Nitrogen fertilization has been recognized as an essential tool towards the establishment of sustainable intensification of pasture-based livestock systems using tropical perennial grasses if, for a given ecosystem it is capable of increasing forage growth, stocking rates and animal performance. This study assessed pasture growth traits, nutritive value, animal and economic responses of Panicum maximum cv. Mombaça guinea grass pastures subjected to different levels of N fertilization (100 (N100), 200 (N200), and 300 (N300) kg N ha⁻¹ yr⁻¹). Pastures were managed under rotational stocking to maintain similar pre (80–90 cm) and post-grazing (45 cm) canopy heights. A partial budget and a Benefit–Cost Analysis were used to assess the economic returns on increasing N fertilization. N300 resulted in greater post-grazing herbage mass. A slightly higher neutral fiber and acid lignin detergent was observed at N100 (P < 0.05); crude protein increased linearly, and in vitro digestible organic matter reached maximum value at 265.4 kg N ha⁻¹ yr⁻¹. Annual averages of animal weight gain were 515, 590 and 660 g d⁻¹, respectively, for N100, N200 and N300. There was a decrease from 3.7 to 1.9 kg of body weight gain per kg of additional N applied when increasing N rates from 100 to 200 and from 100 to 300 kg ha⁻¹. The net profit improved with increasing N levels, but at reducing rates, reaching its maximum at the N300 level. The change from 100 to 200 kg N ha⁻¹ presented the best return, with USD 3.73 for each additional dollar invested, while the change from 200 kg N ha⁻¹ to 300 kg N ha⁻¹ was economically less than optimal, recouping only USD 1.60 for each dollar. The N300 rate presented the highest net profit per hectare (accounting profit), even in a pessimist scenario (25% reduction in production). Despite being profitable, the N300 rate was less than optimal from an economic standpoint, since an additional 100 kg of Nitrogen ha⁻¹ to change from N200 to N300 level reduced both the net returns and the Benefit–Cost ratio. Our results suggest that the economically optimal level of N fertilization for Mombaça guinea grass pasture should be between 200 and 300 kg ha⁻¹.

Panicum maximum grasses are among the most used in Brazil because they have high forage production potential, nutritional value and adaptation to different climate conditions and in poor soils, which have been improved by the application of dolomitic limestone and nitrogen fertilizers and K₂O, P₂O₅. The aim was to evaluate the tillering capacity and structural characteristics of six cultivars of Panicum maximum in the Brazilian semiarid region. The test was configured as a randomized block design with six treatments—the cultivars Aruana, Massai, Mombaça, Tamani, Tanzânia, and Zuri—and four replications. The studied variables included tiller population dynamics, tiller population density (TPD), appearance rate (ApR), mortality (MorB), tiller survival (SuvP), tiller stability index, height, light interception (LI), forage mass (FM), and morphological constituents. As to the population dynamics of tillers, seven generations were evaluated, and the largest number of tillers was observed in the first generation, regardless of the cultivar. Furthermore, the Massai cultivar demonstrated the highest TPD in all generations. Interaction between the cultivar and evaluation period was noted for ApR: the cultivars Tamani and Tanzânia indicated higher ApR at 122 and 137 days after establishment. The cultivar (P = 0.380) and evaluation period (P = 0.4469) had no effect on SuvP; however, higher MorB was detected in the cultivars Aruana and Tamani compared to Mombaça and Zuri, with intermediate values detected in the other cultivars. The highest FM was observed in the cultivars Massai, Mombaça, and Tamani, as well as in the leaf blade of Massai and Mombaça. The cultivars Massai, Mombaça, Tamani, Tanzânia, and Zuri have the potential to be cultivated in areas with marked water deficit and high temperatures, such as the Brazilian semiarid region. The cultivar Massai has a rapid recovery after a period of water scarcity. The cultivar Aruana is not recommended for use in the Brazilian semiarid region under rainfed conditions.

We investigated the effects of nitrogen (N) fertilisation levels on structural, productive and morphogenetic traits, chlorophyll content, tiller number (TN) and macronutrient uptake capacity of three Panicum maximum cultivars (BRS Zuri, BRS Quênia and BRS Tamani). The experiment was laid out in a completely randomised design with five N doses (0, 50, 100, 200, and 400 mg dm ⁻³ ). The concentration of chlorophyll increase linearly with increasing N doses in BRS Zuri. There was a significant interaction effect between cultivars and N doses on forage mass (FM), forage yield (FY), TN and the uptakes of nitrogen, potassium, phosphorus, calcium, magnesium and sulfur. The BRS Zuri had the highest FY and FM independent of the applied N dose. In the dose range of 200 and 400 mg dm ⁻³ of N, there was no increase in the productive performance of BRS Tamani and BRS Quênia, which were similar to each other. N fertilisation increased TN. Higher N doses in the soil translated into greater N uptake by the grasses. Nitrogen application to the soil can increase the production and structural indices of Panicum maximum cultivars and increases grass growth, but its concentration must consider the productive capacity of the plant for this nutrient.

Identifying forage species that are responsive in regions with marked water deficits is one of the greatest challenges for the sustainable development of agriculture. However, information is still lacking about the persistence response of those pastures and their abilities to produce new tissues at the times of water scarcity. We hypothesized that Brachiaria grass has a tillering capacity during water-stress periods. This study thus examined the tillering capacity and structural characteristics of four Brachiaria brizantha cultivars (Xaraés, Piatã, Marandu, and Paiaguás) and one Brachiaria decumbens cultivar (Basilisk) in the Brazilian semi-arid region during the dry season (September to March). The experiment was laid out in a randomized block design with repeated measures over time in which five treatments were tested in four replicates. Tillering parameters, pasture production, and structural variables were evaluated. There was no interaction effect of cultivar × evaluation period on the tiller appearance (p= 0.1774), mortality (p= 0.1952) or survival (p= 0.4469) rates. The highest tiller appearance and mortality rates were observed in Marandu, while the highest survival rates were found in Marandu and Paiaguás. The index of tiller population stability was higher than or equal to 1.0 in all cultivars. Cultivar Basilisk showed the highest herbage mass yield (4448.0 kg DM ha-1), whereas Basilisk exhibited the highest yields of leaf (1845.9 kg DM ha-1), stem (1676.9 kg DM ha-1), and dead material (925.2 kg DM ha-1). The highest leaf:stem ratio (1.8) was found in Marandu. Cultivar Xaraés had the highest canopy (70.8 cm). The B. brizantha and B. decumbens cultivars evaluated in this study have the potential for cultivation in areas with marked water deficits, as is the case of the Brazilian semi-arid region. Cultivars Marandu, Basilisk, and Paiaguás exhibited the greatest tillering dynamics as well as the highest herbage-mass yield.

Due to the conditions in which traditional sheep production systems operate, the evaluation of animal growth from live weight (LW) is limited by the high cost of the livestock scale as well as the sophisticated maintenance required. In this scenario, in recent years, biometric measurements have been investigated as an accurate indirect method to predict the LW of farm animals. Therefore, the present study was undertaken to examine different models for predicting the body weight of growing lambs using the body volume (BV) formula. Body volume, heart girth (HG) and body length (BL) data of 290 lambs aged between two and eight months were recorded. Body volume was calculated from HG and BL data using a formula that calculates the volume of a cylinder. The estimation of LW from the BV formula was achieved through regression equations using three mathematical models (linear, quadratic and exponential). The mean values of LW, HG, BL and BV of the lambs were 29.12±12.04kg, 70.00±11.69cm, 38.40±6.43cm and 23.93±9.90dm3, respectively. The correlation coefficient between LW and BV was r = 0.96 (P<0.001). The quadratic model showed the highest coefficient of determination (0.93) and the lowest prediction error (3.29kg). Under the experimental conditions adopted in this study, it is possible to predict the live weight of growing lambs using the body volume formula.

Estrutura do pasto e desempenho de ovinos em capim-massai na época seca em resposta ao manejo do período das águas