Segui questo link per vedere altri tipi di pubblicazioni sul tema: Sheep.
Tesi sul tema "Sheep"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Sheep".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Corke, M. J. "The welfare of sheep with sheep scab (Psoroptes ovis infestation)". Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598003.
Testo completoAbstract (sommario):
The effects of sheep scab, (Psoroptes ovis infestation) on the welfare of sheep were studied. Flocks of sheep naturally infested with sheep scab and flocks of uninfested sheep, were studied before and after treatment with acaricides. A group of sheep, experimentally infested with Psoroptes ovis mites, were studied throughout the infestation. Behaviour was studied using focal and scan sampling techniques. Sheep scab resulted in increases in rubbing, scratching and biting. Rubbing and scratching in infested sheep were sometimes accompanied by non-functional mouthing, considered to be a stereotypy. Times spent grazing, cudding and idling were not affected by sheep scab, but the bout lengths of grazing and idling were reduced. The experimental group showed an increasing neutrophilia through the infestation, with erratic increases in eosinophil count and fibrinogen, while haemoglobin concentration and haematocrit decreased. Naturally infested flocks showed lymphopenia after treatment. Serum globulin concentrations increased through the infestation, with a concurrent decline in serum albumin. The serum globulin started to decline within one month after treatment. Some lactate dehydrogenase isoenyzme fractions increased during the infestation. Prolactin decreased and β- endorphin increased throughout the experimental infestation, although seasonal factors may have influenced these results. There was no change in pressure nociceptor threshold due to sheep scab. A questionnaire survey of sheep farmers suggested that sheep scab in Britain had increased in incidence and distribution over the last decade. The welfare of sheep infected with sheep scab and the control of sheep scab are discussed in the context of the experimental findings.
2
Glendinning, Laura. "Sheep lung microbiota". Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/29541.
Testo completoAbstract (sommario):
Until recently it was assumed that the healthy mammalian lung did not harbour a microbiota, unlike other body sites. However, through the use of sequencing based technologies this has been shown to not be the case. Low biomass communities of microbes can be identified in the healthy lung and the lung microbiota in various diseases states has been shown to differ form these 'healthy' communities. The sheep respiratory microbiota is of interest from both an animal health perspective and due to the potential use of the sheep as a large animal model for studying the lung microbiota. In this thesis I seek to characterise the composition and variability of the sheep lung microbiota; the differences between the sheep upper and lower respiratory tract bacterial communities and to assess whether exhaled breath condensate collection can be used as a non-invasive lung microbiota sampling method. To study the bacterial communities present in samples I have used 16S rRNA gene sequencing and analysis. In Chapter 3 I examine the inter-individual and spatial variability present within the sheep lung microbiota. Protected specimen brushings were collected from three lung segments in six animals at three time-points. In a separate sheep a greater number of brushings was taken (n=16) in order to examine the amount of variability over a smaller spatial scale. I find that there can be large differences between the bacterial communities isolated from different locations within the lung, even over short distances. Samples also cluster by the sheep from which they were taken, indicating a host specific influence on the lung microbiota. In Chapter 4 I compare whole lung washes and oropharyngeal swabs from 40 lambs in order to examine the differences between the upper and lower respiratory tract microbiotas. I find that oropharyngeal swabs separate into rumen-like or upper respiratory tract-like bacterial communities. Despite the fact that in humans the upper and lower respiratory microbiotas have been shown to have similar compositions, the sheep lung microbiota samples in this study do not resemble either oropharyngeal samples or reagent only controls. In my first two results chapters, lung sampling methods were used which involved either anaesthesia combined with a bronchoscopic procedure (Chapter 3) or samples being taken from dead animals (Chapter 4). In Chapter 5 I assess whether there is a less invasive way of taking lung microbiota samples from a living individual, both to minimise the procedural stress on animals used as models and to increase the pool of potential volunteers for human lung microbiota studies. I compared samples taken via protected specimen brushings to samples taken via exhaled breath condensate collection, a less invasive sampling technique. I find that condensate samples contain less bacterial DNA and different bacteria than brushing samples, indicating that it is unlikely they could be used as a replacement for invasive sampling methods. In my final results chapter I compare the results across Chapters 3, 4 and 5 to identify bacteria which occur consistently in the sheep lung and could therefore potentially be described as core lung microbiota members. In conclusion, while I have found that there are large differences between the sheep lung microbiota and that which has previously been described in humans, the sheep can still be of use as a model in studies where these differences would not have a significant impact, such as in Chapter 5 of this thesis. I have identified several bacterial members of the core sheep lung microbiota which in future it would be interesting to better characterise and to assess whether they play a role in sheep health.
3
Abdulkhaliq, Ahed. "Estimation of phenotypic and genetic parameters for some reproductive traits in Columbia, Suffolk and Targhee sheep breeds". Connect to resource, 1986. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=osu1244132589.
Testo completo
4
Regnault, Timothy Robert Hume. "Orchestrated partitioning of maternal nutrients during ovine pregnancy /". View thesis View thesis, 1997. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030513.111110/index.html.
Testo completoAbstract (sommario):
Thesis (Ph. D. of Philosophy)--University of Western Sydney, Hawkesbury, 1997."A thesis submitted to the School of Agriculture and Rural Development, Faculty of Agriculture and Horticulture, University of Western Sydney Hawkesbury, in part fulfilment of the requirements for the Degree of Doctor of Philosophy." Includes bibliographical references (p. 236-267).
5
Alink, Frances. "Maternal and peri-ovulatory nutritional effects on the expression of the Inverdale (FecX1) fecundity gene in texel X Scottish hillbreed sheep". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25795.
Testo completo
6
Stockman, Catherine Ann. "The physiological and behavioural responses of sheep exposed to heat load within intensive sheep industries". Thesis, Stockman, Catherine Ann (2006) The physiological and behavioural responses of sheep exposed to heat load within intensive sheep industries. PhD thesis, Murdoch University, 2006. https://researchrepository.murdoch.edu.au/id/eprint/437/.
Testo completoAbstract (sommario):
The live export and feedlotting industries are the major intensive sheep industries in Australia. During live shipment, sheep are exposed to prolonged periods of high heat and humidity, with little relief for several days, while environmental conditions in a Western Australian sheep feedlot have not yet been assessed. The research described in this thesis was conducted to determine the physiological responses of sheep to conditions within the live export and feedlotting industries, with particular focus on that of heat stress.
Merino wethers and Awassi rams developed significant change in physiological variables when exposed to prolonged periods of high heat and humidity, such as during long haul, live export voyages to the Northern Hemisphere. Physiological changes such as increased core temperature, respiratory rate, panting score and associated changes in blood gas variables were apparent in Merino wethers. However, Awassi rams showed exceptional ability to maintain homeostasis under the same environmental conditions, with no significant changes in core temperature and only slight alteration in blood gas variables. Results from this study indicated that electrolyte supplementation of sheep during live export would not be warranted because plasma electrolytes did not drastically change and blood gas variables quickly returned to normal following the heat.
Further studies developed methods to determine the critical wet bulb temperature, otherwise known as the heat stress threshold (HST) of Merino rams, ram lambs and wethers exposed to live export conditions. These studies found that ram lambs had a lower HST than both adult rams and wethers. However, both adult rams and wethers had a similar HST. Heat stress thresholds determined from these studies have been used in a model to predict high risk shipments for particular classes of sheep (Stacey 2003).
This thesis also details the environmental conditions within a Western Australian summer feedlot and the physiological responses of cross bred ewes and wethers to these conditions when fed feedlot rations. This study found that temperatures in a typical Western Australian feedlot in summer increased above 40 degrees C with low humidity; however, temperatures generally decreased to be within the sheep's thermoneutral zone at night. Both ewes and wethers had significantly increased core temperatures in response to these conditions, with sheep spending significantly more time in the shade than in the sun during the day. Both ewes and wethers had increased respiratory rates and panting scores during an intensive climate room experiment with similar environmental conditions. However, feed intake did not decrease even when climate room temperatures increased at night and humidity levels were higher than that found in typical feedlot conditions in Western Australia.
Work completed within this thesis has led to a greater understanding of the physiological responses of sheep to prolonged and continuous high heat such as during live export and to conditions of a typical Western Australian summer feedlot. This research has set a foundation for further study of management of sheep during live export and feedlotting.
7
Stockman, Catherine Ann. "The physiological and behavioural responses of sheep exposed to heat load within intensive sheep industries". Stockman, Catherine Ann (2006) The physiological and behavioural responses of sheep exposed to heat load within intensive sheep industries. PhD thesis, Murdoch University, 2006. http://researchrepository.murdoch.edu.au/437/.
Testo completoAbstract (sommario):
The live export and feedlotting industries are the major intensive sheep industries in Australia. During live shipment, sheep are exposed to prolonged periods of high heat and humidity, with little relief for several days, while environmental conditions in a Western Australian sheep feedlot have not yet been assessed. The research described in this thesis was conducted to determine the physiological responses of sheep to conditions within the live export and feedlotting industries, with particular focus on that of heat stress.
Merino wethers and Awassi rams developed significant change in physiological variables when exposed to prolonged periods of high heat and humidity, such as during long haul, live export voyages to the Northern Hemisphere. Physiological changes such as increased core temperature, respiratory rate, panting score and associated changes in blood gas variables were apparent in Merino wethers. However, Awassi rams showed exceptional ability to maintain homeostasis under the same environmental conditions, with no significant changes in core temperature and only slight alteration in blood gas variables. Results from this study indicated that electrolyte supplementation of sheep during live export would not be warranted because plasma electrolytes did not drastically change and blood gas variables quickly returned to normal following the heat.
Further studies developed methods to determine the critical wet bulb temperature, otherwise known as the heat stress threshold (HST) of Merino rams, ram lambs and wethers exposed to live export conditions. These studies found that ram lambs had a lower HST than both adult rams and wethers. However, both adult rams and wethers had a similar HST. Heat stress thresholds determined from these studies have been used in a model to predict high risk shipments for particular classes of sheep (Stacey 2003).
This thesis also details the environmental conditions within a Western Australian summer feedlot and the physiological responses of cross bred ewes and wethers to these conditions when fed feedlot rations. This study found that temperatures in a typical Western Australian feedlot in summer increased above 40 degrees C with low humidity; however, temperatures generally decreased to be within the sheep's thermoneutral zone at night. Both ewes and wethers had significantly increased core temperatures in response to these conditions, with sheep spending significantly more time in the shade than in the sun during the day. Both ewes and wethers had increased respiratory rates and panting scores during an intensive climate room experiment with similar environmental conditions. However, feed intake did not decrease even when climate room temperatures increased at night and humidity levels were higher than that found in typical feedlot conditions in Western Australia.
Work completed within this thesis has led to a greater understanding of the physiological responses of sheep to prolonged and continuous high heat such as during live export and to conditions of a typical Western Australian summer feedlot. This research has set a foundation for further study of management of sheep during live export and feedlotting.
8
Hou, Xian Zhi. "Diet selection in sheep". Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/28250.
Testo completo
9
Ezaz, Zere. "Studies in Menz sheep". Thesis, Bangor University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276196.
Testo completo
10
Mason, Sam. "Toxoplasma gondii in sheep". Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556024.
Testo completoAbstract (sommario):
Toxoplasma gondii infects sheep horizontally (from cat faeces) or vertically (transplacentally). Vertically infected lambs sometimes die. Here, transmission and performance impacts were considered in one Charollais flock and one Swaledale flock. B1-PCR was performed on umbilical cord, heart and brain. MAT was performed on blood and pleural effusion. IgG-ELISA was performed on colostrum. B1-PCR was more sensitive than four other methods, producing a band in 50% of replicates when each replicate contained 0.02 parasite genome copies. 16/243 (6.6%) viable Charollais, 30/263 (11.4%) viable Swaledale, 3/54 non-viable Charollais and 0116 non-viable Swaledale were PCR-positive, showing no difference between flocks. At age four months 64/524 (12.2%) Charollais and 10/329 (3.0%) Swaledale were seropositive, showing relatively high seroprevalence in Charollais. 5/44 non-viable Charollais and 1114 non-viable Swaledale were seropositive. Colostrum ELISA was 75% sensitive and 100% specific relative to serum MAT. 15/408 (3.7%) Charollais and 31139 (2.2%) Swaledale were colostrum ELISA-positive, showing no difference between flocks. PCR positivity was not associated with seropositivity. PCR positivity was randomly dispersed between litters. In Charollais seropositivity was overdispersed between litters, seroprevalence was higher than PCR prevalence, young ewes' lambs were frequently PCR-positive and large litters frequently contained seropositive lambs. Those results might have been due to vertical transmission. In Swaledale, PCR positivity was not associated with ewe age and seropositivity was rare. Those results suggested little transmission. Lamb seroconversion, and colostrum ELISA positivity, were not associated with ewe age. Overall, it is suggested that ewes ingested oocysts but vertical transmission was sometimes interupted by lambing, especially in Swaledale. In eight cases clinical toxoplasmosis was suspected. No evidence was found suggesting subclinical effects of T. gondii leading to reduced lamb survival. Charollais born PCR-positive were relatively light at age two months but that association was not found in Swaledale. Serology did not confirm any stunting effect.
11
Markey, Bryan K. J. "Chlamydial infection of sheep". Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334590.
Testo completo
12
Young, C. S. "Preslaughter handling of sheep". Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233699.
Testo completo
13
Fleischman, Kimberly Ann. "Sheep Hill Community Tree". VCU Scholars Compass, 2004. http://scholarscompass.vcu.edu/etd/1357.
Testo completoAbstract (sommario):
An urban community is a fusion of new and old that is constantly changing. We understand better the plight of a community through raising awareness of its unique history and visual character. Linking individual and community experiences offers an opportunity for dialogue, especially as long-time residents and their new neighbors learn about their different pasts and explore their common future. Community building happens from within, when many individuals sharing common values create positive change.
14
Suhubdy. "Ingestive behaviour in sheep /". St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16725.pdf.
Testo completo
15
Bortolami, Elisa. "Advances in sheep analgesia". Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424188.
Testo completoAbstract (sommario):
Sheep (Ovis aries) are widely used in experimental settings and breeding system, nevertheless pain treatment in this species seems to be overlooked.
The first two studies described in this thesis were designed to evaluate administration of analgesics both in the experimental and clinical setting. The third study evaluated the pharmacokinetics and antinociceptive effects of tramadol and its metabolite O-desmethyltramadol (M1) in sheep in a preclinical model of pain.
The first study consisted of a meta-analysis of the reported use of analgesics in sheep for experimental purposes. Studies involving experimental procedures in sheep carried out in selected years (2008-2011-2014) were identified using a search engine. A total of 75 papers were selected. The study showed that analgesic treatment was often not accurately reported.
The second study consisted of an on-line questionnaire evaluating the current attitudes of Italian practitioners to assessment and treatment of pain in sheep. The questionnaire consisted of five sections regarding the demographic data, analgesic drugs and techniques used to treat pain, attitudes to pain relief and assessment of pain and the knowledge on the topic of sheep analgesia. Only a modest number of questionnaires were returned. The most commonly used drugs by sheep practitioners who replied to the questionnaire were non steroidal anti-inflammatory drugs and local anaesthetics. In the practitioners’ opinion the main reasons for analgesic drugs not to be administered to sheep was the lack of licensed drugs followed by costs, withholding times and regulations. The vast majority of practitioners were interested in improving their knowlwdge on sheep analgesia.
The third study investigated the pharmacokinetic profile and antinociceptive effect of tramadol and M1 following intravenous administration in sheep. Six healthy adult sheep were administered 4 (T4) and 6 (T6) mg/kg of tramadol (T) and saline (SAL) over 2 minutes in a cross over design with a two weeks wash out period. At predetermined time points blood samples were collected, physiological parameters and mechanical nociceptive threshold (NMT) values were recorded. Tramadol and M1 fitted a two compartmental model and a non compartmental model respectively. Pharmacokinetic parameters were similar for T4 and T6. Tramadol and M1 plasma concentrations decreased rapidly. Physiological parameters were not statistically different between groups. No mechanical antinociceptive effects of tramadol were detected, as MNT values did not statistically differ between groups.
In conclusion, these studies showed that there is great scope for improvement in pain assessment and treatment in sheep both in the research than clinical settings. Moreover more experimental and clinical studies regarding the pharmacokinetic and pharmacokinamic effects of analgesic drugs in sheep are advocated in order to improve their welfare.La pecora domestica (Ovis aries) è una delle specie animali più comunemente allevate ed utilizzate nella ricerca biomedica; nonostante questo l’analgesia in questo animale è stata a lungo trascurata. I primi due studi presentati in questa tesi sono stati elaborati allo scopo di valutare la somministrazione di analgesici nell’ambito clinico e sperimentale. Il terzo studio valuta la farmacocinetica e gli effetti antinocicettivi del tramadolo e del suo metabolita O desmethyltramadol (M1). Il primo studio consiste in una meta-analisi sull’ uso di farmaci analgesici riportato nelle pecore utilizzate a fini sperimentali. Studi riguardanti procedure sperimentali in pecore effettuati in anni selezionati (2008-2011-2014) sono stati identificati utilizzando un motore di ricerca. In totale, sono stati selezionati 75 articoli scientifici. Lo studio evidenzia mostra che la terapia antalgica spesso non viene accuratamente riportata. Il secondo studio consiste in un questionario on line redatto allo scopo di valutare l’attuale approccio dei veterinari italiani, che si occupano della specie ovina, alla valutazione ed al trattamento del dolore in questa specie. Il questionario era diviso in cinque sezioni riguardanti i dati demografici, l’uso di farmaci analgesici a tecniche utilizzate per apportare analgesia, e l’approccio utilizzato dai veterinari nella valutazione e trattamento del dolore nella specie ovina, ed, infine, la loro conoscenza riguardo tale argomento. Un numero limitato di veterinari ha completato il questionario. I farmaci più comunemente utilizzati dai veterinari che hanno risposto al questionario sono i farmaci antiinfiammatori non steroidei e gli anestetici locali. Secondo l’opinione dei veterinari, le ragioni principali per cui la terapia analgesica non viene effettuata nella specie ovina erano la mancanza di farmaci registrati, il loro costo, i tempi di sospensione e la regolamentazione riguardante il loro utilizzo. La maggior parte dei veterinari si dimostrava interessata a migliorare le proprie conoscenze riguardo l’analgesia nella specie ovina. Il terzo studio investiga la farmacocinetica e gli effetti antinocicettivi del tramadolo ed M1 dopo somministrazione endovenosa nelle pecore. Due dosi di tramadolo, 4 mg/kg (T4) e 6 mg/kg (T6), e soluzione salina (SAL) sono state somministrate in due minuti a sei pecore adulte e sane in uno studio randomizzato “in cieco” con un periodo di sospensione di due settimane. A tempi predeterminati, sono stati effettuati i prelievi di sangue per l’analisi farmacocinetica, e sono stati registrati i parametri fisiologici e i valori dopo stimolazione nocicettiva meccanica (MNT). Tramadolo ed M1 presentano rispettivamente una cinetica bi-compartimentale e non-compartimentale. I parametri farmacocinetici sono simili per le due dosi T4 e T6. Le concentrazioni plasmatiche di tramadolo ed M1 sono rapidamente diminuite. I parametri fisiologici non sono risultati statisticamente diversi tra i gruppi. Non sono stati evidenziati effetti antinociettivi del tramadolo; infatti i valori di MNT non sono risultati statisticamente diversi tra i gruppi. Concludendo, questi studi hanno dimostrato che ci sono ampi margini di miglioramento nella valutazione e trattamento del dolore nella specie ovina sia in ambito sperimentale sia clinico. Inoltre, sono necessari studi sperimentali e clinici riguardanti la farmacocinetica e farmacodinamica di farmaci analgesici nella specie ovina al fine di migliorarne il benessere.
16
Holmberg, Bradford J. "Influence of the vagus nerve and urocortin on the nutrition-reproduction axis of the ovine /". free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3074407.
Testo completo
17
Hosking, Brenton John. "Evaluation of nutrient intake and digestion in grazing sheep receiving supplements : thesis submitted for the degree of Doctor of Philosophy". Title page, summary and contents only, 1987. http://web4.library.adelaide.edu.au/theses/09PH/09phh826.pdf.
Testo completoAbstract (sommario):
Includes bibliographical references (leaves 290-309) Investigates aspects of the intake and utilization of barley grain and grain legume supplements by sheep fed low quality pasture hay and when grazing mature summer pastures.
18
Wirz-Dittus, Sophie Chantal Wirz-Dittus Sophie Chantal Wirz-Dittus Sophie Chantal. "Salmonella abortusovis infection in sheep /". [S.l.] : [s.n.], 2009. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
Testo completo
19
Hollywood, Mark Anthony. "Innervation of sheep mesenteric lymphatics". Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241384.
Testo completo
20
Hopkins, John. "Lymphoid physiology of the sheep". Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/29805.
Testo completoAbstract (sommario):
The aim of this thesis is to bring together and summarize the results of twenty-five years of active research into the immunology and physiology of the mammalian lymphoid system using the sheep as the model species. For this work I have exploited the cannulation of peripheral lymphatics, which enables the monitoring of lymph, lymphocytes and dendritic cells that are constantly trafficking from the skin or from lymph nodes. The use of this technique in the sheep permits access to large numbers of lymph-borne cells over extensive periods and in a form far closer to their in vivo non-activated state than from any other species. I have organized the publications into four distinct, but interrelated chapters. Chapter 1 is concerned with the physiology of sheep lymphoid cells and describes the use of the cannulated lymphatic model to answer fundamental questions of lymphoid biology. My earliest work was focused on the non-random migration of lymphocytes and the identification of two lymphocyte populations; one associated with the gastrointestinal tract and other mucosal organs and the other with peripheral lymph nodes and the spleen. Later work identified two separate populations of B cells with distinct recirculation properties and also concentrated on the lymph node response to antigen and the role played by antigen in modulating lymphocyte recirculation. Much of my work in the last few years has been concerned with the biology of dendritic cells (DCs), the cell population uniquely able to induce the primary immune response. The "pseudo-afferent" cannulation system in sheep is, arguably the best system for this study, as the isolation procedure does not lead to aberrant changes in cell phenotype and function. Chapter 2 relates the work to characterize the sheep immune system, in order to exploit further the sheep as a species for immunological study. Much of my efforts involved the production and characterization of anti-sheep MHC and CD1 monoclonal antibodies (mAbs). This resulted in the generation of monoclonal reagents that are now the standards used to define the ovine/bovine homologues of MHC class I, and class II and CD1.
21
Jones, Philip Anthony. "B cell differentiation in sheep". Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/30327.
Testo completoAbstract (sommario):
The ileal Peyer's patch (IPP) of lambs is a region of intense lymphopoiesis and B cell development. Monoclonal antibodies against ovine lymphoctye antigens have been used to characterise the IPP lymphocyte. Three murine monoclonal antibodies against ovine IgM, IgG1 and Ig light chain were produced and are described fully. IgM and MHC class II antigens are expressed on the vast majority of IPP cells whilst cells bearing other serum Ig isotypes and T cell antigens are rare. A novel Ig molecule appears to be coexpressed with IgM, it is proposed that this is the ovine equivalent of IgD. IPP cells can be induced to proliferate and differentiate when cultured with lipo-polysaccharide (LPS) and interleukin 2 (IL2). Proliferation is inhibited by rabbit anti-sheep Ig antibodies. Using an ELISA for Ig, it has been possible to quantitate Ig synthesis and secretion. Mean cellular Ig increases greater than 25-fold during differentiation. High-rate secretion begins 4 days after initiation of culture and is virtually complete by day 7. As IPP B cells differentiate to IgM secretion, membrane Ig is rapidly lost so that by day 6, only 15% of cells express Ig on their surfaces. Changes in MHC class II antigens were also studied. Surface expression of MHC class II molecules doubled by 24 hours and slowly declined to resting levels as differentiation proceeded. A large increase in cytoplasmic MHC class II content was noted on day 3. The reasons for this increase are discussed. Kinetic studies suggest that IL2 responsiveness is acquired approximately 20 hours after activation by LPS. The concentration required to give half maximal Ig secretion is 125 pM indicating that the interaction between IL2 and its receptor is one of high affinity. During differentiation, the cells enlarge and show an increase in the cytoplasmic:nuclear ratio. The formation of extensive rough endoplasmic reticulum and additional mitochondria is indicative of the functional changes occurring. This is the first description of a sheep B cell differentiation assay. It is proposed that this system is a suitable model on which to base further studies into the molecular biology of sheep Ig genes, Ig isotype switching and lymphokines and their receptors.
22
Harris, Lisa Kim. "Recreation in mountain sheep habitat". Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/186064.
Testo completoAbstract (sommario):
I described recreational use in mountain sheep (Ovis canadensis mexicana) habitat in the Pusch Ridge Wilderness (PRW), Tucson, Arizona. I also examined human attitudes held by PRW recreationists and homeowners within 1 mile (1.6 km) of PRW boundary towards several mountain sheep management options. I used geographic information system modeling and social science survey methodology. Recreational use along two trails that traverse mountain sheep habitat was frequent (66 individuals/day use Pima Canyon trail, 26 individuals/day use Romero Canyon trail) and primarily limited to the lower 3 miles (4.8 km) of the trails. Compliance with existing dog leash regulations is low (41.8% on Pima Canyon trail, 62.8% on Romero Canyon trail). Recreationists and homeowners within 1 mile (1.6 km) of PRW support the elimination of dogs within PRW and support planned burns of PRW to improve mountain sheep habitat. Recreationists and homeowners also support closing all or parts of PRW to protect the long term viability (>100 years) of the sheep population. Homeowners within 1 mile (1.6 km) of PRW primarily enjoy passive recreational use of PRW (i.e, viewing the wilderness).
23
Tarango, Arambula Luis Antonio. "Desert bighorn sheep in Mexico". Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/289197.
Testo completoAbstract (sommario):
The management of bighorn sheep in Mexico is not based on empirical data. We conducted phone interviews and a literature review to determine published information on desert bighorn sheep in Mexico. Most information on bighorn sheep was published prior to 1983 and focused on population size and structure. We concluded that desert bighorn sheep in Mexico are in need of further research. To provide better management to bighorn sheep, research needs to focus on basic life history strategies (e.g., minimum viable population size, diet, habitat relationships, movements, predation, diseases, and metapopulation dynamics). Bighorn sheep in Mexico have been scarcely studied. We conducted a habitat use study in Rancho el Plomito, Sonora, Mexico from April 1997 to December 1998 and the data were used to determine causes of sexual segregation. Vegetation associations were not used according to their availability. Segregated females formed larger groups, were closer to escape terrain and occupied more rugged areas than males. Sexual segregation exhibited by desert bighorn sheep in Rancho el Plomito may result from different energetic and reproductive strategies for males and females. Females tend to optimize conditions suitable for rearing offspring and males maximize body condition. Bighorn sheep in Mexico are important game animals and are confined to scattered populations (Villa 1.959). Little research has been conducted on desert bighorn sheep and consequently the species is listed in appendix II of CITES (i.e., vulnerable) (Valdez 1997). Tarangb and Krausman (1997) emphasized food selection as a fundamental research topic for the species in Mexico. We conducted a study of diet composition in Sonora, Mexico from April 1997 to December 1998. We identified 41 plant species consumed by desert bighorn sheep. The mean annual diet was composed of browse, forbs, succulents, and grasses. Composition of forage categories in diets of males and females was similar. The coefficient of overlap (Morisita 1959) of diets of male and female bighorns for seasons indicated significant overlap. Sexual segregation of desert bighorn sheep in Sonora, Mexico was not related to forage selection (i.e., botanical composition, forage quality), and suggested that other factors (i.e., physiographic characteristics) were responsible for this segregation.
24
Warrick, Gregory David. "MOUNTAIN SHEEP FORAGING BEHAVIOR (ARIZONA)". Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/291298.
Testo completo
25
Dafoe, Julia Mae. "Effect of supplemental safflower seed and vitamin E to late gestating ewes on lamb growth and thermogenesis". Thesis, Montana State University, 2006. http://etd.lib.montana.edu/etd/2006/dafoe/DafoeJ1206.pdf.
Testo completo
26
Campbell, Angus John Dugald. "The effect of time of shearing on wool production and management of a spring-lambing merino flock /". Connect to thesis, 2006. http://eprints.unimelb.edu.au/archive/00003254.
Testo completo
27
Buller, Nicky. "Molecular epidemiology, clonality and virulence of Dichelobacter nodosus, the agent of ovine footrot". Thesis, Buller, Nicky (2005) Molecular epidemiology, clonality and virulence of Dichelobacter nodosus, the agent of ovine footrot. PhD thesis, Murdoch University, 2005. https://researchrepository.murdoch.edu.au/id/eprint/441/.
Testo completoAbstract (sommario):
Dichelobacter nodosus, an anaerobic bacterium, is the major transmissible agent of ovine footrot. The disease expresses as a virulent or benign lesion in the hoof. Virulence is related to the production of serine proteases, particularly a thermostable protease. Isolates of D. nodosus are characterised according to the type of protease produced (either heat-stable or heat-labile) and the electrophoretogram (zymogram) of the protease. This study reports on the use of the DNA-based typing techniques Pulsed-Field Gel Electrophoresis (PFGE) and Infrequent-Restriction-Site-PCR (IRS-PCR) to investigate the molecular epidemiology of D. nodosus, including a consideration of the relationship between genetic type, zymogram patterns and whole cell protein profiles.
The aim of the project was to obtain a better understanding of D. nodosus strain diversity and dissemination in Australia and its relationship to virulence within the population. The overall intention was to use this information to assist in the long-term control of virulent footrot.
Field isolates of D. nodosus from Western Australia (n = 735), New South Wales (n = 16), Victoria (n = 24) and South Australia (n = 21) were obtained and analysed. Both typing techniques that were used offered good differentiation between isolates for epidemiological purposes, and the results were in general agreement. PFGE provided slightly better discrimination between isolates, with 214 PFGE types (181 from Western Australia) compared to 94 IrsT types (77 from Western Australia). Within this diverse range of molecular types clonality was observed - with clones being defined as clusters of isolates having closely related PFGE types. The strains were categorised as genetically diverse, genetically similar or identified as the same strain. This diversity of genetic types was found overall, within flocks of sheep on a farm and within a single hoof where, on a number of occasions, multiple molecular types and zymogram types were found colonising a single hoof. One isolate that was experimentally inoculated into a flock of sheep produced six different genetic types when tested 12 months after the initial infection. This indicates that D. nodosus undergoes rapid genetic change, which means that follow-up epidemiological investigation of disease outbreaks and trace-backs need to be done as soon after infection as possible. The genetic differences appeared to be due to large insertions or deletions of DNA.
Amongst sheep on some properties, isolates that had a different protease expression and virulence expression were found to have the same molecular type. Investigation of these isolates by SDS-PAGE showed that they also had the same whole cell protein profiles. Isolates from the same clonal groups also had the same protein profile, whereas genetically diverse isolates had different protein profiles. The lack of protein differences between isolates of the same molecular type, or within a clonal group, suggests that the differences in protease thermostability may be due to conformational changes in the protein, rather than to overall detectable genetic change and/or expression of different proteins. These results demonstrate that PFGE typing can be useful in predicting likely phenotypic expression of whole cell proteins. Further work is required to elucidate differences between virulent and benign strains of D. nodosus.
28
Buller, Nicky. "Molecular epidemiology, clonality and virulence of Dichelobacter nodosus, the agent of ovine footrot". Buller, Nicky (2005) Molecular epidemiology, clonality and virulence of Dichelobacter nodosus, the agent of ovine footrot. PhD thesis, Murdoch University, 2005. http://researchrepository.murdoch.edu.au/441/.
Testo completoAbstract (sommario):
Dichelobacter nodosus, an anaerobic bacterium, is the major transmissible agent of ovine footrot. The disease expresses as a virulent or benign lesion in the hoof. Virulence is related to the production of serine proteases, particularly a thermostable protease. Isolates of D. nodosus are characterised according to the type of protease produced (either heat-stable or heat-labile) and the electrophoretogram (zymogram) of the protease. This study reports on the use of the DNA-based typing techniques Pulsed-Field Gel Electrophoresis (PFGE) and Infrequent-Restriction-Site-PCR (IRS-PCR) to investigate the molecular epidemiology of D. nodosus, including a consideration of the relationship between genetic type, zymogram patterns and whole cell protein profiles.
The aim of the project was to obtain a better understanding of D. nodosus strain diversity and dissemination in Australia and its relationship to virulence within the population. The overall intention was to use this information to assist in the long-term control of virulent footrot.
Field isolates of D. nodosus from Western Australia (n = 735), New South Wales (n = 16), Victoria (n = 24) and South Australia (n = 21) were obtained and analysed. Both typing techniques that were used offered good differentiation between isolates for epidemiological purposes, and the results were in general agreement. PFGE provided slightly better discrimination between isolates, with 214 PFGE types (181 from Western Australia) compared to 94 IrsT types (77 from Western Australia). Within this diverse range of molecular types clonality was observed - with clones being defined as clusters of isolates having closely related PFGE types. The strains were categorised as genetically diverse, genetically similar or identified as the same strain. This diversity of genetic types was found overall, within flocks of sheep on a farm and within a single hoof where, on a number of occasions, multiple molecular types and zymogram types were found colonising a single hoof. One isolate that was experimentally inoculated into a flock of sheep produced six different genetic types when tested 12 months after the initial infection. This indicates that D. nodosus undergoes rapid genetic change, which means that follow-up epidemiological investigation of disease outbreaks and trace-backs need to be done as soon after infection as possible. The genetic differences appeared to be due to large insertions or deletions of DNA.
Amongst sheep on some properties, isolates that had a different protease expression and virulence expression were found to have the same molecular type. Investigation of these isolates by SDS-PAGE showed that they also had the same whole cell protein profiles. Isolates from the same clonal groups also had the same protein profile, whereas genetically diverse isolates had different protein profiles. The lack of protein differences between isolates of the same molecular type, or within a clonal group, suggests that the differences in protease thermostability may be due to conformational changes in the protein, rather than to overall detectable genetic change and/or expression of different proteins. These results demonstrate that PFGE typing can be useful in predicting likely phenotypic expression of whole cell proteins. Further work is required to elucidate differences between virulent and benign strains of D. nodosus.
29
Grobler, Hermanus Johannes Fourie. "Veldram performance testing of dorper rams in Namibia : performance testing, progency testing and factors influencing sale price of rams". Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1545.
Testo completoAbstract (sommario):
The study aims to determine the contribution made by available ram growth- and breed standard parameters on the sale price of auctioned rams in Namibia. These findings serve as an indication of the importance ram buyers place on individual parameters in selecting rams for breeding purposes. It furthermore tries to establish whether scientific measurement for the estimation of ram breeding values takes precedence over subjective appraisal. The analysis of the 100 day and 270 day growth performance of the progeny of selected Veldram tested rams were used to evaluate the accuracy of the estimation of ram breeding values and may serve to validate the proper execution of these Veldram tests.
30
au, cstockman@agric wa gov, e Catherine Ann Stockman. "The Physiological and Behavioural Responses of Sheep Exposed to Heat Load within Intensive Sheep Industries". Murdoch University, 2006. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20070820.143149.
Testo completoAbstract (sommario):
The live export and feedlotting industries are the major intensive sheep industries in Australia. During live shipment, sheep are exposed to prolonged periods of high heat and humidity, with little relief for several days, while environmental conditions in a Western Australian sheep feedlot have not yet been assessed. The research described in this thesis was conducted to determine the physiological responses of sheep to conditions within the live export and feedlotting industries, with particular focus on that of heat stress.
Merino wethers and Awassi rams developed significant change in physiological variables when exposed to prolonged periods of high heat and humidity, such as during long haul, live export voyages to the Northern Hemisphere. Physiological changes such as increased core temperature, respiratory rate, panting score and associated changes in blood gas variables were apparent in Merino wethers. However, Awassi rams showed exceptional ability to maintain homeostasis under the same environmental conditions, with no significant changes in core temperature and only slight alteration in blood gas variables. Results from this study indicated that electrolyte supplementation of sheep during live export would not be warranted because plasma electrolytes did not drastically change and blood gas variables quickly returned to normal following the heat.
Further studies developed methods to determine the critical wet bulb temperature, otherwise known as the heat stress threshold (HST) of Merino rams, ram lambs and wethers exposed to live export conditions. These studies found that ram lambs had a lower HST than both adult rams and wethers. However, both adult rams and wethers had a similar HST. Heat stress thresholds determined from these studies have been used in a model to predict high risk shipments for particular classes of sheep (Stacey 2003).
This thesis also details the environmental conditions within a Western Australian summer feedlot and the physiological responses of cross bred ewes and wethers to these conditions when fed feedlot rations. This study found that temperatures in a typical Western Australian feedlot in summer increased above 40¢ªC with low humidity; however, temperatures generally decreased to be within the sheep¡¯s thermoneutral zone at night. Both ewes and wethers had significantly increased core temperatures in response to these conditions, with sheep spending significantly more time in the shade than in the sun during the day. Both ewes and wethers had increased respiratory rates and panting scores during an intensive climate room experiment with similar environmental conditions. However, feed intake did not decrease even when climate room temperatures increased at night and humidity levels were higher than that found in typical feedlot conditions in Western Australia.
Work completed within this thesis has led to a greater understanding of the physiological responses of sheep to prolonged and continuous high heat such as during live export and to conditions of a typical Western Australian summer feedlot. This research has set a foundation for further study of management of sheep during live export and feedlotting.
31
Quintana, Casares Pablo Ignacio. "Studies on the relationship between characteristics of ram semen and fertility". Title page, contents and summary only, 1991. http://web4.library.adelaide.edu.au/theses/09PH/09phq7.pdf.
Testo completoAbstract (sommario):
Includes bibliographical references (leaves 274-316) Examines several aspects of male reproduction in the sheep, and how these are related to fertility in the female when semen is introduced by natural mating or artificial insemination.
32
Jacobs, Salmon Stephanus. "Kwalitatiewe en kwantitatiewe inname van staandehooi van twee Cenchrus ciliaris kultivars (Molopo en Gayndah) deur skape". Pretoria [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-04042007-102237.
Testo completo
33
Neary, Kathleen Ida. "In vitro comparison of satellite cells isolated from normal and callipyge sheep exposed to growth promoting compounds". Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/neary/NearyK0507.pdf.
Testo completo
34
Tudor, G. D. "The influence of diet on the chemical composition of cattle and sheep /". Title page, table of contents and abstract only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09pht912.pdf.
Testo completo
35
Reader, Karen Lee. "A quantitative ultrastructural study of oocytes during the early stages of ovarian follicular development in Booroola and wild-type sheep : a thesis submitted to the Victoria University of Wellington in fulfilment of the requirements for the degree of Master of Science in Cell and Molecular Bioscience /". ResearchArchive@Victoria e-Thesis, 2007. http://hdl.handle.net/10063/270.
Testo completo
36
Lee, Karen. "Reproductive management of semi-intensive Döhne merino ewes fed with different protein supplements". Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-08072009-175647.
Testo completo
37
Nicholls, Natalie Anne Harriette. "Are scrapie-susceptible sheep more productive?" Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/29299.
Testo completoAbstract (sommario):
A relationship between scrapie susceptibility, which is determined by PrP genotype, and valuable production traits has long been noted by sheep farmers, with many claiming that their ‘best’ sheep often are found to be susceptible to scrapie, or have close siblings that are susceptible to scrapie. There have been several historical anecdotal reports to support this observation, but only recently has the hypothesis, that scrapie-susceptible sheep are more productive, been investigated in scientific study. This thesis contains the results of several such studies and is concluded by an investigation into whether the current breeding strategies being encouraged in the UK would be effective at eliminating scrapie from the national sheep flock. In these studies, PrP genotype was compared to objective measures such as lamb weights and Estimating Breeding Values (EBVs), as well as to subjective measurements which were based on a farmer’s judgement of their sheep, with varying results. Analysis of the subjective measurements, rating scores and culling records did not show any association with PrP genotype. The results of the analysis of the EBVs were variable, and inconsistent between farms, with susceptibility to scrapie being associated with both increased and decreased productivity. There was a small association between PrP genotype and lamb weights, which indicated that at eight weeks of age, ARR/ARR lambs were slightly smaller than lambs other more susceptible genotypes. Overall, however, there is no strong evidence that scrapie-susceptible sheep truly are more productive. The final section has shown that with the current suggested breeding strategies, there will still be some risk of scrapie outbreaks in some flocks.
38
Robinson, Brenton Scott. "Choline nutrition and metabolism in sheep /". Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09phr658.pdf.
Testo completo
39
Zhang, Runhou 1963. "Manipulating fatty acids in sheep milk". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102236.
Testo completoAbstract (sommario):
Four studies were conducted to investigate some factors affecting milk fatty acid composition of dairy ewes. The first study was performed to determine the influence of freezing temperatures and storage time on ovine milk composition and cheese making. The other three experiments were conducted to examine the effects of dietary added fats with different profiles of fatty acids from canola, sunflower and flaxseeds on animal performance, nutrient utilization, milk yield and cheese making. The main emphasis was on fatty acid composition, particularly CLA and Omega-3 fatty acids, in milk and cheese. Results showed that: (1) feeding up to 8% of canola, sunflower and flaxseed had no adverse effects on dry matter intake and total tract digestibilities of dry matter, neutral detergent fiber, acid detergent fiber and crude protein, while the digestibilities of fatty acids and gross energy were increased with oilseed supplementation; (2) feeding flaxseed to lactating ewes up to 260g/ewe/d increased milk yield by up to 8.4%, and fat content by up to 14.3% without adversely affecting other milk components or cheese yield and composition; (3) Oilseed supplementation increased milk concentrations of long-chain and unsaturated fatty acids in the expenses of short-chain, medium-chain and saturated fatty acids. The concentrations of CLA and Omega-3 fatty acids were also increased by oilseed supplementation; (4) the manipulated fatty acids profiles can be reflected in cheese; (5) good quality cheese can be produced from ovine milk frozen at -15°C and -25°C for up to 6 months without influencing cheese content of fat and protein and fatty acid composition.In conclusion, ovine milk with nutritionally healthy characteristics can be produced by feeding ewes diets with oilseeds, and freezing storage of milk for up to 6 months at -15°C or -25°C does not significantly affects milk composition including fatty acid composition. The characteristics of milk can be reflected in cheese.
40
Stevenson, Ian Roxburgh. "Male-biased mortality in Soay sheep". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321000.
Testo completo
41
Nassiri, Mohammad Taghi Beigi. "Aspects of prolificacy in Cambridge sheep". Thesis, Bangor University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321435.
Testo completo
42
Kitching, Richard Paul. "Studies on sheep and goat pox". Thesis, University of Edinburgh, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482688.
Testo completo
43
Townsend, S. J. "Genetic diversity and domestication in sheep". Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368146.
Testo completo
44
Toland, Helen M. "Pacemaking in sheep mesenteric lymphatic vessels". Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301060.
Testo completo
45
Beresford, Nicholas A. "Radiocaesium variability in upland sheep flocks". Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273191.
Testo completo
46
McNeil, Christopher John. "Glutamine and lymphocyte metabolism of sheep". Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391973.
Testo completo
47
Philips, Helen Louise. "Enteric and abortion chlamydia in sheep". Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385154.
Testo completo
48
Bates, Anne Elizabeth. "The effect of copper on sheep". Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406722.
Testo completo
49
Hansen, Helle Rüsz. "Investigation of arsenosugar metabolism in sheep". Thesis, University of Aberdeen, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409245.
Testo completoAbstract (sommario):
This thesis describes part of an on-going study of the metabolism of arsenosugars in sheep living on a diet of seaweed. Two major analytical techniques have been combined in a three-pronged approach. ICP-MS has served to quantify total arsenic in seaweed, urine and faeces and has enabled a mass balance to be drawn up indicating that around 86% of ingested arsenic (average 35 mg/d) is excreted in the urine, 13% in the faeces and less than 1% is accumulated in the animal. HPLC-ICP-MS has served to quantify both known and unknown metabolites at down to low ng/g levels in urine and in faeces, though they are often present in mg/g levels in the undiluted samples. Seaweed fed to the sheep, Laminaria digitata and L. hyperborea, contained arsenic mainly (70%) as arsenosugars, a little (2%) as dimethylarsinic acid, DMA(V), and the remainder was inextractable. The principal metabolite seen in the urine and in the faeces was DMA(V). A major problem in these studies has been the low recovery of the chromatography, which has the consequence that the speciation must be considered thus far as incomplete. The chromatographic recoveries, form urine samples alone, have ranged from 4 to 100%. Coupling of ICP-MS and electrospray MS (ES-MS) simultaneously to the outlet of the same HPLC column has permitted the identities of several new compounds to be established. DMAA (dimethylarsinoyl acetic acid) has been found as an arsenosugar metabolite in urine for the first time. The simultaneous coupling was crucial because DMAA co-elutes with methylarsonic acid (MA(V)) from the commonly used PRP-X100 strong anion-exchange column and without the use of a molecular detector it would have been misidentified. A new class of compounds has been identified in the urine samples by ES-MS, in which arsenic in its pentavalent state is bound to sulfur. Dimethylarsinothioic acid (DMAS) has been positively identified by retention time and by molecular mass. It turns out to have apparently the same retention time as a DMA(III) standard.
50
Kaler, Jasmeet. "Epidemiological investigations into lameness in sheep". Thesis, University of Warwick, 2008. http://wrap.warwick.ac.uk/2966/.
Testo completoAbstract (sommario):
Lameness is the greatest health and welfare concern in sheep flocks in the U. K. This thesis presents research on epidemiology of lameness in sheep Most previous studies quantifying lameness and its causes are based on the premise that farmers can identify the causes of lameness and recognise lame versus sound sheep. In 2005, a postal questionnaire was sent to a random sample of English sheep farmers to investigate whether farmers could correctly name six common foot lesions in sheep (interdigital dermatitis (ID), footrot (FR), contagious ovine digital dermatitis (CODD), shelly hoof, foot abscess and toe granuloma) from a characteristic picture and a written description. The same questionnaire of six lesions was presented at a meeting of specialist sheep advisors, primarily veterinarians. Approximately 20% of farmers and 80% of sheep specialists named all 6 lesions correctly, indicating a gap in knowledge between sheep advisors and sheep farmers. In addition, farmers tended to name any hoof horn damage as footrot which might imply that some lame sheep receive incorrect treatment. Management factors associated with the prevalence of farmer estimated lameness (irrespective of farmer recognition of lesions) and the adjusted prevalence of lameness caused by ID and FR among flocks where farmers correctly recognised both lesions were investigated and compared in negative binomial regression models. Farmers who routinely foot trimmed and frequently footbathed their sheep reported a higher prevalence of lameness, ID and FR. Farmers who stocked their sheep at >8ewes/hectare reported a high prevalence of both lameness and ID whilst those who separated `some' or `all' lame sheep at pasture reported a low prevalence of both lameness and ID. Farmers in the east of England reported a lower prevalence of lameness, ID and FR compared with central England. A numerical rating locomotion scoring scale (0-6) was developed to monitor locomotion in sheep in a research setting. There was good agreement between and within trained observers using this scale. This scoring system was used in a longitudinal study on one farm, two groups of sheep (30 in each group) with different treatment regimes (antibiotic injection & antibiotic spray vs. foot trimming and antibiotic spray; and occasional footbathing) for lameness with FR and ID were followed for five weeks to investigate the temporal associations between ID, FR and the effect of different treatments on locomotion. From the examinations it was concluded that even mildly lame sheep can have FR and ID. In a multilevel linear mixed model, there was a significant association between ID, FR and locomotion score with the mean score of 0.25 increasing to 0.43 for sheep with ID and to 2.18 for sheep with FR. In addition, sheep that developed FR had a significantly raised locomotion score the week before FR became clinically apparent. Treatment with antibiotic injection and antibiotic spray significantly reduced the locomotion score of sheep the following week. The movie clips from the locomotion scoring reliability study were used to investigate farmer and sheep specialist recognition of lame sheep and decisions on whether to catch them. A group of farmers from three regions (Devon, Newark and Norfolk) and sheep specialists at a Sheep Veterinary Society meeting were shown eight movie clips of sheep with varying locomotion scores. Although the majority of farmers and sheep specialists identified mildly lame sheep with a locomotion score of 2, only 50% of them would catch such a sheep if it was the only lame sheep in the group. Most farmers and sheep specialists did not catch lame sheep until the lameness was locomotion score 3 or 4. The more frequently farmers caught lame sheep, and the milder the lameness when a decision to catch was taken, the lower the farmer reported prevalence of lameness in the flock. The research in this thesis suggests that farmers, who are the primary carers for lame sheep, do not always name foot lesions correctly and so sheep may receive inappropriate treatment for some lesions. In addition, whilst farmers and sheep specialists can recognise lame sheep, they do not always catch and treat mildly lame sheep. Farmers who caught all mildly lame sheep within a few days of seeing them lame reported a lower prevalence of lameness in their flock. This might be explained by the evidence from this thesis that mildly lame sheep can have FR or ID and so prompt treatment of these lame sheep reduces the prevalence and incidence of FR and ID.