The effects of resynchronization of estrus using the 5 d CO-Synch + CIDR system in beef heifers

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dc.contributor.authorLiles, Amanda Gailen
dc.contributor.committeechairGreiner, Scott P.en
dc.contributor.committeememberBarnes, Michael A.en
dc.contributor.committeememberBeal, Wilfred E.en
dc.contributor.committeememberHall, John B.en
dc.contributor.departmentAnimal and Poultry Sciencesen
dc.date.accessioned2014-03-14T20:43:57Zen
dc.date.adate2008-12-11en
dc.date.available2014-03-14T20:43:57Zen
dc.date.issued2008-08-05en
dc.date.rdate2008-12-11en
dc.date.sdate2008-08-21en
dc.description.abstractRecent efforts have improved synchronization systems that facilitate timed insemination in beef cattle. However, synchronization systems utilizing a single fixed-time artificial insemination (FTAI) frequently result in 25-40% non-pregnant heifers. The purpose of this study was to determine the effectiveness and define economic parameters of a FTAI resynchronization protocol in beef heifers after synchronization using a 5d CO-Synch + CIDR system. Estrus was synchronized in crossbred heifers (n=176) using 5 d CO-Synch + CIDR with FTAI at 72 h. After the initial AI, open heifers received either resynchronization (RS) or natural service (NS) return service treatments. The RS treatment was diagnosed for pregnancy 29 d after the initial AI, and all open heifers were resynchronized using the 5 d CO-Synch + CIDR with FTAI at 72 h. Heifers diagnosed pregnant following initial AI received no further treatment. Heifers in the NS treatment were exposed to fertile bulls from d 14 to d 66 following initial AI. Return to estrus data were collected using the Heat Watch Estrus Alert System. Total AI pregnancies tended to be higher (P=0.07) for RS (69.7%) than NS (56.5%) heifers. Overall pregnancy rate was greater for NS (89.4%) than for RS (69.7%) at the end of the breeding season (P < 0.01). The cost of RS was $128.63 and for NS was $82.50 per pregnancy. The expected average calf value per heifer exposed was $195.84 for RS treatment and $357.62 for NS treatment. This difference was attributed to the increased number of open heifers in the RS treatment. The resynchronization of estrus after the initial FTAI yielded a limited number of pregnancies in the breeding season in this study. However, the resynchronization program also cost more per pregnancy. Further investigation into resynchronization should focus on both biological and economic impacts.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-08212008-221648en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-08212008-221648/en
dc.identifier.urihttp://hdl.handle.net/10919/34684en
dc.publisherVirginia Techen
dc.relation.haspartThesis.12.5.08.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectBeefen
dc.subjectHeiferen
dc.subjectReproductionen
dc.subjectResynchronizationen
dc.subjectEconomicsen
dc.titleThe effects of resynchronization of estrus using the 5 d CO-Synch + CIDR system in beef heifersen
dc.typeThesisen
thesis.degree.disciplineAnimal and Poultry Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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