Breeding synchronization programs have helped take a lot of the guesswork and randomness out of reproductive programs. You can choose from a variety of programs that work off of speciﬁc, timed protocols to help improve breeding and labor efﬁciency.
However, not every cow gets pregnant on the ﬁrst service. Research shows that roughly 30 to 40 percent of dairy cows conceive via ﬁrst artiﬁcial insemination service. That means 60 to 70 percent of cows do not become pregnant the ﬁrst time around.
As a result, producers have been frustrated with how to insert cows back into the synchronization protocol effectively. The key is to quickly identify open cows and get them back into the herd’s synch protocol so you can expose these cows to another AI service in a timely fashion.
New research from the University of Wisconsin, presented at the American Dairy Science Association annual meeting this summer, says that adding a systematic resynch program to your reproductive program can help.
Here’s how it works.
1 Perform your routine synchronization protocol.
You must synchronize cows before you can resynchronize them. Therefore, follow the step-by-step routine prescribed by your reproductive protocol. Be sure to include all eligible cows and follow each step correctly. The herd in the Wisconsin research study followed the presynch strategy for ﬁrst breeding following the farm’s voluntary waiting period.
(Strong compliance is the key to successful use of any synch program. For more information on the various synch programs in use, see the article on page 30 of the February 2002 issue of Dairy Herd Management. You also can ﬁnd it online at www.dairyherd.com in the editorial archives.)
2 Check for pregnancy on day 26 or day 33.
Depending on your veterinarian’s use of ultrasound, and your overall management strategy, you can check for pregnancy on day 26 or day 33. “Ultrasound is not required to implement the program,” notes Paul Fricke, University of Wisconsin extension dairy cattle reproductive specialist. But it does shorten the window between inseminations.
If ultrasound is an option, check cows for pregnancy 26 days after the ﬁrst insemination. Record those diagnosed pregnant in your herd records and remove them from the list of eligible animals to receive the resynch program.
Note any open cows in your records and add them to the list of animals that will receive the next step in your resynch program.
If you rely on palpation to diagnose pregnancy, check cows at 33 days after ﬁrst insemination. Again, record the data and remove pregnant cows from the list of animals eligible for the resynch program.
Keep in mind that a small percentage of cows may be pregnant, but diagnosed as open at this time. And nearly 12 percent of cows declared pregnant at this time will lose the pregnancy by day 56, so be sure to recheck cows in two to three weeks to conﬁrm pregnancy status. If you have any question about a cow’s pregnancy status, do not inject her with a prostaglandin before rechecking her.
3 Give a GnRH injection on day 26 or 33
To resynch cows, give an injection of 2 milliliters (ml.) of GnRH on or around the ﬁrst pregnancy check following ﬁrst insemination. Again, you have some ﬂexibility with the program, says Fricke. “These were the treatment groups we looked at in our study, but there are other strategies that will work,” he explains. “Setting up cows with an injection of GnRH one week before pregnancy check decreases the interval between breedings at the expense of the GnRH administered to pregnant cows.”
You can perform this step at either day 26 or 33. The injection does not interfere with pregnancy status.
If you use ultrasound, on day 26 perform pregnancy checks and inject all cows that are open that same day.
If you palpate cows, on day 33 perform pregnancy checks and inject all cows that are open that same day.
If you palpate cows, but want to shorten the time before you can rebreed, you can inject all cows on day 26 and then perform pregnancy checks on day 33.
Record injection dates and pregnancy status in your herd records.
4 Follow the Ovsynch protocol
The remainder of the resynch program is the same as the standard Ovsynch protocol.
Cows are treated the same at this point, whether they receive synchronization treatment the ﬁrst time or the fourth time, says Richard Pursley, Michigan State University extension dairy reproductive specialist.
Seven days after the GnRH injection, eligible cows receive the labeled dose of a prostaglandin—usually 5 or 6 ml.
Two days later, they receive another 2-ml. injection of GnRH, followed by timed artiﬁcial insemination. You can perform the insemination that same day, or you may wait eight hours after the injection, which may move the insemination to the following day.
Again, note these procedures in your herd records.
“The participating dairy in our study conﬁned all injections and inseminations to two days of the week,” says Fricke. “Everything was performed on a Tuesday or a Thursday, and no reproductive work was done on the weekend.”