A three-year-long field experiment was conducted in a continuous grazing system with a variable stocking rate to evaluate effects of increasing nitrogen levels in Marandu grass ( Brachiaria brizantha Hochst ex A. Rich Stapf “marandu”) on herbage mass, forage accumulation rate (FAR), forage quality, stocking rate (SR), average daily gain (ADG), gain per hectare (GPH), and gain per kg of applied N. The experimental design was completely randomized with four treatments (control without application of N, and 90, 180, and 270 kg N ha −1 year −1 ) and three replicates (paddocks per treatment); nitrogen was applied in the form of urea. Herbage mass, crude protein (CP), FAR, SR, GPH, and the nitrogen nutrition index increased with increasing nitrogen level (P < 0.05), whereas the neutral detergent fibre (NDF), acid detergent fibre, and nitrogen usage efficiency decreased with increasing nitrogen level (P < 0.01). Crude protein was higher than 12% and NDF lower than 60% in all treatments. Nitrogen application rate affected ADG (P < 0.05) but did not fit any equation. The highest ADG was 90 kg N ha −1 year −1 (985 g animal −1 day −1 ). Increasing the nitrogen level is a promising way to improve Marandu grass production, nutritive value, and animal production.

Intensification of tropical grassland can be a strategy to increase beef production, but methods for achieving this should maintain or reduce its environmental impact and should not compromise future food-producing capacity. The objective of this review was to discuss the aspects of grassland management, animal supplementation, the environment, and the socioeconomics of grassland intensification. Reducing environmental impact in the form of, for example, greenhouse gas (GHG) emissions is particularly important in Brazil, which is the second-largest beef producer in the world. Most Brazilian pastures, however, are degraded, representing a considerable opportunity for the mitigation and increase of beef-cattle production, and consequently increasing global protein supply. Moreover, in Brazil, forage production is necessary for seasonal feeding strategies that maintain animal performance during periods of forage scarcity. There are many options to achieve this objective that can be adopted alone or in association. These options include improving grassland management, pasture fertilization, and animal supplementation. Improving grazing management has the potential to mitigate GHG emissions through the reduction of the intensity of CO2 emissions, as well as the preservation of natural areas by reducing the need for expanding pastureland. Limitations to farmers adopting intensification strategies include cultural aspects and the lack of financial resources and technical assistance.

Context Yields from Brazilian beef-production systems do not always match the expected potential of a forage-based beef-production system. This efficiency is dependent on adjustments of grazing intensity and supplement utilisation to achieve higher bodyweight gain and lower methane emission. Therefore, more studies are necessary to evaluate the association between pasture management and supplement doses. Aims The aim of the present study was to determine nutrient intake, nutrient digestibility, animal performance, carcass characteristics and enteric methane emissions of young Nellore bulls grazing Urochloa brizantha cv. Marandu pastures. Methods One hundred and forty-eight yearling bulls (230 ± 17 kg) were randomly assigned to a grazing-by-supplementation strategy that was designed to allocate three different sward heights with differing levels of supplementation during the wet season. Treatment combinations were (1) low sward height with high supplementation (LH-HS, 15-cm sward height and supplementation at 0.6% of bodyweight (BW)); (2) low height with moderate supplementation (LH-MS, 15 cm and 0.3% BW); (3) moderate height with moderate supplementation (MH-MS, 25 cm and 0.3% BW); (4) moderate height with low supplementation (MH-LS, 25 cm and 0.1% BW); (5) high height with low supplementation (HH-LS, 35 cm and 0.1% BW); and (6) high height with no supplementation (HH-WS, 35 cm). Key results Bulls in the HH groups had a greater herbage intake than did those in the LH groups (P &lt; 0.01). Bulls in the LH-HS treatment resulted in a greater (P &lt; 0.01) carcass average daily gain than that obtained with LH-MS, MH-LS or HH-WS treatment. Higher stocking rate with the LH treatment resulted in greater gains per hectare in terms of both BW and carcass (P &lt; 0.01). Carcass yield was greater for bulls maintained with the LH-HS treatment (54.3% BW). Higher enteric methane emissions were observed from bulls under the HH treatments (P &lt; 0.01). Conclusions Comparing carcass gains per hectare and low methane emissions, the present study indicated that pasture management towards a low sward height combined with 0.3% or 0.6% BW supplementation can result in a greater nutrient utilisation efficiency of bulls. Implications Results provided information to obtain better gains per animals and area, also decreasing methane emission of beef cattle production system.

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The effects of differing post-weaning management systems applied during the wet season were evaluated on the performance of 108 young Nelore (Bos taurus indicus) bulls finished on grasslands or feedlot system during the dry season. In Exp. 1, three grazing heights (15 cm, 25 cm, and 35 cm) of Brachiaria brizantha (Hochst ex A. Rich) Stapf Marandu were evaluated during the wet season with bulls receiving 0.3% of body weight (BW) in supplementary feed. In Exp. 2, supplementation levels were decreased as grazing heights were increased such as: (1) low height (15 cm) and high supplementation (0.6% BW) (LH-HS); (2) moderate height (25 cm) and moderate supplementation (0.3% BW) (MH-MS); or (3) high height (35 cm) with no supplementation (HH-NS). In both experiments, at the end of the wet season, a half of the bulls were finished on grasslands and receiving 1.0 kg/100 kg BW of dietary supplementation while the remaining bulls were placed in a feedlot system. A non-linear regression test was applied (linear plateau) to estimate the point of stabilization of DMI on feedlot. The experimental design was completely randomized in a factorial arrangement 3 (post-weaning system) × 2 (finishing systems), consisting of three replicates (lots of three bulls) per treatment (n = 18, each Exp.). In the Exp. 1, the post-weaning system using 35 cm of grazing height had greater BW (P = 0.04) through the finishing phase in comparison with bulls grazing 15 cm of grazing height. However, the ADG during the initial 21 days of the finishing phase was changed by grazing height used during the post-weaning phase (P = 0.004), and by finishing system (P = 0.007). The post-weaning system did not alter the carcass weight (P = 0.63), but the bulls finished on grasslands exhibited greater carcass weight (P = 0.02) than bulls finished on feedlot. In the Exp. 2, non-supplemented bulls (HH-NS) took a longer time (±10%) to DMI stabilization on feedlot (P b 0.01). There were no changes in the carcass weight caused by post-weaning system (P = 0.84), or by finishing system (P = 0.14). The evaluated systems combining increasing grazing height and decreasing supplementation level during the post-weaning phase can be used during the wet season according to the economic background or production target, once these systems do not influence the finishing phase.