Terminal sire crossbreeding systems which improve growth performance while maintaining parasite resistance have the potential to enhance the profitability of hair sheep enterprises. Katahdin (KT, n = 4), Suffolk (SU, n = 3), and Texel (TX, n = 3) rams were randomly mated to KT ewes over two years (Y1, Y2) at the Virginia Tech Southwest Agricultural Research and Extension Center. Post-lambing until weaning (80 d), pairs were managed on fescue pasture. At weaning, lambs (n = 192) were moved to an ungrazed pasture and provided a concentrate pellet daily for a 90 d grazing trial. During this time, BW, strongylid egg count (FEC), FAMACHA score and packed cell volume (PCV) were collected every 14 d. FAMACHA score - 3 was utilized as the basis for anthelmintic treatment. Post-grazing, lambs were fed to approximately 50 kg BW. Lambs were harvested at the Virginia Tech Meat Center and carcass evaluation performed 1 d post-harvest. Statistical analyses were conducted using SAS (SAS Institute Inc., Cary, NC) with Proc MIXED for repeated measures analysis and Proc GLM with Tukey?s test for mean separation. No differences existed between sire breeds for adjusted number of lambs born or number of lambs weaned. Adjusted birth BW was greater for SU-sired lambs than KT-sired and TX-sired (P < 0.05) in Y2. Adjusted weaning BW was smallest for KT-sired lambs compared to SU- and TX-sired lambs (P < 0.05) in both years. During the grazing trials, BW, ADG, lnFEC, FAMACHA and PCV varied over time (P < 0.001) with lower FAMACHA scores for KT-sired lambs than SU- and TX-sired lambs in Y1 (P < 0.05). A greater proportion of SU-sired lambs tended to require deworming than KT-sired lambs (P = 0.08). Adjusted BW post weaning was greater for TX-sired lambs than KT-sired lambs (P < 0.05) in Y1. Post-grazing, BW and ADG varied over time (P < 0.01) with no sire breed differences for ADG. At harvest, SU-sired lambs were heavier than KT-sired lambs (P < 0.05). TX-sired lambs had greater LM area than KT-sired lambs (P = 0.05). KT-sired lambs had the smallest leg scores (P < 0.05). These results indicate the potential of terminal sires (SU- and TX-sires) to improve lamb growth and carcass merit. TX-sired lambs had more similar parasite resistance characteristics to KT-sired Iambs and may have potential as terminal sires in forage based hair sheep production systems. / Master of Science / Katahdin hair sheep have been developed as an easy-care breed adaptable to forage-based production systems. Their enhanced resistance to gastrointestinal parasites has resulted in their rise in popularity among sheep producers in the southeastern United States. However, their lower cutability (muscle to fat ratio) and lighter carcass weights have resulted in economic concerns. Therefore, other breeds (Texel and Suffolk) have been considered for crossbreeding to increase carcass size and muscle improving the market value of lambs produced. Here, Katahdin, Suffolk and Texel sires were mated to Katahdin ewes over two years at the Southwest Virginia Agriculture Research and Extension Center. Lambs were grazed with their dams until weaning at approximately 70 days of age. Post-weaning, lambs were grazed for approximately 90 days during which time body weights and parasite resistance indicators were recorded every two weeks. Lambs were dewormed based on anemia level measured by mucus membrane color (FAMACHA score). After grazing, lambs were fed until they reached approximately 50 kg. Lambs were harvested at the Virginia Tech Meat Center for carcass evaluation. There were no differences between the sire breeds for number of lambs born or weaned per ewe. Suffolk-sired lambs were heaviest at birth in year 2 and at weaning Suffolk- and Texel-sired lambs were heavier than Katahdin-sired in both years. In year 1, Texel-sired lambs were heaviest at the end of the grazing period. FAMACHA scores tended to be lower for Katahdin-sired lambs and Suffolk-sired lambs tended to require greater deworming. At harvest, Suffolk-sired lambs were heavier than Katahdin-sired lambs while the Texel-sired lambs had greater loin muscle area. These results indicate the potential of terminal-sires (Suffolk and Texel) to improve lamb growth. Texel-sired lambs were more similar to Katahdin-sired lambs for resistance traits while increasing carcass muscling and may be a potential terminal option for forage-based production systems.

Made available in DSpace on 2016-08-15T20:31:01Z (GMT). No. of bitstreams: 1 kizzyMFMC_DISSERT.pdf: 774522 bytes, checksum: da3661ec2a393e4af5e31278032e04d2 (MD5) Previous issue date: 2011-09-08 / Despite its known resistance, the sheep are subject to endoparasitoses, which are the main limiting factor for its production worldwide, especially in tropical regions. This study aims to evaluate the changes in parasitic load, serum biochemical and hematological panel, and Famacha scores of mixed-bred sheep naturally infected with nematodes and treated with ivermectin and closantel. The study was conducted at July 2010, in a farm in the municipality of Mossoró, Rio Grande do Norte state, Brazil. We selected 41 animals were divided into three groups: group I- control (without treatment), group II- treated with ivermectin (0.2 mg/kg), and Group III- treated with closantel (5 mg/kg). Stool samples were collected on days 0, 7, 14 and 21 after treatment for quantitative analysis (EPG) and qualitative analysis (stool culture), we used samples from days 0, 14 and 21. The first blood sample was given on day 0, the second and third 24 and 72 hours after the first, respectively the fourth and fifth 7 and 14 days after the first of which analyzed the blood count, serum total protein, albumin and globulins, and albumin/globulins ratio. Famacha scores were determined the degree of each animal at all times of sampling. Closantel administration was effective for the reduction of parasite counts, especially Haemonchus contortus, in evaluated sheep. On the other hand, there was parasite resistance to ivermectin. Famacha data showed negative correlation with packed cell volume, leukocytes, hemoglobin, albumin, total protein, globulin and albumin/globulin ratio. The packed cell volume showed a strong and positive correlation with hemoglobin, albumin and total protein. Treatment with ivermectin and closantel were not responsible for considerable changes in hematological and biochemical parameters evaluated. / Apesar de sua conhecida resistência, os ovinos estão sujeitos as endoparasitoses, sendo este o principal fator limitante para a sua produção em todo o mundo, especialmente em regiões tropicais. Este trabalho objetiva avaliar a carga parasitária, o perfil hematológico e bioquímico sérico, e o grau Famacha de ovinos sem padrão racial definido infectados e tratados com ivermectina e closantel. O trabalho foi realizado no mês de julho de 2010, numa propriedade rural no município de Mossoró-RN. Foram selecionados 41 animais, os quais foram divididos em três grupos: grupo I- controle (sem tratamento), grupo II- tratado com ivermectina (0,2 mg/kg) e Grupo III- tratado com closantel (5 mg/kg). As amostras de fezes foram coletadas nos dias 0, 7, 14 e 21, pós-tratamento para análise quantitativa (OPG) e para análise qualitativa (coprocultura), foram utilizadas amostras nos dias 0, 14 e 21. A primeira coleta de sangue se deu no dia 0, a segunda e a terceira 24 e 72 horas após a primeira, respectivamente, a quarta e a quinta 7 e 14 dias após a primeira, dos quais foram analisados o hemograma, os níveis séricos de proteínas totais, albumina e globulinas, e a relação albumina/globulinas. Foi determinado o grau de anemia pelo método Famacha de cada animal em todos os momentos de coleta de amostras. O tratamento com closantel foi eficaz na redução da carga parasitária, principalmente Haemonchus contortus, nos ovinos avaliados. Por outro lado, houve resistência dos parasitas à ivermectina. Os dados de Famacha apresentaram correlação negativa com volume globular, leucócitos, hemoglobina, albumina, proteínas totais, globulinas e relação albumina/globulinas. O volume globular apresentou uma correlação forte e positiva com hemoglobina, albumina e proteínas totais. Os tratamentos com closantel e ivermectina não foram responsáveis por alterações consideráveis nos parâmetros hematológicos e bioquímicos avaliados.

<p>Studies of hybrid zones offer important insights into the process of speciation. Much of the knowledge to be gained is dependent on an accurate estimation of the strength of pre- and post-zygotic isolation between hybridizing taxa. My results demonstrate that hybridization can variously affect different components of fitness. In Ficedula flycatchers, late-breeding females may directly benefit from pairing with a heterospecific male by gaining access to superior territories. The hybrid offspring possess an immune system that is as equally well functioning as in the parental species (the collared, F. albicollis, and pied flycatcher, F. hypoleuca). However, I found that a severe reduction in fertility persists for at least three generations after the actual hybridization event. Combining all information about the reproductive success of hybridizing individuals and their descendents revealed that postzygotic isolation between flycatchers is very strong; hybridizing individuals leave almost no descendents. This thesis presents one of few comprehensive summaries of the selection for/against assortative mating in a natural hybrid zone. These findings suggest a central role for intrinsic postzygotic isolation as a reproductive barrier separating newly evolved bird species, and contrast previous suggestions that postmating isolation is the slowest of the reproductive barriers to evolve in birds.</p><p>Despite this strong selection against hybridization, pre-mating isolation is incomplete. Hybridization often results from females lacking conspecific partners, but appears to be also caused by errors in species recognition. Much of this error probably reflects the short period of time that pied flycatchers on Gotland and Öland have been in sympatry. Compared to collared flycatchers, pied flycatchers are poorer able to discriminate between conspecific and heterospecific song, and male pied flycatchers more often falsely signal their own identity through heterospecific song copying. However, despite colonising the study site from other sympatric populations and having very little gene flow from allopatry, collared flycatchers also possess traits (e.g. delayed plumage maturation) that increase their hybridization risk. Once pre-mating isolation is strong, the rarity of hybridization probably inhibits further selection against traits promoting interspecific mating, especially when such traits may be beneficial in other contexts. This thesis highlights complex interactions between factors affecting hybridization rate that would not be detected if such a study were not field-based. Furthermore, it showcases likely examples in nature of a number of theoretical objections to the evolution of pre-mating barriers between populations living in sympatry.</p>

Studies of hybrid zones offer important insights into the process of speciation. Much of the knowledge to be gained is dependent on an accurate estimation of the strength of pre- and post-zygotic isolation between hybridizing taxa. My results demonstrate that hybridization can variously affect different components of fitness. In Ficedula flycatchers, late-breeding females may directly benefit from pairing with a heterospecific male by gaining access to superior territories. The hybrid offspring possess an immune system that is as equally well functioning as in the parental species (the collared, F. albicollis, and pied flycatcher, F. hypoleuca). However, I found that a severe reduction in fertility persists for at least three generations after the actual hybridization event. Combining all information about the reproductive success of hybridizing individuals and their descendents revealed that postzygotic isolation between flycatchers is very strong; hybridizing individuals leave almost no descendents. This thesis presents one of few comprehensive summaries of the selection for/against assortative mating in a natural hybrid zone. These findings suggest a central role for intrinsic postzygotic isolation as a reproductive barrier separating newly evolved bird species, and contrast previous suggestions that postmating isolation is the slowest of the reproductive barriers to evolve in birds. Despite this strong selection against hybridization, pre-mating isolation is incomplete. Hybridization often results from females lacking conspecific partners, but appears to be also caused by errors in species recognition. Much of this error probably reflects the short period of time that pied flycatchers on Gotland and Öland have been in sympatry. Compared to collared flycatchers, pied flycatchers are poorer able to discriminate between conspecific and heterospecific song, and male pied flycatchers more often falsely signal their own identity through heterospecific song copying. However, despite colonising the study site from other sympatric populations and having very little gene flow from allopatry, collared flycatchers also possess traits (e.g. delayed plumage maturation) that increase their hybridization risk. Once pre-mating isolation is strong, the rarity of hybridization probably inhibits further selection against traits promoting interspecific mating, especially when such traits may be beneficial in other contexts. This thesis highlights complex interactions between factors affecting hybridization rate that would not be detected if such a study were not field-based. Furthermore, it showcases likely examples in nature of a number of theoretical objections to the evolution of pre-mating barriers between populations living in sympatry.

Tesis por compendio / [ES] La producción en acuicultura se ha visto menguada por aparición de enfermedades en los sistemas de cría de peces. En concreto, en la dorada (Sparus aurata), hay dos parásitos destacados: Enteromyxum leei (Myxozoa) y Enterospora nucleophila (Microsporidia). Hasta la fecha, para ninguno de los dos se ha establecido un cultivo in vitro, y solo para E. leei se ha conseguido establecer un modelo de mantenimiento de la infección in vivo. La presente tesis pretende incrementar el conocimiento sobre estos parásitos y sus relaciones con el hospedador, sentando las bases para generar soluciones que puedan ser aplicadas en la acuicultura. El objetivo con E. leei fue estudiar la inmunidad adquirida inducida en la dorada y la posibilidad de generar herramientas de diagnóstico y vacunas frente a esta enfermedad. Para ello, primero se demostró la resistencia del pez al parásito tras una segunda exposición, la cual duró hasta 16 meses. Además, la resistencia parece estar correlacionada con altos niveles de inmunoglobulina (Ig) M específica en sangre, y una alta expresión de Igs, incluso antes de la re-exposición al parásito. El siguiente paso fue afinar el protocolo de infección con E. leei. Los resultados mostraron que una semana es suficiente para transmitir la infección de E. leei por efluente, independientemente de la temperatura. Tras la demostración de la respuesta adaptativa eficaz frente a E. leei, y al disponer de un modelo de infección refinado, se realizó un ensayo de inmunización pasiva. Aquí, los resultados mostraron que los anticuerpos especi'ficos efectivamente consigue ralentizar la invasión del intestino por el parásito y disminuir los síntomas de la enfermedad. Paralelamente, el resultado del análisis del repertorio de las regiones variables de la IgM e IgT del intestino peces resistentes mostró la inducción de una respuesta policlonal en las ce'lulas B. En base a estos resultados, se realizó una búsqueda de antígenos de E. leei que pudieran ser utilizados como candidatos para la producción de vacunas (análisis proteómico) o herramientas de diagnóstico (análisis in silico). Para ello, se ensambló un transcriptoma de novo utilizando una muestra mixta de intestino de dorada y parásito. Los resultados dieron lugar a 7 y 12 candidatos en la búsqueda in silico y proteómica, respectivamente. En los estudios de E. nucleophila, debido a que fue descrita muy recientemente, el punto de partida fue más básico. Las muestras de este parásito solo se pueden obtener de brotes naturales en piscifactorias. Por ello, primero se realizó un estudio de caracterización de la patología de la infección a partir de peces infectados naturalmente. En etapas tempranas de la infección, el parásito se localiza principalmente en el intestino, pero meses después, la prevalencia en intestino baja e incrementa en los órganos hematopoyéticos y el esto'mago. Los signos clínicos de la infección consistieron en una reducción significativa del crecimiento, emaciación, y palidez de las paredes intestinales. A nivel celular, en los casos ma's graves se observó hipercelularidad en el epitelio intestinal y proliferación de ce'lulas rodlet, un elevado número de linfocitos en la base del epitelio e infiltración de granulocitos acidófilos en el epitelio intestinal. Finalmente se probaron varias formas de transmisión horizontal de E. nucleophila (cohabitación, efluente, intubación oral y anal) con para desarrollar un modelo de mantenimiento in vivo. Se consiguió la transmisión el parásito por todas las vías, pero con una disminución de prevalencia a lo largo del tiempo. Variables como la temperatura, la dosis, y el estado de los peces donantes parecen ser más determinantes que la ruta seleccionada para la transmisión. Entre las rutas probadas, la intubación anal parece ser la más prometedora, pero ninguna de ellas fue capaz de reproducir los signos clínicos observados en las infecciones naturales. / [CA] La producció en aqüicultura s'ha vist minvada per aparició de malalties en els sistemes de cria de peixos. En concret, en l'orada (Sparus aurata), hi ha dos paràsits destacats: Enteromyxum leei (Myxozoa) i Enterospora nucleophila (Microsporidia). Fins avui, per a cap dels dos s'ha establert un cultiu in vitro, i només per a E. leei s'ha aconseguit establir un model de manteniment de la infecció in vivo. La present tesi pretén incrementar el coneixement sobre aquests paràsits i les seves relacions amb l'hoste, establint les bases per a generar solucions que puguin ser aplicades en l'aqüicultura. L'objectiu amb E. leei va ser estudiar la immunitat adquirida induïda en l'orada i la possibilitat de generar eines de diagnòstic i vacunes enfront d'aquesta malaltia. Per a això, primer es va demostrar la resistència del peix al paràsit després d'una segona exposició, la qual va durar fins a 16 mesos. A més, la resistència sembla estar correlacionada amb alts nivells d'immunoglobulina (Ig) M específica en sang, i una alta expressió de Igs, fins i tot abans de la re-exposició al paràsit. El següent pas va ser afinar el protocol d'infecció amb E. leei. Els resultats van mostrar que una setmana és suficient per a transmetre la infecció de E. leei per efluent, independentment de la temperatura. Després de la demostració de la resposta adaptativa eficaç enfront de E. leei, i en disposar d'un model d'infecció refinat, es va realitzar un assaig d'immunització passiva. Aquí, els resultats van mostrar que els anticossos específics efectivament aconsegueix alentir la invasió de l'intestí pel paràsit i disminuir els símptomes de la malaltia. Paral·lelament, el resultat de l'anàlisi del repertori de les regions variables de la IgM i IgT de l'intestí peixos resistents va mostrar la inducció d'una resposta policlonal en les cèl·lules B. Sobre la base d'aquests resultats, es va realitzar una cerca d'antígens de E. leei que poguessin ser utilitzats com a candidats per a la producció de vacunes (anàlisis proteómico) o eines de diagnòstic (anàlisi in silico). Per a això, es va assemblar un transcriptoma de novo utilitzant una mostra mixta d'intestí d'orada i paràsit. Els resultats van donar lloc a 7 i 12 candidats en la cerca in silico i proteòmica, respectivament. En els estudis de E. nucleophila, pel fet que va ser descrita molt recentment, el punt de partida va ser més bàsic. Les mostres d'aquest paràsit només es poden obtenir de brots naturals en piscifactorias. Per això, primer es va realitzar un estudi de caracterització de la patologia de la infecció a partir de peixos infectats naturalment. En etapes primerenques de la infecció, el paràsit es localitza principalment en l'intestí, però mesos després, la prevalença en intestí baixa i incrementa en els òrgans hematopoètics i l'estómac. Els signes clínics de la infecció van consistir en una reducció significativa del creixement, emaciació, i pal·lidesa de les parets intestinals. A nivell cel·lular, en els casos més greus es va observar hipercelularidad en l'epiteli intestinal i proliferació de cèl·lules rodlet, un elevat nombre de limfòcits en la base de l'epiteli i infiltració de granulòcits acidòfils en l'epiteli intestinal. Finalment es van provar diverses formes de transmissió horitzontal de E. nucleophila (cohabitació, efluent, intubació oral i anal) amb per a desenvolupar un model de manteniment in vivo. Es va aconseguir la transmissió el paràsit per totes les vies, però amb una disminució de prevalença al llarg del temps. Variables com la temperatura, la dosi, i l'estat dels peixos donants semblen ser més determinants que la ruta seleccionada per a la transmissió. Entre les rutes provades, la intubació anal sembla ser la més prometedora, però cap d'elles va ser capaç de reproduir els signes clínics observats en les infeccions naturals. / [EN] Aquaculture production is hampered by the emergence of parasite diseases in fish farming systems. Among them, in Sparus aurata, there are two important enteric parasites described: Enteromyxum leei (Myxozoa) Enterospora nucleophila (Microsporidia). To date, no in vitro culture has been established for either parasite, and only for E. leei was it possible to establish a model for maintaining the infection in vivo. The aim of this thesis is to gain new knowledge about these parasites and their relationship with the host, also the basic foundations for generating solutions that can be applied in aquaculture. The general objective for E. leei was to study the acquired immunity induced in gilthead bream and the possibility of generating diagnostic tools and vaccines against this disease. To this end, resistance against the parasite was assessed with a second exposure against the parasite, which showed a resistance for at least 16 months. Besides resistance seemed to be correlated with high levels of specific immunoglobulin (Ig) M in blood, and a high expression of Igs, in particular, the soluble forms, even before re-exposure to the parasite. The next step was refining the protocol for effluent infection with E. leei by studying infection at different exposure time points, temperatures and population densities. The results showed that one week of exposure is sufficient to spread E. leei infection by effluent, regardless of temperature. After demonstrating the resistance against E. leei, and with a refined infection model, a passive immunization assay was performed. The results showed that the serum with specific antibodies effectively slows down the invasion of the gut by the parasite and reduces the symptoms of the disease. At the same time, the analysis of the repertoire of the variable regions of intestinal IgM and IgT showed an induction of a polyclonal response in B cells. On the basis of these results, a research was carried out for E. leei antigens that could have use as candidates for the production of vaccines (proteomic study) or diagnostic tools (in silico study) using the parasite transcriptomic data. To do this, a de novo transcriptome was assembled using a mixed sample of gilthead sea bream and parasite, with a posterior filtrate of the sequences. The In silico and proteomic analysis search resulted in 7 and 12 transcripts, respectively, which are being used for diagnostic and vaccine production. The starting point was more basic in E. nucleophila studies, since this is a recently described disease. The samples of this parasite can only be obtained from natural outbreaks in fish farms. Therefore, first study was carried out to characterize the pathology of the infection of naturally infected fish. In the early stages of the infection, the parasite is mainly located in the intestine, but months later, the prevalence is lower in the intestine and increases in the hematopoietic organs and the stomach. Clinical signs of infection were significant reduction in growth, wasting, and intestinal walls paleness. At the cellular level, in the most severe cases hypercellularity in the intestinal epithelium, proliferation of rodlet cells, high number of lymphocytes at the base of the epithelium and infiltration of acidophilic granulocytes in the intestinal epithelium were observed. Finally, horizontal transmission of E. nucleophila was tried using different transmission methods: cohabitation, effluent, and oral and anal intubation. Transmission of the parasite was achieved with all routes, but there was a decrease in prevalence over time in all cases except for the anal route. Variables such as temperature, dose, and the status of the donor fish appear to be more important than the selected route. Among the routes tested, anal intubation seemed to be the most promising, as it was sustained over a longer period of time, but none of them was able to reproduce the same clinical signs of infection observed in natural infections. / The authors kindly acknowledge the collaboration of anonymous fish farming companies allowing access to the animals during the disease outbreaks. We thank J. Monfort and L. Rodríguez (IATS-CSIC) for the technical assistance on histological processing.This work has been carried out with financial support from the European Union and the Spanish Ministry of Economy and Competitiveness (MINECO) under grant projects ParaFishControl (H2020-634429) and AGL2013-R-48560-C2-2-R, respectively. APS was contracted under ParaFishControl project. Primer sequences and access to the gilthead sea bream transcriptomic database were kindly provided by Prof. J. Pérez-Sánchez of the IATS- Nutrigenomics group. The authors thank I. Vicente for fish maintenance and technical assistance during samplings. The authors thank P. Boudinot (INRAE) for his help in designing and interpreting the immunoglobulin repertoire study and results, J. Pérez-Sánchez (IATS-CSIC) for providing access to the gilthead sea bream genome sequences to perform the repertoire analysis.This work was funded by the European Research Council (ERC Consolidator Grant 2016 725061 TEMUBLYM). / Picard Sánchez, MA. (2021). Control of enteric parasitic diseases of farmed gilthead sea bream: New insights into Enteromyxum leei (Myxozoa) and Enterospora nucleophila (Microsporidia) infections [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/167035 / Compendio