Coastal transition zones form important interlinking regions where marine ecosystems, rivers and estuarine environments significantly influence each other. Coastal rocky shores are key habitats that sustain a variety of primary producers and invertebrates and due to the dynamic nature of coastal ecosystems, suspension-feeders on rocky shores can be influenced by an array of autochthonous and allochthonous food sources. Fatty acid and stable isotope trophic markers were employed to distinguish between regional and temporal changes in the potential food sources to rocky shore suspension-feeders in the Eastern Cape Province of South Africa. The primary aim was to assess the spatial and temporal influences of contrasting river flows on the available food sources to three indigenous coastal suspensionfeeders, namely the volcano barnacle Tetraclita serrata, brown mussel Perna perna and tubebuilding polychaete Gunnarea capensis. This was done by examining the intra- and interspecific changes in the fatty acid and stable isotope signatures of the barnacles, mussels and polychaetes in the adjacent marine environment of a freshwater-restricted (Kariega) and freshwater-dominated (Great Fish) estuary during austral summer and winter. Multivariate and Kruskal-Wallis analyses of variance on the fatty acid and isotopic signatures, respectively, identified significant regional changes in the barnacles and mussels, while only stable isotopes distinguished between the Kariega and Great Fish polychaetes (P < 0.05). In addition, significant temporal changes were observed in consumer fatty acids and isotope values in both regions (P < 0.05). Bacterial sources, detritus and phytoplankton assemblages, which are influenced by hydrology and vegetation, differed between regions and were mainly responsible for the regional and temporal separations. Principal component analyses on the consumer fatty acid signatures distinguished between animals situated upstream (i.e. north) and downstream (i.e. south) of the Kariega Estuary mouth in summer. The north/south separation was mainly due to greater contributions of diatoms to northernlocated animals and dinoflagellates and detritus to southern-located consumers. In addition, the south-flowing Agulhas Current on the eastern shores of southern Africa appeared to influence the north/south separation in the Kariega region, as water leaving the estuary was probably entrained into the south-easterly flowing currents, thereby depositing estuarinederived detritus to southern populations. In general, diatoms and detritus were essential food sources to the filter-feeders in summer, and flagellates, diatoms, zooplankton and detritus were important in winter. Coastal macroalgae was a key food source in the Kariega and Great Fish regions during both seasons. Consistently large levels of diatom markers (16:1n-7 and 20:5n-3) and dinoflagellate markers (22:6n-3) in consumer tissues in the Kariega and Great Fish regions identified that phytoplankton was their dominant food source. The barnacles, mussels and polychaetes had similar fatty acid markers and a fairly narrow δ¹³C range (-16.5 to -14.4 ‰), suggesting that they probably consumed similar food. Carbon isotope analyses, however, separated the suspension-feeders into slightly depleted (barnacles; -16.5 to -16.1 ‰), intermediate (mussels; -15.8 to -15.0 ‰) and enriched (polychaetes; -15.0 to -14.4 ‰) consumers, but did not provide conclusive evidence of their preferences for specific phytoplankton. Conversely, fatty acid analyses highlighted that barnacles and mussels had greater proportions of dinoflagellate markers (22:6n-3; 7.0-15.3 % TFA), while polychaetes had larger diatom levels (20:5n-3; 15.1-22.2 % TFA). In addition, all three species had consistently large contributions from bacterial fatty acids (15:0, i-16:0, 17:0 and i-18:0; 4.2-13.6 % TFA) in summer and winter, and large proportions of saturated fatty acids (33.3-53.1 % TFA) including those with 14 to 18 carbons, indicating that bacterial and detritus food sources played an important role in their diets. Barnacles had small levels of terrestrial markers (18:2n-6 and 18:3n-3; <2.5 % TFA) and demonstrated increased omnivorous feeding compared with the other suspension-feeders [increased levels of 20:1n-11 and 20:1n-9, higher 18:1n-9/18:1n-7 ratios at ~2.1, enriched δ¹⁵N values at ~10.6 ‰; zooplankton (potentially including microzooplankton, larvae and protists) contribution of up to 61 % of the diet]. Mussels contained significant proportions of the terrestrial markers (18:2n-6 and 18:3n-3; >2.5 % TFA) and exhibited intermediate omnivory (intermediate levels of 20:1n-11 and 20:1n-9, intermediate 18:1n-9/18:1n-7 ratios at ~1.3, less enriched δ¹⁵N values at ~7.9 ‰; zooplankton contribution of 10-15 % of the diet). The more depleted nitrogen signatures in the mussels relative to the barnacles and polychaetes possibly illustrated a stronger preference for autotrophic food. Polychaetes mainly consumed plant food sources (i.e. microalgae, macroalgae and detritus; high levels of i-18:0, 18:1n-9, 18:4n-3 and 20:5n-3) and displayed little omnivory (low levels of 20:1n-11 and 20:1n-9, low 18:1n-9/18:1n-7 ratios at ~0.4, intermediate δ¹⁵N values at ~9.1 ‰; zooplankton contribution of <10 % of the diet). The barnacles, mussels and polychaetes are all suspension-feeders, originally presumed to consume the same food sources. The variations observed among the species, therefore, may result from differences in the proportional contributions of the various food sources to their diets as well as distinctions in metabolism. The distinct changes in the fatty acid and stable isotope signatures in all three filter-feeders in the Kariega and Great Fish regions are likely influenced by the diversity in regional vegetation and hydrology in the different systems, combined with interspecific differences in resource partitioning among the species.

No description available.

L’histoire sociale du commerce du bétail et de ses acteurs en Brionnais-Charolais, de la fin du XIXe siècle à nos jours, se confond avec celle de la construction de la filière bovine qui se structure autour de trois spécialités : le naissage, l’embouche et le négoce. Plusieurs étapes, mises en évidence dans la thèse, l’ont jalonnée : développement de l’embouche dans la seconde moitié du XIXe siècle, accès progressif des cultivateurs-éleveurs à l’aisance au cours du XXe siècle, remise en cause des pratiques à partir des années 1960 au profit de l’élevage allaitant. Les apports de cette thèse – réalisée à partir de sources très fragmentaires dans un assemblage qui a nécessité quelque inventivité – à l’histoire rurale, sociale et économique sont multiples. Une mise en perspective des adaptations successives d’un monde agricole en profonde mutation est proposée. L’analyse des changements à l’échelle de la famille, de l’exploitation ou du commerce fait de cette thèse un travail pionnier. Les acteurs de la spécialisation sortent de l’ombre grâce à l’étude, selon une approche prosopographique, d’un corpus d’emboucheurs et de marchands de bestiaux. De même, sont mis en évidence des flux et des réseaux au sein desquels circulent le bétail et l’argent et qui contribuent au désenclavement du territoire observé. Jusqu’au milieu du XXe siècle, la société rurale brionnaise repose sur un équilibre patiemment acquis, bientôt ébranlé par la modernisation de l’agriculture et la Politique agricole commune. La filière s’organise progressivement dans la seconde moitié du XXe siècle. La professionnalisation du négoce de bétail passe par la fin des maquignons et la mise en place de structures coopératives. Au début du XXIe siècle, la question se pose du devenir des commerçants en bestiaux et de l’élevage dans le berceau de la charolaise. / The social history of cattle trade and its actors in Brionnais-Charolais, from the late 19th century up to nowadays merges into the history of the setting up of the cattle industry which has built itself around three fields : breeding, feeding and trade. My thesis reveals the different stages which have marked it up : from the development of cattle feeding in the second half of the 19th century, then the gradual access to wealth by farmers-breeders during the 20th century, to a questioning of old practices since the 1960s, replaced by brood cows breeding. I have carried out my thesis from very fragmentary sources into an assembly of facts (which had required great inventiveness) and shown how much contribution it could bring to the knowledge of rural, social and economical history. I propose a new perspective on the successive adaptations to a profoundly changing agricultural society. I have analyzed in a pioneering way the changes in the family as well as the farm or the trade fields. Thanks to a prosopographical approach, from a corpus of feeders and cattle dealers, this study brings the actors of specialization to light. In the same way, I have revealed the methods and the networks in which cattle and money circulate and which have contributed to opening up the studied area. Until the mid-20th century, the rural Brionnais society had rested on a patiently acquired equilibrium, soon shaken by a modernized agriculture and the Common Agricultural Policy. In the second half of the 20th century, the industry got itself organized gradually. The professionalization of cattle trade goes through the end of cattle dealers and the setting up of cooperatives. In the early 21st century, one has to wonder about the evolution of cattle traders and of breeding itself in the birthplace of Charolais cattle.

Numerous ecological studies have used lipids to determine trophic pathways in aquatic systems, as fatty acid profiles provide time-integrated information on an organism’s assimilated diet. Many of these studies have, however, been based on sample collections with a limited temporal scale. The trophic ecology of pelagic systems has been studied intensively using fatty acid analyses, but very little work has been directed toward benthic communities, with the intertidal being especially neglected. The investigation of trophic pathways within rocky shore communities will help us to better understand system responses to environmental changes. The determination of long term temporal variation of the food web within a community could reveal the type, magnitude, duration and frequency of highly seasonal productivity. Changes in fatty acid profiles through time in primary consumers of intertidal rocky shores are poorly understood, but represent an important step towards a more comprehensive understanding of rocky shore food webs, compared with those derived from snapshot or short-term studies. The aim of this thesis was to clarify the temporal variability in the diets of rocky shore intertidal suspension-feeders (the brown mussels Perna perna and the Cape reef worm, Gunnarea gaimardi) and grazers (the Cape sea urchin Parencinus angulosus and the Goat-eye limpet, Cymbulus oculus) on the south east coast of South Africa using fatty acid profiles, and to investigate the effects of life style (e.g. feeding mode) and life cycle on temporal variations in tissue fatty acid profiles. I had three hypotheses: firstly, that suspension-feeders experience high levels of variability in their diets through time because water quality has the potential to change quickly and drastically, whereas grazers experience less variability in their diets over time since their food sources are more constant. Secondly, the reproductive cycles of the suspension-feeder P. perna and the grazer P. angulosus affect the fatty acid composition of their gonads, with temporal variations in lipid composition reflecting changes in reproduction investment. Thirdly, the total amount of energetic reserves available for reproduction are different for each gender (females allocate more energy to egg production than males allocate to gamete production). To address these aims, fatty acid profiles of suspension-feeders and grazers were investigated over a period of twelve months (from July 2010 to June 2011) at a single site on the south east coast of South Africa. The results showed high variability in the fatty acid composition of both the suspension-feeders strongly related with changes in their food source (suspended particulate material). Furthermore, similar temporal changes in fatty acid profiles of the two suspension-feeders were observed over time, reflecting their common diet and life style. There were some inter-specific differences in the suspension-feeders, likely originating from differences in their particle capturing mechanisms. Grazers showed less variability through time compared with the suspension-feeders, with the limpets being more consistent than the sea urchins. The temporal variability in the sea urchin diets may have resulted from the highly diverse and heterogeneous food sources available to them, whereas limpets may be more selective and have a limited range of diet items. Differences between the two grazer species may have arose from differences in their feeding strategies and intertidal zonation. The fatty acid compositions of gonad tissues in both P. perna and P. angulosus showed temporal variability strongly related to reproductive cycle. Differences in the fatty acid values between females and males were apparent, with females richer in total and polyunsaturated fatty acids than males. Spawning and gametogenesis influenced the variability of fatty acids through time in both species, suggesting the importance of considering the reproductive cycle when studying lipids in rocky shore species. Little evidence of lipid transfer between muscles and gonads was seen, suggesting the importance of direct lipid storage into the reproductive tissues. The influence of diet and life history of intertidal consumers on the temporal variability of their fatty acid compositions is important to understand, as it provides us with a better understanding of the functioning of rocky shore systems. There is an enormous potential for future research in this field of study.

No description available.

[ES] La acuicultura es una de las principales actividades en el ámbito de la producción animal. Su progreso está delimitado por la dependencia de materias primas de origen tanto marino como terrestre, ambas necesarias para la elaboración de piensos destinados a la alimentación de las especies en cultivo. La introducción de nuevas materias primas o sustancias destinadas a la mejora de la fisiología de la especie (piensos funcionales) puede comprometer la palatabilidad de los piensos, su consumo y por extensión el crecimiento de los animales. El objetivo principal de esta tesis fue encontrar aditivos sensoriales (saborizantes) que puedan sobrepasar los efectos negativos sobre la palatabilidad de los piensos inducidos por la inclusión de materias vegetales en la elaboración de los piensos para cultivo de la dorada (Sparus aurata). Para ello, evaluamos la funcionalidad de los sistemas de auto-demanda en el estudio del comportamiento alimenticio de esta especie, profundizando en su posible utilidad en la discriminación sensorial/gustativa de los piensos. Evaluamos el efecto de estrógenos y andrógenos no aromatizables sobre la ingesta como posibles factores anti-nutricionales presentes en los piensos de sustitución. Estudiamos el efecto de dos saborizantes sobre la ingesta y dinámica de crecimiento de la dorada y finalmente estudiamos el posible efecto de estos sobre la anorexia inducida por el estrés. Los resultados demuestran que la dorada se adapta bien a los sistemas de auto-demanda y estos pueden ser utilizados para el estudio de su comportamiento alimenticio. Utilizando estos sistemas hemos demostrado que la dorada puede discriminar entre diferentes piensos en función de la presencia de elementos fuertemente amargos o de elementos saborizantes que pueden además ayudar a sobrepasar los efectos negativos del estrés sobre la ingesta. Finalmente, demostramos que esta especie es especialmente sensible a la presencia de estrógenos o andrógenos no aromatizables en la composición del pienso sugiriendo que los elementos estrogénicos o androgénicos pueden actuar como elementos anti-nutricionales. / [CA] L'aqüicultura és una de les principals activitats en l'àmbit de la producció animal. El seu progrés està delimitat per la dependència de matèries primeres d'origen tant marí com terrestre, totes dues necessàries per a l'elaboració de pinsos destinats a l'alimentació de les espècies en cultiu. La introducció de noves matèries primeres o substàncies destinades a la millora de la fisiologia de l'espècie (pinsos funcionals) pot comprometre la palatabilitat dels pinsos, el seu consum i per extensió el creixement dels animals. L'objectiu principal d'aquesta tesi va ser trobar additius sensorials (saboritzants) que puguen sobrepassar els efectes negatius sobre la palatabilitat dels pinsos induïts per la inclusió de matèries vegetals en l'elaboració dels pinsos per a cultiu de l'orada (Sparus aurata). Per això, avaluem la funcionalitat dels sistemes d'auto-demanda en l'estudi del comportament alimentari d'aquesta espècie, aprofundint en la seua possible utilitat en la discriminació sensorial/gustativa dels pinsos. Avaluem l'efecte d'estrògens i andrògens no aromatizables sobre la ingesta com a possibles factors anti-nutricionals presents en els pinsos de substitució. Estudiem l'efecte de dos saboritzants sobre la ingesta i dinàmica de creixement de l'orada i finalment estudiem el possible efecte d'aquests sobre l'anorèxia induïda per l'estrés. Els resultats demostren que l'orada s'adapta bé als sistemes d'auto-demanda i aquests poden ser utilitzats per a l'estudi del seu comportament alimentari. Utilitzant aquests sistemes hem demostrat que l'orada pot discriminar entre diferents pinsos en funció de la presència d'elements fortament amargs o d'elements saboritzants que poden a més ajudar a sobrepassar els efectes negatius de l'estrés sobre la ingesta. Finalment, vam demostrar que aquesta espècie és especialment sensible a la presència d'estrògens o andrògens no aromatizables en la composició del pinso suggerint que els elements estrogènics o androgènics poden actuar com a elements anti-nutricionals. / [EN] Aquaculture is one of the main activities within the animal production. Its progress is constricted by the dependency raw materials with marine and terrestrial origin both critical for the production of feed diets for cultured species. The incorporation of new raw materials or functional substances driven to the improvement of animal physiology (functional feed) can compromise the palatability of diets, consumption and by extension animal growth. The main issue of this thesis was to find sensorial enhancers that can overcome the negative effects on diet palatability induced by the inclusion of vegetal rows in the elaboration of feed for seabream culture (Sparus aurata). To that end we test the functionality of self-feeding systems in the study of feeding behaviour of this species deepening in the study of sensory/gustatory feed discrimination. We also evaluate the effect of both oestrogens and no-aromatized androgen on food intake as potential anti-nutritionals included in the substitution diets. In addition, we studied the effect of flavourings on seabream feeding behaviour and growth performance and finally we studied the potential effect on stress-induced anorexia. Results demonstrated that seabream adapts perfectly to self-feeding systems that can be used for the study its feeding behaviour. Using self-feeding systems, we have also demonstrated that seabream can discriminate between different diets by association to potent sour deterrents of flavourings that can help to overcome the negative effects of stress on feeding behaviour. Finally, we demonstrate that seabream is especially sensible to the presence of oestrogen or androgens in the diet compositing suggesting its potential role as anti-nutritional elements. / Puchol Soriano, S. (2022). Regulación temporal y sensorial de la ingesta en la dorada (Sparus aurata) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181576 / TESIS

[ES] El objetivo central de la presente tesis doctoral fue estudiar la influencia de la frecuencia de alimentación en el rendimiento productivo del camarón, y para ello se desarrollaron tres ensayos considerando distintos aspectos de dicha frecuencia alimentaria y otros complementarios. En el primero se estudió el número diario de comidas (1, 2, 4 y 6) y el horario de las mismas (día y noche), empleando dos tipos de fabricación del alimento, granulado y extrusionado. En el segundo se ensayaron dos y cuatro comidas y dos tasas de alimentación (80 y 100% de la saciedad), junto con la inclusión de dos hidrolizados de pescado. En el tercer ensayo se evaluaron tres técnicas de alimentación en campo, manual, automática mediante alimentadores temporizados y automática con ecosonda, que originaron diversas frecuencias de alimentación, número y horario de las comidas, utilizando alimento granulado y extrusionado. Los resultados del primer experimento sugieren que el alimento extruido suministrado en horario diurno tiene el potencial de mejorar la tasa de crecimiento, y una mayor frecuencia podría representar una estrategia adecuada para preservar la calidad del agua. La presente investigación es la primera en demostrar que el proceso de extrusión mejora la calidad del agua¿ por lo tanto, los alimentos extruidos podrían reducir el impacto de la contaminación de los efluentes y mejorar la sostenibilidad de la producción de camarón. En un segundo estudio se evaluaron los efectos de la frecuencia de alimentación y la restricción de la ración sobre el crecimiento, la supervivencia y el factor de conversión alimenticia (FCR), en juveniles de L. vannamei (0,8 ± 0,06 g) alimentados con dos tipos de dietas en el transcurso de 53 días.. Los resultados demostraron una mejora en la conversión alimenticia cuando se ofrece el 80% de la ración, en comparación con el 100% (FCR=1,64 ± 0,19 vs 1,93 ± 0,12 respectivamente), sin embargo, esto se logró a expensas del crecimiento (5,79 ± 0,31 g vs 6,23 ± 0,51 g respectivamente). No se observaron diferencias en el incremento de peso al comparar los diferentes tipos de hidrolizados (HFFO y HFNI). Finalmente, un tercer estudio consistió en un análisis de 3 técnicas de alimentación del camarón empleadas en las granjas camaroneras comerciales: manual (técnica 1), automática con ajuste de tiempo (técnica 2) y automática con detección de sonido (técnica 3), las cuales fueron utilizadas para suministrar ambos alimentos: granulados (P) y extruidos (E). El estudio se llevó a cabo en 639 estanques de tierra con 6-12 ha localizadas en la provincia de Guayas, Ecuador, durante el periodo 2018-2020. La densidad media de siembra fue de 18 postlarvas/m2 con ciclos de producción entre 100 y 130 días. Los resultados mostraron que la tasa de crecimiento de la alimentación automática con alimentadores, técnicas 2 y 3 (1,52 ± 0,24 y 1,72 ± 0,26 g/semana, respectivamente), con alimento extrusionado, fue superior al obtenido con la técnica manual 1 (1,44 ± 0,24 g/ semana), pero no hubieron diferencias significativas para el alimento granulado (1,39 ± 0,30; 1,43 ± 0,21 y 1,49 ± 0,30 respectivamente). El FCR de las técnicas 1 a 3 fue de 1,92 ± 0,49; 1,89 ± 0,54 y 1,67 ± 0,32 respectivamente con alimento extruido, siendo el mejor el obtenido con la eco-sonda, mientras que para el alimento granulado ocurrió lo contario (1,72 ± 0,46; 1,65 ± 0,25 y 1,96 ± 0,54 respectivamente). No se observaron diferencias significativas (p>0,05) en las tasas de supervivencia entre los tratamientos. El coste por kilo más bajo ($2,86/ kg) se obtuvo con la combinación de alimentación sónica y dietas extruidas. La problemática de la frecuencia de alimentación queda superada con la utilización de alimentadores de auto demanda con detección sónica, y con el empleo de alimento extrusionado, que origina un mejor crecimiento y conversión y una mejor calidad del agua de los estanques. / [CA] L'objectiu central de la present tesi doctoral va ser estudiar la influència de la freqüència d'alimentació en el rendiment productiu de la gambeta, i per a això es van desenvolupar tres assajos considerant diferents aspectes d'esta freqüència alimentària i altres complementaris. En el primer es va estudiar el nombre diari de menjars (1, 2, 4 i 6) i l'horari de les mateixes (dia i nit), emprant dos tipus de fabricació de l'aliment, granulat i extrusionado. En el segon es van assajar dos i quatre menjars i dues taxes d'alimentació (80 i 100% de la sacietat), juntament amb la inclusió de dos hidrolitzats de peix. En el tercer assaig es van avaluar tres tècniques d'alimentació en camp, manual, automàtica mitjançant menjadores temporitzades i automàtica amb ecosonda, que van originar diverses freqüències d'alimentació, número i horari dels menjars, utilitzant aliment granulat i extrusionado. Els resultats del primer experiment suggerixen que l'aliment extruit subministrat en horari diürn té el potencial de millorar la taxa de creixement, i una major freqüència podria representar una estratègia adequada per a preservar la qualitat de l'aigua. La present investigació és la primera a demostrar que el procés d'extrusió millora la qualitat de l'aigua¿ per tant, els aliments extruits podrien reduir l'impacte de la contaminació dels efluents i millorar la sostenibilitat de la producció de gambeta. En un segon estudi es van avaluar els efectes de la freqüència d'alimentació i la restricció de la ració sobre el creixement, la supervivència i el factor de conversió alimentosa (FCR), en juvenils de L. vannamei (0,8 ± 0,06 g) alimentats amb dos tipus de dietes en el transcurs de 53 dies. Els resultats van demostrar una millora en la conversió alimentosa quan s'oferix el 80% de la ració, en comparació amb el 100% (FCR=1,64 ± 0,19 vs 1,93 ± 0,12 respectivament), tanmateix, això es va aconseguir a costa del creixement (5,79 ± 0,31 g *vs 6,23 ± 0,51 g respectivament). No es van observar diferències en l'increment de pes en comparar els diferents tipus d'hidrolitzats (HFFO i HFNI). Finalment, un tercer estudi va consistir en una anàlisi de 3 tècniques d'alimentació de la gambeta emprades en les granges camaroneras comercials: manual (tècnica 1), automàtica amb ajust de temps (tècnica 2) i automàtica amb detecció de so (tècnica 3), les quals van ser utilitzades per a subministrar tots dos aliment granulado (P) i aliment extruit (E). L'estudi es va dur a terme en 639 estanys de terra amb 6-12 ha localitzades a la província de Guayas, l'Equador, durant el període 2018-2020. La densitat mitjana de sembra va ser de 18 postlarvae/m² amb cicles de producció entre 100 i 130 dies. Els resultats van mostrar que la taxa de creixement de l'alimentació automàtica amb menjadores, tècniques 2 i 3 (1,52 ± 0,24 i 1,72 ± 0,26 g/setmana, respectivament), amb aliment extrusionado, va ser superior a l'obtingut amb la tècnica manual 1 (1,44 ± 0,24 g/ setmana), però no van haver diferències significatives per a l'aliment granulat (1,39 ± 0,30; 1,43 ± 0,21 i 1,49 ± 0,30 respectivament). El FCR de les tècniques 1 a 3 va ser de 1,92 ± 0,49; 1,89 ± 0,54 i 1,67 ± 0,32 respectivament amb aliment extruit, sent el millor l'obtingut amb l'eco-sonda, mentre que per a l'aliment granulat va ocórrer el contario (1,72 ± 0,46; 1,65 ± 0,25 i 1,96 ± 0,54 respectivament. No es van observar diferències significatives (p>0,05) en les taxes de supervivència entre els tractaments. El cost per quilo més baix ($2,86/ kg) es va obtindre amb la combinació d'alimentació sònica i dietes extruides. La problemàtica de la freqüència d'alimentació queda superada amb la utilització de menjadores d'acte demanda amb detecció sònica, i amb l'ús d'aliment extrusionado, que origina un millor creixement i conversió i una millor qualitat de l'aigua dels estanys. / [EN] The aim of this doctoral thesis was to study the influence of feeding frequency on the productive performance of shrimp, and for this purpose three trials were developed considering different aspects of feeding frequency and other complementary ones. In the first, the daily number of meals (1, 2, 4 and 6) and their timing (day and night) were studied, using two types of feed manufacturing processes, granulated and extruded. In the second, two and four meals and two feeding rates (80 and 100% satiety) were tested, along with the inclusion of two fish hydrolysates. In the third trial, three feeding techniques were evaluated in the field: manual, automatic using timed feeders and automatic with echo sounders, which gave rise to various feeding frequencies, number and timing of meals, using granulated and extruded feed. The results of first experiment suggest that extruded feed fed during daylight hours has the potential to improve growth rate, and greater frequency could represent an appropriate strategy to preserve water quality. The present research is the first to demonstrate that the extrusion process improves water quality; therefore, extruded feeds could reduce the impact of effluent pollution and improve the sustainability of shrimp production. In a second study, the effects of feeding frequency and ration restriction on growth, survival and feed conversion factor (FCR) were evaluated in juveniles of L. vannamei (0.8 ± 0.06 g) fed two types of diets over the course of 53 days. The results demonstrated an improvement in feed conversion when 80% of the ration was offered, compared to 100% (FCR=1.64 ± 0.19 vs 1.93 ± 0.12 respectively), however, this was achieved at the expense of growth (5.79 ± 0.31 g vs 6.23 ± 0.51 g respectively). No differences were observed in weight increase when comparing the different types of hydrolysates (HFFO and HFNI). Finally, a third study consisted of an analysis of 3 shrimp feeding techniques used in commercial shrimp farms: manual (technique 1), automatic with time adjustment (technique 2) and automatic with sound detection (technique 3), the which were used to supply both pelletized feed (P) and extruded feed (E). The study was carried out in 639 earthen ponds with 6-12 ha located in the province of Guayas, Ecuador, during the period 2018-2020. The average stocking density was 18 postlarvae/m2 with production cycles between 100 and 130 days. The results showed that the growth rate of automatic feeding with feeders, techniques 2 and 3 (1.52 ± 0.24 and 1.72 ± 0.26 g/week, respectively), with extruded feed, was higher than that obtained with manual technique 1 (1.44 ± 0.24 g/week), but there were no significant differences for the pelleted feed (1.39 ± 0.30; 1.43 ± 0.21 and 1.49 ± 0. 30 respectively). The FCA of techniques 1 to 3 was 1.92 ± 0.49; 1.89 ± 0.54 and 1.67 ± 0.32 respectively with extruded feed, the best was the one obtained with the echo-probe, while the opposite occurred for granulated feed (1.72 ± 0.46; 1 .65 ± 0.25 and 1.96 ± 0.54 respectively. No significant differences (p>0.05) were observed in survival rates between treatments. The lowest cost per kilo ($2.86/kg) was obtained with the combination of sonic feeding and extruded diets. The problem of feeding frequency is overcome with the use of self-demand feeders with sonic detection, and with the use of extruded feed, which causes better growth and conversion and better water quality in the ponds. / Espinoza Ortega, MA. (2024). Efecto de la frecuencia de alimentación en la respuesta alimenticia del Camarón Blanco del Pacífico (Litopenaeus Vannamei) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/204638