Progesterone, follicular, and estrual responses to progesterone-based estrus and ovulation synchronization protocols at five stages of the estrous cycle

K-REx Repository

Show simple item record

dc.contributor.author Stevenson, Jeffrey S.
dc.date.accessioned 2010-11-23T14:57:05Z
dc.date.available 2010-11-23T14:57:05Z
dc.date.issued 2010-11-23
dc.identifier.uri http://hdl.handle.net/2097/6633
dc.description Dairy Research, 2008 is known as Dairy Day, 2008 en
dc.description.abstract The objective of this study was to monitor changes in ovarian status in heifers exposed to a progesterone insert with or without concurrent gonadotropin-releasing hormone (GnRH) injection. Estrus was manipulated in 283 heifers (31 breeding clusters) by administering GnRH, progesterone, and prostaglandin F2α (PGF2α) at 5 stages of the estrous cycle. Estrus was presynchronized with a progesterone insert for 7 days before PGF2α was administered 24 hours before insert removal. Successive clusters of heifers were assigned to treatments (2 heifers per treatment) on cycle day 2, 5, 10, 15, and 18. Treatments consisted of a progesterone insert (day 0) for 7 days plus (1) PGF2α on day 6, 24 hours before insert removal (early PGF); (2) GnRH on day 0 + early PGF2α (GnRH + early PGF); (3) PGF2α at insert removal (late PGF); or (4) GnRH on day 0 + late PGF (GnRH + late PGF). Controls received GnRH on day 0 and PGF2α on day 7. Ovaries were scanned by transrectal ultrasonography on days 0, 2, 7, 9, and 11 to assess follicle diameters and ovulation. Blood was collected on days 0, 2, 6, 7, 8, and 9 to quantify serum concentrations of progesterone. Insemination occurred after detected estrus or by timed artificial insemination (TAI) 64 hours after insert removal. Only 25% of 141 GnRH-treated heifers ovulated by day 2; twice as many ovulated when treatment was initiated on day 5 (46.4%) than on other cycle days (20.3%). Compared with controls, progesterone concentration was greater in all progesterone-treated heifers on days 2 and 6. Early- vs. late-PGF treatment resulted in less progesterone on days 7 and 8. Pregnancy rates were less after TAI (44%) than after detected estrus (56%) and less in controls than in all progesterone treatments. Heifers in which treatments were initiated on day 10 of the cycle had the most consistent (estrus vs. TAI) pregnancy rates (65.4%) compared with heifers in which treatments were initiated on other cycle days. Compared with controls, more progesterone-treated heifers ovulated by 96 hours after insert removal. Application of the progesterone insert reduced variance of the interval to estrus after insert removal (or PGF2α injection in controls) by 1.6-fold compared with controls. These results do not support use of GnRH in a progesterone-based synchronization protocol. en_US
dc.publisher Kansas State University. Agricultural Experiment Station and Cooperative Extension Service en_US
dc.relation.isPartOf Dairy Day, 2008 en_US
dc.relation.isPartOf Kansas Agricultural Experiment Station contribution; no. 09-134-S en_US
dc.relation.isPartOf Report of progress (Kansas State University. Agricultural Experiment Station and Cooperative Extension Service); 1002 en_US
dc.subject Progesterone en_US
dc.subject Follicular en_US
dc.subject Estrual en_US
dc.subject Ovulation en_US
dc.title Progesterone, follicular, and estrual responses to progesterone-based estrus and ovulation synchronization protocols at five stages of the estrous cycle en_US
dc.type Conference paper en_US
dc.date.published 2008 en_US
dc.citation.epage 20 en_US
dc.citation.spage 12 en_US
dc.contributor.authoreid jss en_US

Files in this item


Files Size Format View

This item appears in the following Collection(s)

Show simple item record