RESUMO: O presente estudo testou se a biomassa radicular de misturas compostas por gramíneas é maior do que os seus respectivos monocultivos. Os tratamentos foram monocultivos de Arrhenatherum elatius, Festuca arundinacea, Dactylis glomerata e uma mistura delas, cultivadas em um solo rico em nutrientes. A biomassa da raiz foi avaliada uma vez por estação em três profundidades de solo (0-5, 5-10 e 10-20 cm). Os pastos mistos apresentaram a maior biomassa radicular e isso pode ser explicado pela maior concentração de raízes na camada superficial do solo (0-5 cm). Esses achados reforçam a necessidade de práticas permanentes de conservação do solo para não prejudicar os benefícios da biomassa radicular mais abundante encontrada nos pastos mistos.

ABSTRACT: In this study we tested whether the root biomass of mixtures composed by grass species is greater than their respective monocultures. The treatments were monocultures of Arrhenatherum elatius, Festuca arundinacea, Dactylis glomerata, and a mixture of them, cultivated in a rich-soil environment. Root biomass was evaluated on a single evaluation per season at three soil depths (0-5, 5-10, and 10-20 cm). Mixed swards presented the greatest root biomass, and this was explained by a greater concentration in the topsoil layer (0-5 cm). These findings reinforce the need for permanent soil conservation practices to not jeopardize the benefits of the more abundant root biomass reported in the mixed swards.

ABSTRACT: This study evaluated the leaf area index (LAI) recovery mechanisms and forage accumulation rates on the regrowth of different grass species subjected to different defoliation intensities. For that purpose, plots of Pennisetum clandestinum (kikuyugrass), Lolium multiflorum (annual ryegrass), and Avena strigosa (black oats) were defoliated from 20 to 80 % of their initial heights (25, 20, and 25 cm, respectively). At different increments in height, forage samples were collected to ground level and used to estimate tiller population density (TPD), leaf area per tiller (LA), and forage mass. From these data, we calculated the leaf area index (LAI), average leaf area index (aLAI), and average and instantaneous forage accumulation rate (FAR and IFAR, respectively). Data were plotted over time (days) to describe LAI recovery and forage accumulation rates. As the defoliation intensity increased, greater canopy heights were needed for pastures to achieve their maximum forage accumulation rates, which required longer regrowth intervals. The need for high tiller recruitment after defoliation, which delayed canopy LAI recovery, seemed to be one of the main cause. Thus, grazing management strategies that involve costly tiller recruitment could decrease both overall forage production and sward persistence over time. However, the plant ability to recover LAI after successive intense defoliations seems to be species-dependent and related to their phenotypic plasticity.

RESUMO Dois experimentos complementares foram conduzidos para investigar as relações entre a estrutura do dossel de pastagens de Pennisetum clandestinum (capim-quicuiu) criadas por estratégias de lotação intermitente e o consumo de forragem por bovinos. O primeiro (Exp. I) avaliou o efeito de diferentes alturas em pré-pastejo (10, 15, 20 e 25 cm) associadas com uma única severidade de desfolhação (50% das alturas iniciais). No segundo (Exp. II) quatro severidades de desfolhação (40, 50, 60 ou 70% da altura total) foram combinadas com uma única altura inicial (25 cm). As variáveis analisadas foram: i) composição morfológica, massa e densidade do estrato de pastejo; ii) consumo de forragem. Os dados foram analisados por contrastes de polinômios ortogonais. Entretanto, para uma melhor caracterização das diferenças entre tratamentos, optou-se por comparar as médias de consumo pelo teste de Tukey. De modo geral, o consumo de forragem diminuiu com a redução da altura em pré-pastejo (Exp. I; P=0,03) ou com o aumento da severidade de desfolhação (Exp. II; P=0,02), em resposta as estruturas criadas antes e durante o processo de ocupação. Ademais, houve uma aparente abdicação dos animais em compensar estas condições com ajustes no comportamento ingestivo. Concluiu-se que alturas em pré-pastejo menores que 25 cm ou severidades de desfolhação maiores que 40% reduzem o consumo de forragem por bovinos em pastos de capim-quicuiu sob lotação intermitente.

ABSTRACT Two complementary experiments were conducted to investigate the relationships between the canopy structure of Pennisetum clandestinum (kikuyugrass) pastures created by intermittent stocking strategies and daily herbage intake by cattle. The first experiment (Exp. I) evaluated the relationship between different pre-grazing heights (10, 15, 20, and 25 cm) and a single defoliation intensity (50% reduction in the initial heights). In the second experiment (Exp. II), four defoliation intensities (40, 50, 60, or 70% reduction in height) were combined with a single pre-grazing height (25 cm). The following variables were analyzed: i) plant-part composition, herbage mass, and bulk density of the grazing layer; and ii) daily herbage intake. The data were analyzed using orthogonal polynomial contrasts. The Tukey-Kramer test was used to compare daily herbage intake means so that the differences among treatments could be characterized. In general, herbage intake decreased as the pre-grazing canopy height decreased (Exp. I; P = 0.03) and as defoliation intensity increased (Exp. II; P = 0.02). These response patterns were associated with canopy structure, both that existing before and that created during the stocking period. In conclusion, pre-grazing heights lower than 25 cm or defoliation intensities greater than 40% reduce daily herbage intake by cattle in kikuyugrass pastures under intermittent stocking.

ABSTRACT This study aimed to evaluate the milk fatty acid (FA) composition of unsupplemented dairy cows grazing on elephantgrass (Pennisetum purpureum Schum. cv. Pioneiro) pastures under three grazing management strategies: pre-grazing height of 120 cm with defoliation intensities of 50 and 70% of the initial height (treatments 120/50 and 120/70) and pre-grazing height of 90 cm with defoliation intensity of 70% (treatment 90/70). Treatments were repeated three times in a complete randomized block design. Tester animals were six multiparous Holsteins cows grouped into pairs according to days in milk and milk yield and allocated to blocks. Individual milk samples were collected after the first and second days of grazing (two-day occupation period) and analyzed for FA composition. Milk fat from 120/50 and 90/70 treatments resulted in higher concentrations of C4:0, C6:0, C17:0 anteiso, rumenic acid (RA), vacenic acid (VA), trans-12 C18:1, trans-13/14 C18:1, cis-11 C18:1, cis-12 C18:1, cis-9, trans-12 C18:2, trans-11, cis-15 C18:2, and total polyunsaturated fatty acids. Additionally, both SCD14 (cis-9 14:1/14:0 + cis-9 14:1) and SCDRA (RA/VA + RA) desaturase indices were reduced in milk fat from cows subjected to 120/50 and 90/70 treatments. On average, the milk fat levels of RA and VA observed in our study were greater than those reported in most studies with tropical grass-based diets and similar to levels usually found in cows grazing on temperate pastures. Overall, our results showed that milk with a desirable fatty acid composition is produced by cows grazing on a tropical grass (elephantgrass cv. Pioneiro), with the combination of a pre-grazing height of 120 cm and a defoliation intensity of 50% of the initial height, being a practical management strategy to achieve this goal.

Resumo: O objetivo deste trabalho foi avaliar a dinâmica e a estabilidade populacional de perfilhos do capim-caninha (Andropogon lateralis) em pastagem natural submetida a diferentes alturas de manejo, sob método de lotação intermitente. O experimento foi realizado em delineamento de blocos ao acaso, com quatro tratamentos e quatro repetições, em 16 unidades experimentais de 875 m2 cada uma. Os tratamentos consistiram de quatro alturas pré-pastejo de capim-caninha (12, 20, 28 e 36 cm), que foi pastejado a até 40% da altura inicial. Com o uso da técnica de perfilhos marcados, avaliou-se a dinâmica de aparecimento e morte de perfilhos ao longo de 18 meses, de outubro de 2015 até março de 2017. Os resultados indicam que a utilização de diferentes alturas de manejo em campo nativo não afeta a estabilidade da população de perfilhos do capim-caninha e que, independentemente do manejo empregado, a via de persistência desta espécie é baseada, principalmente, na manutenção de altas taxas de sobrevivência de perfilhos.

Abstract: The objective of this work was to evaluate tiller dynamics and population stability of Andropogon lateralis in a natural pasture subjected to grazing height management under intermittent stocking method. The experiment was carried out in a randomized complete block design with four treatments and four replicates, in 16 experimental units of 875 m2 each. The treatments consisted of four pre-grazing heights of A. lateralis (12, 20, 28, and 36 cm), which was grazed until its initial height was reduced by 40%. Dynamics of tiller birth and death were evaluated using the marked tiller technique over a period of 18 months, from October 2015 to March 2017. The results indicate that the use of different heights for the management of natural pastures does not affect the stability of the tiller population of A. lateralis and that, regardless of the management strategy, the persistent pathway of this species is mainly based on the maintenance of high-tiller survival rates.

RESUMO: Cyclocephala flavipennis Arrow, 1914 (Coleoptera: Melolonthidae), conhecido popularmente como coró-pequeno, é um inseto amplamente disseminado na região sul do Brasil. Embora seja encontrado com frequência em áreas cultivadas com cereais de inverno não é considerado inseto praga, por alimentar-se preferencialmente de palha e restos de plantas. Entretanto, nos anos de 2015 e 2016 foi identificado como causador de danos em pastagens perenes de inverno em Lages, Santa Catarina, Brasil. Os danos foram observados em reboleiras e promoveram redução na massa e profundidade de raízes, resultando em perda de vigor, senescência acelerada da parte aérea e morte de perfilhos de plantas de Festuca arundinacea Schreb. e Dacytilis glomerata L.

ABSTRACT: Cyclocephala flavipennis Arrow, 1914 (Coleoptera: Melolonthidae), popularly known as white grub, is an insect widely disseminated in the South Region of Brazil. Despite the frequent occurrence of this white grub in areas cultivated with winter cereals, it is generally not considered a pest, since it feeds on straw and dead plant material. However, in 2015 and 2016, this insect has been identified as the damage-causing agent in the perennial winter pastures in Lages, Santa Catarina, Brazil. Damage was observed in patches and caused reduction in root depth and mass, resulting in loss of vigor, accelerated senescence in aerial parts, and death of tillers in Festuca arundinacea Schreb. and Dactylis glomerata L. plants.

Resumo O objetivo deste trabalho foi avaliar o acúmulo de forragem durante o período de ocupação pelos animais em pastos de capim-quicuiu (Pennisetum clandestinum Hochst. Ex. Chiov.) manejados sob lotação intermitente. Os tratamentos consistiram de quatro proporções de desfolhação (remoção de 40, 50, 60 e 70% da altura inicial) partindo de uma mesma altura em pré-pastejo (20 cm). Foram avaliadas: taxas de alongamento foliar e colmos e senescência de folhas, índice de área foliar e taxa de acúmulo de forragem. Adicionalmente, dez perfilhos por faixa foram avaliados para as mesmas variáveis dentro de gaiolas de exclusão. Os efeitos linear, quadrático e cúbico da severidade de desfolhação foram avaliados por contrastes de polinômios ortogonais com 5% de nível de significância. Houve relação linear e inversa entre a porcentagem do índice de área foliar removido e o alongamento de lâminas foliares e o acúmulo de forragem. As taxas de alongamento de folhas em perfilhos bem como o acúmulo de forragem nas áreas excluídas do pastejo foram maiores em relação aos pastos submetidos a desfolhação. Durante o período de rebaixamento de pastos manejados sob lotação intermitente ocorre acúmulo de forragem e o mesmo é linear e inversamente associado à proporção da área foliar removida.

Abstract The aim of this study was to evaluate the forage accumulation during the stocking period on Kikuyu grass pastures (Pennisetum clandestinum Hochst. Ex. Chiov) subjected to intermittent stocking. Treatments consisted of four defoliation levels (removal of 40, 50, 60, and 70% relative to the initial height) starting from the same pre-grazing height (20 cm). The following variables were evaluated: leaf and stem elongation rates (evaluated during four times across the period of occupation), leaf area index, and forage accumulation rates. Additionally, ten tillers/strip were evaluated for the same variables into exclusion cages. The linear, quadratic and cubic effects of severity of defoliation were evaluated by orthogonal polynomials contrasts with 5% of significance level. There was a linear and inverse relationship between the proportion of removed leaf area index with leaf elongation and herbage accumulation rate. The leaf elongation rate in individual tillers and the forage accumulation rates of tillers on excluded areas from grazing were greater than those under grazing. During the stocking period on pastures submitted to intermittent grazing, forage accumulation was observed and it was linear and negatively correlated with the proportion of leaf area removed.

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.

RESUMO: O azevém anual (Lolium multuflorum Lam) é uma das plantas forrageiras de clima temperado mais cultivadas no mundo. Apesar disso, há poucas informações sobre o processo de alongamento de colmos para essa espécie durante seu crescimento vegetativo. Tal informação seria útil para o manejo mais adequado desta espécie. Assim, o objetivo do presente trabalho foi avaliar o acúmulo de forragem e as taxas de alongamento de colmos em pastos de azevém anual submetidos à lotação intermitente. O delineamento experimental foi completamente casualizado em arranjo factorial 2x2, com três repetições. Os tratamentos consistiram na combinação de duas alturas em pré-pastejo (15 e 25cm), associadas com duas alturas de resíduo (4 e 8cm). A maior taxa de acúmulo de forragem foi observada nos pastos manejadas com 25cm, associadas com alturas de resíduo de 8cm. Entretanto, a taxa de acúmulo de folhas foi similar para pastos manejados com 8cm de resíduo, independente da altura em pré-pastejo (15 ou 25cm). A taxa de alongamento de colmos em perfilhos de azevém anual aumentaram rapidamente quando os pastos atingiram uma altura de 18cm, condição onde havia uma relativa baixa competição por luz, sugerindo que: 1) alturas em pré-pastejo entre 18 e 20cm em pastos de azevém anual poderia ser usada como um limite máximo de altura quando o objetivo for minimizar a contribuição de colmos na forragem acumulada; e 2) parece que o alongamento de colmos é um processo inevitável (independente de competição por luz) e isso poderia estar relacionado com a força necessária de colmos, pseudocolmos e bainhas para suportar o peso de folhas cada vez maiores e mais pesadas.

ABSTRACT: Italian ryegrass (Lolium multiflorum Lam) is one of the most cultivated temperate annual forage crop around the world. Despite that, there is little information about the process of stem elongation during its vegetative growth. This information would be useful for grazing management purposes. Thus, the aim of this study was to assess the herbage accumulation and stem elongation rates in annual ryegrass pastures submitted to intermittent stocking. The experimental design used was a completely randomized 2x2 factorial with three replications. The treatments were defined by the combination of two pre-grazing heights (15 and 25cm) associated with two post-grazing heights (4 and 8cm). The herbage accumulation rates were higher in pastures with 25cm pre-grazing associated with post-grazing heights of 8cm. However, leaf production rate was only affected by post-grazing height, with higher values being recorded for stubbles heights of 8cm, regardless of pre-grazing height. Stem elongation rates in annual ryegrass tillers increased rapidly when pastures reached around 18cm, a condition where there was a relatively low competition for light, suggesting that; 1) pre-grazing heights of 18 to 20cm in annual ryegrass could be used as a upper limit for grazing management purposes whether the objective is to minimize stem contribution in accumulated herbage and 2) It seems that stem elongation is as inevitable process (independently of competition for light) and that this could be related to the necessary strength of stems, pseudostems and sheaths to support larger and heavier leaves.

As características morfogênicas e estruturais das plantas forrageiras, bem como os processos de crescimento e senescência de tecidos podem variar de acordo com as estratégias de manejo utilizadas. O objetivo deste trabalho foi avaliar o processo de rebrotação em pastos de capim-elefante, cultivar 'Pioneiro', submetidos a duas alturas em pré-pastejo (90 e 120cm) combinadas com duas severidades de desfolhação (50 e 70% da altura inicial). Ao longo das fases de rebrotação, ocorreu uma diminuição das taxas de alongamento foliar (TAF), aparecimento de folhas (TAP) e da densidade populacional de perfilhos aéreos (DPPA), aumento das taxas de senescência foliares (TSF) e alongamento de colmo mais pseudocolmo (TACP). A severidade de desfolha de 70% aliada à altura em pré-pastejo de 120cm comprometeu o processo de rebrotação do capim-elefante cv. 'Pioneiro', devendo este ser manejado com altura máxima de 90cm e com severidade de desfolha não excedendo 50% da altura inicial.

The morphogenetic and structural characteristics of forage plants and the processes of growth and senescence in tissues may vary according to the grazing management strategies used. This research aimed to assess the process of regrowth in elephant grass swards Cv. 'Pioneiro' submitted to two pre-grazing heights (90 and 120cm) combined with two levels of defoliation (50 and 70%). A reduction of the leaf elongation rate (LER) was observed during the regrowth stages, in addition to a reduction in the rate of leaf appearance (LAR) and aerial tiller population density (ATPD). In contrast, an increase was observed in leaf senescence (LSR) and stem and pseudo stem elongation rates (SER). The severe defoliation (70%) combined with a pre-grazing height of 120cm compromised the regrowth of elephant grass cv. 'Pioneiro', which must be managed with a maximum height of 90cm and maximum level of defoliation of 50% of the initial height.

We assessed the accumulation dynamics of forage and its components in Elephant grass cv. Napier (Pennisetum purpureum Schum.) that were subjected to three post-grazing height treatments (30, 50, and 70 cm) from February through May 2009 (experiment one) and December 2009 through May 2010 (experiment two). In experiment one, the grazing events started when the light interception by the canopy reached 95%. The same was adopted for experiment two, except for the first grazing event, which was based on the height of the apical meristems of basal tillers. The experimental design for both experiments was a randomized complete block with three replications. The pastures that were managed at a post-grazing height of 30 cm exhibited lower rates of leaf and stem growth, total growth and forage accumulation than those that were managed at 50 or 70 cm, indicating that post-grazing height affects Elephant grass. The pastures that were managed at 50 cm exhibited relatively stable accumulation rates and less stem accumulation. Pastures managed at 70 cm of pos-grazing height presented more leaf and stem accumulation. Most apical meristems of Elephant grass should be removed in the first grazing when they reach the post-grazing target height of 50 cm. The elevation in the residual post-grazing height, especially in the summer, raises the regrowth vigor in the Elephant grass cv. Napier pasture. The post-grazing height of 30 cm reduces the growth of the Elephant grass cv. Napier.

O objetivo deste trabalho foi avaliar a densidade populacional de perfilhos, a massa de forragem, o padrão populacional de perfilhamento e o índice de estabilidade de pastagens de azevém anual (Lolium multiflorum) estabelecidas após os cultivos de soja ou milho, submetidas a diferentes métodos e intensidades de pastejo por cordeiros. Foram avaliados os métodos de pastejo rotativo e contínuo, sob as intensidades moderada (oferta de forragem correspondente a 2,5 vezes o potencial de consumo de cordeiros) e baixa (correspondente a 5,0 vezes). Utilizou-se o delineamento experimental de blocos ao acaso, em arranjo fatorial 2x2x2, com quatro repetições. As avaliações foram feitas mensalmente, entre agosto e outubro de 2010, durante a fase de pastejo. A densidade populacional de perfilhos apresentou diferenças significativas para métodos e intensidades de pastejo, e foi maior na área previamente cultivada com soja. As maiores massas de forragem foram observadas em pastagens subsequentes à soja e com baixa intensidade de pastejo, enquanto as menores, nas pastagens subsequentes ao milho e com moderada intensidade de pastejo. No período de florescimento, a densidade de perfilhos reduziu-se e suas massas individuais aumentaram. A intensidade de pastejo moderada reduz o percentual de perfilhos florescidos. A redução da densidade de perfilhos durante o florescimento não compromete o índice de estabilidade do pasto.

The objective of this work was to evaluate tiller density, herbage mass, pattern of tiller population, and sward stability index in Italian ryegrass (Lolium multiflorum) pastures established after soybean or corn, subjected to different stocking methods and grazing intensities by sheep. Rotational or continuous stockings were evaluated under moderate (forage allowance equivalent to 2.5 times the potential consumption of lambs) and low grazing intensities (equivalent to 5.0 times). It was used a completely randomized block design, with a 2x2x2 factorial arrangement with four replicates. Evaluations were done monthly, between August and October 2010, during the pasture period. The tiller population density differed significantly with stocking methods and grazing intensities and was higher in the area previously cultivated with soybean, in the evaluation performed in August. The highest herbage masses were observed in pastures established after soybean at low‑grazing intensity, whereas the lowest were observed in pastures established after corn with moderate grazing intensity. During the reproductive period, tillering density reduced, and the individual tiller mass increased. Moderate grazing intensity reduces the percentage of fertile tillers. Reduction in tiller density during flowering does not affect the sward stability index.

The objective of this study was to evaluate the morphogenetic and structural characteristics of Aruana guineagrass pastures (Panicum maximum cv. Aruana) subjected to rotational stocking by sheep. The treatments corresponded to grazing when swards reached 95 or 98% of interception of incident light (LI) until post-grazing heights of 10 and 15cm and were allocated to experimental units (plots of 196 m²), according to a 2 × 2 factorial arrangement in a completely randomized design, with three replications, from January to May 2009. The morphogenetic assessments included: leaf appearance and elongation rates (LAR and LER), phyllochron (PHY) and leaf life span (LLS). Structural evaluations assessed the number of green leaves (NGL), dead leaves (NDL) and expanded leaves (NEL) per tiller, tiller population density (TPD) and final leaf length (FLL). The pre-grazing sward height relatively constant during the experimental period, with values ranging between 30 and 40 cm for treatments of 95 and 98% of LI, respectively, indicating potential for the development and use of management practices based on pasture conditions goals. The morphogenetic and structural characteristics were influenced by the frequency and intensity of grazing adopted, as well as by the seasons, implying that the capacity and speed for the recovery of Aruana grass pastures after grazing depend mainly on the management and edaphoclimatic conditions. The best grazing management for Aruana guineagrass is 95% canopy light interception, i.e., 30 cm pre-grazing height pastures interrupted when reaching 15 cm residue.

O objetivo deste estudo foi determinar a participação relativa de colmo na estrutura vertical de pastos de capim Aruana e azevém anual submetidos a estratégias de pastejo intermitente por ovinos. Os tratamentos para o capim Aruana corresponderam a pastejos realizados quando os pastos atingiam 95 e 98% de interceptação da luz incidente (IL) até as alturas pós-pastejo de 10 e 15cm. Para o azevém anual, os tratamentos corresponderam a pastejos realizados quando os pastos atingiam 15 e 25cm de altura pré-pastejo até as alturas pós-pastejo de 4 e 8cm. O delineamento experimental utilizado para as duas espécies foi inteiramente casualizado, em arranjo fatorial 2x2, com três repetições. Para quantificação da massa de colmo na estrutura vertical dos pastos, foram realizadas duas amostragens no pré-pastejo por unidade experimental (piquetes de 196m²) utilizando-se um quadrado de 25cm x 25cm de lado, em cada ciclo de pastejo. As amostras foram coletadas de forma estratificada a cada 5cm até o nível do solo. Após o corte estratificado, o material foi separado em colmo, folhas e material morto. Independente da espécie vegetal ou da altura de entrada, aproximadamente 90% de todo o colmo dos pastos encontra-se presente até 50% da altura do pasto, indicando que possíveis reduções em consumo a partir desse momento no rebaixamento podem ser atribuídas a dificuldades em manipulação e apreensão da forragem.

The aim of this study was to determine the relative contribution of stem in the vertical structure of Aruana guineagrass and annual ryegrass pastures submitted to strategies of rotational grazing by sheep. Treatments for Aruana guineagrass corresponded to grazing when the swards intercepted 95 and 98% of the incident light (LI) until the post-grazing heights of 10 and 15cm. For annual ryegrass, treatments corresponded to grazing when the swards reached 15 and 25cm (pre-grazing heights) until the post-grazing of 4 and 8cm. The experimental design for two species was a completely randomized in a 2x2 factorial scheme, with three replications. To quantify the stem mass present at each 5cm in the vertical structure of the pastures two samples were taken per experimental unit (paddocks of 196m²) using a square of 25cmx25cm. Cut samples was separated in leaves, stem and dead material. Regardless of plant species or pre-grazing height, approximately 90% of the stem is present up to 50% of sward height, suggesting that reported intake reduction beyond this point can be attributed to difficulties in forage manipulation and apprehension.