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dc.contributor.advisorWilliams, Gary L.
dc.creatorMorton, Stephanie
dc.date.accessioned2005-02-17T21:05:07Z
dc.date.available2005-02-17T21:05:07Z
dc.date.created2004-12
dc.date.issued2005-02-17
dc.identifier.urihttp://hdl.handle.net/1969.1/1551
dc.description.abstractObjectives were to determine if low-dose, continuous infusion of GnRH from Fall to Spring, would prevent seasonal anovulation in mares. Twenty Quarter Horse mares, ages 18 mo to 24 yrs, were stratified by age and body condition score and assigned randomly to either a saline control (n = 9) or GnRH (n = 11) treatment group. Treatments were instituted between September 23 and October 9, 2002. Gonadotropinreleasing hormone was delivered in 0.9% physiological saline via Alzet osmotic minipumps (Model 2004) placed sc at the base of the neck, with Silastic sham pumps placed in control mares. Pumps were inserted on day 3 following ovulation or during the follicular phase if ovulation had not occurred. Delivery rate of GnRH was 2.5 ug/h (60 ug/d) for the first 60 d, followed by 5.0 ug/h (120 ug/d) thereafter, with all pumps replaced every 30 d. By December 1, all mares had become anovulatory and remained anovulatory until February. Mean serum concentrations of LH were not affected by treatment in anovulatory mares. In contrast, control mares that exhibited ovulatory cycles after treatment onset had higher (P < 0.05) mean concentrations of LH during all phases of the estrous cycle except diestrus. Mean serum concentrations of FSH were not affected by treatment, but were lower (P < 0.05) from November though January relative to all other months in anovulatory mares. Interovulatory intervals in mares that cycled temporarily did not differ between groups. Ovulatory control mares had slightly larger (P < 0.10) follicles overall than GnRH-treated mares; however, ovulatory follicle diameters for control and GnRH-treated mares did not differ. Ovulatory control mares had higher (P < 0.10) mean concentrations of progesterone during metestrus and late diestrus. In a subgroup of control (n =5) and GnRH-treated (n = 5) mares, total releasable pools of LH in response to 1 mg GnRH did not differ between groups. Ovulation resumed in 3 control and 3 GnRH-treated mares by March 30. Results indicate that continuous infusion of native GnRH at the doses employed herein is not sufficient to maintain ovulatory cycles during the anovulatory season.en
dc.format.extent1352190 bytesen
dc.format.mediumelectronicen
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.publisherTexas A&M University
dc.subjectgonadotropin-releasing hormoneen
dc.subjectGnRHen
dc.subjectequineen
dc.subjectanovulatoryen
dc.titleEffects of continuous treatment with gonadotropin-releasing hormone during the anovulatory season on gonadotropin secretion, follicular dynamics and ovulation in the mareen
dc.typeBooken
dc.typeThesisen
thesis.degree.departmentAnimal Scienceen
thesis.degree.disciplinePhysiology of Reproductionen
thesis.degree.grantorTexas A&M Universityen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelMastersen
dc.contributor.committeeMemberHinrichs, Katrin
dc.contributor.committeeMemberHarms, Paul G.
dc.type.genreElectronic Thesisen
dc.type.materialtexten
dc.format.digitalOriginborn digitalen


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