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Angus Journal
Copyright © 2014
Angus Journal


Keys to Successful Estrus Synchronization and AI

by Troy Smith for Angus Journal®

STILLWATER, Okla. (Oct. 8, 2014) — We keep hearing that, in order to meet the needs of the 9 billion souls expected to inhabit this planet by 2050, beef production efficiency must improve. According to South Dakota State University animal scientist George Perry, beef currently represents 22% of the world’s meat production. In order to continue providing their current share of the supply, beef producers must double production in the next 35 years. It seems like a daunting task. To meet it, increasing numbers of cow-calf producers are considering use of estrus synchronization and artificial insemination (AI) to hasten genetic improvement of their herds.

George Perry“Data shows that heifers with reproductive tract scores of 4 and 5 achieve higher conception rates and are likely to stay in the herd longer,” explained George Perry.

Speaking during the Applied Reproductive Strategies in Beef Cattle (ARSBC) symposium Oct. 8-9 in Stillwater, Okla., Perry called synchronized AI a powerful tool for genetic improvement. He warned, however, that producers must consider whether they are really ready to implement a synchronization protocol, by reviewing their herds’ reproductive performance for the past few years.

“Has the pregnancy rate at the end of a 60- to 85-day breeding season been 85% or better?” asked Perry. “If it has, then you need to evaluate whether your heifers and cows are good candidates for an estrus synchronization and AI program.”

Discussing criteria for evaluating the suitability of heifers, Perry said replacement candidates should not have received growth-promoting implants. Producers must consider how they can have heifers developed to an appropriate breeding weight. Additionally, a minimum of 50% of heifers should have reached puberty and begun normal estrous cycles. Perry said sexual maturity can be determined through reproductive tract scoring performed four to six weeks prior to breeding.

“Data shows that heifers with reproductive tract scores of 4 and 5 achieve higher conception rates and are likely to stay in the herd longer,” explained Perry.

Body condition is an important consideration when evaluating the suitability of mature cows for estrus synchronization. Perry said body condition score (BCS) at the time of calving should be 5 or greater, since cows calving in poor condition typically experience a longer postpartum period of anestrus before they start cycling again. Cows that experience calving difficulty may also exhibit a longer postpartum interval.

Perry said timing of vaccinations may also affect the success of synchronization and AI. He recommended that heifers be vaccinated early and no boosters be given within 30 days prior to breeding time, especially when using a modified-live virus (MLV) vaccine. Similarly, cows should not be vaccinated within 30 days prior to breeding.

Noting that multiple synchronization protocols have been developed and used successfully, Perry said the key is compliance with the protocol. Use all products correctly by delivering correct dosages at the prescribed time. Similarly, insemination must be administered correctly and at the correct time.

Perry emphasized the importance of maintaining proper nutrition following breeding. A sudden change of diet can cause stress leading to embryonic loss. For example, heifers that had been drylotted and fed a ration up until breeding time, and have little or no grazing experience, should not be turned out to grass immediately after breeding.

Trucking recently-inseminated females to another location also can induce stress that may cause embryo mortality. Perry said the greatest risk to embryo survival exists from Day 5 to Day 42 following insemination. He recommended shipping cows immediately after insemination, or waiting until after Day 45. However, some risk remains until after 60 days.

According to Perry, genetic improvement through artificial insemination has become more practical through advancements in synchronization protocols, but success hinges on good management.


Perry spoke during Wednesday’s ARSBC session focused on reproductive management. For more information, visit the Newsroom at www.appliedreprostrategies.com to view his PowerPoint, read the proceedings or listen to the presentation.

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 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.