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Angus Journal
Copyright © 2015
Angus Journal

Physiological Factors
Affecting AI Pregnancy Rates

Success with synchronized artificial insemination takes attention to detail, adherence to protocol.

STAUNTON, Va. (Oct. 15, 2013) — When producers consult University of Missouri (MU) animal scientist Michael Smith about using synchronized artificial insemination (AI) for the first time, they commonly want to know what they might expect with regard to pregnancy rate. Smith explains that pregnancy rate depends on both estrous detection rate and AI conception rate, and many factors can affect each.

In a presentation during the Applied Reproductive Strategies in Beef Cattle (ARSBC) Symposium Oct. 15-16, in Staunton, Va., Smith discussed those factors, including

  1. 1. management practices that increase the probability of success with synchronized AI;
  2. 2. the importance of estrus expression to establishment of pregnancy;
  3. 3. physiological mechanisms that influence pregnancy rate following synchronized AI; and
  4. 4. reasons why pregnancy rate may be lower than expected.
Michael Smith

The first management consideration is to determine if heifers or cows are suitable candidates for synchronized AI, said Michael Smith, MU.

“The main thing I want to emphasize,” said Smith, “ is when it comes to reproductive management, the things you do well will not compensate for the mistakes you make. Instead, the mistakes you make cancel out all the things you do well.”

Smith said the first management consideration is to determine if heifers or cows are suitable candidates for synchronized AI. Herds that have experienced poor pregnancy rates during recent years — in heifers or cows — probably aren’t ready. Neither can optimum results be expected among heifers that have received growth implants. Heifer candidates must have been developed to an appropriate target weight and a minimum of 50% of heifers should have reproductive tract scores of 4 or better.

Smith said mature cows should have had an appropriate body condition score (at least BCS 5) at calving, as well as at breeding time. Producers must also allow for sufficient time postpartum before initiating a synchronization protocol.

Smith also advised careful selection of a synchronization protocol appropriate for the producer’s goals. He said it is helpful for producers to have a basic understanding of how protocols work and emphasized the importance of implementing protocols precisely. Care should also be taken in choosing AI sires and semen should be obtained from a reputable source.

“The success of any estrus-based artificial insemination program requires detecting animals in standing estrus and inseminating them at the correct time relative to detection of estrus,” stated Smith. “Failing to detect estrus or errors in accurately detecting estrus can result in significant economic losses.”

Smith emphasized adherence to recommended times of insemination following heat detection or with timed AI. He noted that if insemination occurs too early, semen quality might be compromised before fertilization takes place. If performed too late, egg quality may have deteriorated. Both situations jeopardize success.

“Meeting expectations requires careful attention to details,” said Smith. “Understanding principles of why synchronization protocols work helps us see why we need to do it right. It can also help us troubleshoot when results aren’t as successful as expected.”

Smith spoke during Tuesday's ARSBC session focused on management influences on the success of AI programs. For more information, visit the Newsroom at to listen to his presentation and to view his PowerPoint slides and proceedings paper.

Comprehensive coverage of the symposium is available online at Compiled by the Angus Journal editorial team, the site is made possible through sponsorship by the Beef Reproduction Task Force.

Editor's Note: This article was written under contract or by staff of the Angus Journal. To request reprint permission and guidelines, contact Shauna Rose Hermel, editor, at 816-383-5270.