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Source: South Dakota State University news release

With calving underway, next year's calf crop may be the last thing cattle producers are thinking about, but according to Robin Salverson, SDSU Extension Cow/Calf Field Specialist, it's never too late.

"With bull sales underway and 2015 AI beef sire directories available, it is time to think about breeding season - especially if you will be using synchronization," Salverson said. "Depending on which protocol is selected, it could be more than 39 days from start of the program to artificial insemination. This means, if you begin breeding May 13 for a February 10 calving date, you will need to start synchronizing heifers April 3."

Beef Reproduction Task Force
Based on research data and field use the Beef Reproduction Task Force composed of representatives of AI and pharmaceutical companies, veterinarians, and reproductive specialists, have developed a list of synchronization protocols recommended for heifers.

"There are some great apps available to cattle producers that provide synchronization and breeding calendars for both heifers and cows," Salverson said. "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 do not use a cow protocol on heifers."

Likewise, Salverson said producers need to follow the protocol, give the proper hormone injection or insert at the right time and don't expect to jump start all heifers that are not cycling.

She encourages producers to follow Beef Quality Assurance guidelines when giving injectable hormones. "Giving the injection in the rump because it is administered "closer to the ovary" of the heifer does not increase the efficacy or speed of the hormone, Salverson explained. "All drugs must enter the blood system and travel to the heart and lungs before reaching the target organ (i.e. ovaries)."

She reminded cattle producers that the adage more is always better does not work with melengestrol acetate (MGA). "First, it is illegal to use MGA off label. Secondly MGA is absorbed in the fat and will take longer to clear from the heifer's system when fed at a rate higher than 0.5 mg per head per day creating problems with estrus (heat) responses and subsequent timing of prostaglandin injection," she said.

Proper handling techniques
When handling all hormones, including CIDR, Salverson said cattle producers need to wear latex or non-latex gloves regardless of gender. "It doesn't matter if you are a male or female, you need to protect yourself from these hormones," she said. "For example, prostaglandin is a smooth muscle contractor, our intestines are the largest smooth muscle in the human body. If prostaglandin is absorbed through the skin it can "tie up" the digestive system."

She added that hormones function in the human body like they do in a heifer therefore, extreme care should be taken when handling all synchronization hormones.

Because there are several protocols for heifers, Salverson said each protocol has been put into one of three categories: 1) Heat Detection Protocol; 2) Heat Detection and Time AI Protocol and 3) Fixed Time AI Protocol.

Heat Detection Protocols: Heifers in these protocols should be inseminated 6 to 12 hours after the first observation of standing heat., Heat detection should occur during peak heat activity (48 to 72 hours after prostaglandin injection), 3 times per day for at least 1 hour per check period. This results in a total of 3 hours minimum with 5 to 6 hours of heat detection being better. Recommended heat detection protocols for heifers include:

* 1 Shot PG (Prostaglandin)
* 7 Day CIDRŽ - PG

Heat Detect and Time AI (TAI) Protocols: These protocols include a combination of both heat detection and timed insemination. Heifers observed in heat should be inseminated 6 to 12 hours after standing heat. Heat detection should be done for approximately 3 days after PG injection, all heifers not showing heat will be given an injection of GnRH and inseminated (i.e. timed insemination). The amount of time spent on heat detection is reduced with early responders having a better chance of conceiving compared to a single fixed-timed AI. The recommended Heat Detect and Time AI protocols include:

* Select Synch + CIDRŽ & TAI
* 14-day CIDRŽ - PG & TAI

Fixed-Time AI (TAI) Protocols: With a fixed-time protocol, all heifers are inseminated at a pre-determined time and no heat detection has to occur. In general heifer pregnancy rates for fixed-time AI protocols tend to be 5 to 10% lower than heat detection alone. When considering these protocols, synchronize no more females than can be inseminated in a 3 to 4 hour period of time. Recommended Fixed-Time AI protocols include:

* 7-day CO-Synch + CIDRŽ
* 5-day CO-Synch+ CIDRŽ
* 14-day CIDRŽ - PG

For more information related to estrous synchronization, contact Robin Salverson, SDSU Extension Cow/Calf Field Specialist at or 605-374-4177 or Dr. George Perry, SDSU Extension Beef Reproductive Management Specialist at or 605-688-5456.

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