395 research outputs found

    CONSERVB: A numerical method to compute soil water content and temperature profiles under a bare surface

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    A comprehensive, yet fairly simple model of water disposition in a bare soil profile under the sequential impact of rain storms and other atmospheric influences, as they occur from hour to hour is presented. This model is intended mostly to support field studies of soil moisture dynamics by our current team, to serve as a background for the microwave measurements, and, eventually, to serve as a point of departure for soil moisture predictions for estimates based in part upon airborne measurements. The main distinction of the current model is that it accounts not only for the moisture flow in the soil-atmosphere system, but also for the energy flow and, hence, calculates system temperatures. Also, the model is of a dynamic nature, capable of supporting any required degree of resolution in time and space. Much critical testing of the sample is needed before the complexities of the hydrology of a vegetated surface can be related meaningfully to microwave observations

    Investigation of remote sensing techniques of measuring soil moisture

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    Major activities described include development and evaluation of theoretical models that describe both active and passive microwave sensing of soil moisture, the evaluation of these models for their applicability, the execution of a controlled field experiment during which passive microwave measurements were acquired to validate these models, and evaluation of previously acquired aircraft microwave measurements. The development of a root zone soil water and soil temperature profile model and the calibration and evaluation of gamma ray attenuation probes for measuring soil moisture profiles are considered. The analysis of spatial variability of soil information as related to remote sensing is discussed as well as the implementation of an instrumented field site for acquisition of soil moisture and meteorologic information for use in validating the soil water profile and soil temperature profile models

    Leucaena in Latin American farming systems : Challenges for development

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    Insights in nutrition programs for the developing ruminant

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    As the world population grows and resources for food animal production become more limited, animal efficiency must increase. The dairy industry has made progress in reducing age at first calving from 27 to 25 mo., but heifers remain unproductive for over half of their life while still consuming resources. As pre-ruminants, offering restricted amounts of milk to neonatal heifers (conventional system) increases concentrate consumption which drives rumen development. However, accelerated milk programs improve pre-weaning growth rate and the balance between these two systems is still under continuous investigation. Solid feed is important for papillary and musculature development in addition to establishment of a microbial population, which increase transition success when calves are weaned gradually. Furthermore, the optimal target weight for calving is 550 kg at 23 to 24.5 mo., which increases 305-d lactation yield. Increased milk production is desired, but a costly rearing period without producing milk only increases as age at first calving increases, which also increases total number of replacement heifers and total herd green-house emissions. Strategies to achieve desired body weight and age at first calving while reducing input include, using compensatory growth, restricting intake and precision feeding. Compensatory growth can increase average daily gain and feed efficiency; moreover, precision feeding increases feed efficiency even further by reducing nutrient metabolic costs in comparison to ad- libitum systems. Restricting intake provides increased rumen retention time for fiber, non-structural carbohydrates, protein, and other nutrients to be highly digested. Nutrient digestibility is important when comparing these feeding methods because dry matter intake has the greatest impact on efficiency, specifically when different amounts of forages are fed. Using different strategies during the weaning, pre-pubertal and post-pubertal period of dairy heifers can significantly improve performance, nutrient and resources utilization during this conditioning growing phase of dairy cattle.A medida que la población mundial crece y los alimentos se vuelven más limitados, la eficiencia animal debe aumentar. La industria láctea ha progresado en la reducción de la edad al primer parto de 27 a 25 meses, pero las vaquillas siguen siendo improductivas durante más de la mitad de su vida mientras consumen recursos. Como pre-rumiantes, ofrecer cantidades restringidas de leche a las vaquillas neonatales (sistema convencional) aumenta el consumo de concentrado, lo que impulsa el desarrollo del rumen. Sin embargo, los programas acelerados de leche mejoran la tasa de crecimiento previo al destete y el equilibrio entre estos dos sistemas aún está bajo investigación continua. La alimentación sólida es importante para el desarrollo papilar y la musculatura, además del establecimiento de una población microbiana, que aumenta el éxito de la transición cuando los terneros se destetan gradualmente. El peso objetivo para el parto es 550 kg de 23 a 24.5 meses, lo que aumenta el rendimiento de lactancia de 305 días. Si no se reduce el periodo de cría, aumenta el número de vaquillas de reemplazo y las emisiones totales de gases invernadero. Las estrategias para lograr el peso corporal y la edad deseados al primer parto al tiempo que se reducen los insumos incluyen el uso de crecimiento compensatorio, la restricción de la ingesta y la alimentación de precisión. El crecimiento compensatorio puede aumentar la ganancia diaria promedio y la eficiencia alimenticia; Además, la alimentación de precisión aumenta aún más la eficiencia alimenticia al reducir los costos metabólicos de los nutrientes en comparación con los sistemas ad-libitum. La ingesta restringida proporciona un mayor tiempo de retención del rumen para que la fibra, los carbohidratos no estructurales, las proteínas y otros nutrientes sean altamente digeridos

    Screening unsaturated fat sources included to low and high forage diets with different fat dietary concentration using an in vitro gas production system

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    Fat inclusion can increase energy density of diets fed to ruminants, but detrimental effects to nutrient digestion have been reported. There is evidence that not all fat sources have this negative response and this effect can vary depending on the forage concentration in the diet. The objective of this experiment was to determine the effects of including different types of unsaturated fats to high and low forage diets in vitro digestibility and fermentation. An experiment was conducted using an in vitro gas production (GP) system. Treatments included either low forage (LF; 35%) or high forage (HF; 70%) with 2 dietary fat concentrations (6 or 9%) and of 7 different fat source treatments (control + 6 different types of unsaturated fat sources). The control diet had a basal level of fat in the diet [3% fat (0% fat inclusion); and fat sources were added to attain 6% or 9% fat and consisted of (Coconut oil, CO; Poultry fat, PF; Palm oil, PO; Palm kernel oil, PKO; Ca Salts, MEG; Soybean oil, SOY)]. Modules (GP) were randomly assigned to treatments in a 2×2×7 factorial design and incubated for two 24 h runs. A randomized complete block design with 4 replicates per treatment and 2 runs was used. Run was the blocking factor. Data were analyzed using the MIXED procedure of SAS. Apparent digestibility (AD) for DM, OM, NDF, ADF and true dry matter digestibility (TDMD) were higher in LF-treatment. Cumulative gas produced in mL was greater in LF (P = 0.01). Fat concentration had no effect on AD, but the 6% fat had a higher gas production (P = 0.03; 109.6 vs. 103.5 mL ± 2.44). The CO had the highest DM AD followed by SOY and PF (54.5, 51.8, and 50.6% ± 0.48) and cumulative gas production followed same pattern. The TDMD and OM AD were higher in CO, however the NDF and ADF AD were higher in MEG-fed modules. Final pH was not affected by treatments. Final NH3N concentration was greater in HF and 9% fat. These results suggest that LF diets with high dietary fat concentration can be utilized and different types of fat sources may improve DM and fiber rumen digestibility
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