Evaluation of 72 h Cosynch and 5 or 7 d post-AI gonadotropin releasing hormone on first service pregnancy rate in lactating dairy cows

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dc.contributor.authorMink, Matthew Ryanen
dc.contributor.committeechairNebel, Raymond L.en
dc.contributor.committeememberKasimanickam, Ramanathanen
dc.contributor.committeememberPearson, Ronald E.en
dc.contributor.departmentDairy Scienceen
dc.date.accessioned2014-03-14T21:35:58Zen
dc.date.adate2006-06-12en
dc.date.available2014-03-14T21:35:58Zen
dc.date.issued2006-05-09en
dc.date.rdate2006-06-12en
dc.date.sdate2006-05-11en
dc.description.abstractTwo studies were conducted to evaluate the effects of 5 or 7 d post-AI GnRH on first service PR, plasma P4, and CL volume in lactating dairy cows synchronized using 72 h Cosynch. All cows were synchronized and randomly assigned to one of three treatment groups: Control – no additional GnRH; 5 d – GnRH 5 d after TAI; 7 d – GnRH 7 d after TAI. In the first study, P4 concentrations were evaluated in samples collected at five separate times and CL volume and number were recorded at 30 d pregnancy examination for Holstein (n = 77) and Jersey (n = 33) cows. GnRH treatment did not affect PR (Control - 47.2%, 5 d GnRH - 40.5%, 7 d GnRH – 44.7%) or P4, but increased TCLV compared to controls (Control – 7.33 cm3, 5 and 7 d GnRH – 10.77 cm3). Incidence of accessory CL increased PR (94.7 vs. 60.6%), P4 (6.95 vs. 5.88 ng/mL), and TCLV (15.51 vs. 6.78 cm3) compared to cows with a spontaneous CL. Cows classified as cycling based on P4 evaluation had significantly higher PR than acyclic cows (54.4 vs. 16.1%). In the second study, Holstein cows (n = 1055) were submitted to the same experimental protocol and evaluated for first service PR. Post-AI GnRH treatment did not significantly affect PR. Primiparous cows (32.8%) tended to have higher PR than multiparous cows (27.6%), but GnRH treatment had no influence on this relationship. In conclusion, GnRH post-AI did not affect PR. Further evaluation of accessory CL incidence is warranted as it significantly affected PR. (Abbreviations: AI – artificial insemination, CL – corpus luteum, PR – conception rate, P4 – progesterone, TCLV – total corpus luteum volume)en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-05112006-161419en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05112006-161419/en
dc.identifier.urihttp://hdl.handle.net/10919/42590en
dc.publisherVirginia Techen
dc.relation.haspartMSThesisMRM.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectpost AIen
dc.subjectgonadotropin releasing hormoneen
dc.subjectsynchronizationen
dc.subjectdairy cowen
dc.subjectconception rateen
dc.titleEvaluation of 72 h Cosynch and 5 or 7 d post-AI gonadotropin releasing hormone on first service pregnancy rate in lactating dairy cowsen
dc.typeThesisen
thesis.degree.disciplineDairy Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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