Effect of Timing of Insemination and Synchronization of Estrus Method on Artificial Insemination (AI) Pregnancy Rates in Beef Heifers

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dc.contributor.authorDorsey, Benjamin Reeseen
dc.contributor.committeechairHall, John B.en
dc.contributor.committeememberNebel, Raymond L.en
dc.contributor.committeememberWhittier, William D.en
dc.contributor.committeememberWahlberg, Mark L.en
dc.contributor.departmentAnimal and Poultry Sciencesen
dc.date.accessioned2014-03-14T21:37:01Zen
dc.date.adate2005-07-20en
dc.date.available2014-03-14T21:37:01Zen
dc.date.issued2005-04-25en
dc.date.rdate2005-07-20en
dc.date.sdate2005-06-07en
dc.description.abstractObjectives were to evaluate time of insemination relative to estrus and synchronization with melengestrol acetate (MGA) plus prostaglandin (PG) or progesterone insert (CIDR) plus PG on AI pregnancy rate in beef heifers (n = 662) during Fall or Spring. Fall heifers (n = 349) received MGA-PG (MGA for 14 d followed by PG on d 18) or CIDR-PG (CIDR for 7 d, PG administered 1 d before CIDR removal). Estrus was monitored by HeatWatch® (n = 200) or visually (n = 149). Spring heifers (n = 313) underwent CIDR-PG with detection of estrus by HeatWatch®. Heifers not in estrus by 96-100 h after PG were bred AI as non-responsive AI (NRAI). Across seasons, 548 heifers were bred following estrus (EAI). Heifers synchronized during the Fall with MGA received more (P < 0.05) mounts than Fall CIDR heifers (76.8 ± 6.7 and 47.6 ± 7.4, respectively), but duration of estrus was similar. Fall CIDR heifers had greater (P < 0.05) mounting activity and duration of estrus (47.9 ± 5.2 mounts and 15.5 ± 1.1 h) compared to Spring CIDR heifers (34.5 ± 3.1 mounts and 12.7 ± 0.6 h). Heifers grouped in 4 h blocks from 0 to 24 h had no difference (P > 0.05) in pregnancy rates (mean 62.5 %). Treatment had no effect (P > 0.05) on EAI pregnancy rates. Pregnancy rates across seasons for EAI, NRAI and overall was 61.0 %, 26.3 %, and 54.5%. In conclusion, a 24 h window may exist to successfully AI heifers.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-06072005-135822en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-06072005-135822/en
dc.identifier.urihttp://hdl.handle.net/10919/42873en
dc.publisherVirginia Techen
dc.relation.haspartDorseyThesisPDF.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectSynchronization of Estrusen
dc.subjectHeifersen
dc.subjectCIDRen
dc.subjectAIen
dc.titleEffect of Timing of Insemination and Synchronization of Estrus Method on Artificial Insemination (AI) Pregnancy Rates 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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