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Superintendent
David Davis
21262 Genoa Road
Linneus, MO 64653
Phone: 660 895-5121
FAX: 660 895=5122
Email:
DavisDK@missouri.edu
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April - June, 2007
Forage Systems Update
Vol 16, No. 2
Comparison of timing of fixed-time AI following the
CO-Synch + CIDR protocol in beef cows
D.C. Busch1, D.J. Schafer2, N.R. Leitman1, D.J. Wilson1, J.K Haden2, M.F. Smith1, and D. J. Patterson1
1University of Missouri-Columbia, 2MFA Inc., Columbia, MO
- Animals: Suckled, crossbred Angus beef cows (n=435) at two locations were assigned to treatment within age groups by calving date and BCS.
- Estrus detection was performed at location 1 using the HeatWatch® Estrous Detection System (Transmitters were fitted on the day of CIDR removal to characterize estrus distribution prior to fixed-time AI).
- Three different AI sires were used (Location 1 = 3, and Location 2 = 1). One of the sires used at location 1 was the same sire used at location 2.
- Cows were exposed to fertile bulls 11-12 days after fixed-time AI.
- Pregnancy rate to fixed-time AI was determined with ultrasound 56-64 days after AI.
SUMMARY AND CONCLUSIONS
Overall there was no difference (P = 0.21) between treatments in the resulting fixed-time AI (TAI) pregnancy rates in all cows.
However, in cows ? 3-years-old, TAI pregnancy rates were significantly higher (P < 0.05) when TAI was performed 66 hours after PG and CIDR removal compared to TAI at 54 hours.
In 2-year-old cows, TAI pregnancy rates were not statistically different (P = 0.17), but TAI at 54 hours resulted in numerically higher pregnancy rates.
There were significantly more (P = 0.01) cows in heat prior to TAI when AI was performed at 66 hours compared to 54 hours.
Cows that showed estrus prior to AI had a significantly higher (P < 0.01) pregnancy rate than cows that did not show estrus.
 | Cystorelin®, Factrel®, Fertagyl®, OvaCyst® |
 | Estrumate®, In-Synch®, Lutalyse®, ProstaMate®, estroPLAN® |
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