Micrometeorological techniques are effective in measuring methane (CH4) emission rates at the herd scale, but their suitability as verification tools for emissions mitigation depends on the uncertainty with which they can detect a treatment difference. An experiment was designed to test for a range of techniques whether they could detect a change in weekly mean emission rate from a herd of cattle, in response to a controlled change in feed supply. The cattle were kept in an enclosure and fed pasture baleage, of amounts increasing from one week to the next. Methane emission rates were measured at the herd scale by the following techniques: (1) an external tracer-ratio technique, releasing nitrous oxide (N2O) from canisters on the animals' necks and measuring line-averaged CH4 and N2O mole fractions with Fourier-transform infra-red (FTIR) spectrometers deployed upwind and downwind of the cattle, (2) a mass-budget technique using vertical profiles of wind speed and CH4 mole fraction, (3) a dispersion model, applied separately to CH4 mole fraction data from the FTIR spectrometers, the vertical profile, and a laser system measuring along four paths surrounding the enclosure. For reference, enteric CH4 emissions were also measured at the animal scale on a daily basis, using an enteric tracer-ratio technique (with SF6 as the tracer). The animal-scale technique showed that mean CH4 emissions increased less than linearly with increasing feed intake. The herd-scale techniques showed that the emission rates followed a diurnal pattern, with the maximum about 2 h after the feed was offered. The herd-scale techniques could detect the weekly changes in emission levels, except that the two vertical-profile techniques (mass-budget technique and dispersion model applied to profile) failed to resolve the first step change. The weekly emission rates from the external tracer-ratio technique and the dispersion model, applied to data from either the two FTIR paths or the four laser paths, agreed within ±10% with the enteric tracer-ratio technique. By contrast, the two vertical-profile techniques gave 33-68% higher weekly emission rates. It is shown with a sensitivity study that systematically uneven animal distribution within the enclosure could explain some of this discrepancy. Another cause for bias was the data yield of the vertical-profile techniques being higher at day-time than at night-time, thus giving more weight to times of larger emission rates. The techniques using line-averaged mole fractions were less sensitive to the exact locations of emission sources and less prone to data loss from unsuitable wind directions; these advantages outweighed the lack of a method to calibrate CH4 mole fractions in situ. rates at the herd scale, but their suitability as verification tools for emissions mitigation 3 depends on the uncertainty with which they can detect a treatment difference. An 4 experiment was designed to test for a range of techniques whether they could detect a 5 change in weekly mean emission rate from a herd o...

This study aimed at determining the nutritional efficiency of Kikuyu grass, when it is cultivated at different altitudes and defoliated with a different number of leaves per tiller. Four farms, with Kikuyu crops (Cenchrus clandestinus), were selected, two in an average altitude of 2,552 m.a.s.l. and two in average altitude of 2,914 m.a.s.l. In each farm, there were established eight plots of 4 m2 each (four treatments, two replicates). For 10 months, the pastures were defoliated when they presented 4, 5, 6, and 7 leaves per tiller (treatments) at 5 cm above ground when 90% of the tillers reached the number of leaves corresponding to each treatment. Data were analyzed as serial experiments using a completely randomized block (farms) design with an analysis of variance. The leaf appearance interval was higher for the highest altitude (8 vs. 10 days) but vary among treatments at a lower altitude (P<0.05). Pastures at higher altitudes were shorter (8.9 vs. 13.5 cm), but its height varied among treatments depending on the altitude (P<0.001). The quality of the pastures was similar, except for the ones with seven leaves per tiller at 2,552 m.a.s.l. that had less protein and in vitro dry matter digestibility (P<0.01). The nutrient yield was higher for the pastures cultivated at 2,552 m.a.s.l. (P<0.001), and, at this altitude, pastures defoliated with five leaves had the largest nutrient yield. The Kikuyu cultivated at higher altitudes grows slowly and yield fewer nutrients independently of the number of leaves per tiller.

<p>La baja oferta de alimento, problema que aqueja a un alto porcentaje de la población ganadera de Colombia, se asocia,en gran medida, a la selección equivocada de especies forrajeras; es decir, con frecuencia las especies sembradas no están adaptadas a la oferta mbiental de una región en particular. Para atenuar el riesgo de la baja oferta forrajera, sin incurrir en costos asociados al cambio de la oferta ambiental, es preciso aprovechar las habilidades fisiológicas de las especies para hacer frente al ambiente donde crecen. Para ello, se desarrolló un sistema de toma de decisiones para la selección de especies forrajeras (STDF), herramienta básica en la transferencia de tecnología agropecuaria que tiene por objetivo atenuar la incertidumbre al definir las especies forrajeras aptas para un ambiente determinado. El sistema se desarrolló a partir de fundamentos básicos de la gestión del conocimiento, por lo que en su construcción no se diseñó ningún experimento, sino que se aprovechó la información existente en el país, proveniente de evaluaciones realizadas en el pasado. A partir de la información recabada, se generó una base de datos de requerimientos de las especies, de tal forma que el sistema, desarrollado e implementado sobre ASP.NET en C# y base de datos SQL Server, relaciona ambientes y requerimientos de cultivos. Dicho sistema permite a los usuarios realizar procesos de búsqueda y selección de especies de pastos y forrajes de acuerdo con las condiciones edafoclimáticas de una determinada finca o región, de manera sencilla y amigable.</p>