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The determination of biomass flows can assist on improving pasture fertilization techniques, contributing to identify the best management methods and, in relation the use of fertilizers. Nitrogen deficiency in pastures can reduce forage production. On the other hand, there is an environmental concern on nitrogen (N) losses when this nutrient is used in excess and this concern guides the search for new grazing systems that optimize its use. Leaf biomass flow, intensity and frequency of defoliation were evaluated in Alexandergrass (Urochloa plantaginea (Link) Hitch) fertilized with Zero, 100, 200 or 300 kg/ha nitrogen (N) as urea. The grazing method was put and take stocking in order to keep the forage mass at 3,000 kg/ha DM. The experimental animals were Angus heifers with an initial age of 15 months and body weight of 241.5±5 kg. The experimental design was completely randomized following a repeated measure arrangement, with four treatments and variable number of experimental units. The highest growth of leaf blades was achieved with 100 kg/ha N. Senescence and intake flows and defoliation intensity were similar among the N levels used. The frequency of return to the same tiller (days) was influenced by N levels and evaluation periods. Our findings recommend the use of 100 kg/ha N in Alexandergrass pasture. A determinação dos fluxos de biomassa pode auxiliar no aperfeiçoamento das técnicas de adubação de pastagens, pois contribui para a identificação das melhores formas de manejo, que incluem o uso de fertilizantes. A deficiência de N em pastagens pode reduzir a produção de forragem. Por outro lado, existe uma preocupação ambiental relativa às perdas de nitrogênio (N) quando esse nutriente é utilizado em excesso e essa preocupação direciona a pesquisa para novos sistemas de pastejo que otimizem o uso deste nutriente. Os fluxos de biomassa foliar, a intensidade e frequência de desfolha foram avaliados quando o papuã (Urochloa plantaginea (Link) Hitch) foi adubado com Zero, 100, 200 ou 300 kg/ha de nitrogênio (N), na forma de ureia. O método de pastejo foi contínuo com número variável de animais para manter a massa de forragem em 3000 kg/ha de MS. Os animais experimentais foram bezerras Angus com idade e peso corporal médio inicial de 15 meses e 241,5±5 kg, respectivamente. O delineamento experimental foi inteiramente casualizado, com medidas repetidas no tempo, com quatro tratamentos e número variável de unidades experimentais. O uso de 100 kg/ha de N proporcionou maior fluxo de crescimento de lâminas foliares. Os fluxos de senescência e de consumo e a intensidade de desfolha foram similares nos níveis de N utilizados. A frequência de retorno dos animais ao mesmo perfilho (dias) foi influenciado pelos níveis de N e períodos de avaliação. É recomendada a utilização de 100 kg/ha de N em pastagem de papuã.

The experiment evaluated the morphogenesis and structure of Tifton 85 (Cynodon spp.) cultivated in subtropical climate and fertilized with nitrogen (N). The experiment was a completely randomized design with four levels of N (Zero; 75; 150 or 225 kg ha-1) in nine replicates per area. The experimental animals were Suffolk female lambs. The grazing method was continuous to maintain the sward height at 15 cm ± 10%. The stem expansion increased by 0.000027 cm degree-days-1 to each kg N applied (linear model). According to nonlinear model, the highest stem expansion (0.0226 cm degree-days-1) was observed with the use 220.1 kg ha-1 N. The leaf lifespan fitted a linear regression model, with increase of 50 degree-days leaf -1, comparing the levels zero and 225 kg ha-1 of N. According to nonlinear regression model, the longest leaf lifespan (407.1 degree-days) was observed with the use 208.8 kg ha-1 N. With the maintenance of sward height at approximately 15 cm, we recommended to use 200 kg ha-1 N in Tifton 85 cultivated in subtropical climate. RESUMO. Objetivou-se estudar a morfogênese e a estrutura do Tifton 85 (Cynodon spp.) cultivado em clima subtropical e adubado com nitrogênio (N). O delineamento experimental foi o inteiramente casualizado com quatro níveis de N (Zero; 75; 150 e 225 kg ha-1) em nove repetições por área. Os animais experimentais foram borregas das raças Suffolk. O método de pastejo foi o contínuo para manter a altura do dossel em 15 cm ± 10%. A taxa de expansão de colmos aumenta 0,000027 cm graus-dia-1 para cada kg de N aplicado (modelo linear). De acordo com o modelo não linear, o maior valor de taxa de expansão (0,0226 cm graus-dia-1) foi observado com 220,1 kg ha-1 de N. A duração de vida das folhas ajustou-se ao modelo de regressão linear, com aumento de 50 graus-dia folha-1 comparando-se às doses de 0 e 225 kg ha-1 de N. Conforme o modelo não linear, o maior valor de duração de vida da folha (407,1 graus-dia) foi atingido com 208,8 kg ha-1 de N. Com a manutenção da altura do dossel em aproximadamente 15 cm de altura, recomenda-se utilizar 200 kg ha-1 de N em Tifton 85 cultivado em clima subtropical.

This experiment evaluated forage production, sward structure, stocking rate, weight gain per area and nutritive value of forage as grazed by beef heifers on Alexandergrass (Urochloa plantaginea (Link) Hitch) pasture fertilized with nitrogen (N): 0; 100; 200 or 300 kg of N/ha. The experiment was a completely randomized design following a repeated measurement arrangement. The experimental animals were Angus heifers with initial age and weight of 15 months and 241.5±5 kg, respectively. The grazing method was continuous, with put-and-take stocking. N utilization, regardless of the level, increase by 25% the daily forage accumulation rate and the weight gain per area by 23%. The level of 97.2 kg N/ha leads to a higher leaf blade mass and increases by 20% the leaf:stem ratio. Alterations in sward structure changes the nutritive value of forage as grazed. The utilization of 112.7 kg of N/ha allows the highest stocking rate (2049.8 kg of BW/ha), equivalent to 7.5 heifers per hectare. Nesse experimento objetivou-se estudar a produção de forragem, estrutura do dossel, taxa de lotação, ganho de peso por área e o valor nutritivo da forragem aparentemente consumida por bezerras de corte em pastagem de papuã (Urochloa plantaginea (Link) Hitch) adubada com nitrogênio (N): 0; 100; 200 ou 300 kg/ha. O delineamento experimental foi inteiramente casualizado, com medidas repetidas no tempo. Os animais experimentais foram bezerras da raça Angus com idade e peso iniciais de 15 meses e 241±5 kg, respectivamente. O método de pastejo foi contínuo, com número variável de animais. A utilização de N, independente da quantidade, aumentou em 25% a taxa de acúmulo de forragem. A adubação com N proporciona aumento de 25% na taxa de acúmulo diária de forragem e 23% no ganho de peso por área. A dose de 97,2 kg/ha de N proporciona maior massa de lâminas foliares e aumento de 20% na razão folha:colmo. As alterações na estrutura do dossel modificam o valor nutritivo da forragem da simulação de pastejo. A dose de 112,7 kg/ha de N permite a manutenção da maior taxa de lotação (2049,8 kg/ha de PC), equivalendo a 7,5 bezerras por hectare.

This study was conducted to evaluate the ingestive behavior, displacement patterns and meal dynamics of beef heifers in Alexandergrass pasture (Urochloa plantaginea (Link.) Hitch) receiving different amounts of oat grain: 0, 0.80 and 1.12% of body weight (BW). The grazing method was continuous with put-and-take stocking. The experimental design was completely randomized following a repeated measure arrangement. The grazing time decreased and the idling time increased when beef heifers were supplemented, independently of supplement amount, while the rumination time was similar across supplement amounts. The number of feeding stations per minute and the number of steps taken between each feeding station were similar regardless of supplementation. When receiving 1.12% of BW of oat grain, heifers remained longer in each feeding station and took fewer steps per minute. The number of meals decreased and the duration of breaks between meals increased when heifers received oat grain. The duration of each meal was similar for heifers receiving supplement than for those that did not. Understanding how animals adjust their grazing behavior and cope with changing environmental dynamics is essential for the development of management strategies designed to optimize animal production.

Foi avaliado o efeito de diferentes frequências de suplementação sobre o uso da pastagem (fluxo de tecido foliar, intensidade e frequência de desfolhação) em papuã (Urochloa plantaginea (Link) Hitch). As bezerras de corte permaneceram exclusivamente em pastejo ou receberam grão inteiro de aveia durante sete ou cinco dias por semana (de segunda à sexta feira). A quantidade semanal de suplemento foi similar nas duas frequências. O delineamento experimental foi inteiramente casualizado, com medidas repetidas no tempo, três tratamentos e duas repetições de área. Os fluxos de tecidos, a frequência e intensidade de desfolhação são similares quando as bezerras permanecem exclusivamente em pastejo ou recebem grão de aveia em diferentes frequências. The effects of several supplementation frequencies on forage use (leaf tissue flow, intensity and frequency of defoliation) in Alexandergrass (Urochloa plantaginea (Link) Hitch) were evaluated. The heifers remained exclusively on pasture or received whole oat grain seven days/week or five days/week (Monday to Friday). The weekly amount of supplement was similar for both frequencies. The experimental design was completely randomized following a repeated measure arrangement, with three treatments and two area replications. Leaf tissue flow, frequency and intensity of defoliation are similar when heifers remain exclusively on Alexandergrass pasture or receive oat grain on different frequencies.

The experiment aimed at evaluating leaf biomass flow, intensity and frequency of defoliation of Alexandergrass (Urochloa plantaginea (Link) Hitch) by beef heifers exclusively on pasture or that grazed and received protein salt. A completely randomized experimental design was used with repeated measures over time, two treatments and two area replications, with three Angus test heifers by paddock. Leaf blade intake flow is 18% superior for heifers exclusively on pasture. Grazing intensity (59.8%) is similar when heifers receive protein salt or not. Heifers receiving protein salt reduce by one day the defoliation frequency of tillers. The supply of protein salt for beef heifers grazing Alexandergrass affects the herbivore-plant relationship, decreasing intake flow and leaf blade defoliation frequency.

A joint data analysis was performed to characterize forage intake rate and patterns of use of time by grazing heifers in cold season pastures. Heifers received or not energetic supplementation at different phenological stages of grasses (vegetative, pre-flowering and flowering). Experiments involved 360 heifers with initial age of eight months and average body weight of 145 ± 17 kg, on continuous grazing method and variable number of animals. Supplementaed heifers consumed 17.0% less forage and 22.2% less leaf blades than heifers exclusively on pasture. Grazing activity was concentrated in the afternoon shift, regardless of the feeding system and phenological stages evaluated, with the longest event of rumination during the night. Forage intake rate is similar, regardless of supplement intake and phenological stages of grasses. RESUMO Foi realizada uma análise conjunta de dados, com o objetivo de caracterizar a taxa de ingestão de forragem e os padrões de uso do tempo por novilhas em pastejo de forrageiras de estação fria. Essas novilhas recebiam ou não suplemento energético nos diferentes estádios fenológicos do pasto (vegetativo, pré-florescimento e florescimento). Os experimentos envolveram 360 novilhas, com idade inicial de oito meses e peso corporal médio de 145 ± 17 kg. O método de pastejo foi o de lotação contínua, com número variável de animais. Novilhas recebendo suplemento consumiram 17,0% a menos de forragem e 22,2% a menos de lâminas foliares que as novilhas exclusivamente em pastejo. A atividade de pastejo foi concentrada no turno da tarde, independente do sistema alimentar e dos estádios fenológicos avaliados, e no turno da noite acontece o evento mais longo de ruminação. A taxa de ingestão de forragem é semelhante, independente do consumo de suplemento e dos estádios fenológicos dos pastos.

This study investigated the tiller dynamics of Italian ryegrass (Lolium multiflorum Lam) under low and high stocking rates. These rates were determined by heifers exclusively on pasture or grazing and supplemented with oats and corn grain. The experimental design was completely randomized with repeated measurements over time, with two stocking rates, three and six replications of area for low and high stocking rates, respectively. The appearance rate (1.0 tillers tiller -1 m -2 ), survival rate (0.8 tillers tiller -1 m -2 ), population stability index (1.6) and site occupation (0.3) were similar for high and low stocking rates. The tiller density was similar for different stocking rates. The first generation of tillers was 56% of the tiller population at end of the ryegrass cycle. The increase by 22.5% in the stocking rate derived from the use of supplements for grazing heifers did not alter the tiller dynamics of ryegrass.