Estrous synchronization using GnRH and CIDRs
University of Minnesota’s Cliff Lamb shares research on best protocols for applying these synchronization systems.

Don't synchronize heifers the way you would your cows, warned Cliff Lamb, University of Minnesota Grand Rapids.

BILLINGS, MONTANA (July 6, 2005) — The beef industry’s newest tools for synchronization — CIDR® and gonadotropin-releasing hormone (GnRH) protocols — will yield industry-accepted pregnancy rates among cows and heifers if implemented properly, according to University of Minnesota beef reproduction specialist Cliff Lamb. Lamb made his remarks to a full house attending the reproduction symposium hosted by the National Association of Animal Breeders (NAAB) at the annual Beef Improvement Federation (BIF) conference July 6-9 in Billings, Mont.

There are four current CIDR protocols being researched, and Lamb says research has shown all of these programs work well and realistically will yield 50%-53% pregnancy rates.

The most recent research shows that the CO-Synch+CIDR protocol yields the most impressive pregnancy rates for a fixed-time artificial insemination (AI) protocol, Lamb says. The Select Synch+CIDR with timed-AI treatment garners the most estrus response and, therefore, yields the most consistent overall pregnancy rates. In an eight-state trial with 14 herd locations, Lamb reports, Select Synch+CIDR and clean-up timed AI at 84 hours yielded an average 58% conception rate.

Among heifers, the Select Synch+CIDR protocol most frequently yields the greatest pregnancy rates and provides a reliable alternative to MGA/prostaglandin, Lamb adds. He says the biggest difference in managing synchronization programs between heifers and cows is timing. The research indicates for best results heifers should be time-AIed at 54-60 hours, while cows yield better results if the timed AI is conducted at 60-66 hours.

Additionally, Lamb says research is showing there is little difference in pregnancy rates if GnRH is administered first in the program or after the CIDR is removed. However, he says, research is indicating that timed AI with heat detection will improve pregnancy rates by about 10%.

Most importantly, Lamb says, like any other synchronization program, nutrition, management and weather will affect the response of cows to GnRH and CIDR-based estrus synchronization systems. Specifically, body condition, parity and days since calving need to be monitored to ensure cows breed back. He recommends cows be managed for a body condition score (BCS) of 5.5 to 6 and be more than 50 days postpartum for the best response to synchronization.

Additional Points:
Lamb also answered these common questions about CIDR-based synchronization systems:

Is there a difference in gender ratio with synchronization systems? He says no. In their trials they found 53% bulls and 47% heifers, which was very similar to the ratios in natural-service herds.

Is there an optimum herd size that synchronization works best with? Again, Lamb says no. He says with the right facilities and labor there is no limit to how many animals can be synchronized.

Are there differences between the CIDRs available in the United States compared to those from Canada or Mexico? Lamb says there is no difference; they all release the same amount of progesterone.

Can CIDRs be used a second time? Lamb says this is being done, but he does not recommend it, especially because of the risk of transferring diseases.

Will leaving CIDRs in for 14 days vs. the standard 7 days yield better results? Lamb says new research is being conducted in this area, especially as a tool with heifers, but there are no specific results that can be presented at this time.

Lastly, Lamb encourages producers considering a synchronization system to analyze the protocols that are printed inside AI catalogs and use them as guides. He says those are the systems that have been researched and proven to work. He also encouraged producers to work with experts to define and implement reproductive management procedures designed specifically for their herd.

— by Kindra Gordon, field editor, Angus Productions Inc.
© Copyright 2005 Angus Productions Inc.

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