Trabajos Finales de Graduación EMV - PCVET

URI permanente para esta colecciónhttp://10.0.96.45:4000/handle/11056/14604

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Medición de las emisiones de óxido nitroso y metano entérico en ganado Brahman bajo pastura tipo cayman (Brachiaria hybrid cv) en la estación experimental los Diamantes
(Universidad Nacional, Costa Rica, 2017-06) Jiménez Araya, Jorge; Abarca Monge, Sergio
In the first study, the objective of this study was to quantify the daily pattern of nitrous oxide (N2O) emissions in a Brachiaria hybrid cv under grazing with Brahman cattle, located at the experimental station Los Diamantes (Guápiles, Costa Rica). Measurements were performed with 8 static cameras, for 6 days, with 7 repeated one-hour samplings distributed between 6 am and 6 pm. The N2O emission variable presented a biased distribution to the right with a mean of 0.12 ± 0.17, equivalent to 10.62 kg / ha / year and a median of 0.06 mg / m2 / h. The emission pattern of N2O throughout the day was heterogeneous with values ranging from 0.09 to 0.17 mg / N2O / m2. The N2O emission variable was analyzed by a generalized linear mixed model that assumed a lognormal distribution for the dependent variable (N2O emission) and considered the fixed effects of day, time, camera and the interactions hour × day, camera × hour , camera × day and the random effect of time (camera × day). A highly significant effect (P <0.001) was observed for all effects analyzed, except for the camera × hour interaction. The marginal hourly averages show a non-linear pattern, with a slight decrease between 6:00 and 8:00 a.m, followed by a rising trend until 4:00 p.m., to decline again until 6:00 p.m. The marginal means in the hours of greatest emission were 0.06 (14:00) and 0.07 (16:00) mg / m2 / h, which differed significantly (P <0.05) only with respect to the hours of the morning (6:00 a.m. to 10:00 p.m.). There was also a significant variation in the emission patterns of different days and different cameras. It was concluded that for the evaluated site there is no single time of higher N2O emission, probably due to the reduced temperature variation. This suggests that for practical purposes an emission measurement range can be used between 10:00 am and 4:00 p.m. The second study estimated the pattern of enteric methane emissions in cattle under grazing. Ten methane measurements were performed at approximately 35 day intervals in 8 Brahman cattle (initial weight 300 kg, D.E 22.54 kg) using the sulfur hexafluoride (SF6) technique. The animals had an average weight gain of 0.69 kg / d (D.E0.046), with a consumption of 12.6 kg DM animal / d (SD 2.2). The mean CH4 emission was 141.4 g / animal / day (DE 38 g) and the total emission accumulated during the 388 test days was 54.2 kg / animal / total (SD 6.84). The variable CH4 emission was analyzed by a regression model, assuming a lognormal distribution, including the fixed effects of the animal, the live weight covariate and the interaction between both. Significant effects (P <0.001) were observed for all evaluated effects. For all animals, a decreasing homogeneous pattern was observed in CH4 emission according to the progress of the test, although significant differences were observed in the reduction rates. The animals in earlier stages, with lower weight and lower DM consumption, were those that presented a higher emission of CH4. It is concluded that the factor that had a more significant effect on the emissions was the live weight, in addition it was demonstrated that there is significant individual variation in the level of CH4 emissions.
Propuesta de alternativas de reducción de gases de efecto invernadero (GEI) para los sistemas lecheros de San Joaquín de Tuis, Turrialba, Costa Rica
(Universidad Nacional, Costa Rica, 2015-03) García Orozco, Karen Lineth; Abarca Monge, Sergio
El objetivo general del presente estudio fue contribuir al desarrollo de pequeños productores ganaderos mediante la elaboración de una propuesta de alternativas de reducción de GEI para los sistemas lecheros de San Joaquín de Tuis, Turrialba. La primera parte del estudio se centró en la identificación y caracterización de tipologías de producción mediante técnicas de análisis multivariado. Se aplicó una encuesta a 21 productores, en la cual se contemplaron variables de tipo ambiental, productivas, sociales y físicas. Se identificaron dos grupos de producción representativos. El primero un sistema con bajo nivel tecnológico, responde a fincas de bajos niveles productivos con una mayor superficie ganadera, con escaso nivel tecnológico y poca aplicación de Prácticas Silvopastoriles (SSP). El segundo representa un sistema de mediano nivel tecnológico, integra fincas con mayores rendimientos productivos en menor cantidad de área destinada a pastoreo, reciben asistencia técnica y adoptan prácticas sostenibles en mayor medida. La segunda parte del estudio se enfocó en la construcción de un modelo de simulación estocástico con la finalidad de estimar el balance (Captura Emisión) de las fincas de las tipologías previamente detalladas. Los resultados revelan que la mayor emisión proviene del sistema con BNT con 34,4(±8,6) tonCO2e/año, mientras que el grupo de MNT emite 28,6(±6,1) tonCO2e/año, logrando un balance más eficiente y una mayor captura. Se evaluó el impacto potencial de implementar tres estrategias de mitigación en la tipología de BNT que fueron: 1) Mejorar la estructura del hato, 2) Incrementar las áreas de pasto mejorado y árboles en potreros, e 3) Incrementar el área de bosque secundario. La opción 3 es la intervención de mayor impacto sobre el balance, debido a que logra un superávit de 9,6 CO2e ton/año. Entre tanto, las intervenciones combinadas alcanzan un superávit de 28,8 CO2e ton/año. Las estrategias que combinan mecanismos que reducen los factores asociados a una mayor emisión y, que a su vez, promueven los componentes asociados a una superior captura tendrán más impacto que intervenciones unilaterales.

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Examinando Trabajos Finales de Graduación EMV - PCVET por Autor "Abarca Monge, Sergio"