Synchronization protocols have revolutionized the way you manage your breeding program. They’ve removed much of the guesswork and enabled you to more consistently schedule labor and cow flow.
However, despite strict adherence to a synchronization plan, half or more of your cows do not become pregnant on the first insemination. That leaves a significant portion of your herd in need of yet another insemination. By using a “rapid-resynch” program, you can rebreed those cows just two days after a pregnancy check confirmed they were open.
If you currently use Ovsynch to resynch cows (please see “Resynch your synch program” from the October 2003 issue of Dairy Herd Management), a rapid-resynch protocol will allow you to perform second inseminations a week earlier than before. That’s because cows retain a good level of synchrony from the initial protocol that you can use to your advantage.
In other cases, you may be able to shorten the interval to second insemination by as many as 24 days. Here’s how:
Step 1. Follow your usual synchronization protocol.
You must first synchronize your cows before you can resynchronize them. Therefore, follow your regular protocol for first breeding as prescribed by your reproductive-management team.
Step 2. Determine cow pregnancy status.
Conduct a pregnancy check at day 28 to 30 following first breeding, depending on your current protocol’s schedule and the type of technology used. If your veterinarian cannot consistently diagnose pregnancies at days 28 to 30, you will need to use ultrasound to do so, or alter the protocol.
Make sure you’re checking a group of cows that are at about the same stage in your protocol. (See “Why this works” sidebar for more explanation.)
Do not take any resynch steps, like injecting cows with a prostaglandin, until pregnancy status is known.
If the cow is confirmed pregnant, no more action is required at this time. If she is confirmed open, proceed to step three.
Step 3. Inject all open cows with prostaglandin.
Take this action immediately following the pregnancy diagnosis while labor and cows are readily available. Use a labeled dose of product to ensure the best results.
Step 4. Inject cows with GnRH 48 hours later.
This is where the rapid-resynch protocol differs from resynching cows to Ovsynch, or waiting for the cow to come into heat on her own. With rapid resynch, you give an injection of GnRH 48 hours after completing step 3.
Again, use a labeled dose of product to ensure the best results.
This routine fits perfectly with a Tuesday-Thursday cow-handling schedule — pregnancy check on Tuesday and required injections and/or breeding on Thursday — common in many synch programs. If you follow a different schedule, you’ll need to adjust your labor and cow flow accordingly.
Step 5. Breed cows in the program
You may breed cows immediately following the GnRH injection, or you may choose to breed anytime within 24 hours, explains Matt Lucy, professor of reproductive physiology at the
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Step 6. Re-enroll open cows
Cows that did not conceive with a second, third, fourth, and higher insemination may be re-enrolled into the rapid-resynch protocol at the next subsequent pregnancy check. Begin at step 2 and repeat the protocol as necessary.
Exceptions for step two
if your veterinarian prefers to wait until day 35 to 40 to diagnose pregnancy, you will need to alter the protocol in step two.
In this situation, inject all cows in your breeding group with a labeled dose of GnRH seven days prior to pregnancy checks. (Pregnancies will not be harmed by this injection.)
Then, follow the remaining steps in the protocol following the pregnancy check at days 35 to 40.
Why this works
Because estrous cycles of cows are synchronized with timed-breeding programs, such as Ovsynch, it’s possible to put that to use down the line with an abbreviated “rapid-resynch” program.
“We’ve found that it probably isn’t necessary to go through the entire Ovsynch protocol again,” says Matt Lucy, professor of reproductive physiology at the
Instead, cows can be bred within 48 to 72 hours of pregnancy checks.
In this protocol, cows are checked for pregnancy at day 28-30 following timed AI. This timing is important because open cows in your breeding group generally come into heat on day 20-24 after timed AI, meaning they are in days four to 10 of the new repeat estrous cycle.
And, this early phase of the next estrous cycle represents a period when a prostaglandin-responsive corpus luteum (CL) and a dominant follicle are present in the ovary.
“We know that the response of this new CL to prostaglandin increases after day seven of the cycle,” adds Jeff Stevenson, animal science professor at
Thus, it is possible to use a simple two-injection system to resynchronize open cows:
Prostaglandin to regress the CL,
GnRH 48 hours later to induce ovulation.