Effects of increasing nitrogen levels in Mombasa grass on pasture characteristics, chemical composition, and beef cattle performance in the humid tropics of the Amazon.

Improving beef cattle production in pasture-based systems without expanding agricultural land has been the focus of several studies over the last decades. Nitrogen fertilization is one of the available strategies with high potential to optimize cattle performance in tropical systems. This study aimed to evaluate the effects of increasing nitrogen levels (150, 300, and 450 kg ha-1 of N year-1) in Megathyrsus maximus cv. Mombasa in the humid tropics of the Amazon. The following parameters were evaluated: pasture agronomic characteristics, herbage chemical composition, and beef cattle performance. A total of 24 nine-month-old Nellore bulls with initial mean weight of 173 ± 1.95 kg were used for the performance test. The experimental design was a randomized block with three treatments. Herbage mass and leaf mass contents were increased by the highest nitrogen level (P < 0.05). Nitrogen levels elevated the forage accumulation rate, final leaf blade length, and pre-grazing canopy height(P < 0.05). The crude protein content increased at the highest N level (P < 0.05). The neutral detergent fiber and acid detergent fiber contents decreased with increasing N levels. The stocking rate and total weight gain per hectare were higher in bulls grazing pastures fertilized with 450 compared with 150 kg ha-1 of N year-1(P < 0.05). The average daily gain was influenced by N levels (P < 0.05). Nitrogen levels at 300 and 450 kg increased animal weight gain and productivity per area by increasing forage yield and improving the chemical composition of Mombasa grass.

Structural characteristics and chemical composition of andropogon grass pasture managed under different defoliation intensities and rest periods / Características estruturais e composição química do pasto de capim-andropógon manejado sob diferentes intensidades de desfolha e períodos de descanso

This study aimed to evaluate the agronomic, structural traits and chemical composition of andropogon grass subjected to different defoliation intensities and rest periods. Two defoliation intensities (15 and 30 cm) and four rest periods (25; 35, 45 and 55 days) were evaluated in a factorial completely randomized design, with four replications. The rest period promoted a linear decreasing effect (P <0.05) on the dry biomass of leaf blades in the two defoliation intensities. The dry biomass of stems showed an increasing linear effect (P <0.05) according to the rest periods in the two defoliation intensities. Production was recorded at 2427.71; 2907.39; 3325.72 and 3749.45 kg ha−1 for the periods of 25; 35; 45 and 55 days, respectively. The dry matter content showed an increasing linear effect (P <0.05) as a function of the rest periods evaluated in the two defoliation intensities. The rest period indicated a decreasing linear trend (P <0.05) for the crude protein content in the two defoliation intensities. A decrease of 0.9 and 0.7 g kg−1 was verified for each day of the rest period. For each additional day in the rest period, there was an increase of 1.2 and 1.5 g kg−1 DM in the neutral detergent fiber content at intensities of 15 and 30 cm. The andropogon grass pasture managed with a 25-day rest period and defoliation intensity of 30 cm showed high leaf/stem ratio and good nutritional value.(AU)

Objetivou-se avaliar as características agronômicas, estruturais e a composição química da forragem de capim-andropogon submetido e diferentes intensidades de desfolha e períodos de descanso. Foram avaliadas duas intensidades de desfolha (15 e 30 cm) e quatro períodos de descanso (25; 35; 45 e 55 dias) em delineamento inteiramente casualizado em arranjo fatorial, com quatro repetições. O período de descanso proporcionou efeito linear decrescente (P<0,05) sobre a biomassa de lâminas foliares secas nas duas intensidades de desfolha. A biomassa de colmos secos apresentou efeito linear crescente (P<0,05) em função dos períodos de descanso nas duas intensidades de desfolha. Foi registrado produção de 2427,71; 2907,39; 3325,72 e 3749,45 kg ha-1 para os períodos de 25;35; 45 e 55 dias, respectivamente. O teor de matéria seca apresentou efeito linear crescente (P<0,05) em função dos períodos de descanso avaliados nas duas intensidades de desfolha. O período de descanso indicou comportamento linear decrescente (P<0,05) para o teor de proteína bruta nas duas intensidades de desfolha. Foi registrado diminuição de 0,9 e 0,7 g kg-1 para cada dia de período de descanso. Para cada dia a mais de período de descanso foi registrado aumento de 1,2 e 1,5 g kg-1 de MS no teor de fibra em detergente neutro nas intensidades de 15 e 30 cm. O pasto de capim-andropógon manejado com período de descanso de 25 dias e intensidade de desfolha de 30 cm apresentou alta relação folha/colmo e bom valor nutricional.(AU)

Structural characteristics and chemical composition of andropogon grass pasture managed under different defoliation intensities and rest periods / Características estruturais e composição química do pasto de capim-andropógon manejado sob diferentes intensidades de desfolha e períodos de descanso

This study aimed to evaluate the agronomic, structural traits and chemical composition of andropogon grass subjected to different defoliation intensities and rest periods. Two defoliation intensities (15 and 30 cm) and four rest periods (25; 35, 45 and 55 days) were evaluated in a factorial completely randomized design, with four replications. The rest period promoted a linear decreasing effect (P <0.05) on the dry biomass of leaf blades in the two defoliation intensities. The dry biomass of stems showed an increasing linear effect (P <0.05) according to the rest periods in the two defoliation intensities. Production was recorded at 2427.71; 2907.39; 3325.72 and 3749.45 kg ha−1 for the periods of 25; 35; 45 and 55 days, respectively. The dry matter content showed an increasing linear effect (P <0.05) as a function of the rest periods evaluated in the two defoliation intensities. The rest period indicated a decreasing linear trend (P <0.05) for the crude protein content in the two defoliation intensities. A decrease of 0.9 and 0.7 g kg−1 was verified for each day of the rest period. For each additional day in the rest period, there was an increase of 1.2 and 1.5 g kg−1 DM in the neutral detergent fiber content at intensities of 15 and 30 cm. The andropogon grass pasture managed with a 25-day rest period and defoliation intensity of 30 cm showed high leaf/stem ratio and good nutritional value.

Objetivou-se avaliar as características agronômicas, estruturais e a composição química da forragem de capim-andropogon submetido e diferentes intensidades de desfolha e períodos de descanso. Foram avaliadas duas intensidades de desfolha (15 e 30 cm) e quatro períodos de descanso (25; 35; 45 e 55 dias) em delineamento inteiramente casualizado em arranjo fatorial, com quatro repetições. O período de descanso proporcionou efeito linear decrescente (P<0,05) sobre a biomassa de lâminas foliares secas nas duas intensidades de desfolha. A biomassa de colmos secos apresentou efeito linear crescente (P<0,05) em função dos períodos de descanso nas duas intensidades de desfolha. Foi registrado produção de 2427,71; 2907,39; 3325,72 e 3749,45 kg ha-1 para os períodos de 25;35; 45 e 55 dias, respectivamente. O teor de matéria seca apresentou efeito linear crescente (P<0,05) em função dos períodos de descanso avaliados nas duas intensidades de desfolha. O período de descanso indicou comportamento linear decrescente (P<0,05) para o teor de proteína bruta nas duas intensidades de desfolha. Foi registrado diminuição de 0,9 e 0,7 g kg-1 para cada dia de período de descanso. Para cada dia a mais de período de descanso foi registrado aumento de 1,2 e 1,5 g kg-1 de MS no teor de fibra em detergente neutro nas intensidades de 15 e 30 cm. O pasto de capim-andropógon manejado com período de descanso de 25 dias e intensidade de desfolha de 30 cm apresentou alta relação folha/colmo e bom valor nutricional.