Decreasing the interval between GnRH and PGF₂α from 7 to 5 days and lengthening proestrus increases timed-AI pregnancy rates in beef cows

Four experiments were conducted in postpartum beef cows to evaluate the influence of reducing the interval from GnRH to PGF₂α from 7 to 5d in a Select-Synch+CIDR or CO-Synch+CIDR estrous synchronization program. In Expt 1, cows (n =156) were treated with either a 7 or 5d Select-Synch+CIDR program. A...

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Published inTheriogenology Vol. 69; no. 7; pp. 843 - 851
Main Authors Bridges, G.A, Helser, L.A, Grum, D.E, Mussard, M.L, Gasser, C.L, Day, M.L
Format Journal Article
LanguageEnglish
Published [Oxford]: Butterworth-Heinemann; [New York]: Elsevier Science 15.04.2008
Subjects
artificial insemination
beef cows
conception
conception rate
controlled internal drug release devices
estrus
estrus synchronization
gonadotropin-releasing hormone
hormonal regulation
injection timing
intramuscular injection
luteolysis
pregnancy rate
progesterone
prostaglandins
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ISSN0093-691X
DOI10.1016/j.theriogenology.2007.12.011

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Summary:Four experiments were conducted in postpartum beef cows to evaluate the influence of reducing the interval from GnRH to PGF₂α from 7 to 5d in a Select-Synch+CIDR or CO-Synch+CIDR estrous synchronization program. In Expt 1, cows (n =156) were treated with either a 7 or 5d Select-Synch+CIDR program. A second PGF₂α treatment was given to all cows in all experiments at 12h after the initial PGF₂α (to ensure that luteolysis occurred with the 5d program). Estrous response, interval to estrus, conception rate, and first service AI pregnancy rates were similar between treatments. In Expt 2, cows (n =223) were treated with either a 7 or 5d CO-Synch+CIDR program, with timed-AI concomitant with GnRH at 60h after PGF₂α. Timed-AI pregnancy rates were similar between treatments. In Expt 3 (n =223) and 4 (n =400) cows were treated with either a 7 or 5d CO-Synch+CIDR program with timed-AI concurrent with GnRH at either 60h (7d) or 72h (5d) after CIDR withdrawal. Timed-AI pregnancy rates were 13.3% (P <0.05; Expt 3) and 9.1% (P <0.05; Expt 4) greater for the 5 than 7d program. In conclusion, timed-AI pregnancy rates were improved with a 5d CO-Synch+CIDR program with timed-AI at 72h after CIDR withdrawal, compared to a 7d CO-Synch+CIDR program with timed-AI at 60h after CIDR withdrawal.
Bibliography:http://dx.doi.org/10.1016/j.theriogenology.2007.12.011
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ISSN:0093-691X
DOI:10.1016/j.theriogenology.2007.12.011