Strategic grazing management decreases nitrogen excretion intensity of dairy cows

ABSTRACT: There is limited information regarding both nitrogen (N) and energy partitioning of dairy cows grazing wellmanaged tropical pastures. The objective of this study was to investigate the N and energy partitioning of midlactation dairy cows on rotationally grazed elephant grass using two pregrazing targets: 95 % or maximum canopy light interception (LI95% or LIMax) during regrowth. The study used 26 Holstein × Jersey dairy cows arranged in a randomized complete block design with three 40day periods of sampling. Grazing at LI95% increased organic matter and crude protein intake by 20 % (p 0.05) which resulted in a 9 % increase in fat corrected milk yield (p 0.05) relative to LIMax. Cows grazing at LI95% had greater concentration of total volatile fatty acids, butyrate and valerate (p 0.05), and smaller acetate (p 0.05) than those grazing at LIMax. Intake of net energy for lactation (NEL) and NEL secreted in milk were greater (p 0.05), while partitioning of NEL towards maintenance tended to be greater (p = 0.07) for cows grazing at LI95% than those grazing at LIMax. Milk urea nitrogen and both urine and fecal N excretion were greater for cows grazing at LI95% (p 0.05), but N excretion intensity was lower than in cows grazing at LIMax (p 0.05). Strategic grazing management using the LI95% pregrazing target increases N losses through both urine and feces; however, it reduces N excretion intensity of dairy cows by 9 %.

Strategic grazing management decreases nitrogen excretion intensity of dairy cows

There is limited information regarding both nitrogen (N) and energy partitioning of dairy cows grazing well–managed tropical pastures. The objective of this study was to investigate the N and energy partitioning of mid–lactation dairy cows on rotationally grazed elephant grass using two pre–grazing targets: 95 % or maximum canopy light interception (LI95% or LIMax) during regrowth. The study used 26 Holstein × Jersey dairy cows arranged in a randomized complete block design with three 40–day periods of sampling. Grazing at LI95% increased organic matter and crude protein intake by 20 % (p ≤ 0.05) which resulted in a 9 % increase in fat corrected milk yield (p ≤ 0.05) relative to LIMax. Cows grazing at LI95% had greater concentration of total volatile fatty acids, butyrate and valerate (p ≤ 0.05), and smaller acetate (p ≤ 0.05) than those grazing at LIMax. Intake of net energy for lactation (NEL) and NEL secreted in milk were greater (p ≤ 0.05), while partitioning of NEL towards maintenance tended to be greater (p = 0.07) for cows grazing at LI95% than those grazing at LIMax. Milk urea nitrogen and both urine and fecal N excretion were greater for cows grazing at LI95% (p ≤ 0.05), but N excretion intensity was lower than in cows grazing at LIMax (p ≤ 0.05). Strategic grazing management using the LI95% pre–grazing target increases N losses through both urine and feces; however, it reduces N excretion intensity of dairy cows by 9 %.

Strategic grazing management decreases nitrogen excretion intensity of dairy cows

There is limited information regarding both nitrogen (N) and energy partitioning of dairy cows grazing well­managed tropical pastures. The objective of this study was to investigate the N and energy partitioning of mid­lactation dairy cows on rotationally grazed elephant grass using two pre­grazing targets: 95 % or maximum canopy light interception (LI95% or LIMax) during regrowth. The study used 26 Holstein × Jersey dairy cows arranged in a randomized complete block design with three 40­day periods of sampling. Grazing at LI95% increased organic matter and crude protein intake by 20 % (p ≤ 0.05) which resulted in a 9 % increase in fat corrected milk yield (p ≤ 0.05) relative to LIMax. Cows grazing at LI95% had greater concentration of total volatile fatty acids, butyrate and valerate (p ≤ 0.05), and smaller acetate (p ≤ 0.05) than those grazing at LIMax. Intake of net energy for lactation (NEL) and NEL secreted in milk were greater (p ≤ 0.05), while partitioning of NEL towards maintenance tended to be greater (p = 0.07) for cows grazing at LI95% than those grazing at LIMax. Milk urea nitrogen and both urine and fecal N excretion were greater for cows grazing at LI95% (p ≤ 0.05), but N excretion intensity was lower than in cows grazing at LIMax (p ≤ 0.05). Strategic grazing management using the LI95% pre­grazing target increases N losses through both urine and feces; however, it reduces N excretion intensity of dairy cows by 9 %.

Effect of grazing management strategies on the yield and nutritional value of Marandu grass in the semiarid of Brazil / Efeito de estratégias de manejo do pastejo na produtividade e valor nutricional do capim-Marandu no semiárido brasileiro

The objective of this study was to evaluate the effects of two grazing management strategies on structural, productive and nutritional parameters of Marandu grass (Urochloa brizantha cv. Marandu). A completely randomized block design with two pasture management strategies and eight replications (blocks) was used. The grazing management strategies were: (1) low intensity rotational grazing (LI), with a pre-grazing sward height of 40 cm and a post-grazing sward height of 24 cm, i.e., a defoliation intensity of 50%; (2) High intensity rotational grazing (HI), with a pre-grazing sward height of 40 cm and a post-grazing sward height of 10 cm (±70% defoliation intensity). Pastures were sampled before and after grazing for estimation of forage mass, forage accumulation rate, structural characteristics, nutritional value and dry matter intake. The LI strategy resulted in higher dry matter production than HI before (18.33%) and after grazing (49.06%), increasing pre-grazing forage density by 13.21% (P < 0.05). The production of potentially digestible dry matter was highest (P < 0.05) in LI strategy (21.3% before and 39.6% after grazing, respectively). Higher post-grazing green forage mass (45%) increased the residual crude protein in LI. The LI management strategy increased forage mass production and can be used in Marandu grass pastures.(AU)

Objetivou-se por meio deste trabalho avaliar os efeitos de duas estratégias de manejo do pastejo sobre os parâmetros estruturais, produtivos e nutricionais do capim-Marandu (Urochloa brizantha cv. Marandu). O delineamento experimental foi em blocos casualizados com duas estratégias de manejo da pastagem e oito repetições (blocos). As estratégias de manejo do pastejo foram: (1) pastejo rotacional menos intensivo (LI), com altura do pasto pré-pastejo de 40 cm e altura do pasto pós-pastejo de 24 cm, ou seja, intensidade de desfolha de 50%; (2) pastejo rotativo mais intensivo (HI), com altura do pasto pré-pastejo de 40 cm e altura do pasto pós-pastejo de 10 cm (±70% densidade de desfolha). As pastagens foram amostradas antes e após o pastejo para estimativa da massa de forragem, taxa de acúmulo de forragem, características estruturais, valor nutricional e consumo de matéria seca. A estratégia LI resultou em maior produção de matéria seca do que HI antes (18,33%) e após pastejo (49,06%), aumentando a densidade de forragem prépastejo em 13,21% (P < 0,05). A produção de matéria seca potencialmente digestível foi maior (P < 0,05) na estratégia LI (21,3% antes e 39,6% após o pastejo, respectivamente). Maior matéria seca verde total póspastejo (45%) aumentou a proteína bruta residual em LI. A estratégia de manejo da LI aumentou a produção em massa de forragem e pode ser utilizada em pastagens de capim-Marandu.(AU)

Floristic diversification of spreading liverseed grass pasture according to different cutting intensities, obtained by grazing simulation

This study aimed to evaluate the impacts of different forage cutting intensities, obtained by grazing simulation, on the floristic diversity and productivity of a pasture cultivated with spreading liverseed grass. The experiment was set up in a randomized block design, with four replications and treatments arranged in a 5×2 factorial scheme, with five levels of cutting intensity of the simulated grazing (0, 25, 50, 75, and 95% of the forage canopy) associated with two levels of weed coexistence (presence and absence). The evaluations of floristic diversity, number of individuals, and total dry matter of weeds were obtained at 15, 30, 45, 60, and 90 days after grazing simulation (DAGS). All plots were evaluated at the end of the experimental period (90 DAGS) for the amount of dry biomass produced by the pasture. The results showed that higher forage cutting intensities, obtained by grazing simulation, increased the floristic diversity, the number of individuals, and the dry matter accumulated by weeds in a pasture grown with spreading liverseed grass, reducing by up to 56% theproduction of total dry matter of the forage.(AU)

Floristic diversification of spreading liverseed grass pasture according to different cutting intensities, obtained by grazing simulation

This study aimed to evaluate the impacts of different forage cutting intensities, obtained by grazing simulation, on the floristic diversity and productivity of a pasture cultivated with spreading liverseed grass. The experiment was set up in a randomized block design, with four replications and treatments arranged in a 5×2 factorial scheme, with five levels of cutting intensity of the simulated grazing (0, 25, 50, 75, and 95% of the forage canopy) associated with two levels of weed coexistence (presence and absence). The evaluations of floristic diversity, number of individuals, and total dry matter of weeds were obtained at 15, 30, 45, 60, and 90 days after grazing simulation (DAGS). All plots were evaluated at the end of the experimental period (90 DAGS) for the amount of dry biomass produced by the pasture. The results showed that higher forage cutting intensities, obtained by grazing simulation, increased the floristic diversity, the number of individuals, and the dry matter accumulated by weeds in a pasture grown with spreading liverseed grass, reducing by up to 56% theproduction of total dry matter of the forage.

Grazing heights, stocking rate, soil structure, and water infiltration in a crop-livestock integration / Alturas de pastejo, carga animal, estrutura e infiltração de água no solo em integração lavoura-pecuária

Grazing intensity on palisade grass as a function of grazing height in a crop-livestock integration (CLI) system alters the structural soil quality and water infiltration. This study aimed to verify the magnitude of the stocking rate and shoot and root dry matter of palisade grass at the end of the fifth cattle grazing period of an experiment in the CLI system on the visual evaluation of soil structure (VESS), soil-water infiltration rate, and basic infiltration rate (BIR) as a function of grazing heights on Urochloa brizantha cv. MG 5 Vitória in the northwestern Paraná State, Brazil. The experimental design consisted of randomized blocks with three replications and 1-ha experimental plots on an Oxisol. Four treatments with grazing heights of 10, 20, 30, and 40 cm were used in the CLI system, controlled with variable stocking rates of Purunã cattle in the autumn/winter season on Urochloa brizantha cv. MG 5 Vitória in succession to soybean in the summer. The maximum soil water infiltration was stabilized at 30 cm of grazing height of the palisade grass under continuous grazing in the CLI system. The increase in the stocking rate decreased the shoot dry matter of palisade grass, soil water infiltration, and structural soil quality.(AU)

A intensidade de pastejo da braquiária em função da altura de pastejo em sistema de integração lavourapecuária (ILP) altera a qualidade estrutural do solo e a infiltração da água. Com este trabalho teve-se por objetivo verificar ao final do quinto período de pastejo bovino de um experimento em sistema de ILP, qual a magnitude da carga animal, matéria seca da parte aérea e de raízes de braquiária, sobre a avaliação visual da estrutura do solo (VESS), a taxa de infiltração de água no solo e a velocidade básica de infiltração (VIB) em função da alturas de pastejos em braquiária Urochloa brizantha cv. MG 5 Vitória, na Região Noroeste do Estado do Paraná, Brasil. O delineamento experimental é de blocos casualizados, com três repetições, em parcelas experimentais de 1 ha, em um Latossolo Vermelho distrófico. Foram utilizados quatro tratamentos com alturas de pastejo de 10, 20, 30 e 40 cm em sistema de ILP controlados com carga animal variável de bovinos da raça Purunã no período de outono/inverno, em braquiária Urochloa brizantha cv. MG 5 Vitória em sucessão a soja no verão. A máxima infiltração da água no solo se estabiliza em 30 cm de altura de pastejo da braquiária em pastejo contínuo em sistema ILP. O aumento da carga animal diminuiu a matéria seca da parte aérea de braquiária, infiltração de água e a qualidade estrutural do solo.(AU)

Grazing heights, stocking rate, soil structure, and water infiltration in a crop-livestock integration / Alturas de pastejo, carga animal, estrutura e infiltração de água no solo em integração lavoura-pecuária

Grazing intensity on palisade grass as a function of grazing height in a crop-livestock integration (CLI) system alters the structural soil quality and water infiltration. This study aimed to verify the magnitude of the stocking rate and shoot and root dry matter of palisade grass at the end of the fifth cattle grazing period of an experiment in the CLI system on the visual evaluation of soil structure (VESS), soil-water infiltration rate, and basic infiltration rate (BIR) as a function of grazing heights on Urochloa brizantha cv. MG 5 Vitória in the northwestern Paraná State, Brazil. The experimental design consisted of randomized blocks with three replications and 1-ha experimental plots on an Oxisol. Four treatments with grazing heights of 10, 20, 30, and 40 cm were used in the CLI system, controlled with variable stocking rates of Purunã cattle in the autumn/winter season on Urochloa brizantha cv. MG 5 Vitória in succession to soybean in the summer. The maximum soil water infiltration was stabilized at 30 cm of grazing height of the palisade grass under continuous grazing in the CLI system. The increase in the stocking rate decreased the shoot dry matter of palisade grass, soil water infiltration, and structural soil quality.

A intensidade de pastejo da braquiária em função da altura de pastejo em sistema de integração lavourapecuária (ILP) altera a qualidade estrutural do solo e a infiltração da água. Com este trabalho teve-se por objetivo verificar ao final do quinto período de pastejo bovino de um experimento em sistema de ILP, qual a magnitude da carga animal, matéria seca da parte aérea e de raízes de braquiária, sobre a avaliação visual da estrutura do solo (VESS), a taxa de infiltração de água no solo e a velocidade básica de infiltração (VIB) em função da alturas de pastejos em braquiária Urochloa brizantha cv. MG 5 Vitória, na Região Noroeste do Estado do Paraná, Brasil. O delineamento experimental é de blocos casualizados, com três repetições, em parcelas experimentais de 1 ha, em um Latossolo Vermelho distrófico. Foram utilizados quatro tratamentos com alturas de pastejo de 10, 20, 30 e 40 cm em sistema de ILP controlados com carga animal variável de bovinos da raça Purunã no período de outono/inverno, em braquiária Urochloa brizantha cv. MG 5 Vitória em sucessão a soja no verão. A máxima infiltração da água no solo se estabiliza em 30 cm de altura de pastejo da braquiária em pastejo contínuo em sistema ILP. O aumento da carga animal diminuiu a matéria seca da parte aérea de braquiária, infiltração de água e a qualidade estrutural do solo.

Grazing height and nitrogen fertilization strategy in black oat/maize succession / Altura de pastejo e estratégia de adubação nitrogenada na sucessão aveia preta/milho

This study was developed to examine the effect of combining nitrogen (N) fertilization strategies and pasture management heights on animal and grain production in an Integrated Crop-Livestock System. The experiment was carried out in the municipality of Abelardo Luz - SC, Brazil, between April 2017 and April 2018. A randomized-block design was adopted, with the treatments arranged in a 2×2 factorial arrangement with three replicates. The first factor was the height of the pasture managed under continuous grazing: high (HH, 20 cm) or low (LH, 12 cm). The second factor corresponded to the N application times: in the winter, in the pasture (NP), and in the summer, in the grain crop (NG), in a single N rate of 200 kg ha-1 as topdressing. The forage species used during the pasture phase was black oat (Avena strigosa Schreb), and the pasture was grazed by Nellore × Charolais crossbred steers with an initial body weight of 260 kg. The summer crop was maize (Zea mays). Average daily gain (ADG) and herbage allowance were higher in HH than in LH, whereas animal load was higher in HH. Between the N application times, the animal load was higher in NP. Pasture management height and N fertilization strategy did not affect the variables of number of rows per ear, number of grains per row, thousand-grain weight, or total grain yield, which overall averaged 14,090 kg ha-1. In conclusion, the inversion of nitrogen fertilization between the periods of winter pasture production and grain crop and the management height of the black oat pasture do not compromise the production of maize grains in the summer, or animal production per area. However, steer performance is greater (higher ADG) when the pasture is managed at 20 cm, whereas a high grazing intensity significantly reduces straw on the soil.(AU)

O objetivo deste estudo foi avaliar o efeito da combinação de estratégias de adubação nitrogenada e de alturas de manejo da pastagem sobre a produção animal e de grãos em um Sistema Integrado de Produção Agropecuária. O experimento foi conduzido no município de Abelardo Luz-SC, entre abril de 2017 a abril de 2018. O delineamento experimental utilizado foi blocos ao acaso e os tratamentos dispostos em arranjo fatorial 2x2 com três repetições. O primeiro fator foi a altura do pasto manejado com lotação contínua: alta altura (AA) (20 cm) e baixa altura (BA) (12 cm). O segundo fator foram as épocas de aplicação do nitrogênio: na pastagem de inverno (NP), e na cultura de grãos, no verão (NG), em dose única de 200 kg N ha-1 em cobertura. A espécie forrageira utilizada durante a fase pastagem foi a aveia preta (Avena strigosa Schreb) e o pastejo foi realizado por novilhos cruza Nelore x Charolês com peso corporal inicial de 260 kg. A cultura de verão foi o milho (Zea mays). O ganho médio diário (GMD) e a oferta de forragem foram maiores em AA comparativamente à BA, enquanto a carga animal foi maior em BA. Para as épocas de aplicação do N, a carga animal foi maior em NP. As variáveis número de fileiras por espiga, número de grãos por fileira e peso de mil grãos não foram afetadas pelo manejo da altura do pasto e nem pela estratégia de adubação nitrogenada, bem como a produção total de grãos, que apresentou média geral de 14.090 kg ha-1. Concluiu-se que a inversão da adubação nitrogenada entre os períodos de produção de pasto de inverno e de cultivo de grãos, e a altura de manejo da pastagem de aveia preta não comprometem a produção de grãos de milho no verão e nem a produção animal por área. Entretanto, o desempenho dos novilhos é maior (maior GMD) quando o pasto é manejado a 20 cm, enquanto a alta intensidade de pastejo reduz significativamente a palhada sobre o solo.(AU)

Defoliation intensity and leaf area index recovery in defoliated swards: implications for forage accumulation

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.

Defoliation intensity and leaf area index recovery in defoliated swards: implications for forage accumulation

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.(AU)

Influence of climatic conditions on tympanic temperature and milk production in grazing cows

The present study aimed to analyze large volumes of tympanic temperature (TT) data to identify its use as a physiological indicator of climatic conditions and its relationship with milk production in grazing cows under tropical lowland conditions. Three dairy farms and 21 multiparous early lactation cows were included in the study. Seven animals were equipped with tympanic temperature wireless sensors within each farm, and permanent information was collected hourly for 22 days on average. Ambient temperature (AT), relative humidity (RH), wind speed (WS), precipitation (PP), and THI information were obtained from meteorological stations located close to each farm. Statistical analyses included Spearman correlations and random coefficient regression models (P < 0.05). TT presented moderate and significant correlations with AT (0.35 to 0.49), SR (0.25 to 0.32), THI (0.35 to 0.49), and RH (-0.35 to -0.49). Climatic variables like AT, PP, SR, and WS were the most contributing factors to TT prediction (R2 =0.42 to 0.86). Grazing dairy cows in tropical scenarios accumulate heat during the day and dissipate it at nighttime, although higher producing animals deal with more problems to reach thermal homeostasis. Correlations between TT and daily milk production varied according to animal yield; however, higher TT values were related to the most productive cows. The effect of TT on milk production prediction was not conclusive among farms, possibly by animal management or others characteristics of the systems. TT determination through remote sensors allows a reliable diagnosis of the physiological temperature response to climatic conditions.

Sheep and goat feeding behavior profile in grazing systems

Feeding behavior analysis provides information about the relationships between animals and pastures. Therefore, this review aims to describe some aspects of the feeding behavior profiles of both sheep and goats in grazing systems. The structure of the pasture is a key factor in the feeding behavior of grazing animals. The amount of feed consumed in a given period of time is affected by the number of meals, duration and velocity of swallowing, changes in grazing time, bite rate, bite weight, and quality of ingested forage. The different phenological stages of forage also influence the animals strategies to optimize their intake, which consequently changes their behavioral activities. Sheep and goats tend to be more selective than cattle, and young animals are more selective than older animals; this selectivity characteristicis one of the most important aspects to be observed in pasture management. According to the degree of selectivity, the animals will intake forages of higher or lower nutritive quality. In addition, the intensity and distribution of their daily activities (grazing, ruminating, and resting)are influenced by several factors, such as the availability and nutritive value of the pasture, its management, the animal activity in the group, and the predominant climatic conditions of the region.(AU)

Sheep and goat feeding behavior profile in grazing systems

Feeding behavior analysis provides information about the relationships between animals and pastures. Therefore, this review aims to describe some aspects of the feeding behavior profiles of both sheep and goats in grazing systems. The structure of the pasture is a key factor in the feeding behavior of grazing animals. The amount of feed consumed in a given period of time is affected by the number of meals, duration and velocity of swallowing, changes in grazing time, bite rate, bite weight, and quality of ingested forage. The different phenological stages of forage also influence the animals’ strategies to optimize their intake, which consequently changes their behavioral activities. Sheep and goats tend to be more selective than cattle, and young animals are more selective than older animals; this selectivity characteristicis one of the most important aspects to be observed in pasture management. According to the degree of selectivity, the animals will intake forages of higher or lower nutritive quality. In addition, the intensity and distribution of their daily activities (grazing, ruminating, and resting)are influenced by several factors, such as the availability and nutritive value of the pasture, its management, the animal activity in the group, and the predominant climatic conditions of the region.

Grazing height targets for Alexandergrass pastures under continuous stocking in integrated crop-livestock system

The aim of this experiment was to identify grazing height targets for Alexandergrass pastures under continuous stocking in integrated crop-livestock system (ICLS). For this purpose, twelve pastures were cultivated into an ICLS area, and maintained at 10, 20, 30, or 40 cm using grazing goats. The following variables were analyzed: leaf and herbage mass, accumulation rate, and allowance; leaf:stem ratio; chemical composition of hand-plucked samples; stocking rate; average daily gain and gain per area. The data were submitted to regression and correlation analysis. Significance was set at 5% (P≤0.05). The main results were: i) herbage and leaf lamina mass increased linearly with grazing height, and pastures maintained at 20 cm already presented the minimum amount recommended for soil cover in ICLS; ii) animal performance achieved an upper asymptotic plateau in pastures maintained around 30-40 cm and it was highly correlated with both grazing height and forage availability (mass and allowance). Alexandergrass pastures under continuous stocking in ICLS should be maintained between 30-40 cm to improve both cover crop biomass and animal performance.(AU)

O objetivo deste trabalho foi identificar alturas de manejo para pastos de papuã sob lotação contínua em sistemas de integração lavoura-pecuária (ILP). Para tanto, doze pastos foram cultivados em uma área de ILP e mantidos em 10, 20, 30 ou 40 cm por meio de lotação contínua com caprinos. As seguintes variáveis foram analisadas: massa; taxa de acúmulo e oferta de forragem e de folhas; relação lâmina:colmo; composição química de amostras de simulação de pastejo; carga animal; ganho médio diário e produção animal por área. Os dados foram submetidos a análises de regressão e correlação. A significância adotada foi de 5% (P≤0,05). Os principais resultados foram: i) houve um aumento linear na massa de forragem e folhas com o aumento da altura de manejo e pastos com mais de 20 cm já apresentavam a quantidade mínima recomendada para cobertura de solo em ILP ii) o desempenho animal atingiu um platô assintótico nos pastos manejados entre 30-40 cm e foi altamente correlacionado com a altura de manejo e a disponibilidade de forragem (massa e oferta). Pastos de Papuã manejados sob lotação contínua em ILP devem ser mantidos entre 30-40 cm para favorecer a produção de biomassa de cobertura e o desempenho animal.(AU)

Manejo ecofisiológico das gramíneas Megathyrsus maximus (Panicum maximum) cv. Tanzânia, Mombaça e Massai / Ecophysiological management of grasses Megathyrsus maximus (Panicum maximum) cv. Tanzânia, Mombaça and Massai / Manejo ecofisiológico de las gramíneas Megathyrsus maximus (Panicum maximum) cv. Tanzânia, Mombaça e Massai

Objetivou-se com esta revisão apresentar informações práticas referentes ao manejo de algumas subespécies de gramíneas tropicais da espécie Megathyrsus maximus e sua relação com a composição bromatológica e resposta de crescimento a adubação e ao processo de colheita pelos animais, bem como o efeito deste sobre a estrutura do pasto. Devido a sazonalidade da intensidade luminosa e principalmente do regime de chuvas é importante esclarecer que para os sistemas de produção a pasto (sistema de lotação contínua ou intermitente) devem ser executadas estratégias para o período de entressafra (secas), estas estratégias podem ser de suplementação (com concentrado e/ou volumoso), variação da taxa de lotação, ou ambas. Independentemente de outras variáveis para o capim-Massai e para as outras cultivares estudadas o período de colheita ideal se dá em plantas com 3,5±0,5 folhas expandidas. De maneira geral para Megathyrsus maximus cv Tanzânia sob regime de lotação contínua e carga animal variável, recomenda-se a altura de pastejo entre 40 e 60 cm, e para lotação intermitente (pastejo rotacionado) o ideal é a entrada com ±65 cm de dossel (parte aérea) e 25 a 30 cm para o resíduo pós pastejo. Ao ser utilizado como silagem este mesmo cultivar deve ser cortado entre 42 e 63 dias após o plantio. Para o capim-Mombaça em regime de lotação intermitente a entrada dos animais deve ocorrer com altura aproximada de 80 cm e saída de 40 cm, e para lotação contínua a altura ideal é de 50 a 75 cm. O manejo correto das pastagens é um processo complexo devido às variações das condições climáticas ao longo do ano, diferentes tipos de solo (com características físicas e químicas diferentes), categorias e hábitos de pastejo das diferentes espécies animais...

The aim with this review was to present practical information regarding the management of some tropical grasses species of the Megathyrsus maximus species and its relationship with bromatological composition and growth response to fertilization and the harvesting process by animals, as well as the effect of this on the pasture structure. Due to the seasonality of the light intensity and mainly the rainfall regime it is important to clarify that for pasture production systems (continuous or intermittent stocking system) strategies should be implemented for the off-season forage production (dry), it they may be supplementation (with concentrate and/or voluminous food), stocking rate variation, or both. Regardless of other variables for Massai grass and for the other cultivars studied, the ideal harvest period occurs in plants with 3.5±0.5 leaves expanded. In general for Megathyrsus maximus cv Tanzania under continuous stocking (continuous grazing) and variable number of animals, grazing height between 40 and 60 cm is recommended, and for intermittent stocking (rotated grazing) the entry with ±65 cm canopy (aerial part) is ideal and 25 to 30 cm for the residue after grazing. When used with silage this same cultivar should be cut between 42 and 63 days after planting. For Mombasa grass under intermittent stocking, the animals should enter at a height of approximately 80 cm and exit at 40 cm, and for continuous stocking the ideal height is 50 to 75 cm. Correct pasture management is a complex process due to varying climatic conditions throughout the year, different soil types (with different physical and chemical characteristics), categories and grazing habits of different animal species, and the diversity of cultivars of grass that are released without studies necessary for the knowledge of the...

El objetivo con esta revisión fue presentar información práctica sobre el manejo de algunas subespecies de especies de gramíneas tropicales de Megathyrsus maximusy su relación con la composición bromatológica y larespuesta de crecimiento a la fertilización y el proceso de recolección por parte de los animales, así como el efecto de esto en el estructura del pasto. Debido a la estacionalidad de la intensidad de la luz y principalmente al régimen de lluvias, es importante aclarar que para los sistemas de producción de pasturas (sistema de pastoreo continuo o intermitente) se deben implementar estrategias fuera de temporada (seco), pueden ser suplementos (con concentrado y/o forraje), variación de la tasa de almacenamiento de los animales, o ambos. Independientemente de otras variables para el pasto Massai y para los otros cultivares estudiados, el período ideal de cosecha ocurre en plantas con 3.5 ±0.5 hojas expandidas. En términos generales, para Megathyrsus maximuscv Tanzania, con almacenamiento continuo ( pastoreo continuo) y númerode animales variable, se recomienda una altura de pastoreo entre 40 y 60 cm, y para el almacenamiento intermitente (pastoreo rotativo), la entrada con dosel (parte aérea) de ±65 cm es ideal, y de 25 a 30 cm para el residuo después del pastoreo. Cuando se usa con ensilaje, este mismo cultivar debe cortarse entre 42 y 63 días después de la siembra. Para los pastos de Mombasa con almacenamiento intermitente los animales deben ingresar a una altura de aproximadamente 80 cm y salir a 40 cm, y para el almacenamiento continuo la altura ideal es de 50 a 75 cm. El manejo correcto de los pastos es un proceso complejo debido a las condiciones climáticas variables durante todo el año, los diferentes tipos de suelo (con diferentes características físicas y químicas), las categorías y los hábitos de pastoreo de diferentes especies animales, y la gran diversidad de cultivares de pasto que se libera sin...

Manejo ecofisiológico das gramíneas Megathyrsus maximus (Panicum maximum) cv. Tanzânia, Mombaça e Massai / Ecophysiological management of grasses Megathyrsus maximus (Panicum maximum) cv. Tanzânia, Mombaça and Massai / Manejo ecofisiológico de las gramíneas Megathyrsus maximus (Panicum maximum) cv. Tanzânia, Mombaça e Massai

Objetivou-se com esta revisão apresentar informações práticas referentes ao manejo de algumas subespécies de gramíneas tropicais da espécie Megathyrsus maximus e sua relação com a composição bromatológica e resposta de crescimento a adubação e ao processo de colheita pelos animais, bem como o efeito deste sobre a estrutura do pasto. Devido a sazonalidade da intensidade luminosa e principalmente do regime de chuvas é importante esclarecer que para os sistemas de produção a pasto (sistema de lotação contínua ou intermitente) devem ser executadas estratégias para o período de entressafra (secas), estas estratégias podem ser de suplementação (com concentrado e/ou volumoso), variação da taxa de lotação, ou ambas. Independentemente de outras variáveis para o capim-Massai e para as outras cultivares estudadas o período de colheita ideal se dá em plantas com 3,5±0,5 folhas expandidas. De maneira geral para Megathyrsus maximus cv Tanzânia sob regime de lotação contínua e carga animal variável, recomenda-se a altura de pastejo entre 40 e 60 cm, e para lotação intermitente (pastejo rotacionado) o ideal é a entrada com ±65 cm de dossel (parte aérea) e 25 a 30 cm para o resíduo pós pastejo. Ao ser utilizado como silagem este mesmo cultivar deve ser cortado entre 42 e 63 dias após o plantio. Para o capim-Mombaça em regime de lotação intermitente a entrada dos animais deve ocorrer com altura aproximada de 80 cm e saída de 40 cm, e para lotação contínua a altura ideal é de 50 a 75 cm. O manejo correto das pastagens é um processo complexo devido às variações das condições climáticas ao longo do ano, diferentes tipos de solo (com características físicas e químicas diferentes), categorias e hábitos de pastejo das diferentes espécies animais...(AU)

The aim with this review was to present practical information regarding the management of some tropical grasses species of the Megathyrsus maximus species and its relationship with bromatological composition and growth response to fertilization and the harvesting process by animals, as well as the effect of this on the pasture structure. Due to the seasonality of the light intensity and mainly the rainfall regime it is important to clarify that for pasture production systems (continuous or intermittent stocking system) strategies should be implemented for the off-season forage production (dry), it they may be supplementation (with concentrate and/or voluminous food), stocking rate variation, or both. Regardless of other variables for Massai grass and for the other cultivars studied, the ideal harvest period occurs in plants with 3.5±0.5 leaves expanded. In general for Megathyrsus maximus cv Tanzania under continuous stocking (continuous grazing) and variable number of animals, grazing height between 40 and 60 cm is recommended, and for intermittent stocking (rotated grazing) the entry with ±65 cm canopy (aerial part) is ideal and 25 to 30 cm for the residue after grazing. When used with silage this same cultivar should be cut between 42 and 63 days after planting. For Mombasa grass under intermittent stocking, the animals should enter at a height of approximately 80 cm and exit at 40 cm, and for continuous stocking the ideal height is 50 to 75 cm. Correct pasture management is a complex process due to varying climatic conditions throughout the year, different soil types (with different physical and chemical characteristics), categories and grazing habits of different animal species, and the diversity of cultivars of grass that are released without studies necessary for the knowledge of the...(AU)

El objetivo con esta revisión fue presentar información práctica sobre el manejo de algunas subespecies de especies de gramíneas tropicales de Megathyrsus maximusy su relación con la composición bromatológica y larespuesta de crecimiento a la fertilización y el proceso de recolección por parte de los animales, así como el efecto de esto en el estructura del pasto. Debido a la estacionalidad de la intensidad de la luz y principalmente al régimen de lluvias, es importante aclarar que para los sistemas de producción de pasturas (sistema de pastoreo continuo o intermitente) se deben implementar estrategias fuera de temporada (seco), pueden ser suplementos (con concentrado y/o forraje), variación de la tasa de almacenamiento de los animales, o ambos. Independientemente de otras variables para el pasto Massai y para los otros cultivares estudiados, el período ideal de cosecha ocurre en plantas con 3.5 ±0.5 hojas expandidas. En términos generales, para Megathyrsus maximuscv Tanzania, con almacenamiento continuo ( pastoreo continuo) y númerode animales variable, se recomienda una altura de pastoreo entre 40 y 60 cm, y para el almacenamiento intermitente (pastoreo rotativo), la entrada con dosel (parte aérea) de ±65 cm es ideal, y de 25 a 30 cm para el residuo después del pastoreo. Cuando se usa con ensilaje, este mismo cultivar debe cortarse entre 42 y 63 días después de la siembra. Para los pastos de Mombasa con almacenamiento intermitente los animales deben ingresar a una altura de aproximadamente 80 cm y salir a 40 cm, y para el almacenamiento continuo la altura ideal es de 50 a 75 cm. El manejo correcto de los pastos es un proceso complejo debido a las condiciones climáticas variables durante todo el año, los diferentes tipos de suelo (con diferentes características físicas y químicas), las categorías y los hábitos de pastoreo de diferentes especies animales, y la gran diversidad de cultivares de pasto que se libera sin...(AU)

Effect of post-grazing residual leaf blade-length on the regrowth vigor of Piatã grass grazed under intermittent stocking / Efeito do comprimento residual de lâmina foliar pós-pastejo no vigor de rebrotação de capim Piatã pastejado sob lotação intermitente

The objective of this study was to evaluate the effect of post-grazing residual leaf blades (RLB) of different lengths on the morphogenic and structural characteristics of Urochloa brizantha 'Piatã' grazed upon by beef cattle. A completely randomized design was used, with three RLB lengths (2, 4, and 6 cm) and two paddocks as replicates over two grazing seasons (wet and wet-dry transition). To monitor the weekly forage growth, two representative clumps and 48 tillers per treatment were marked after grazing. The procedure continued until the plants reached the target pre-grazing height of 35-40 cm. Morphogenic characteristics were not affected by the treatments or seasons, with minor changes observed in mean sheath length (MSL) within season and tiller population density (TPD). The MSL reached its peak value of 210.37 mm during the wet season relative to 175.89 mm during the wet-dry transition. The TPD reached its lowest value (680 tillers m <->2) at the highest defoliation intensity (2 cm) relative to that at the lowest defoliation intensity (720 tillers m <->2). The different RLB lengths modified canopy height variably; canopy height was the highest with the 6 cm leaves (24.31 cm), but did not vary between the 2 cm and 4 cm leaves. The post-grazing leaf area index and interception of photosynthetically active radiation were modified by season. The highest defoliation intensity (2 cm) increased the rest period by seven days when compared with the lowest defoliation intensity (6 cm).(AU)

Objetivou-se avaliar o efeito de diferentes comprimentos de lâmina foliar residual (RLF) pós-pastejo sobre as respostas morfogênicas e estruturais do capim Urochloa brizantha cv. Piatã pastejado por bovinos de corte. O delineamento experimental utilizado foi o inteiramente casualizado, com três RLF (2, 4 e 6 cm) e duas repetições de piquetes, ao longo de duas estações (águas e transição águas-seca). Após o pastejo dos bovinos eram marcadas duas touceiras representativas, e 48 perfilhos por tratamento, para o acompanhamento semanal do crescimento forrageiro, durante o período necessário para as plantas atingirem as metas de alturas pré-pastejo determinada entre 35 e 40 cm. As características morfogênicas não diferenciaram entre os tratamentos e estações, que promoveu pouca alteração nas características estruturais, apenas comprimento médio de bainha (CMB) na estação e densidade populacional de perfilhos (DPP). O maior valor encontrado para CMB, foi na estação das águas 210,37 mm versus 175,89 mm para a transição. A DPP apresentou o menor valor (680 perfilhos m <->2) com a maior remoção (2 cm) em relação ao de menor remoção (720 perfilhos m <->2). As diferentes remoções de lâmina foliar proporcionou alteração na altura de saída, em que o tratamento 6 cm apresentou a maior altura (24,31 cm), não diferenciando os demais tratamentos. O índice de área foliar (IAF) e interceptação da radiação fotossinteticamente ativa (IRFA) foram modificados no pós pastejo. A maior remoção de lâmina foliar (2 cm) teve o seu período de descanso (PD) aumentado em 7 dias, em relação a menor remoção (6 cm).(AU)

Effect of goat grazing of black oat with different plots and corn yield with different nitrogen levels in succession / Efeito do pastejo de caprinos com diferentes lotações em pastagem de aveia preta e rendimento de milho com distintas adubações nitrogenadas em sucessão

This study aimed to evaluate the performance of goats grazing black oat (Avena strigosa) fed with different levels of supplementation as well as its influence on soil resistance to penetration and corn yield grown in succession with increasing levels of N top dressing. In the winter, ten monthold Boer goats received supplementation levels at 0, 5, 10, and 15 g kg-1 of body weight, in continuous stocking grazing, with variable stocking rate, and with a control without grazing. In the summer, the main plots were divided into sub-plots and N was applied at increasing levels in top dressing on the corn crop (0, 50, 100, and 150 kg ha-1 of N as urea). In the winter, the forage sward mass and its forage production, stocking rate, animal live weight gain and soil resistance to penetration were evaluated. In the summer, the corn yield components were evaluated. Stocking rate increased as supplement levels increased, which also increased the intensity of trampling and hence the resistance to soil penetration in the surface layer without affecting the grain yield of the corn grown in succession. When winter grazing is in accordance with the forage height and the fertilization, it reduces the need for nitrogen in the summer to obtain the corn yield produced in ungrazed areas in the winter.

Este estudo teve por objetivo avaliar diferentes níveis de suplementação em caprinos, sob pastejo de aveia preta, e sua influência na resistência do solo à penetração e no rendimento de grãos de milho, cultivado em sucessão com crescentes doses de N em cobertura. No inverno os tratamentos se constituíram do uso de suplemento alimentar correspondente a 0, 5, 10 e 15 g kg-1 do peso vivo de fêmeas de caprinos da raça Boer, com 10 meses de idade, em pastejo de aveia preta cv. IAPAR 61 e um tratamento sem pastejo. No verão as parcelas foram subdivididas e aplicadas doses crescentes de N em cobertura na cultura do milho (0, 50, 100 e 150 kg ha-1 de N na forma de ureia). No inverno foram avaliados: altura de dossel, massa de forragem e produção da forragem; carga e ganho de peso animal; e resistência do solo à penetração. No verão foram avaliados os componentes de rendimento do milho. Maiores níveis de suplementação, no inverno, aumenta a capacidade suporte da área de pastagem, o que eleva a intensidade de pisoteio e, consequentemente, a resistência do solo à penetração na camada superficial, sem afetar, no entanto, o rendimento de grãos de milho cultivado em sucessão. O pastejo no inverno, quando realizado respeitando a altura da forragem e adubação, reduz a necessidade de N em cobertura no verão para a obtenção do mesmo rendimento de grãos de milho de áreas sem pastejo no inverno.

Effect of goat grazing of black oat with different plots and corn yield with different nitrogen levels in succession / Efeito do pastejo de caprinos com diferentes lotações em pastagem de aveia preta e rendimento de milho com distintas adubações nitrogenadas em sucessão

This study aimed to evaluate the performance of goats grazing black oat (Avena strigosa) fed with different levels of supplementation as well as its influence on soil resistance to penetration and corn yield grown in succession with increasing levels of N top dressing. In the winter, ten monthold Boer goats received supplementation levels at 0, 5, 10, and 15 g kg-1 of body weight, in continuous stocking grazing, with variable stocking rate, and with a control without grazing. In the summer, the main plots were divided into sub-plots and N was applied at increasing levels in top dressing on the corn crop (0, 50, 100, and 150 kg ha-1 of N as urea). In the winter, the forage sward mass and its forage production, stocking rate, animal live weight gain and soil resistance to penetration were evaluated. In the summer, the corn yield components were evaluated. Stocking rate increased as supplement levels increased, which also increased the intensity of trampling and hence the resistance to soil penetration in the surface layer without affecting the grain yield of the corn grown in succession. When winter grazing is in accordance with the forage height and the fertilization, it reduces the need for nitrogen in the summer to obtain the corn yield produced in ungrazed areas in the winter.(AU)

Este estudo teve por objetivo avaliar diferentes níveis de suplementação em caprinos, sob pastejo de aveia preta, e sua influência na resistência do solo à penetração e no rendimento de grãos de milho, cultivado em sucessão com crescentes doses de N em cobertura. No inverno os tratamentos se constituíram do uso de suplemento alimentar correspondente a 0, 5, 10 e 15 g kg-1 do peso vivo de fêmeas de caprinos da raça Boer, com 10 meses de idade, em pastejo de aveia preta cv. IAPAR 61 e um tratamento sem pastejo. No verão as parcelas foram subdivididas e aplicadas doses crescentes de N em cobertura na cultura do milho (0, 50, 100 e 150 kg ha-1 de N na forma de ureia). No inverno foram avaliados: altura de dossel, massa de forragem e produção da forragem; carga e ganho de peso animal; e resistência do solo à penetração. No verão foram avaliados os componentes de rendimento do milho. Maiores níveis de suplementação, no inverno, aumenta a capacidade suporte da área de pastagem, o que eleva a intensidade de pisoteio e, consequentemente, a resistência do solo à penetração na camada superficial, sem afetar, no entanto, o rendimento de grãos de milho cultivado em sucessão. O pastejo no inverno, quando realizado respeitando a altura da forragem e adubação, reduz a necessidade de N em cobertura no verão para a obtenção do mesmo rendimento de grãos de milho de áreas sem pastejo no inverno.(AU)