de forragem e maiores teores de proteína bruta e digestibilidade in vitro da matéria orgânica e menores teores de fibra em detergente neutro na fração folha, quando manejados com 95% de IL nas condições de pré-pastejo, com 30 cm de altura do dossel, associada com 15 cm de altura de resíduo.

Abstract: The objective of this work was to evaluate the forage accumulation and nutritional value of the Urochloa hybrid 'BRS RB331 Ipyporã' (Urochloa brizantha x Urochloa ruziziensis) subjected to intermittent grazing. The treatments corresponded to combinations of the pre-grazing conditions, interception of 95% of incident light and maximum light interception, and of the post-grazing heights, 10 and 15 cm, in a randomized complete block design with a 2x2 factorial arrangement and four replicates. Pastures grazed at 95% of light interception showed higher forage accumulation rate, proportion of leaves, leaf:stem ratio, crude protein content, and basal tiller population density (BTPD), in comparison with those managed at maximum light interception. Pastures managed with post-grazing heights of 15 cm showed greater BTPD than those managed at 10 cm and showed a slightly variation in BTPD among the evaluated seasons of the year, regardless of the treatment. Pastures of the interspecific hybrid of Urochloa 'BRS RB331 Ipyporã' show greater forage accumulation and higher crude protein content and in vitro organic matter digestibility, and lower content of neutral detergent fiber in the leaf fraction, when managed with 95% LI under pre-grazing conditions of 30-cm sward height, associated with a post-grazing 15-cm sward height.

ABSTRACT The objective of the present study was to evaluate live weight gain per animal and per area and its relationship with the characteristics of pastures of Brachiaria brizantha cv. Paiaguás and Piatã. A randomized blocks experimental design was used, with two treatments and six replicates. The experimental area was 8.0 ha, divided into twelve paddocks of 0.67 ha. The grazing method used was continuous stocking, with variable stocking rate. Three tester steers were used per paddock. Sward heights were measured once a week, and the stocking rate (SR) was adjusted using regulator steers to maintain the sward height at 30 cm. Pasture samples were collected once a month, and herbage accumulation rate (HAR), percentage of leaves (PL), leaf:stem ratio (LSR), and nutritive value (NV) were determined. Animals were weighed every 28 days. No differences between the two cultivars were observed during the wet season for any of the evaluated parameters. However, cv. Paiaguás presented higher HAR and, consequently, higher SR than cv. Piatã during the dry season. As a result of its higher regrowth, cv. Paiaguás pastures presented significantly higher PL, LSR, and NV and, consequently, significantly higher average daily live weight gain. These differences resulted in higher live weight gain per area for Paiaguás grass (695 kg/ha per year) than for Piatã grass (645 kg/ha per year). Thus, Brachiaria brizantha cv. Paiaguás is a good alternative to decrease the temporary forage shortage and for the diversification of pastures in the Cerrado biome region.

Grazing strategy is a key element in the determination of sward structure, herbage nutritive value and animal performance. We aimed to compare the herbage characteristics and performance of livestock in pastures of Panicum maximum cv. Tanzania managed, using two rotational stocking strategies, which provided either a fixed-length rest period (FRP) of 35 days in the spring and fall and 30 days in the summer, or a variable-length rest period (VRP), determined by the time required for the canopy to achieve 70 cm in height. The pastures were evaluated in the pregrazing condition for forage mass (FM); leaf (LP), stem (SP) and dead matter (DP) percentages; and nutritive value (NV). The animals were weighed every 28 days. Pastures managed with the FRPs exhibited greater FMs, SPs and DPs and lower LPs and NVs than those managed with the VRPs. The average daily livestock weight gain was greater during the spring and summer for the VRP than for the FRP pastures, resulting in an average animal weight gain per area of 990 and 860 kg ha−¹ wet period−¹ for the pastures managed with the VRPs and FRPs, respectively. Thus, pasture rest periods that were maintained after the sward reached 70 cm in height reduced the animal performance on Tanzania guinea grass.

A definição dos princípios adequados de manejo do pastejo capazes de possibilitar que as pastagens mantenham-se produtivas e persistentes tem sido uma preocupação constante dos pesquisadores brasileiros. No entanto, foi durante as duas últimas décadas que ocorreram grandes mudanças e um avanço significativo na compreensão dos processos determinantes da correta utilização das plantas forrageiras tropicais em pastagens. Este texto tem por objetivo apresentar e discutir os principais resultados obtidos sobre o manejo do pastejo de alguns cultivares de Panicum maximum e de Brachiaria brizantha, bem como a importância da utilização de metas de pasto como guia de campo para o monitoramento e controle do processo de pastejo para planejar e recomendar práticas de manejo eficientes.

Defining a proper grazing management that allows pasture to remain productive and persistent has been a constant concern of Brazilian researchers. However, it was in the last two decades that significant changes have taken place regarding the understanding of important processes determining the use of tropical forage plants in pastures. The objective of this article is to present and discuss the main results on grazing management of some Panicum maximum and Brachiaria brizantha cultivars, as well as the importance of using pasture goals to guide planning, controlling and recommending efficient grazing management practices.

O objetivo deste trabalho foi avaliar o acúmulo de forragem, a estrutura do dossel, o valor nutritivo, o consumo de forragem e a produção animal, em pastos de Urochloa humidicola sob lotação contínua. As cultivares BRS Tupi e Comum foram avaliadas durante os períodos de seca e das águas (julho de 2011 a agosto de 2012), em delineamento experimental de blocos ao acaso, com dois tratamentos e seis repetições. Mensalmente, os animais foram pesados e os pastos amostrados para a determinação de: taxa de acúmulo de forragem (TAF); massa de forragem; percentagens de folha (PF), colmo e material morto (PM); e valor nutritivo. O consumo de matéria seca (CMS) foi determinado uma vez a cada período. 'BRS Tupi' apresentou maiores TAF e PF e menor PM do que a 'Comum', durante o período das águas. O valor nutritivo, o CMS e o ganho médio diário foram semelhantes entre as duas cultivares. O conteúdo de proteína bruta da forragem - 6,0 e 5,0%, respectivamente, para os períodos das águas e seco - foi o principal fator limitante ao CMS. 'BRS Tupi' recebeu maior taxa de lotação e, consequentemente, possibilitou maior ganho de peso vivo por área (192 kg ha-1 por ano) do que a 'Comum' (126 kg ha-1 por ano). A 'BRS Tupi' é uma boa alternativa para a diversificação de pastagens em solos de baixa fertilidade sujeitos a alagamento temporário.

The objective of this work was to evaluate forage accumulation, canopy structure, nutritive value, forage intake, and animal production in pastures of Urochloa humidicola under continuous stocking. The cultivars BRS Tupi and Comum were evaluated during the drought and wet periods (July 2011 to August 2012), in a randomized complete block experimental design, with two treatments and six replicates. Monthly, the animals were weighted and the pastures sampled for the determination of: forage accumulation rate (FAR); forage mass; percentages of leaves (PL), culms, and dead material (DL); and nutritive value. Forage intake (FI) was determined once a period. 'BRS Tupi' had a higher FAR, PL, and DL than 'Comum', during the wet period. The nutritive value, FI and the daily weight gain were similar between both cultivars. Forage protein content - 6.0 and 5.0%, for the wet and drought periods, respectively - was the main limiting factor for FI. 'BRS Tupi' had higher stocking rates and, consequently, made possible a higher live weight gain per area (192 kg ha-1 per year) than 'Comum' (126 kg ha-1 per year). 'BRS Tupi' is a good alternative for diversification of pastures in soils with low fertility that are temporarily subjected to flooding.

O objetivo deste trabalho foi avaliar o valor nutritivo, a estrutura do dossel e a produção animal de novilhos em pastos de capim-piatã (Urochloa brizantha, cultivar Piatã), manejados a 15, 30 e 45 cm de altura, sob lotação contínua. Utilizou-se o delineamento experimental de blocos ao acaso, com duas repetições e três alturas. As alturas dos pastos foram monitoradas duas vezes por semana, e as taxas de lotação ajustadas. Mensalmente, os pastos foram amostrados e os animais foram pesados. Não houve diferença no valor nutritivo dos pastos manejados com diferentes alturas. Os ganhos médios diários de 650 g por novilho foram semelhantes entre as diferentes alturas de manejo. A taxa de lotação foi menor para o pasto com 45 cm (2,4 UA ha-1), intermediária para o de 30 cm (3,1 UA ha-1) e maior para o manejado com 15 cm (3,8 UA ha-1), o que resultou em maior ganho por área dos pastos manejados com 15 cm (1.050 kg ha-1) e 30 cm (910 kg ha-1) de altura, quando comparados ao manejado a 45 cm (635 kg ha-1). O capim-piatã apresenta grande flexibilidade de manejo sob lotação contínua e pode ser manejado entre 15 e 45 cm de altura.

The objective of this work was to evaluate the nutritive value, sward structure, and animal performance of steers on piatã palisade grass pastures (Urochloa brizantha, cultivar Piatã), managed at 15, 30, and 45 cm sward heights, under continuous stocking. A randomized block design, with two replicates and three sward heights, was used. Sward height was measured twice a week, and the stocking rate was adjusted. Monthly, the pastures were sampled and the animals were weighted. There was no difference in the nutritive value of the pastures managed with different heights. The average daily gain of 650 g per steer was similar among the different sward heights. The stocking rate was lower for the pasture managed at 45 cm (2.4 AU ha-1), intermediary for the one with 30 cm (3.1 AU ha-1), and higher for the one managed at 15 cm (3.8 AU ha-1), resulting in greater gain per area for the pastures managed at a height of 15 cm (1,050 kg ha-1) and 30 cm (910 kg ha-1) than for the one managed at 45 cm (635 kg ha-1). Piatã palisade grass shows great flexibility under continuous stocking and can be managed between 15 and 45 cm sward height.

Os objetivos deste estudo foram avaliar as características morfogênicas e estruturais e o acúmulo de forragem do capim-marandu, submetido a três alturas de pastejo, sob lotação contínua. O delineamento experimental foi de blocos completos casualizados, com duas repetições e três alturas: 15; 30 e 45cm. O pasto manejado com 15cm de altura apresentou as maiores taxa de aparecimento de folhas e densidade de perfilhos basilares. O acúmulo de forragem foi semelhante entre as alturas de pastejo. Com base nas características da planta, o capim-marandu pode ser utilizado entre 15 e 45cm de altura do dossel.

The objectives of this study were to evaluate the morphological and structural characteristics and the herbage accumulation, in (Brachiaria brizantha cv. 'Marandu') marandu palisadegrass pastures subjected to three grazing heights under continuous stocking. It was used a randomized block design, with two replicates and three sward heights 15, 30 and 45cm. The biggest leaf appearance and the smallest basal tiller densities decreased were found in 15cm pasture The herbage accumulation was similar among the pastures managed with different grazing intensities. The marandu palisadegrass presents high management flexibility, and may be utilized between 15 and 45cm sward height.

The objective of this research was to assess morphogenetic and structural characteristics of tillers of guinea grass cv. Tanzania at different ages. The pastures of guinea grass were managed in six pasture conditions related to the combination of three frequencies (90, 95, and 99% light interception) and two post-grazing heights (25 and 50 cm). In these six pastures conditions, three tiller ages were evaluated (young, mature, and old). The design was of completely randomized block with three replications. Young tillers exhibited higher leaf appearance rate and leaf elongation rate and, consequently, higher final leaf length and number of live leaves than mature and old tillers, regardless of the pasture condition. On pastures managed with 90 or 95% light interception associated with a post-grazing height of 25 cm, old tillers presented longer leaf lifespan than young and mature ones. There is a progressive reduction in the vigor of growth of pastures of guinea grass cv. Tanzania with advancing tiller age.

This study was conducted in order to evaluate the morphogenetic and structural characteristics of guinea grass cv. Mombasa under three post-grazing heights (intense - 30 cm, lenient - 50 cm and variable - 50 in spring-summer and 30 cm in autumn-winter) when sward light interception reached 95% during regrowth. Post-grazing heights were allocated to experimental units (0.25 ha) in a completely randomized block design with three replications. Post-grazing heights affected only leaf elongation rate and the number of live leaves. Pastures managed with variable post-grazing height showed higher leaf elongation rate in the summer of 2007. This management strategy also resulted in a higher number of live leaves. During the spring of 2006, plants showed lower leaf elongation rate, leaf appearance rate and number of live leaves, and greater phyllochron and leaf lifespan. In contrast, during the summer of 2007, the leaf appearance rate, leaf elongation rate, number of live leaves, and final leaf length were greater while phyllochron, stem elongation rate, and leaf senescence rate were lower. The management of the guinea grass cv. Mombasa with intense or variable post-grazing height throughout the year seems to represent an interesting management target, in terms of leaf appearance rate and number of live leaves.

This experiment was carried out to analyze the tillering dynamics of the species Panicum maximum cv. Mombaca subjected to three post-grazing heights: residue of 30 cm (30); residue of 50 cm (50); and residue of 50 cm during spring and summer, lowered to 40 cm in the first fall season grazing and to 30 cm in the following grazing cycle, resuming to 50 cm after the first grazing of the following spring season (50-30). Grazings were initiated whenever the swards intercepted 95% of the incident light. The post-grazing heights were allocated in the experimental units in a completely randomized block design with three replications. The density of basal tillers did not vary between the residual heights evaluated. Swards managed with variable residual height (50-30) presented higher rates of appearance and mortality of basal tillers during the summer of 2007, indicating high tiller renovation. Regardless of the post-grazing height evaluated, lower rates of appearance of basal tillers were found in the spring of 2006. The stability index of guinea grass cv. Mombaca was close to 1.0 throughout the experimental period. Swards managed with variable post-grazing present structural changes able to improve the regrowth vigor, which may be important to maximize the use of the forage species in the production system.