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Comparison of three CIDR-based fixed-time AI protocols in beef heifers.

G A Bridges1, S L Lake2, S G Kruse3

  • 1North Central Research and Outreach Center, University of Minnesota, Grand Rapids 55744 gbridges@umn.edu.

Journal of Animal Science
|May 8, 2014
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Summary

Three fixed-time artificial insemination (FTAI) protocols for beef heifers showed similar pregnancy success rates. Heifer puberty status at the start of synchronization significantly impacted pregnancy outcomes, with pubertal heifers achieving higher success.

Keywords:
Beef heifersCIDRestrous synchronizationfixed-time AI

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Area of Science:

  • Reproductive biology
  • Veterinary science
  • Animal science

Background:

  • Fixed-time artificial insemination (FTAI) protocols eliminate the need for estrus detection in beef heifers.
  • Several CIDR-based protocols, including 5-day CO-Synch + CIDR (5dCO), 6-day PGF2α + CIDR (PG-6dCIDR), and 14-day CIDR-PG, are effective for synchronizing estrus and ovulation.
  • Variations in protocol duration and methodology exist among these FTAI synchronization strategies.

Purpose of the Study:

  • To compare fixed-time artificial insemination (FTAI) pregnancy rates in beef heifers synchronized using three distinct CIDR-based protocols.
  • To evaluate the influence of different FTAI synchronization protocols on pregnancy success in virgin beef heifers.
  • To assess the impact of estrous cycling status at the initiation of synchronization on FTAI pregnancy rates.

Main Methods:

  • 801 virgin beef heifers across four locations were assigned to one of three synchronization protocols: 5dCO, PG-6dCIDR, or 14dCIDR-PG.
  • Protocols involved timed administration of GnRH, PGF2α, and controlled intravaginal progesterone inserts (CIDRs), with FTAI occurring at specific time points.
  • Pregnancy was diagnosed via transrectal ultrasonography 35-40 days post-FTAI; estrous cycling status was determined prior to protocol initiation.

Main Results:

  • Fixed-time AI pregnancy success rates did not significantly differ among the three CIDR-based protocols (62.6% for 5dCO, 56.9% for PG-6dCIDR, and 53.3% for 14dCIDR-PG).
  • Fewer heifers in the 14dCIDR-PG treatment were pubertal at synchronization initiation compared to the 5dCO and PG-6dCIDR treatments.
  • Heifers that were pubertal at the start of synchronization exhibited significantly higher pregnancy success rates (60.7%) compared to prepubertal heifers (47.3%).

Conclusions:

  • All three evaluated CIDR-based FTAI protocols resulted in comparable pregnancy success rates in beef heifers.
  • The attainment of puberty prior to the initiation of synchronization protocols is a critical factor influencing FTAI pregnancy success.
  • Management strategies aimed at ensuring heifers are pubertal before synchronization may enhance overall reproductive efficiency in beef operations.