The latest generation of estrus synchronization protocols employs two strategies that are key to the more widespread adoption of synchronized artificial insemination (AI) in beef herds. That's the message reproductive physiologist Cliff Lamb carried to attendees of the Robert E. Taylor Memorial Symposium: Applied Reproductive Strategies in Beef Cattle, in Fort Collins, Colo.

“These strategies include minimizing the number of times cattle must be put through a cattle-handling facility and they eliminate detection of estrus by employing timed AI,” said Lamb, who is director of the University of Florida's North Florida Research and Education Center. “High priority needs to be placed on transferring these current reproductive management tools and technology to producers, veterinarians and industry personnel to ensure they are adopted at the producer level and to provide the necessary technical support to achieve optimum results.”

He attributed the increased success of modern estrus synchronization protocols to incorporation of the CIDR - an intravaginal progesterone insert used in conjunction with other hormones. Upon insertion, blood progesterone levels rise rapidly, reaching maximal concentrations within an hour after insertion. Concentrations are maintained while the insert is in place, but progesterone levels are quickly eliminated after removal.

Inclusion of the CIDR in the CO-Synch procedure is the most researched alternative and the primary timed-AI protocol recommended by the Beef Reproduction Task force for use in beef cows.

“Results of the most recent CIDR-based studies indicated that, for a timed-AI protocol, the five- or seven-day CO-Synch + CIDR protocols yield the most impressive pregnancy rates, whereas the Select Synch + CIDR and timed-AI treatment yields the best overall pregnancy rates,” Lamb said.

Research has been conducted to determine whether the CIDR could be utilized to enhance reproductive performance in herds employing natural service, he said. Insertion of a CIDR occurred seven days prior to the breeding season, with removal on the day bulls were introduced to the herd. Results showed no increase in overall pregnancy rates, but more cows conceived during the first 10 days of the breeding season.

Copies of the various synchronization and AI protocols recommended by the Beef Reproduction Task Force for breeding cows and heifers are available in the symposium proceedings. The proceedings are available as a printed copy ($25) or on CD ($10). For more information, contact Nancy Weiss at nancy.weiss@colostate.edu or 970-491-7604.

The Robert E. Taylor Memorial Symposium is conducted by Colorado State University every other year to provide current, research-based information for improving profitability in the beef cattle industry.

The ARSBC program was developed by the Beef Cattle Reproduction Task Force to improve understanding and application of reproductive technologies, including AI, estrus synchronization and factors affecting male fertility. In 2008, CSU and the Task Force collaborated to provide the symposium in Fort Collins.