Mangement Improves AI Conception
Physiological factors affect pregnancy rate to artificial insemination.
SIOUX FALLS, S.D. (Dec. 3, 2012) — University of Missouri animal scientist Michael Smith says it is common for cow-calf producers new to estrous synchronization and artificial insemination (AI) to ask what kind of pregnancy rate can be expected. Speaking to a Sioux Falls, S.D., crowd during the Applied Reproductive Strategies in Beef Cattle (ARSBC) symposium Dec. 3-4, 2012, Smith said it’s best to have realistic expectations. He called a 67% pregnancy rate to a single insemination very good, but actual results depend on multiple factors. Results may be far less satisfactory unless careful attention is paid to the details of managing a synchronized AI program.
"When it comes to reproductive management, the things you do well will not compensate for the mistakes you make,” Smith stated. “Instead, the mistakes you make cancel out all the things you do well.”
Before adopting AI, Smith advised consideration of whether the producer’s heifers and cows are good candidates for estrous synchronization. If previous heifer and cow pregnancy rates at the end of the breeding season have been less than 85%, there may be management issues to address before initiating a synchronized AI program.
According to Smith, replacement heifer candidates should not have received growth-promoting implants. They should have been developed to an appropriate target weight by breeding time, and should have undergone reproductive tract evaluation.
“We recommend that a minimum of 50% of the heifers have a reproductive tract score equal or greater than 4 by approximately six weeks before the start of breeding,” Smith said.
Considerations for cows include choosing animals that delivered a previous calf unassisted. They should have been in good body condition at calving — at least a body condition score 5 — and have been allowed an adequate period of recovery from calving to the subsequent breeding season. Smith recommended a herd average of 45-50 days.
Smith said the choice of synchronization protocol will be influenced by each producer’s time and labor constraints. Protocol cost may be another factor. He advised producers to consider whether they want to check heat and inseminate 12 hours following detection of standing heat, or inseminate all animals at a predetermined time. Another option is to detect estrus for 72 to 84 hours, depending upon the protocol, and inseminate any cows not detected in estrus at a fixed time.
Click here to view larger image of Table 1: Effect of estrous
detection and conception rate in cattle.
Smith emphasized that estrous-synchronization protocols must be followed precisely. Each product must be administered at the correct dose and at the correct time. Understanding the basic principles of the bovine estrous cycle and how the products synchronize estrus and ovulation can be helpful in reducing the probability of administering the wrong product at the wrong time (see Smith’s proceedings paper for greater detail).
"While estrous-synchronization products and protocols have changed over time, the basic physiological principles underlying how these products work have not," Smith stated. "An understanding of the importance of estrous expression and the basic physiological factors affecting pregnancy rate following estrous synchronization and artificial insemination can facilitate the application of these technologies."
Smith spoke during Monday's ARSBC session focused on the importance of estrus. For more information, visit the Newsroom at www.appliedreprostrategies.com to listen to his presentation and to view his PowerPoint slides and proceedings paper.
Comprehensive coverage of the symposium is available online at www.appliedreprostrategies.com. Compiled by the Angus Journal editorial team, the site is made possible through sponsorship by the Beef Reproductive Task Force and LiveAuctions.tv.
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.