Temperature and acidification variability reduce physiological performance in the intertidal zone porcelain crab Petrolisthes//cinctipes

We show here that increased variability of temperature and pH synergistically negatively affects the energetics of intertidal zone crabs. Under future climate scenarios, coastal ecosystems are projected to have increased extremes of low tide-associated thermal stress and ocean acidification-associated low pH, the individual or interactive effects of which have yet to be determined. To characterize energetic consequences of exposure to increased variability of pH and temperature, we exposed porcelain crabs, Petrolisthes cinctipes, to conditions that simulated current and future intertidal zone thermal and pH environments. During the daily low tide, specimens were exposed to no, moderate or extreme heating, and during the daily high tide experienced no, moderate or extreme acidification. Respiration rate and cardiac thermal limits were assessed following 2.5 weeks of acclimation. Thermal variation had a larger overall effect than pH variation, though there was an interactive effect between the two environmental drivers. Under the most extreme temperature and pH combination, respiration rate decreased while heat tolerance increased, indicating a smaller overall aerobic energy budget (i.e. a reduced O2 consumption rate) of which a larger portion is devoted to basal maintenance (i.e. greater thermal tolerance indicating induction of the cellular stress response). These results suggest the potential for negative long-term ecological consequences for intertidal ectotherms exposed to increased extremes in pH and temperature due to reduced energy for behavior and reproduction.

Modelling and Simulation of Moored Devices for Ocean Currents Energy Harnessing

The main objective of this paper is the presentation of modelling solutions off loating devices that can be used for harnessing energy from ocean currents. It has been structured into three main parts. First, the growing current interest in marine renewable energy in general, and in extracting energy from currents in particular, is presented, showing the large number of solutions that are emerging and some of the most significant types. GESMEY generator is presented in second section. It is based on a new concept that has been patented by the Universidad Politécnica de Madrid and which is currently being developed through a collaborative agreement with the SOERMAR Foundation. The main feature of this generator is that on operation is fully submerged, and no other facilities are required to move to floating state for maintenance, which greatly increases its performance. Third part of the article is devoted to present the modelling and simulation challenges that arise in the development of devices for harnessing the energy of marine currents, along with some solutions which have been adopted within the frame of the GESMEY Project, making particular emphasis on the dynamics of the generator and its control

An energy-efficient strategy for combined RSS-PDR indoor localization

We propose an optimization-based framework to minimize the energy consumption in a sensor network when using an indoor localization system based on the combination of received signal strength (RSS) and pedestrian dead reckoning (PDR). The objective is to find the RSS localization frequency and the number of RSS measurements used at each localization round that jointly minimize the total consumed energy, while ensuring at the same time a desired accuracy in the localization result. The optimization approach leverages practical models to predict the localization error and the overall energy consumption for combined RSS-PDR localization systems. The performance of the proposed strategy is assessed through simulation, showing energy savings with respect to other approaches while guaranteeing a target accuracy.

Review of the Performance of Residential PV systems in Belgium

The main objective of this paper is to review the state of the art of residential PV systems in Belgium by the analysis of the operational data of 993 installations. For that, three main questions are posed: how much energy do they produce? What level of performance is associated to their production? Which are the key parameters that most influence their quality? This work brings answers to these questions. A middling commercial PV system, optimally oriented, produces a mean annual energy of 892 kWh/kWp. As a whole, the orientation of PV generators causes energy productions to be some 6% inferior to optimally oriented PV systems. The mean performance ratio is 78% and the mean performance index is 85%. That is to say, the energy produced by a typical PV system in Belgium is 15% inferior to the energy produced by a very high quality PV system. Finally, on average, the real power of the PV modules falls 5% below its corresponding nominal power announced on the manufacturer's datasheet. Differences between real and nominal power of up to 16% have been detected.

Review of the Performance of Residential PV systems in France

The main objective of this paper is to review the state of the art of residential PV systems in France. This is done analyzing the operational data of 6868 installations. Three main questions are posed. How much energy do they produce? What level of performance is associated to their production? Which are the key parameters that most influence their quality? During the year 2010, the PV systems in France have produced a mean annual energy of 1163 kWh/kWp. As a whole, the orientation of PV generators causes energy productions to be some 7% inferior to optimally oriented PV systems. The mean Performance Ratio is 76% and the mean Performance Index is 85%. That is to say, the energy produced by a typical PV system in France is 15% inferior to the energy produced by a very high quality PV system. On average, the real power of the PV modules falls 4.9% below its corresponding nominal power announced on the manufacturer's datasheet. A brief analysis by PV modules technology has led to relevant observations about two technologies in particular. On the one hand, the PV systems equipped with heterojunction with intrinsic thin layer (HIT) modules show performances higher than average. On the other hand, the systems equipped with the copper indium (di)selenide (CIS) modules show a real power that is 16% lower than their nominal value.

Energy-Entropy-Momentum integration of discrete thermo-visco-elastic dynamics.

A novel time integration scheme is presented for the numerical solution of the dynamics of discrete systems consisting of point masses and thermo-visco-elastic springs. Even considering fully coupled constitutive laws for the elements, the obtained solutions strictly preserve the two laws of thermo dynamics and the symmetries of the continuum evolution equations. Moreover, the unconditional control over the energy and the entropy growth have the effect of stabilizing the numerical solution, allowing the use of larger time steps than those suitable for comparable implicit algorithms. Proofs for these claims are provided in the article as well as numerical examples that illustrate the performance of the method.

Performance Analysis of 10,000 Residential PV Systems in France and Belgium

The main objective of this paper is to review the state of the art of residential PV systems in France and Belgium. This is done analyzing the operational data of 10650 PV systems (9657 located in France and 993 in Belgium). Three main questions are posed. How much energy do they produce? What level of performance is associated to their production? Which are the key parameters that most influence their quality? During the year 2010, the PV systems in France have produced a mean annual energy of 1163 kWh/kWp in France and 852 kWh/kWp in Belgium. As a whole, the orientation of PV generators causes energy productions to be some 7% inferior to optimally oriented PV systems. The mean Performance Ratio is 76% in France and 78% in Belgium, and the mean Performance Index is 85% in both countries. On average, the real power of the PV modules falls 4.9% below its corresponding nominal power announced on the manufacturer?s datasheet. A brief analysis by PV modules technology has lead to relevant observations about two technologies in particular. On the one hand, the PV systems equipped with Heterojunction with Intrinsic. Thin layer (HIT) modules show performances higher than average. On the other hand, the systems equipped with Copper Indium (di)Selenide (CIS) modules show a real power that is 16 % lower than their nominal value.

Cost and energy efficient reconfigurable embedded platform using Spartan-6 FPGAs

Modern FPGAs with run-time reconfiguration allow the implementation of complex systems offering both the flexibility of software-based solutions combined with the performance of hardware. This combination of characteristics, together with the development of new specific methodologies, make feasible to reach new points of the system design space, and make embedded systems built on these platforms acquire more and more importance. However, the practical exploitation of this technique in fields that traditionally have relied on resource restricted embedded systems, is mainly limited by strict power consumption requirements, the cost and the high dependence of DPR techniques with the specific features of the device technology underneath. In this work, we tackle the previously reported problems, designing a reconfigurable platform based on the low-cost and low-power consuming Spartan-6 FPGA family. The full process to develop the platform will be detailed in the paper from scratch. In addition, the implementation of the reconfiguration mechanism, including two profiles, is reported. The first profile is a low-area and low-speed reconfiguration engine based mainly on software functions running on the embedded processor, while the other one is a hardware version of the same engine, implemented in the FPGA logic. This reconfiguration hardware block has been originally designed to the Virtex-5 family, and its porting process will be also described in this work, facing the interoperability problem among different families.

Performance Modeling of Fresnel-Based CPV Systems: Effects of Deformations under Real Operation Conditions

Getting a lower energy cost has always been a challenge for concentrated photovoltaic. The FK concentrator enhances the performance (efficiency, acceptance angle and manufacturing tolerances) of the conventional CPV system based on a Fresnel primary stage and a secondary lens, while keeping its simplicity and potentially low‐cost manufacturing. At the same time F‐XTP (Fresnel lens+reflective prism), at the first glance has better cost potential but significantly higher sensitivity to manufacturing errors. This work presents comparison of these two approaches applied to two main technologies of Fresnel lens production (PMMA and Silicone on Glass) and effect of standard deformations that occur under real operation conditions

Digital Control Implementation to Reduce the Cost and Improve the Performance of the Control Stage of an Industrial Switched-Mode Power Supply

The main objective of this work is the design and implementation of the digital control stage of a 280W AC/DC industrial power supply in a single low-cost microcontroller to replace the analog control stage. The switch-mode power supply (SMPS) consists of a PFC boost converter with fixed frequency operation and a variable frequency LLC series resonant DC/DC converter. Input voltage range is 85VRMS-550VRMS and the output voltage range is 24V-28V. A digital controller is especially suitable for this kind of SMPS to implement its multiple functionalities and to keep the efficiency and the performance high over the wide range of input voltages. Additional advantages of the digital control are reliability and size. The optimized design and implementation of the digital control stage it is presented. Experimental results show the stable operation of the controlled system and an estimation of the cost reduction achieved with the digital control stage.

Stability and Transient Performance Assessment in a COTS-Module-Based Distributed DC/DC System

This paper introduces a method to analyze and predict stability and transient performance of a distributed system where COTS (Commercial-off-the-shelf) modules share an input filter. The presented procedure is based on the measured data from the input and output terminals of the power modules. The required information for the analysis is obtained by performing frequency response measurements for each converter. This attained data is utilized to compute special transfer functions, which partly determine the source and load interactions within the converters. The system level dynamic description is constructed based on the measured and computed transfer functions introducing cross-coupling mechanisms within the system. System stability can be studied based on the well-known impedance- related minor-loop gain at an arbitrary interface within the system.

Energy/power consumption model for an embedded processor board

This dissertation, whose research has been conducted at the Group of Electronic and Microelectronic Design (GDEM) within the framework of the project Power Consumption Control in Multimedia Terminals (PCCMUTE), focuses on the development of an energy estimation model for the battery-powered embedded processor board. The main objectives and contributions of the work are summarized as follows: A model is proposed to obtain the accurate energy estimation results based on the linear correlation between the performance monitoring counters (PMCs) and energy consumption. the uniqueness of the appropriate PMCs for each different system, the modeling methodology is improved to obtain stable accuracies with slight variations among multiple scenarios and to be repeatable in other systems. It includes two steps: the former, the PMC-filter, to identify the most proper set among the available PMCs of a system and the latter, the k-fold cross validation method, to avoid the bias during the model training stage. The methodology is implemented on a commercial embedded board running the 2.6.34 Linux kernel and the PAPI, a cross-platform interface to configure and access PMCs. The results show that the methodology is able to keep a good stability in different scenarios and provide robust estimation results with the average relative error being less than 5%. Este trabajo fin de máster, cuya investigación se ha desarrollado en el Grupo de Diseño Electrónico y Microelectrónico (GDEM) en el marco del proyecto PccMuTe, se centra en el desarrollo de un modelo de estimación de energía para un sistema empotrado alimentado por batería. Los objetivos principales y las contribuciones de esta tesis se resumen como sigue: Se propone un modelo para obtener estimaciones precisas del consumo de energía de un sistema empotrado. El modelo se basa en la correlación lineal entre los valores de los contadores de prestaciones y el consumo de energía. Considerando la particularidad de los contadores de prestaciones en cada sistema, la metodología de modelado se ha mejorado para obtener precisiones estables, con ligeras variaciones entre escenarios múltiples y para replicar los resultados en diferentes sistemas. La metodología incluye dos etapas: la primera, filtrado-PMC, que consiste en identificar el conjunto más apropiado de contadores de prestaciones de entre los disponibles en un sistema y la segunda, el método de validación cruzada de K iteraciones, cuyo fin es evitar los sesgos durante la fase de entrenamiento. La metodología se implementa en un sistema empotrado que ejecuta el kernel 2.6.34 de Linux y PAPI, un interfaz multiplataforma para configurar y acceder a los contadores. Los resultados muestran que esta metodología consigue una buena estabilidad en diferentes escenarios y proporciona unos resultados robustos de estimación con un error medio relativo inferior al 5%.

Energy and power aware scheduling algorithm modeling for battery powered embedded systems

Energy management has always been recognized as a challenge in mobile systems, especially in modern OS-based mobile systems where multi-functioning are widely supported. Nowadays, it is common for a mobile system user to run multiple applications simultaneously while having a target battery lifetime in mind for a specific application. Traditional OS-level power management (PM) policies make their best effort to save energy under performance constraint, but fail to guarantee a target lifetime, leaving the painful trading off between the total performance of applications and the target lifetime to the user itself. This thesis provides a new way to deal with the problem. It is advocated that a strong energy-aware PM scheme should first guarantee a user-specified battery lifetime to a target application by restricting the average power of those less important applications, and in addition to that, maximize the total performance of applications without harming the lifetime guarantee. As a support, energy, instead of CPU or transmission bandwidth, should be globally managed as the first-class resource by the OS. As the first-stage work of a complete PM scheme, this thesis presents the energy-based fair queuing scheduling, a novel class of energy-aware scheduling algorithms which, in combination with a mechanism of battery discharge rate restricting, systematically manage energy as the first-class resource with the objective of guaranteeing a user-specified battery lifetime for a target application in OS-based mobile systems. Energy-based fair queuing is a cross-application of the traditional fair queuing in the energy management domain. It assigns a power share to each task, and manages energy by proportionally serving energy to tasks according to their assigned power shares. The proportional energy use establishes proportional share of the system power among tasks, which guarantees a minimum power for each task and thus, avoids energy starvation on any task. Energy-based fair queuing treats all tasks equally as one type and supports periodical time-sensitive tasks by allocating each of them a share of system power that is adequate to meet the highest energy demand in all periods. However, an overly conservative power share is usually required to guarantee the meeting of all time constraints. To provide more effective and flexible support for various types of time-sensitive tasks in general purpose operating systems, an extra real-time friendly mechanism is introduced to combine priority-based scheduling into the energy-based fair queuing. Since a method is available to control the maximum time one time-sensitive task can run with priority, the power control and time-constraint meeting can be flexibly traded off. A SystemC-based test-bench is designed to assess the algorithms. Simulation results show the success of the energy-based fair queuing in achieving proportional energy use, time-constraint meeting, and a proper trading off between them. La gestión de energía en los sistema móviles está considerada hoy en día como un reto fundamental, notándose, especialmente, en aquellos terminales que utilizando un sistema operativo implementan múltiples funciones. Es común en los sistemas móviles actuales ejecutar simultaneamente diferentes aplicaciones y tener, para una de ellas, un objetivo de tiempo de uso de la batería. Tradicionalmente, las políticas de gestión de consumo de potencia de los sistemas operativos hacen lo que está en sus manos para ahorrar energía y satisfacer sus requisitos de prestaciones, pero no son capaces de proporcionar un objetivo de tiempo de utilización del sistema, dejando al usuario la difícil tarea de buscar un compromiso entre prestaciones y tiempo de utilización del sistema. Esta tesis, como contribución, proporciona una nueva manera de afrontar el problema. En ella se establece que un esquema de gestión de consumo de energía debería, en primer lugar, garantizar, para una aplicación dada, un tiempo mínimo de utilización de la batería que estuviera especificado por el usuario, restringiendo la potencia media consumida por las aplicaciones que se puedan considerar menos importantes y, en segundo lugar, maximizar las prestaciones globales sin comprometer la garantía de utilización de la batería. Como soporte de lo anterior, la energía, en lugar del tiempo de CPU o el ancho de banda, debería gestionarse globalmente por el sistema operativo como recurso de primera clase. Como primera fase en el desarrollo completo de un esquema de gestión de consumo, esta tesis presenta un algoritmo de planificación de encolado equitativo (fair queueing) basado en el consumo de energía, es decir, una nueva clase de algoritmos de planificación que, en combinación con mecanismos que restrinjan la tasa de descarga de una batería, gestionen de forma sistemática la energía como recurso de primera clase, con el objetivo de garantizar, para una aplicación dada, un tiempo de uso de la batería, definido por el usuario, en sistemas móviles empotrados. El encolado equitativo de energía es una extensión al dominio de la energía del encolado equitativo tradicional. Esta clase de algoritmos asigna una reserva de potencia a cada tarea y gestiona la energía sirviéndola de manera proporcional a su reserva. Este uso proporcional de la energía garantiza que cada tarea reciba una porción de potencia y evita que haya tareas que se vean privadas de recibir energía por otras con un comportamiento más ambicioso. Esta clase de algoritmos trata a todas las tareas por igual y puede planificar tareas periódicas en tiempo real asignando a cada una de ellas una reserva de potencia que es adecuada para proporcionar la mayor de las cantidades de energía demandadas por período. Sin embargo, es posible demostrar que sólo se consigue cumplir con los requisitos impuestos por todos los plazos temporales con reservas de potencia extremadamente conservadoras. En esta tesis, para proporcionar un soporte más flexible y eficiente para diferentes tipos de tareas de tiempo real junto con el resto de tareas, se combina un mecanismo de planificación basado en prioridades con el encolado equitativo basado en energía. En esta clase de algoritmos, gracias al método introducido, que controla el tiempo que se ejecuta con prioridad una tarea de tiempo real, se puede establecer un compromiso entre el cumplimiento de los requisitos de tiempo real y el consumo de potencia. Para evaluar los algoritmos, se ha diseñado en SystemC un banco de pruebas. Los resultados muestran que el algoritmo de encolado equitativo basado en el consumo de energía consigue el balance entre el uso proporcional a la energía reservada y el cumplimiento de los requisitos de tiempo real.

Risk sharing with Multilateral Financial Institutions in infrastructure and energy project financing : effect on capital relief for commercial banks

(Matsukawa and Habeck, 2007) analyse the main instruments for risk mitigation in infrastructure financing with Multilateral Financial Institutions (MFIs). Their review coincided with the global financial crisis of 2007-08, and is highly relevant in current times considering the sovereign debt crisis, the lack of available capital and the increases in bank regulation in Western economies. The current macroeconomic environment has seen a slowdown in the level of finance for infrastructure projects, as they pose a higher credit risk given their requirements for long term investments. The rationale for this work is to look for innovative solutions that are focused on the credit risk mitigation of infrastructure and energy projects whilst optimizing the economic capital allocation for commercial banks. This objective is achieved through risk-sharing with MFIs and looking for capital relief in project finance transactions. This research finds out the answer to the main question: "What is the impact of risk-sharing with MFIs on project finance transactions to increase their efficiency and viability?", and is developed from the perspective of a commercial bank assessing the economic capital used and analysing the relevant variables for it: Probability of Default, Loss Given Default and Recovery Rates, (Altman, 2010). An overview of project finance for the infrastructure and energy sectors in terms of the volume of transactions worldwide is outlined, along with a summary of risk-sharing financing with MFIs. A review of the current regulatory framework beneath risk-sharing in structured finance with MFIs is also analysed. From here, the impact of risk-sharing and the diversification effect in infrastructure and energy projects is assessed, from the perspective of economic capital allocation for a commercial bank. CreditMetrics (J. P. Morgan, 1997) is applied over an existing well diversified portfolio of project finance infrastructure and energy investments, working with the main risk capital measures: economic capital, RAROC, and EVA. The conclusions of this research show that economic capital allocation on a portfolio of project finance along with risk-sharing with MFIs have a huge impact on capital relief whilst increasing performance profitability for commercial banks. There is an outstanding diversification effect due to the portfolio, which is combined with risk mitigation and an improvement in recovery rates through Partial Credit Guarantees issued by MFIs. A stress test scenario analysis is applied to the current assumptions and credit risk model, considering a downgrade in the rating for the commercial bank (lender) and an increase of default in emerging countries, presenting a direct impact on economic capital, through an increase in expected loss and a decrease in performance profitability. Getting capital relief through risk-sharing makes it more viable for commercial banks to finance infrastructure and energy projects, with the beneficial effect of a direct impact of these investments on GDP growth and employment. The main contribution of this work is to promote a strategic economic capital allocation in infrastructure and energy financing through innovative risk-sharing with MFIs and economic pricing to create economic value added for banks, and to allow the financing of more infrastructure and energy projects. This work suggests several topics for further research in relation to issues analysed. (Matsukawa and Habeck, 2007) analizan los principales instrumentos de mitigación de riesgos en las Instituciones Financieras Multilaterales (IFMs) para la financiación de infraestructuras. Su presentación coincidió con el inicio de la crisis financiera en Agosto de 2007, y sus consecuencias persisten en la actualidad, destacando la deuda soberana en economías desarrolladas y los problemas capitalización de los bancos. Este entorno macroeconómico ha ralentizado la financiación de proyectos de infraestructuras. El actual trabajo de investigación tiene su motivación en la búsqueda de soluciones para la financiación de proyectos de infraestructuras y de energía, mitigando los riesgos inherentes, con el objeto de reducir el consumo de capital económico en los bancos financiadores. Este objetivo se alcanza compartiendo el riesgo de la financiación con IFMs, a través de estructuras de risk-sharing. La investigación responde la pregunta: "Cuál es el impacto de risk-sharing con IFMs, en la financiación de proyectos para aumentar su eficiencia y viabilidad?". El trabajo se desarrolla desde el enfoque de un banco comercial, estimando el consumo de capital económico en la financiación de proyectos y analizando las principales variables del riesgo de crédito, Probability of Default, Loss Given Default and Recovery Rates, (Altman, 2010). La investigación presenta las cifras globales de Project Finance en los sectores de infraestructuras y de energía, y analiza el marco regulatorio internacional en relación al consumo de capital económico en la financiación de proyectos en los que participan IFMs. A continuación, el trabajo modeliza una cartera real, bien diversificada, de Project Finance de infraestructuras y de energía, aplicando la metodología CreditMet- rics (J. P. Morgan, 1997). Su objeto es estimar el consumo de capital económico y la rentabilidad de la cartera de proyectos a través del RAROC y EVA. La modelización permite estimar el efecto diversificación y la liberación de capital económico consecuencia del risk-sharing. Los resultados muestran el enorme impacto del efecto diversificación de la cartera, así como de las garantías parciales de las IFMs que mitigan riesgos, mejoran el recovery rate de los proyectos y reducen el consumo de capital económico para el banco comercial, mientras aumentan la rentabilidad, RAROC, y crean valor económico, EVA. En escenarios económicos de inestabilidad, empeoramiento del rating de los bancos, aumentos de default en los proyectos y de correlación en las carteras, hay un impacto directo en el capital económico y en la pérdida de rentabilidad. La liberación de capital económico, como se plantea en la presente investigación, permitirá financiar más proyectos de infraestructuras y de energía, lo que repercutirá en un mayor crecimiento económico y creación de empleo. La principal contribución de este trabajo es promover la gestión activa del capital económico en la financiación de infraestructuras y de proyectos energéticos, a través de estructuras innovadoras de risk-sharing con IFMs y de creación de valor económico en los bancos comerciales, lo que mejoraría su eficiencia y capitalización. La aportación metodológica del trabajo se convierte por su originalidad en una contribución, que sugiere y facilita nuevas líneas de investigación académica en las principales variables del riesgo de crédito que afectan al capital económico en la financiación de proyectos.

Influence of nutritional and management practices on productive performance and egg quality of brown egg-laying hens = Influencia de factores nutricionales y de manejo sobre la productividad y calidad del huevo en gallinas ponedoras rubias

El objetivo general de esta Tesis Doctoral fue estudiar la influencia de diversos factores nutricionales y de manejo sobre la productividad y la calidad del huevo en gallinas ponedoras comerciales rubias. Los factores estudiados fueron: 1) Cereal principal y tipo de grasa en la dieta; 2) Nivel de proteína bruta y grasa en la dieta; 3) Nivel energético de la dieta; 4) Peso vivo al inicio del período de puesta. En el experimento 1, la influencia del cereal principal en la dieta y el tipo de grasa suplementada en la dieta sobre los parámetros productivos y la calidad del huevo fue estudiado en 756 gallinas rubias de la estirpe Lohmann desde la sem 22 hasta las 54 de vida. El experimento se realizó mediante un diseño completamente al azar con 9 tratamientos ordenados factorialmente, con 3 cereales bases (maíz, trigo blando y cebada) y 3 tipos de grasa que variaban en su contenido en ácido linoléico (aceite de soja, oleína vegetal mezcla y manteca). Todas las dietas satisfacian las recomendaciones nutricionales para gallinas ponedoras rubias según el NRC (1994) y FEDNA (2008). La unidad experimental fue la jaula para todas las variables. Cada tratamiento fue replicado 4 veces, y la unidad experimental estuvo formada por 21 gallinas alojadas en grupos de 7. Las dietas fueron formuladas con un contenido nutritivo similar, excepto para el ácido linoléico, que varió en función del tipo de cereal y grasa utilizado. Así, dependiendo de la combinación de estos elementos el contenido de este ácido graso varió desde un 0.8% (dieta trigo-manteca) a un 3.4% (dieta maíz-aceite de soja). Este rango de ácido linoléico permitió estimar el nivel mínimo de este nutriente en el pienso que permite maximizar el peso del huevo. Los parámetros productivos y la calidad del huevo se controlaron cada 28 días y el peso de las aves se midió individualmente al inicio y al final del experimento con el objetivo de estudiar la variación en el peso vivo de los animales. No se observaron interacciones entre el tipo de cereal y grasa en la dieta para ninguna de las variables productivas estudiadas. Los tratamientos experimentales no afectaron a las principales variables productivas (porcentaje de puesta, peso del huevo y masa de huevo). Sin embargo, la ganancia de peso fue mayor en gallinas alimentadas con maíz o trigo que las gallinas alimentadas con cebada (243 vs. 238 vs. 202 g, respectivamente; P< 0.05). En el mismo sentido, las gallinas alimentadas con manteca obtuvieron una mayor ganancia de peso que las gallinas alimentadas con aceite de soja u oleína vegetal (251 vs. 221 vs. 210 g, respectivamente; P< 0.05). En cuanto a las variables estudiadas en relación con la calidad del huevo, ninguna de las variables estudiadas se vio afectada por el tratamiento experimental, salvo la pigmentación de la yema. Así, las gallinas alimentadas con maíz como cereal principal obtuvieron una mayor puntuación en relación con la escala de color que las gallinas alimentadas con trigo y con cebada (9.0 vs. 8.3 vs. 8.3, respectivamente; P< 0.001). La pigmentación de la yema también se vio afectada por el tipo de grasa en la dieta, así, las gallinas alimentadas con manteca obtuvieron una mayor puntuación de color en relación con la escala de color que las gallinas alimentadas con aceite de soja u oleína vegetal (8.9 vs. 8.5 vs. 8.2, respectivamente; P< 0.001). La influencia del contenido en ácido linoléico respecto al peso de huevo y masa de huevo fue mayor a medida que el contenido de dicho ácido graso se redujo en la dieta. Así, la influencia de la dieta en los radios peso de huevo/g linoléico ingerido y masa de huevo/g linoléico ingerido fue significativamente mayor a medida que el contenido en dicho ácido graso disminuyo en la dieta (P< 0.001). Los resultados del ensayo indican que las gallinas ponedoras rubias no necesitan más de un 1.0% de ácido linoléico en la dieta para maximizar la producción y el tamaño del huevo. Además, se pudo concluir que los 3 cereales y las 3 grasas utilizadas pueden sustituirse en la dieta sin ningún perjuicio productivo o referente a la calidad del huevo siempre que los requerimientos de los animales sean cubiertos. En el experimento 2, la influencia del nivel de proteína bruta y el contenido de grasa de la dieta sobre los parámetros productivos y la calidad del huevo fue estudiado en 672 gallinas ponedoras rubias de la estirpe Lohmann entre las sem 22 y 50 de vida. El experimento fue conducido mediante un diseño completamente al azar con 8 tratamientos ordenados factorialmente con 4 dietas y 2 pesos vivos distintos al inicio de puesta (1592 vs. 1860g). Tres de esas dietas diferían en el contenido de proteína bruta (16.5%, 17.5% y 18.5%) y tenían un contenido en grasa añadida de 1.8%. La cuarta dieta tenía el nivel proteico más elevado (18.5%) pero fue suplementada con 3.6% de grasa añadida en vez de 1.8%. Cada tratamiento fue replicado 4 veces y la unidad experimental consistió en 21 gallinas alojadas dentro de grupos de 7 animales en 3 jaulas contiguas. Todas las dietas fueron isocalóricas (2750 kcal EMAn/kg) y cubrieron las recomendaciones en aminoácidos para gallinas ponedoras rubias (Arg, Ile, Lys, Met, Thr, Trp, TSAA y Val) según el NRC (1994) y FEDNA (2008). Los efectos de los tratamientos sobre las variables productivas y la calidad de huevo fueron estudiados cada 28 días. La dieta no afecto a ninguna de las variables productivas estudiadas a lo largo del período productivo. Sin embargo, el peso inicial origino que las gallinas pesadas consumieran más (120.6 vs. 113.9 g; P< 0.001), obtuvieran un porcentaje de puesta mayor (92.5 vs. 89.8%; P< 0.01) y un peso del huevo mayor (64.9 vs. 62.4 g; P< 0.001) que las gallinas ligeras. El peso inicial de las gallinas no afecto al IC por kg de huevo ni a la mortalidad, sin embargo, la ganancia de peso fue mayor (289 vs. 233 g; P< 0.01) y el IC por docena de huevos fue mejor (1.52 vs. 1.57; P< 0.01) en las gallinas ligeras que en las gallinas pesadas. En cuanto a la calidad del huevo, la dieta no influyó sobre ninguna de las variables estudiadas. Los resultados del ensayo muestran que las gallinas ponedoras rubias, independientemente de su peso vivo al inicio de la puesta, no necesitan una cantidad de proteína bruta superior a 16.5% para maximizar la producción, asegurando que las dietas cubren los requerimientos en AA indispensables. Asimismo, se puedo concluir que las gallinas con un peso más elevado al inicio de puesta producen más masa de huevo que las gallinas con un peso más bajo debido a que las primeras producen más cantidad de huevos y más pesados. Sin embargo, ambos grupos de peso obtuvieron el mismo IC por kg de huevo y las gallinas más livianas en peso obtuvieron un mejor IC por docena de huevo que las pesadas. En el experimento 3 la influencia de la concentración energética sobre los parámetros productivos y la calidad del huevo fue estudiada en 520 gallinas ponedoras rubias de la estirpe Hy-Line en el período 24-59 sem de vida. Se utilizaron 8 tratamientos ordenados factorialmente con 4 dietas que variaron en el contenido energético (2650, 2750, 2850 y 2950 kcal EMAn/kg) y 2 pesos vivos distintos al inicio del período de puesta (1733 vs. 1606g). Cada tratamiento fue replicado 5 veces y la unidad experimental consistió en una jaula con 13 aves. Todas las dietas se diseñaron para que tuvieran una concentración nutritiva similar por unidad energética. Las variables productivas y de calidad de huevo se estudiaron mediante controles cada 28 días desde el inicio del experimento. No se observaron interacciones entre el nivel energético y el peso inicial del ave para ninguna de las variables estudiadas. Un incremento en la concentración energética de la dieta incrementó la producción de huevos (88.8 % vs. 91.2 % vs. 92.7 % vs. 90.5 %), masa de huevo (56.1 g/d vs. 58.1 g/d vs. 58.8 g/d vs. 58.1 g/d), y eficiencia energética (5.42 vs. 5.39 vs. 5.38 vs. 5.58 kcal EMA/g huevo) de forma lineal y cuadrática (P< 0.05) y afectó significativamente a la ganancia de peso (255 g vs. 300 g vs. 325 g vs. 359 g; P<0.05) . Sin embargo, un incremento en la concentración energética provocó un descenso lineal en el consumo de los animales (115 g vs. 114 g vs. 111 g vs. 110 g; P< 0.001) y un descenso lineal y cuadrático en el IC por kg de huevo (2.05 vs. 1.96 vs. 1.89 vs. 1.89; P< 0.01). En cuanto a la calidad del huevo, un incremento en el contenido energético de la dieta provocó una reducción en la calidad del albumen de forma lineal en forma de reducción de Unidades Haugh (88.4 vs. 87.8 vs. 86.3 vs. 84.7; P< 0.001), asimismo el incremento de energía redujo de forma lineal la proporción relativa de cáscara en el huevo (9.7 vs. 9.6 vs. 9.6 vs. 9.5; P< 0.001). Sin embargo, el incremento energético propició un incremento lineal en la pigmentación de la yema del huevo (7.4 vs. 7.4 vs. 7.6 vs. 7.9; P< 0.001). El peso vivo al inicio de la prueba afecto a las variables productivas y a la calidad del huevo. Así, los huevos procedentes de gallinas pesadas al inicio de puesta tuvieron una mayor proporción de yema (25.7 % vs. 25.3 %; P< 0.001) y menor de albumen (64.7 vs. 65.0; P< 0.01) y cáscara (9.5 vs. 9.6; P< 0.05) respecto de los huevos procedentes de gallinas ligeras. Consecuentemente, el ratio yema:albumen fue mayor (0.40 vs. 0.39; P< 0.001) para las gallinas pesadas. Según los resultados del experimento se pudo concluir que las actuales gallinas ponedoras rubias responden con incrementos en la producción y en la masa del huevo a incrementos en la concentración energética hasta un límite que se sitúa en 2850 kcal EMAn/kg. Asimismo, los resultados obtenidos entre los 2 grupos de peso al inicio de puesta demostraron que las gallinas pesadas al inicio de puesta tienen un mayor consumo y producen huevos más pesados, con el consecuente aumento de la masa del huevo respecto de gallinas más ligeras. Sin embargo, el IC por kg de huevo fue el mismo en ambos grupos de gallinas y el IC por docena de huevo fue mejor en las gallinas ligeras. Asimismo, la eficiencia energética fue mejor en las gallinas ligeras. Abstract The general aim of this PhD Thesis was to study the influence of different nutritional factors and management on the productivity and egg quality of comercial Brown laying hens. The factor studied were: 1) The effect of the main cereal and type of fat of the diet; 2) The effect of crude protein and fat content of the diet; 3) The effect of energy concentration of the diet; 4) The effect of initial body weight of the hens at the onset of lay period. In experiment 1, the influence of the main cereal and type of supplemental fat in the diet on productive performance and egg quality of the eggs was studied in 756 Lohmann brown-egg laying hens from 22 to 54 wk of age. The experiment was conducted as a completely randomized design with 9 treatments arranged factorially with 3 cereals (dented corn, soft wheat, and barley) and 3 types of fat (soy oil, acidulated vegetable soapstocks, and lard). Each treatment was replicated 4 times (21 hens per replicate). All diets were formulated according to NRC (1994) and FEDNA (2008) to have similar nutrient content except for linoleic acid that ranged from 0.8 (wheat-lard diet) to 3.4% (corn-soy bean oil) depending on the combination of cereal and fat source used. This approach will allow to estimate the minimum level of linoleic acid in the diets that maximizes egg weight. Productive performance and egg quality traits were recorded every 28 d and BW of the hens was measured individually at the beginning and at the end of the experiment. No significant interactions between main factors were detected for any of the variables studied. Egg production, egg weight, and egg mass were not affected by dietary treatment. Body weight gain was higher (243 vs. 238 vs. 202 g; P<0.05) for hens fed corn or wheat than for hens fed barley and also for hens fed lard than for hens fed soy oil or acidulated vegetable soapstocks (251 vs. 221 vs. 210 g; P< 0.05). Egg quality was not influenced by dietary treatment except for yolk color that was greater (9.0 vs. 8.3 vs. 8.3; P< 0.001) for hens fed corn than for hens fed wheat or barley and for hens fed lard than for hens fed soy oil or acidulated vegetable soapstocks (8.9 vs. 8.5 vs. 8.2, respectivamente; P< 0.001). The influence of linoleic acid on egg weight and egg mass was higher when the fatty acid was reduced in the diet. Thus, the influence of the diet in egg weight/g linoleic acid intake and egg mass/g linolec acid intake was higher when the amount of this fatty acid decreased in the diet (P< 0.001). It is concluded that brown egg laying hens do not need more than 1.0% of linoleic acid in the diet (1.16 g/hen/d) to maximize egg production and egg size. The 3 cereals and the 3 fat sources tested can replace each other in the diet provided that the linoleic acid requirements to maximize egg size are met. In experiment 2, the influence of CP and fat content of the diet on performance and egg quality traits was studied in 672 Lohmann brown egg-laying hens from 22 to 50 wk of age. The experiment was conducted as a completely randomized design with 8 treatments arranged factorially with 4 diets and 2 initial BW of the hens (1,592 vs. 1,860 g). Three of these diets differed in the CP content (16.5, 17.5, and 18.5%) and included 1.8% added fat. The fourth diet had also 18.5% CP but was supplemented with 3.6% fat instead of 1.8% fat. Each treatment was replicated 4 times and the experimental unit consisted of 21 hens allocated in groups of 7 in 3 adjacent cages. All diets were isocaloric (2,750 kcal AME/kg) and met the recommendations of brown egg-laying hens for digestible Arg, Ile, Lys, Met, Thr, Trp, TSAA, and Val. Productive performance and egg quality were recorded by replicate every 28-d. For the entire experimental period, diet did not affect any of the productive performance traits studied but the heavier hens had higher ADFI (120.6 vs. 113.9g; P< 0.001), egg production (92.5 vs. 89.8%; P< 0.01), and egg weight (64.9 vs. 62.4g; P< 0.001) than the lighter hens. Initial BW did not affect feed conversion per kilogram of eggs or hen mortality but BW gain was higher (289 vs. 233g; P< 0.01) and FCR per dozen of eggs was better (1.52 vs. 1.57; P< 0.01) for the lighter than for the heavier hens. None of the egg quality variables studied was affected by dietary treatment or initial BW of the hens. It is concluded that brown egg-laying hens, irrespective of their initial BW, do not need more than 16.5% CP to maximize egg production provided that the diet meet the requirements for key indispensable amino acids. Heavier hens produce more eggs that are larger than lighter hens but feed efficiency per kilogram of eggs is not affected. In experiment 3, the influence of AMEn concentration of the diet on productive performance and egg quality traits was studied in 520 Hy-Line brown egg-laying hens differing in initial BW from 24 to 59 wks of age. There were 8 treatments arranged factorially with 4 diets varying in energy content (2,650, 2,750, 2,850, and 2,950 kcal AMEn/kg) and 2 initial BW of the hens (1,733 vs. 1,606 g). Each treatment was replicated 5 times (13 hens per replicate) and all diets had similar nutrient content per unit of energy. No interactions between energy content of the diet and initial BW of the hens were detected for any trait. An increase in energy concentration of the diet increased (linear, P< 0.05; quadratic P< 0.05) egg production (88.8 % vs. 91.2 % vs. 92.7 % vs. 90.5 %), egg mass (56.1 g/d vs. 58.1 g/d vs. 58.8 g/d vs. 58.1 g/d), energy efficiency (5.42 vs. 5.39 vs. 5.38 vs. 5.58 kcal AMEn/g of egg), and BW gain (255 g vs. 300 g vs. 325 g vs. 359 g; P<0.05) but decreased ADFI (115 g vs. 114 g vs. 111 g vs. 110 g; P< linear, P< 0.001) and FCR per kg of eggs (2.05 vs. 1.96 vs. 1.89 vs. 1.89; linear, P< 0.01; quadratic P< 0.01). An increase in energy content of the diet reduced Haugh units (88.4 vs. 87.8 vs. 86.3 vs. 84.7; P< 0.01) and the proportion of shell in the egg (9.7 vs. 9.6 vs. 9.6 vs. 9.5; P< 0.001). Feed intake (114.6 vs. 111.1 g/hen per day), AMEn intake (321 vs. 311 kcal/hen per day), egg weight (64.2 vs. 63.0 g), and egg mass (58.5 vs. 57.0 g) were higher for the heavier than for the lighter hens (P<0.01) but FCR per kg of eggs and energy efficiency were not affected. Eggs from the heavier hens had higher proportion of yolk (25.7 % vs. 25.3 %; P< 0.001) and lower of albumen (64.7 vs. 65.0; P< 0.01) and shell (9.5 vs. 9.6; P< 0.05) than eggs from the lighter hens. Consequently, the yolk to albumen ratio was higher (0.40 vs. 0.39; P< 0.001) for the heavier hens. It is concluded that brown egg-laying hens respond with increases in egg production and egg mass, to increases in AMEn concentration of the diet up to 2,850 kcal/kg. Heavy hens had higher feed intake and produced heavier eggs and more egg mass than light hens. However, energy efficiency was better for the lighter hens.