Synchronization Protocols for Cows
by Troy Smith for Angus Productions Inc.
NASHVILLE, TENN. (Aug. 5, 2010) — According to Cliff Lamb, a researcher at the North Florida Research and Education Center, the application of artificial insemination (AI) in U.S. beef herds continues to grow. Evidence exists in the more than 4 million units of semen used annually by the beef industry. During the Applied Reproductive Strategies in Beef Cattle (ARSBC) Conference, in Nashville, Tenn., Lamb credited increased use of AI to the development of more reliable and practical protocols for estrous synchronization.
Lamb presented a review of the development of various protocols for use in mature cows, including introduction of the CIDR® (controlled internal drug release) vaginal insert. He noted how the CIDR device has provided an alternative to melangestrol acetate (MGA) for delivering a progestin to inhibit estrus until progestin withdrawal. While MGA, which is delivered orally, is approved for suppression of estrus in heifers, the Federal Drug Administration (FDA) has not approved its use in mature cows.
The most recent research, Lamb said, has concentrated on three areas: 1) development of protocols that rely solely on fixed-time AI; 2) systems requiring a maximum of three animal handlings; and 3) ensuring that the systems are effective for use with both cycling and anestrous females. Lamb said inclusion of the CIDR in the CO-Synch procedure appears to be the most research alternative for synchronizing cows.
The seven-day CO-Synch+CIDR involves injection of gonadotropin-releasing hormone (GnRH) at the time of CIDR insertion, followed seven days later by injection of prostaglandin (PG) and CIDR removal. Insemination is performed 66 hours after that, along with another injection of GnRH.
More recently, a five-day CO-Synch+CIDR protocol was developed. It involves GnRH injection simultaneous to CIDR insertion, followed five days later with CIDR removal and administration of two injections of PG — the first at CIDR removal and the second administered 12 hours later. Timed AI is performed 72 hours after the first PG and CIDR removal concurrent with a second GnRH injection. Some research results suggest the five-day protocol offers some improvement to pregnancy rates, but it requires handling cows a second time on the day CIDRs are removed.
“Both are very good systems. Studies suggest comparable results for percentage of cows pregnant on first insemination,” said Lamb, noting that the (seven-day) CO-Synch + CIDR protocol is the primary fixed-time AI protocol recommended by the Beef Reproduction Task force for use in beef cows.
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