Dissertationen zum Thema „Australian merino sheep Physiology“

"May 2002" Includes bibliographical references (leaves 148-164) Describes a series of novel experiments designed to enhance our understanding of nutrient utilisation for growth of wool and the whole body.

Bibliography: leaves 281-316. Presents investigations on pubertal development in South Australian merino ram lambs and examines the effect of active and passive immunizations against oestradiol-17ℓ or oestrone on testicular maturation.

Ewes at two sites were fed to be either condition score 2 or 3 by Day 90 of pregnancy and then grazed on various levels of feed-on-offer (FOO) from Day 90 of pregnancy until weaning, to investigate whether nutrition of Merino ewes during pregnancy and lactation affected the muscle, fat and immunity to worms of their progeny. Eye muscle and fat depth at the C-site, and faecal worm egg counts (FWECs) of the progeny were measured between 7 - 27 months of age. Ewe condition score at day 90 of pregnancy did not impact largely on the eye muscle depth, fat depth or FWEC of the progeny. Increasing FOO available to ewes during the last 60 days of pregnancy and throughout lactation increased the eye muscle depth of progeny at one site and decreased the fat depth of progeny at the other site (P<0.05), but did not affect the majority of FWECs of the progeny at either site. The FWECs of the progeny were low, indicating a relatively low larval challenge, which limits the likelihood of differences in immunity to worms between the progeny being expressed. This Masters demonstrated that levels of nutrition available to Merino ewes typical of commercial grazing conditions had only small effects on the eye muscle and fat depth at the C-site, and on the faecal worm egg counts of their progeny

Bibliography : leaves 120-133. Defines the sources of reproductive wastage in FecB FecÊ Booroola Merino x South Australian Merino ewes and examines factors associated with the survival of embryos, fetuses and lambs with the aim of improving net reproduction efficiency. Experiments were conducted to define the problem; to examine factors affecting embryonic and fetal loss; and, to investigate factors influencing wastage at lambing.

Muscular dystrophies (MDs) are neuromuscular disorders characterised by chronic, usually progressive, skeletal muscle weakness. Individuals often lose walking ability and can suffer terminal cardiorespiratory complications. Determining the genetics of a disease helps provide diagnosis, prognosis, genetic counselling, and the basis for rational therapeutic design. A naturally occurring sheep model of autosomal recessive congenital MD was identified in WA in the 1950’s and preserved as a research colony. The pathological features and distribution of this MD is novel. A sheep model of MD is incredibly valuable; sheep have similar skeletal muscle mass to humans, representing a significant improvement over smaller mammals in which to trial therapies. Successfully characterising the causative gene(s) would enable a possible target for new therapies and may open new lines of investigation into better understanding and treatment of MD in humans. This project utilised a two-pronged approach to investigate the genetics of this ovine MD. First, bioinformatics analysis of SNP genotyping for multiple individuals in the flock by a 50,000 SNP array in combination with the latest sheep genome reference build released by the International Sheep Genome Consortium, enabling homozygosity mapping, genetic linkage and association mapping. Second, molecular biological approaches further explored the identified prime candidate gene by cDNA sequencing. This research project identified ROCK2 as the prime candidate gene most likely harbouring a mutation causing the muscular dystrophy in this internationally unique ovine model. It also demonstrated for the first time in sheep the existence of ROCK2m, an isoform of ROCK2 preferentially expressed in skeletal muscle. This work has set the stage for further investigations into ROCK2m and the ovine MD which will hopefully pinpoint the causative disease mutation.

Thesis (PhD)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: This study describes: • the comparison of the enzymatic activities of the two ovine cytochrome P450 17 - hydroxylase/17,20-lyase (CYP17) isoforms expressed in non-steroidogenic COS-1 cells. The Km and Vmax values for the metabolism of pregnenolone and progesterone were determined, while time-dependent metabolism of pregnenolone, 17-hydroxypregenolone, progesterone and 17-hydroxyprogesterone was also reported. The cloning and sequencing of ovine cytochrome b5 is reported and was co-expressed with CYP17. The results showed that the wild type 1 (WT1) isoform of ovine CYP17 produce more cortisol precursors than the wild type 2 (WT2) isoform; • the analysis of the frequency distribution of the CYP17 genotypes within a South African Merino population, which were divergently selected for (H-line) or against (L-line) the ability of a ewe to rear multiple offspring per birthing opportunity. It was observed that the CYP17 frequency distribution was the same within the H- and L-line, with 78.3 % heterozygous WT1/WT2 and 21.7 % homozygous WT1/WT1. No homozygous WT2/WT2 individuals were identified; • the development of a UPLC-MS/MS method for the separation and quantification of all thirteen adrenal steroids that are produced in the adrenal gland; • the relative contribution of the CYP17 genotypes in the total steroidogenic output in adult adrenocortical cells from the adrenal glands of H- and L-line sheep, with particular emphasis on cortisol production. The adrenocortical cells from the H-line sheep showed a marked higher cortisol production than the L-line, while adrenocortical cells from homozygous WT1/WT1 sheep also produced more cortisol than heterozygous WT1/WT2 sheep; • the blood cortisol responses upon the stimulation of the HPA axis by insulin induced hypoglycaemia of the H- and L-line sheep with known CYP17 genotypes. It was observed that the CYP17 genotype and selection line are important factors affecting the cortisol responses of sheep, where L-line heterozygous WT1/WT2 sheep showed the lowest cortisol response and glucose recovery; • the association of the CYP17 genotype with behavioural responses of H- and L-line sheep to flock isolation stress, as well as the association of the CYP17 genotype with ewe reproduction and lamb output. While reproduction seemed to be unaffected by the CYP17 genotype, the behavioural stress responses of sheep to flock isolation correlated with the CYP17 genotype, where the heterozygous WT1/WT2 genotype was associated with a wilder nature.
AFRIKAANSE OPSOMMING: Hierdie studie ondersoek: • die vergelyking van die ensiemaktiwiteite vir twee isoforme van skaap sitochroom P450 17 -hidroksilase/17,20-liase (CYP17), wat uitgedruk was in nie-steroïed genererende COS- 1 selle. Die Km and Vmax waardes was bepaal vir die metabolisme van pregnenoloon en progesteroon, terwyl die tyd-afhanklike metabolisme van pregnenoloon, 17- hidroksiepregnenoloon, progesteroon en 17-hidroksieprogesteroon ook gerapporteer word. Die klonering en volgorde bepaling van skaap sitochroom b5 was gedoen en gevolglik was sitochroom b5 saam met CYP17 uitgedruk in COS-1 selle. Die resultate het gewys dat wilde tipe 1 (WT1) meer voorlopers van kortisol produseer as wilde tipe 2 (WT2); • die frekwensie distrubusie van die CYP17 genotipes in ‘n Suid-Afrikaanse Merino populasie, waar skape in teenoorgestelde rigtings geselekteer was vir (H-lyn) of teen (L-lyn) die vermoë van ‘n ooi om geboorte te gee aan veelvoudige lammers per lamgeleentheid. Die frekwensie distrubusie van CYP17 was dieselfde in beide die H- en L-lyn, waar 78.3 % van die populasie heterosigoties WT1/WT2 en 21.7 % homosigoties WT1/WT1 was. Geen homosigote WT2/WT2 individue was geïdentifiseer nie; • die ontwikkeling van ‘n UPLC-MS/MS metode vir die skeiding en kwantifisering van al dertien steroïede wat natuurlik geproduseer word in die bynier van die skaap; • die relatiewe bydrae van die CYP17 isoforme tot die totale steroïedale uitsette vanuit die bynier kortex selle, vanaf die byniere van H- en L-lyn skape, waar klem geplaas word op die produksie van kortisol. Die bynierselle van die H-lyn skape het aansienlik meer kortisol produseer as die L-lyn, terwyl die bynierselle van die homosigotiese WT1/WT1 skape ook meer kortisol produseer het as heterosigotiese WT1/WT2 skape; • die bloed kortisol in reaksie tot die stimulering van die hipotalamus-hipofise-adrenale aksis, deur insulien geïnduseerde hipoglisemiese stress, in skape van die H- en L-lyne met bekende CYP17 genotipes. Dit was gevind dat die kortisol reaksie geaffekteer word deur beide die CYP17 genotipe en seleksie lyn, waar L-lyn heterosigotiese WT1/WT2 skape die minste kortisol geproduseer het en die stadigste herstel van glukose vlakke getoon het; • die assosiasie tussen die CYP17 genotipe en die gedrags reaksies op trop-isolasie, sowel as ooi-reproduksie en lamuitset, van die H- en L-lyn skape. Die reproduksie parameters was onafhanklik van die CYP17 genotipe, terwyl ‘n sterk assosiasie gevind was tussen die CYP17 genotipe en gedrags reaksies op trop-isolasie. Die heterosigotiese WT1/WT2 skape het ‘n wilder natuur getoon gedurende trop-isolasie in vergelyking met homosigotiese WT1/WT1 skape.

Includes bibliographical references (leaves 276-2970. Investigations presented involve 18 hour to 5 day old South Australian merino lambs. Some twin lambs were available for comparative studies. Examines the relationship between the strength of ewe-lamb bond and the lamb's ability to follow the mother, the energy availability and usage in the lamb, particularly for locomotion, and the metabolic and cardiorespiratory responses to locomotion.

"May 2002"
Includes bibliographical references (leaves 148-164)
xi, 164 leaves : ill. ; 30 cm.
Describes a series of novel experiments designed to enhance our understanding of nutrient utilisation for growth of wool and the whole body.
Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Science, 2002

Bibliography: leaves 325-341. Skin and fleece measurements were recorded at different ages for both male and female sheep from the Turretfield Merino Resource Flock and used to estimate the heritability of each trait and the phenotypic and genetic correlations among and between the skin and fleece traits. Generally, the heritability of each trait was high, which indicates that both the fleece and skin traits should respond well to selection.

Includes bibliographies.
1 v. : ill. ; 30 cm.
The present study provides a detailed account of the anatomical and neurohistological structure of the temporomandibular joint (TMJ) in foetal and adult Australian Merino sheep. The purpose is to describe the innervation of the joint and to determine the possible roles of both afferent receptor structures and neuropeptides in the pathophysiology of experimentally induced osteoarthritis.
Thesis (Ph.D.)--University of Adelaide, Dept. of Anatomical Science, 1997

Includes bibliographical references (leaves 325-341).
xxvii, 341 leaves : ill. ; 30 cm.
Skin and fleece measurements were recorded at different ages for both male and female sheep from the Turretfield Merino Resource Flock and used to estimate the heritability of each trait and the phenotypic and genetic correlations among and between the skin and fleece traits. Generally, the heritability of each trait was high, which indicates that both the fleece and skin traits should respond well to selection.
Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Science, 2001

Orientação: João Cannas da Silva; co-orientação: João Diogo Pereira
Os fatores que influenciam a reprodução em ovinos trata-se de um tema de tamanha importância em Medicina Veterinária, que, com o passar do tempo tem sido dada mais ênfase, com o intuito de melhorar o índice reprodutivo de uma forma positiva em ovinos. Os pontos mais importantes para o sucesso reprodutivo são, o conhecimento da fisiologia reprodutiva tanto da fêmea como do macho, técnicas de sincronização de cios, saber dirigir um bom exame andrológico em machos, nutrição e também não menos importantes partos distócicos. Pretendeu-se com este trabalho identificar pontos-chave do foro reprodutivo, com o intuito de se proceder a alterações simples nas explorações que podem fazer toda a diferença no sucesso reprodutivo, tendo em conta que a produção animal cresce de dia para dia e não se justifica existir tantas falhas a nível reprodutivo. Foram descritos três casos clínicos relacionados com o tema, todos eles acompanhados no estágio curricular. Foi realizada uma apresentação e valorização da raça Merino da Beira baixa, visto esta ser uma raça autóctone, valorizando o que temos de bom no nosso país, não deixando cair em esquecimento, uma raça que está em vias de extinção.
The factors that influence the reproduction in sheep it is a topic of such importance in veterinary medicine, as time is going, more emphasis has been given to this theme, in order to improve a positive way the reproductive index in sheep. Important points in the influence of reproductive success were considered, the knowledge of the reproductive physiology of both the female and the male, techniques of heat synchronization, knowing how to direct a good andrological examination in males, nutrition and also not less important dystocic births. The aim of this work was to identify key points about the theme of reproduction, to allowed simple changes in farms that can make all the difference in reproductive success, considering that animal production its growing day by day and that does not justified the amount of failures at reproductive level. There were described three clinical cases related to the theme, where all of them were carried out at professional internship. There was also a presentation and recognition of Merino breed from Beira Baixa, as it is an autochthonous breed, thus valuing what is good in our country, not letting it fall into forgetfulness, as it is a breed that is on the verge of extinction.

VSR Dukkipati (2007). A search for genetic factors influencing immune responses to Mycobacterium avium subspecies paratuberculosis. Doctoral thesis, Massey University, Palmerston North, New Zealand. A study was conducted to identify associations between genetic markers and immune responses in Australian fine-wool Merino sheep to a killed Mycobacterium avium subspecies paratuberculosis (Map) vaccine (GudairTM). Blood samples and immune response data (antibody and interferon gamma, IFN-gamma results) were obtained from 934 sheep from a longterm Map vaccination trial undertaken on three independent properties in New South Wales, Australia. Blood samples were genotyped for eight microsatellite markers that included four (DYMS1, OLADRW, OLADRB and SMHCC1) from the Ovar-Mhc region, two each from the SLC11A1 (OVINRA1 and OVINRA2) and IFN-gamma (o(IFN)gamma and OarKP6) gene regions. Vaccination with GudairTM induced strong antibody and IFN-gamma responses as early as two weeks post-vaccination. Between-property differences in magnitude and trend of immune responses, concomitant with season of vaccination and magnitude of natural infection prevalent in individual flocks, were evident. Immune responses in controls on all the three properties remained consistently low, except for slightly elevated IFN-gamma levels at a few time points in controls of properties 2 and 3, concomitant with exposure to natural infection. There were only 2 alleles and 3 genotypes for marker o(IFN)gamma but other loci exhibited extensive polymorphisms, the most occurring at OLADRW which had 42 alleles and 137 genotypes. Heterozygosities varied between 33% (OVINRA2) and 87% (SMHCC1), while polymorphic information contents ranged from 0.31 (o(IFN)gamma) to 0.88 (OLADRW). Genotypes at loci DYMS1, OLADRB, SMHCC1, OVINRA1 and o(IFN)gamma were in Hardy- Weinberg equilibrium (HWE), while those at OarKP6 were in HWE only when rare alleles (<1.0% frequency) were pooled with the closest size class. Departure from HWE, resulting from possible preferential amplification of alleles in heterozygotes, was evident at OLADRW and OVINRA2. Associations between immune responses and genetic polymorphisms at the marker loci were examined by analysing both genotypic and allelic affects. The study revealed several genotypes/alleles at different marker loci to be significantly associated with antibody and IFN-gamma responses to vaccination with GudairTM. However, the majority of those effects were inconsistent across the three properties. Based on significance and consistency in effects across the three properties, five genotypes (two at DYMS1 and one each at OLADRB, SMHCC1 and OVINRA1) and three alleles (one each at DYMS1, OLADRB and o(IFN)gamma) were considered either ‘probable’ or ‘most likely’ to be associated with low IFN-gamma responses, while a genotype at o(IFN)gamma was considered ‘most likely’ to influence high IFN-gamma responses. An allele at OarKP6 was considered ‘probable’ to be associated with low antibody responses to vaccination. Considering the significance of IFN-gamma responses in protection against Map, it is likely that the identified genotype/alleles influencing IFN-gamma responses to vaccination would also influence immune responses to natural Map infections. However, further studies need to be conducted to determine the role of these marker genotypes/alleles in protection against paratuberculosis under natural infection conditions. Key words: paratuberculosis, OJD, Johne’s disease, sheep, immune response, genetic markers, gene polymorphisms, MHC, SLC11A1, IFN-gamma