RESUMO
The aim of this study was to measure methane emissions (CH4) and herbage intake, and, on the basis of these results, obtain the methane yield (MY, methane yield as g CH4/kg dry matter intake (DMI) and Ym, methane yield as a percentage of Gross Energy intake), from beef cows grazing on native grasslands. We used forty pregnant heifers, with two treatments of herbage allowance (HA) adjusted seasonally (8 and 5 kg dry matter (DM)/kg cattle live weight (LW), on average), during autumn, winter and spring. Methane emissions (207 g CH4/d), organic matter intake (OMI, 7.7 kg organic matter (OM)/d), MY (23.6 g CH4/kg DMI) and Ym (7.4%), were similar between treatments. On the other hand, all variables had a marked increase in spring (10.8 kg OM/d and 312 g CH4/d), except for Ym. The methane emission factor from Intergovernmental Panel on Climate Change (IPCC) Tier 2 estimated with these results was 78 kg CH4/head/year. The results show that methane emissions and intake were influenced by the season, but not by the HA analyzed in this study. This information for cow-calf systems in native grasslands in Uruguay can be used in National greenhouse gases (GHG) inventories, representing a relevant contribution to global GHG inventories.
RESUMO
Methane emissions from ruminants are a major contributor to agricultural greenhouse gas emissions. Thus, eight different forage species were combined in binary mixtures with Lolium perenne in increasing proportions, in vitro, to determine their methane reduction potential in ruminants. Species were sampled in two consecutive years where possible. The aims were: a) to determine if mixtures with specific forages, particularly those rich in plant specialized metabolites (PSM), can reduce methane emissions compared to ryegrass monocultures, b) to identify whether there is a linear-dose effect relationship in methane emissions from the legume or herb addition, and c) whether these effects are maintained across sampling years. Results showed that all dicot species studied, including the non-tannin-containing species, reduced methane production. The tannin-rich species, Sanguisorba minor and Lotus pedunculatus, showed the greatest methane reduction potential of up to 33%. Due to concomitant reductions in the forage digestibility, Cichorium intybus yielded the lowest methane emissions per digestible forage unit. Contrary to total gas production, methane production was less predictable, with a tendency for the lowest methane production being obtained with a 67.5% share of the legume or herb partner species. Thus, linear increments in the partner species share did not result in linear changes in methane concentration. The methane reduction potential differed across sampling years, but the species ranking in methane concentration was stable.
RESUMO
Tendencias y proyecciones de la educación superior: La evolución de la población. Las proyecciones de la población hasta el año 2025.- Evolución y proyecciones de la educación superior: Educación media. Educación superior.- Evolución y perspectivas de la economía ecuatoriana: Tendencias generales de la economía. Evolución del PIB sectorial y subsectorial. Proyecciones de la economía. Proyecciones del PIB por sectores y subsectores.- Tendencias y proyecciones de empleo, desempleo y subempleo en el Ecuadorlo.- Factores complementarios que podrían modificar la estructura futura de la economía: La incorporación del país en el Pacto Andino y al nuevo mercado mundial. El proceso de modernización de la economía. La desburocratización del Estado y el proceso de privatización de las empresas estatales.- Demandas futuras de profesionales, de investigación científica y de extensión a la comunidad: Ramas profesionales que tendrán mayor demanda en la próxima década. Áreas de desarrollo e investigación tecnológica que se demandarán de la Universidad en el futuro y áreas de desarrollo social que requerirán del apoyo de la comunidad universitaria
