Brazil has the largest herd of beef cattle in the world, estimated at approximately 200 million animals. Production is predominantly pasture-based and low input and hence time to slaughter is long, which promotes high methane (CH 4) emissions per kg of product. The objective of this study was to investigate the impact of increasing animal productivity using fertilizers, forage legumes, supplements and concentrates, on the emissions of greenhouse gases (GHGs) in five scenarios for beef production in Brazil. A life cycle analysis (LCA) approach, from birth of calves to mature animals ready for slaughter at the farm gate, was utilized using Tier 2 methodologies of the IPCC and the results expressed in equivalents of carbon dioxide (CO 2 eq) per kg of carcass produced. Fossil CO 2 emitted in the production of supplements, feeds and fertilizers was included using standard LCA techniques. The first four scenarios were based solely on cattle production on pasture, ranging from degraded Brachiaria pastures, through to a mixed legume/Brachiaria pasture and improved N-fertilized pastures of Guinea grass (Panicum maximum). Scenario 5 was the most intensive and was also based on an N-fertilized Guinea grass pasture, but with a 75-day finishing period in confinement with total mixed ration (TMR). Across the scenarios from 1 to 5 the increase in digestibility promoted a reduction in the forage intake per unit of animal weight gain and a concomitant reduction in CH 4 emissions. For the estimation of nitrous oxide (N 2 O) emissions from animal excreta, emission factors from a study in the Cerrado region were utilized which postulated lower emission from dung than from urine and much lower emissions in the long dry season in this region. The greatest impact of intensification of the beef production systems was a 7-fold reduction of the area necessary for production from 320 to 45 m 2 /kg carcass. Carcass production increased from 43 to 65 Mg per herd across the scenarios from 1 to 5, and total emissions per kg carcass were estimated to be reduced from 58.3 to 29.4 kg CO 2 eq/kg carcass. Even though animal weight gain was lower in the mixed grass-legume scenario (3) than for the N-fertilized Guinea grass pastures (scenarios 4 and 5) GHG emissions per kg carcass were similar as the legume N 2 fixation input had no fossil-fuel cost. A large source of uncertainty for the construction of such LCAs was the lack of data for enteric CH 4 emissions from cattle grazing tropical forages.
The objective of this study was to determine the effect of dietary nitrate on methane emission and rumen fermentation parameters in Nellore × Guzera (Bos indicus) beef cattle fed a sugarcane based diet. The experiment was conducted with 16 steers weighing 283 ± 49 kg (mean ± SD), 6 rumen cannulated and 10 intact steers, in a cross-over design. The animals were blocked according to BW and presence or absence of rumen cannula and randomly allocated to either the nitrate diet (22 g nitrate/kg DM) or the control diet made isonitrogenous by the addition of urea. The diets consisted of freshly chopped sugarcane and concentrate (60:40 on DM basis), fed as a mixed ration. A 16-d adaptation period was used to allow the rumen microbes to adapt to dietary nitrate. Methane emission was measured using the sulfur hexafluoride tracer technique. Dry matter intake (P = 0.09) tended to be less when nitrate was present in the diet compared with the control, 6.60 and 7.05 kg/d DMI, respectively. The daily methane production was reduced (P < 0.01) by 32% when steers were fed the nitrate diet (85 g/d) compared with the urea diet (125 g/d). Methane emission per kilogram DMI was 27% less (P < 0.01) on the nitrate diet (13.3 g methane/kg DMI) than on the control diet (18.2 g methane/kg DMI). Methane losses as a fraction of gross energy intake (GEI) were less (P < 0.01) on the nitrate diet (4.2% of GEI) than on the control diet (5.9% of GEI). Nitrate mitigated enteric methane production by 87% of the theoretical potential. The rumen fluid ammonia-nitrogen (NH(3)-N()) concentration was significantly greater (P < 0.05) for the nitrate diet. The total concentration of VFA was not affected (P = 0.61) by nitrate in the diet, while the proportion of acetic acid tended to be greater (P = 0.09), propionic acid less (P = 0.06) and acetate/propionate ratio tended to be greater (P = 0.06) for the nitrate diet. Dietary nitrate reduced enteric methane emission in beef cattle fed sugarcane based diet.
Resumo -O objetivo deste trabalho foi avaliar metas de manejo para capim-marandu (Urochloa brizantha cv. Marandu) submetido a pastejo rotativo e a doses de nitrogênio, de janeiro de 2009 a abril de 2010. Os tratamentos consistiram da combinação de duas frequências de pastejo (altura pré-pastejo de 25 e 35 cm) e de duas doses de fertilizante nitrogenado (50 e 200 kg ha -1 por ano) em delineamento de blocos ao acaso com arranjo fatorial 2x2 e quatro repetições. A altura de pós-pastejo estipulada foi de 15 cm. Maiores valores de ganho de peso médio por animal por dia (0,629 e 0,511 kg dia -1 ) e por hectare (886 e 674 kg ha -1 ), bem como de taxa de lotação (3,13 e 2,85 UA ha -1 ), foram observados nos pastos manejados com altura pré-pastejo de 25 cm. A aplicação de 200 kg ha -1 de N resultou em aumentos na percentagem de folhas na massa de forragem pós-pastejo, nas taxas de acúmulo de forragem, na taxa de lotação e no ganho de peso por área. A mais adequada estratégia de manejo corresponde à altura pré-pastejo de 25 cm, independentemente da dose de nitrogênio utilizada.Termos para indexação: Urochloa brizantha, altura do dossel, altura pré-pastejo, altura pós-pastejo, manejo do pastejo, taxa de lotação. Weight gain and animal productivity on Marandu palisade grass under rotational stocking and nitrogen fertilizationAbstract -The objective of this work was to assess management targets for marandu palisade grass (Urochloa brizantha cv. Marandu) subjected to rotational stocking and to nitrogen fertilization rates, from January 2009 to April 2010. Treatments consisted of a combination of two grazing frequencies (pre-grazing heights of 25 and 35 cm) and two levels of nitrogen application (50 and 200 kg ha -1 per year). in a completely randomized block design, in a 2x2 factorial arrangement, with four replicates. The established post-grazing height was 15 cm. Greater values of daily weight gain per animal per day (0.629 and 0.511 kg day -1 ), weight gain per hectare (886 and 674 kg ha -1 ), and stocking rate (3.13 and 2.85 AU ha -1 ) were found for pre-grazing height of 25 cm. The application of 200 kg ha -1 of N increased the percentage of leaves in post-grazing forage mass, forage accumulation rate, stocking rate, as well as weight gain per hectare. The best grazing strategy corresponds to the pre-grazing height of 25 cm, regardless of the nitrogen application.
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