University of Missouri-Columbia
MU Forage Systems
Agricultural Experiment Station
College of Agriculture, Food and Natural Resources
Map
Driving directions
Linneus, Linn County

Grazing School

    2009 Brochure

Workshops

Research

Faculty

News

Weather

Contact us

Superintendent
David Davis
21262 Genoa Road
Linneus, MO 64653
Phone: 660 895-5121
FAX: 660 895=5122
Email: DavisDK@missouri.edu

April - June, 2007

Forage Systems Update
Vol 16, No. 2

line
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®

    		•
    The Missouri Agricultural Experiment Station is the research arm of the
    College of Agriculture, Food and Natural Resources
    at the University of Missouri-Columbia

    Site maintained by people at AgEBB
    agebb@missouri.edu