Evaluation of human chorionic gonadotropin as a replacement for GnRH in an ovulation synchronization protocol before fixed-time insemination

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dc.contributor.author Burns, M.G.
dc.contributor.author Buttrey, B.S.
dc.contributor.author Eborn, D.R.
dc.contributor.author Larson, J.E.
dc.contributor.author Lovaas, B.J.
dc.contributor.author Lamb, G.C.
dc.contributor.author Stevenson, Jeffrey S.
dc.contributor.author Olson, K. C.
dc.date.accessioned 2010-01-21T20:16:28Z
dc.date.available 2010-01-21T20:16:28Z
dc.date.issued 2010-01-21T20:16:28Z
dc.identifier.uri http://hdl.handle.net/2097/2417
dc.description.abstract Two experiments were conducted to evaluate the difference between gonadotropinreleasing hormone (GnRH) and human chorionic gonadotropin (hCG) given at the beginning of a timed AI protocol and their effects on fertility. In Experiment 1, beef cows (n = 672) at six different locations were assigned randomly to treatments based on age, body condition, and days postpartum. On day −10, cattle were treated with GnRH or hCG and a progesterone-releasing controlled internal drug release (CIDR) insert was placed in the vagina. An injection of PGF2α was given and CIDR inserts were removed on day −3. Cows were inseminated at one fixed timed at 62 hr (day 0) after CIDR insert removal. Pregnancy was diagnosed at 33 days (range of 32 to 35) after insemination to determine pregnancy rates. For cows that were pregnant after the first insemination, a second pregnancy diagnosis was conducted 35 days (range of 33 to 37) after the first diagnosis to determine pregnancy survival. Pregnancy rates were reduced by the hCG injection compared with the GnRH injection (39.1 vs. 53.5%). In Experiment 2, cattle were assigned randomly to three treatments, balanced evenly across the two treatments (GnRH vs. hCG) applied in Experiment 1. Cows were injected with GnRH, hCG, or saline seven days before the first pregnancy diagnosis of cows inseminated in Experiment 1. At the time of pregnancy diagnosis, cattle found not pregnant (n = 328) were given PGF2α and inseminated 56 hours later. A second pregnancy diagnosis was conducted 35 days (range of 33 to 37) after the second insemination to determine pregnancy rate at the second AI. Injections of GnRH, hCG, or saline had no effect on pregnancy rates of cows already pregnant to the first insemination. Pregnancy rates after second insemination in cows given an injection of hCG or GnRH, however, tended to be reduced. Percentage of cows pregnant after two timed inseminations exceeded 60% without any need to detect estrus. en_US
dc.publisher Kansas State University. Agricultural Experiment Station and Cooperative Extension Service en_US
dc.relation.isPartOf Cattlemen's Day, 2007 en_US
dc.relation.isPartOf Kansas Agricultural Experiment Station contribution; no. 07-179-S en_US
dc.relation.isPartOf Report of progress (Kansas State University. Agricultural Experiment Station and Cooperative Extension Service); 978 en_US
dc.subject Beef en_US
dc.subject Cattle en_US
dc.subject Gonadotropin releasing hormone (GnRH) en_US
dc.subject CIDR en_US
dc.subject Ovulation en_US
dc.title Evaluation of human chorionic gonadotropin as a replacement for GnRH in an ovulation synchronization protocol before fixed-time insemination en_US
dc.type Conference paper en_US
dc.date.published 2007 en_US
dc.citation.epage 11 en_US
dc.citation.spage 8 en_US
dc.description.conference Cattlemen's Day, 2007, Kansas State University, Manhattan, KS, March 2, 2007 en_US
dc.contributor.authoreid kcolson en_US


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