Does grazing management provide opportunities to mitigate methane emissions by ruminants in pastoral ecosystems?

Agriculture, and livestock production in particular, is criticized for being a contributor to global environmental change, including emissions of greenhouse gases (GHG). Methane (CH4) from grazing ruminants accounts for most of livestock's carbon footprint because a large share of them are reared under suboptimal grazing conditions, usually resulting in both low herbage intake and animal performance. Consequently, the CH4 quota attributed to animal maintenance is spread across few or no animal outputs, increasing the CH4 intensity [g CH4/kg live weight (LW) gain or g CH4/kg milk yield]. In this review, the generalized idea relating tropical pastures with low quality and intrinsically higher CH4 intensity is challenged by showing evidence that emissions from animals grazing tropical pastures can equal those of temperate grasses. We demonstrate the medium-to-high mitigation potential of some grazing management strategies to mitigate CH4 emissions from grazing ruminants and stress the predominant role that sward canopy structure (e.g., height) has over animal behavioral responses (e.g., intake rate), daily forage intake and resulting CH4 emissions. From this ecological perspective, we identify a grazing management concept aiming to offer the best sward structure that allows animals to optimize their daily herbage intake, creating opportunities to reduce CH4 intensity. We show the trade-off between animal performance and CH4 intensity, stressing that mitigation is substantial when grazing management is conducted under light-to-moderate intensities and optimize herbage intake and animal performance. We conclude that optimizing LW gain of grazing sheep and cattle to a threshold of 0.14 and 0.7 kg/day, respectively, would dramatically reduce CH4 intensity to approximately 0.2 kg CH4/kg LW gain, as observed in some intensive feeding systems. This could represent a mitigation potential of around 55% for livestock commodities in pasture-based systems. Our results offer new insights to the debate concerning mitigation of environmental impacts of pastoral ecosystems.

Characterization of Forage Utilization and Pasture Management Practices on Florida Horse Operations.

This study used an online survey to gather information on forage utilization and pasture management practices implemented on horse farms in Florida. We hypothesized that pastures were inadequately managed and underutilized, resulting in greater reliance on hay. Data from 80 complete responses were submitted to descriptive analysis and Fisher's exact test. Significantly associated variables were also evaluated using multiple correspondence analysis. The primary function of the facility most reported was recreational horse use (62%). Nearly all operations (n = 79) had pasture available, with 57% reporting housing horses on pasture full time (24 hr/d) and 48% reporting implementation of rotational stocking. Most respondents reported using a combination of hay and pasture (57.5%) as their primary source of forage, followed by pasture only (32.5%) and hay only (10%). Pasture maintenance was performed by 82% of respondents, and 6% did not implement any type of pasture management. Primary forage fed to the horses was related to the type of pasture management implemented (P = .0313) and turnout practices (P = .0003). The multiple correspondence analysis showed that relying on hay as the primary source of forage was associated with a shorter duration of pasture access and lack of pasture management. Most operations did not have their hay (89%) or pasture (94%) analyzed for nutrient composition. Despite pasture availability, lack of adequate pasture management appeared to contribute to a greater dependence on hay feeding. Pasture management practices and forage analysis are potential areas for horse owner education in Florida.

Seleção a campo de rizóbios nativos para cornichão / Field selection of native rhizobio for bird’s-foot trefoil

O cornichão (Lotus corniculatus L.) tem sido apontado como uma das forrageiras mais promissoras para o uso no Rio Grande do Sul. No entanto, pouco se conhece a respeito da interação dessas plantas com os rizóbios nativos em condições de campo. Este estudo visou a avaliar a eficiência das interações entre rizóbios e plantas de Lotus corniculatus cv. 'São Gabriel' em condições de campo. O experimento foi conduzido na Estação Experimental Agronômica da UFRGS com delineamento de blocos ao acaso com quatro repetições. Os tratamentos estudados foram: dois controles sem inoculação (um com a adição de 80kg ha-1 de nitrogênio na forma de uréia e outro sem a adição de nitrogênio); inoculação com rizóbios: estirpes SEMIA 816, recomendada no Brasil, U510, recomendada no Uruguai, U512, em estudo no Uruguai, e quatro isolados de rizóbios nativos (UFRGS Lc322, UFRGS Lc349, UFRGS Lc269 e Iso 7). O isolado UFRGS Lc322 e a estirpe U510 são mais eficientes do que a estirpe SEMIA 816, recomendada para cornichão no país. Além disso, a produção de forragem das plantas inoculadas com o isolado UFRGS Lc322 e a estirpe U510 superou a obtida com a adição de 80kg ha-1 de nitrogênio.

The bird's-foot trefoil (Lotus corniculatus L.) has been pointed as one of the most promising forage plants for use in Rio Grande do Sul. However, there is lack of information about the interaction of those plants with the native rhizobia in field conditions. This study aimed to evaluate the efficiency of interactions between rhizobia and plants of Lotus corniculatus cv. 'São Gabriel' in field conditions. The experiment was carried out in the Agronomic Experimental Station (EEA) of the Federal University of Rio Grande do Sul (UFRGS), using random block design with four replications. The treatments were: two controls without inoculation (one with the addition of urea corresponding to 80kg ha-1 of nitrogen and other without nitrogen addition); inoculation with rhizobia: strain SEMIA 816, recommended in Brazil, U150 recommended in Uruguay and U512, being studied in Uruguay, and four rhizobia isolates (UFRGS Lc322, UFRGS Lc349, UFRGS Lc269 e Iso 7). The rhizobia isolate Lc322 and the strain U510 are more efficient than the strain SEMIA 816, which is recommended for bird's-foot trefoil in the country. Furthermore, the forage production of plants inoculated with the isolate Lc322 and the strain U510 surpassed that, with the addition of 80kg ha-1 of nitrogen.