Thesis (Ph. D.)--University OF MICHIGAN.

During the nonbreeding season (July), three groups of five Dorset x Leicester x Suffolk rams were assessed over a period of 5 days. One group of rams (control) was implanted (sc) with five 5cm empty Silastic capsules (i.d. 3.4mm, o.d. 4.6mm); two other groups, designated as Low-E$ sb2$ and High-E$ sb2$, received five estradiol filled capsules of either 5cm or 10cm, respectively for 4 days. Estradiol treatment elevated serum estradiol concentration about 150% in the Low-E$ sb2$ groups (15.7 $ pm$ 1.3 pg/ml) and 300% in the High-E$ sb2$ groups (26.6 $ pm$ 2.4 pg/ml) compared with controls (6.3 $ pm$ 0.8 pg/ml). In the absence of LH pulsing, mean LH, FSH and testosterone concentrations were all decreased significantly (P $<$.05) with increasing estradiol concentration, while PRL concentration was increased (P $<$.05) by as much as 105%. In the LH-pulsed groups, LH-peak height on day 4 was comparable for all three groups of rams and peak frequency was, as expected, consistently increased to 4 peaks per 6 hours. The increase in mean testosterone concentration (P $<$.05) in all three groups was due to an increase in testosterone baseline concentration and testosterone peak frequency.

Thesis (Ph. D.)--University OF MICHIGAN.

Previous studies of the control of reproduction in Rhabdomys pumilio have shown that day length alone does not inhibit spermatogenesis, that a reduction in food availability and ambient temperature results in an inhibition of gametogenesis, that females are more susceptible to inhibition than are males, and that mice that are able to maintain a body fat store in the face of an energetic challenge, are less likely to show reproductive inhibition than those that lose their fat store. In the present study, field and laboratory experiments were conducted to examine the effects of winter food supplementation on reproduction and population dynamics, and the effects of exogenous GnRH, leptin and mercaptoacetate (MA) on reproductive activity of Rhabdomys pumilio exposed to an energetic challenge. In the field food supplementation experiments in Thomas Baines Nature Reserve (2000, 2001), there was no winter inhibition of reproduction and provision of supplementary food had little effect. While at Mountain Zebra National Park (2002) winter was harsher, females became reproductively inactive, spermatogenesis continued and the provision of extra food resulted in higher rates of individual growth and larger reproductive organs. Treatment of mice that had been exposed to a prolonged energetic challenge, with exogenous GnRH (1µg/mouse/treatment) resulted in an increase in the masses of the testes and epididymides, and in the activity of the reproductive organs. Treatment with exogenous leptin (40µg/mouse/treatment), concurrently with an energetic challenge, countered the negative effects of the energetic challenge, and treated males had larger reproductive organs. MA (600µmol/kg body mass), given concurrently with an energetic challenge, did not inhibit fat metabolism, although the high-fat diet countered the effects of the energetic challenge. Results suggest that the first response of male Rhabdomys pumilio to an energetic challenge is a reduction in the size of the reproductive organs, without an inhibition of spermatogenesis. It is likely that this effect is mediated via white fat and leptin, and leptin’s influence on the hypothalamic-pituitary-gonad axis. Results of the study support the suggestion that females are more sensitive to reproductive inhibition than males and that reproduction in Rhabdomys pumilio is truly opportunistic.

Titre de l'écran-titre (visionné le 7 juillet 2023) / Les techniques de reproduction assistée (TRA) sont d'importants outils de la révolution génomique de l'industrie laitière. En dépit de l'amélioration fulgurante des taux de succès de la fécondation in vitro (FIV) et malgré l'engouement croissant pour les embryons bovins produits in vitro, certains problèmes restent à résoudre pour assurer la totale innocuité de ces interventions en reproduction. En effet, l'avancée rapide de la recherche en épigénétique a mis au jour l'influence possible de l'environnement artificiel durant la période critique qu'est le développement embryonnaire précoce. Bien que l'incidence de troubles développementaux majeurs tel le syndrome du « gros veau » ait beaucoup diminuée avec l'adoption de meilleures pratiques de culture embryonnaire, un ensemble d'indices probants suggère que des modifications à long terme plus subtiles affectent toujours le métabolisme, la croissance, la fertilité et donc la productivité des animaux découlant de ces pratiques. Les travaux menés dans le cadre de cette thèse reposent sur l'hypothèse que la FIV chez les bovins laitiers a des effets sur la programmation épigénétique de l'embryon ce qui peut affecter le phénotype postnatal. La première partie de cette thèse consistait à évaluer la qualité de la programmation épigénétique d'embryons bovins produits in vitro en fonction de paramètres comme l'âge de la donneuse d'ovocytes et le type de milieu de culture. Pour ce faire, nous avons évalué par pyroséquençage la méthylation de l'ADN de gènes soumis à l'empreinte parentale d'embryons bovins au jour 7 et 12 produits dans différentes conditions. Pour chaque gène, nous avons observé une méthylation globalement moins élevée ainsi qu'une plus grande variabilité chez les trois groupes d'embryons produits in vitro étudiés. Afin de pallier des contraintes techniques et d'évaluer les conséquences réelles des différences moléculaires observées, nous avons comparé la population de vaches du Québec conçues par FIV avec celles conçues par insémination artificielle (IA) et transfert embryonnaire (TE) pour des critères de santé, fertilité et productivité. L'analyse de cohorte rétrospective n'a pas révélé, en tenant compte des valeurs d'élevage supérieures des animaux issus de TE et de FIV, de différences significatives entre les méthodes de conception pour la production de lait des filles lors de leurs trois premières lactations. Par contre, les animaux produits par FIV montrent une fertilité légèrement réduite, des temps de gestation plus longs et une incidence relative de maladie commune différente du reste de la population. De façon logique avec leur rôle dans l'industrie de la génétique laitière, l'indice de performance à vie (IPV) moyen des animaux conçus par FIV est supérieur. Cependant, entre 2012 et 2019, le taux d'amélioration de l'IPV des animaux conçus par FIV était près de deux fois moins rapide que celui de la population générale. Nous postulons qu'une pénalité épigénétique, cohérente avec et potentiellement dérivée des différences moléculaires trouvées dans les embryons à la suite des TRA diminue le progrès génétique intergénérationnel et explique les altérations phénotypiques observées. Par la qualité et la quantité des données disponibles, nos travaux ont permis d'illustrer avec une résolution jamais égalée les causes et les impacts des conditions de développement précoce des gamètes et des embryons. Nos résultats mettent en évidence les défis de l'amélioration de la génétique laitière d'élite tout en attestant des progrès réalisés par l'industrie pour minimiser les perturbations épigénétiques sévères menant à des syndromes graves de dérégulation de l'empreinte parentale. Cependant, les TRA laissent toujours des traces bien détectables à la fois au niveau moléculaire chez les embryons et au niveau physiologique chez les animaux à l'âge adulte. Ces résultats permettront ainsi aux producteurs laitiers canadiens de prendre des décisions éclairées sur la méthode de conception à utiliser pour constituer leur troupeau en tenant compte des avantages et inconvénients de ces approches. Nos travaux permettront aussi d'orienter la recherche et les efforts de l'industrie de la génétique laitière en les équipant d'un nouvel outil pour détecter les perturbations épigénétiques à la suite des TRA. De manière similaire, l'analyse épidémiologique développée permettra de surveiller à l'échelle de la population l'évolution de santé et productivité des animaux qui découlent de ces techniques. / Assisted reproduction technologies (ART) are important tools in the genomic revolution of the dairy industry. Despite the phenomenal improvement in the success rates of in vitro fertilization (IVF) and the growing popularity of bovine embryos produced in vitro, certain problems remain to be resolved to ensure the total safety of these interventions in reproduction. Indeed, advances in epigenetic research have revealed the possible influence of the artificial environment during the critical period of early embryonic development. Although the incidence of major developmental disorders such as the large offspring syndrome has been greatly reduced with the adoption of better embryo culture practices, a body of evidence suggests that more subtle long-term changes still affect metabolism, growth, fertility and thus the productivity of animals resulting from these practices. The work carried out in this thesis is based on the hypothesis that epigenetic differences caused by the ovarian and in vitro environment during the last part of folliculogenesis and embryonic culture are responsible for long term phenotypic difference well into the productive life of dairy cows. The first part of this thesis consisted in evaluating the quality of the epigenetic programming of bovine embryos produced in vitro under different conditions such as the type of culture medium or the age of the oocyte donor. To achieve this, we evaluated the DNA methylation of imprinted genes of day 7 and day 12 bovine embryos by pyrosequencing. For each gene, we observed an overall lower methylation as well as a greater variability in the three groups of in vitro conditions we examined. In order to overcome technical constraints and to assess the real consequences of the molecular differences observed, we compared Quebec's population of IVF derived of cows with those conceived by artificial insemination (AI) and multiple ovulation embryo transfer (MOET). Our analysis focused on health, fertility and productivity parameters. The conducted retrospective cohort study did not reveal any significant differences between conception methods for milk production of daughters in their first three lactations when taking into account the higher breeding values of animals derived from MOET and IVF. On the other hand, IVF animals showed a slightly reduced fertility, longer gestations and a relative incidence of common disease different from the rest of the population. Consistent with their role in the dairy genetics industry, the average lifetime performance index (LPI) of IVF animals was higher. However, between 2012 and 2019, the rate of improvement in LPI of IVF derived population was nearly half that of the AI population. We postulate that an epigenetic penalty, consistent with and potentially caused by the molecular differences found in embryos following ART decreases intergenerational genetic progress and explains the observed phenotypic alterations. Thanks to the quality and quantity of the data available, our work has made it possible to illustrate with unprecedented resolution the causes and long-term impacts of the gametes and early embryos environments. Our results highlight the challenges of elite dairy genetics improvement while attesting to the progress industry has made to minimize epigenetic dysregulation leading to severe imprinting disorders. However, ART still leave detectable traces both at the molecular level in embryos and at the physiological level in adult animals. These results will allow Canadian dairy producers to make informed decisions on the conception method to use to build their herd by considering the advantages and disadvantages of each approach. Our work will also help guide future research and efforts of the dairy genetics industry to address the identified problems by equipping them with a new tool to detect epigenetic disturbances following ART. Similarly, the epidemiological analysis developed will make it possible to monitor at the population level the evolution of animal health and productivity resulting from these techniques.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

2 pp. / Every ranch has unique labor and range resources. It is important to develop a nutrition and management program that is well matched to each individual ranch. Doing this can dramatically improve reproduction and ultimately the economic return to the ranch.

Ovarian stimulation plays a pivotal role in assisted reproductive therapies, to increase the number of embryos available for treatment; however, there is no clear consensus from meta-analyses in the literature which, if any, of the preparations in use are superior in terms of clinical outcomes. The aim of this thesis was to examine the effect of common human gonadotrophin preparations with different half lives and LH activity (hMG, rFSH and Pergoveris) on embryo quality and resulting offspring, compared to non- stimulated negative controls and positive PMSG treated controls, using the mouse model. The studies in this thesis indicated that an LH ceiling threshold is evident during folliculogenesis, where the use of long acting LH preparations resulted in higher numbers of fragmented oocytes, absent of cumulus cells (P<0.001), reduced expression of the pro and anti-angiogenic factors, MYHII and PEDF in cumulus cells (P<0.05), increased embryonic developmental arrest (P<0.001) and perturbed IGF2 (P<0.05) and VEGFA gene expression in resulting blastocysts (P<0.01), compared to negative controls. Use of preparations containing LH bioactivity resulted in offspring with altered total body weight trajectories and internal organ weight abnormalities (P<0.05), which were, in some instances, compounded by in vitro culture. In addition, we elucidated a relationship between FSH half life differences between urinary and recombinant preparations and embryo quality. The urinary human gonadotrophin preparation, hMG, could yield developmentally competent embryos at lower concentrations, than the recombinant Pergoveris treatment. In addition to FSH, these preparations contain LH and both low doses of preparations composed of short half life rFSH and rLH and high doses of preparations containing long acting LH bioactivity, resulted in the highest rates of developmental arrest. These groups were observed to have complete absence of H19 expression. The results of this thesis provide clear evidence that ovarian stimulation does negatively impact the embryo and subsequent offspring and provides support for an LH ceiling threshold, above which detrimental effects occur, both on in vitro embryo development and in vivo foetal development, which later effects postnatal growth.

No description available.

Thesis (MScAgric)--Stellenbosch University, 1978. / In title Greek letter 'alpha' is in subscript. / ENGLISH ABSTRACT: 1. Preliminary observations proved that an intramuscular injection of 62,5pg Cloprostenol terminates the oestrus cycle of ewes. Higher dosages (1251jg, 250pg and 500pg) caused a more abrupt termination of the cycle and more synchronised occurrence of oestrus. However, 125pg was only effective in terminating the oestrus cycle when injected between days 4 and 14. 2. In order to overcome this refractory period to Cloprostenol treatment, (days 15 through oestrus to day 4 of the oestrus cycle) ewes were treated with intravaginal progestogen sponges for 8 - 9 days and injected with Cloprostenol on the day of sponge withdrawal. A dosage of 31,251ig proved adequate, but conception rates were significantly lower at the first post treatment oestrus (mean 63,7%) as compared to the second post treatment oestrus (mean 81,9%). The change in the serum progesterone concentration following the cessation of treatment was not affected by the dosage of Cloprostenol (31,251g; 62,5pg and 125pg), but the position of the LH peak relative to the onset of oestrus varied markedly. The stage of the cycle when the intravaginal sponge treatment started had a significant affect on the interval between the cessation of treatment, the onset of oestrus and the LH peak. 3. The time of Cloprostenol administration relative to intravaginal sponge withdrawal (-48, -24 and 0h) showed no significant effect on either the oestrus response or the duration of oestrus. However, for the group receiving the prostaglandin injection at sponge withdrawal (Oh) the interval between cessation of treatment and oestrus showed a marked decrease as the onset of the progestogen treatment progressed from day 2 to day 17 of the oestrus cycle. The reproductive efficiencies of the three respective treatment groups did not differ significantly from each other, neither was there a significant difference between the reproductive performances at the first and the second post treatment oestrus. 4. An alternative method of bypassing the refractory period of the corpus luteum to prostaglandin is by giving two injections of prostaglandin 8 to 14 days apart. In this experiment different dosages (31,25pg; 62,5pg; 125pg and 250pg) of Cloprostenol were injected at a 10 day interval. Mn increase in the dosage was followed by a significant increase in the oestrus response (50,0%; 56,3%; 81,3% and 100,0% respectively). The higher dosages (250pg) of Cloprostenol cause more rapid and complete luteolysis as is reflected in the decrease in plasma progesterone concentration, while lower dosages (31,25pg and 62,5pg) often fail. 5. The reproductive efficiencies of ewes treated with the intravaginal progestogen sponge (MAP), an intravaginal progestogen sponge (MAP) followed by an injection of Cloprostenol (125pg), a double injection of 250pg Cloprostenol at a 9 day interval and a control groupwere compared. The oestrus response, the interval from cessation of treatment to the onset of oestrus and the duration of oestrus did not differ significantly for the respective groups. The mean conception rate of ewes treated with a double injection of Cloprostenol at a 9 day interval was significantly lower (36%) than that of the other groups (mean of 71,9%). G. In a 2 x 2 factorial experiment the reproductive efficiency of ewes treated with a double injection of prostaglandin at a 10 day interval and of a group of progestogen sponge (MAP) treated ewes were compared following insemination at observed oestrus and insemination at a predetermined time. The prostaglandin treated group was inseminated at 60 and 72 hours following the last injection of Cloprostenol and the sponge treated group at 48 and 60 hours following sponge withdrawal. Although the conception rates of the ewes were about 10% lower following fixed time A.I. as compared to A.I. at obs'arved oestrus, these differences were not significant. 7. The reproductive efficiencies of ewes treated with two injections of prostaglandin (Cloprostenol) administered at intervals of 9, 10 and 11 days, were compared. The conception rates of ewes in these treatment groups were 11,1%; 40,0% and 70,0% respectively and that of the control group 82,4%. These differences indicate the importance of injecting Cloprostenol at an interval of at least 11 days. / AFRIKAANSE OPSOMMING: 1. Voorlopige waarnemings bewys dat intramuskulere inspuiting van 62,5pg Cloprostenol die estrus siklus van ooie beeindig. Hoer dosisse (125pg, 2501jg en 500pg) veroorsaak 'n meer effektiewe en meer gesinkroniseerde estrus reaksie. Die gebruik van 124ig Cloprostenol is gevind om voldoende te wees om effektiewe luteoliese te veroorsaak vanaf dag 4 tot 14 van die estrus siklus. 2. Die sinkronisasie van die estrus periode met Cloprostenol is gedoen met 'n voorafbehandeling van intravaginale sponse, bevattende medroksie-progesteroon asetaat vir 8 - 9 dae, om die refraktoriese periode te oorbrug (dag 15 - 3). Die aanteeldoeltreffendheid van die verskillende behandelde groepe het geen noemenswaardige patroon gevolg nie, alhoewel die vrugbaarheid betekenisvol verskil het vir die eerste nabehandelings estrus (gemid. 63,7%) en die tweede (normals) na-behandelings estrus (gemid. 81,9%). Aangaande die serum progesteroon konsentrasies is gevind dat die tempo van .afname in progesteroon konsentrasie na begindiging van behandeling, nie betekenisvol beinvloed is deur die verskillende dosisse (31,2514; 62,5pg en 125pg) van prostaglandien nie— Heelwat variasie in die posisie van die LH piek t.o.v. die begin van estrus is gevind en dit was duidelik dat die stadium van die estrus siklus betekenisvolle effek op die interval tussen die beeindiging van behandeling en die voorkoms van die LH piek het. 3. Dit is gevind dat die tyd (-48, -24 en Oh) van Cloprostenol toediening relatief tot intravaginale spans onttrekking geen betekenisvolle effek op beide die estrus reaksie of die lengte van die estrus periode het nie. Alhoewel, vir die groep wat 'n prostaalandien inspuiting by spans onttrekking ontvang het (Oh), is 'n duidelike afname in die interval tussen die beeindiging van behandeling en estrus waargeneem soos die - stadium van progesteroon behandeling gewissel het van dag 2 tot dag 17 van die estrus siklus. Die aanteeldoeltreffendheid vir die onderskeie behandelings groepe het nie betekenisvol verskil van mekaar nie en oak was dear geen betekenisvoile verskil in die aanteeldoeltreffendheid by die eerste en tweede (normale) na-behandelings estrus nie. 4. 'n Alternatiewe metode am die refraktoriese periode van die corpus luteum tot prostaglandien te oorbrug, is deur die toediening van twee inspuitings prostaglandien 8 tot 14 dae uitmekaar. Verskillende dosisse (31,25pg; 62,5pg: 125pg en 250/4) Cloprostenol is gegee met 'n 10 dae interval tussen die inspuitings. Vermeerdering van die dosis is gevolg deur 'n betekenisvolle verhoging in die estrus reaksie (50,0%; 56,3%; 81,3% en 100,0% respektiewelik). Die hoer dosisse (2501jg) Cloprostenol veroorsaak meer vinnige en doeltreffende luteoliese terwyl die laer dosiese (31,25pg en 62,5pg) dikwels ondoeltreffend is. Die 250pg Cloprostenol groep het die vinnigste afname in die gemiddelde serum progesteroon konsentrasie getoon. 5. Die aanteeldoeltreffendheid tussen intravaginaleprogesteroon sponse (MAP) gevolg deur 'n inspuiting van Cloprostenol (125pg), 'n dubbele inspuiting Cloprostenol met 'n 9 dae interval en 'n kontrole groep is vergelyk. Die estrus reaksie, die interval vanaf beeindiging van behandelino tot begin van estrus en die lengte van die estrus periode het nie betekenisvol verskil vir die verskillende groepe nie. Die gemiddelde konsepsie syfer van ooie behandel met 'n dubbele inspuiting Cloprostenol met 'n 9 dae interval, was betekenisvol laer (36%) as die ender groepe (gemid. 71,9%). 6. In 'n 2 x 2 faktoriale eksperiment is vrugbaarheid, na inseminasie op waargeneemde estrus en inseminasie wat op 'n tydsbasis uitgevoer is, tussen dubbele inspuiting prostaglandien groep met 'n 10 dae interval en 'n intravaginale MAP) spons groep vergelyk. Die dubbel inspuiting groep is geinsemineer 60 en 72 uur na die laaste inspuiting en die spons groep is geinsemineer 48 en 60 uur na spons onttrekking. Alhoewel die konsepsie syfers van ooie ongeveer 10% leer was na inseminasie op 'n vasgestelde tyd teenoor inseminasie na waargeneemde estrus, was die verskil nie betekenisvol nie.