After several years of research, cows can now be successfully inseminated at a predetermined fixed time (timed AI) with no heat detection and have comparable pregnancy rates to those achieved by heat detection. This has opened new doors for cow synchronization. However, there are still considerations that need to be taken before selecting the synchronization protocol for cows including: facilities, time and availability to heat detect, cost, experience and the body condition score and number of days after calving.
Cows need to be at a body condition score 5 or better during the breeding season and be at least 50 days post calving to help increase the success of the synchronization protocol. If there are young, thin and or late calving cows in the herd, it is likely they are not cycling. The addition of a progestin such as a CIDR® in the protocol can help jump start some of these non-cycling cows. However, caution needs to be taken; the CIDR® or other progestins are not the "cure all" for thin, young and late calving cows and one should look at whether it is cost effective to synchronize these cows.
The Beef Reproduction Task Force composed of representatives of the AI and pharmaceutical companies, veterinarians and reproductive specialist have developed a list of synchronization protocols recommended for cows based on research data and field use. The recommended protocols can be found in the AI catalogs and on the Beef Reproduction Task Force website.
Take note that not all protocols are for both cows and heifers. There is a difference in physiological response between heifers and cows. It is important that you use a cow protocol. Likewise, follow the protocol; give the proper hormone injection at the right time. Know what the purpose of each hormone is and how it affects the estrous cycle. Refer to the SDSU Extension Extras – The Bovine Estrous Cycle (FS921A) and Understanding Estrous Synchronization of Cattle (FS921C) for more information.
The recommended cow estrous synchronization protocols have been put into one of three categories:
- Heat Detection Protocol
- Heat Detection and Time AI Protocol
- Fixed Time AI Protocol
Heat Detection Protocols: Cows in these protocols should be inseminated 6 to 12 hours after the first observation of standing heat. During peak heat activity which is approximately 48 to 72 hours after prostaglandin; heat detection should occur at a minimum of 3 times per day for at least 1 hour per check for a total of 3 hours with 5 to 6 hours of heat detection being better. Refer to the SDSU Extension Extra Detection of Standing Estrus In Cattle (FS921B) for more information on detecting heat. The heat detection protocols for cows include:
- Select Synch
- Select Synch + CIDR®
- PG 6-day CIDR®
Heat Detect and Time AI (TAI) Protocols: These protocols include a combination of both heat detection and timed insemination. Cows observed in heat should be inseminated 6 to 12 hours after standing heat. After approximately 3 days of heat detection, all cows not showing heat after the PG injection will be given an injection of GnRH and inseminated (i.e. timed insemination). The amount of time spent on heat detection is reduced and early responders have a better chance of conceiving compared to a single fixed-timed AI. The Heat Detect and Time AI protocols include:
- Select Synch &; TAI
- Select Synch + CIDR® &; TAI
- PG 6 –day CIDR® &; TAI
Fixed-Time AI (TAI) Protocols: In a fixed-time AI protocol, all cows are inseminated at a pre-determined time no heat detection occurs. Research has shown that pregnancy rates of fixed timed AI protocols have been as successful as protocols with heat detection. It is important, when considering these fixed timed AI protocols, only synchronize the number of cows that can be inseminated in a 3 to 4 hour period. Fixed-Time AI protocols include:
- 7-day CO-Synch + CIDR®
- 5-day CO-Synch + CIDR®
Refer to the Applied Reproductive Strategies in Beef Cattle website for details on the 2012 synchronization protocols for cows and heifers. Likewise, another resource for cattle producers is the Estrous Synchronization Planner. The planner develops a calendar for application of the protocols and can compare costs of three different protocols. This is a free planner for producers.
Source: Robin Salverson