Select Sires

Kansas State Synchronization Research
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired Dec. 11, 2003
With Mel DeJarnette,
reproductive specialist,
Select Sires Inc.

This week’s reproductive moment is with Select Sires’ Mel DeJarnette and Mel you’re talking about synchronization, and there’s been some new work from Kansas State.

Yes Bill. One of the major problems producers have with implementing the Ovsynch program is the hassle factor associated with locking cows up at different times of the day for injections and breeding. In most herds there is a single time during the day that is most convenient to handle the cows for the injections and A.I. In some herds the 18-hour interval between the second GNRH and the A.I. of the Ovsynch program these cows need to be locked up when it is very inconvenient to do so. Recognizing this hassle factor as a limitation of Ovsynch, Select Sires funded a research project conducted by Dr. Jeff Stevenson of Kansas State University to investigate the fertility potential of several more user-friendly options.

Each treatment we evaluated was designed to keep all the timings and all injections and A.I. in multiples of 24 hours so that a single lock up time at the same time each day could be used to administer the protocol. In the first treatment cows were both bred and given GnRH at 48 hours after the prostaglandin, which is a protocol well known to beef producers as Cosynch. In the second treatment, cows received GnRH at 48 hours after prostaglandin but were bred 24 hours later. The third treatment was similar to first, except all cows received the Cosynch GnRH and fixed time A.I. at 72 hours after the prostaglandin instead of 48.

The trends were the same across the two-herd study and the 72-hour Cosynch achieved the greatest pregnancy rates at 35 percent, with the other two treatments averaging about 25 to 30 percent. The 72-hour Cosynch approach also eliminates one animal-handling event by giving the GnRH and the breeding at the same time. Now although all cows in this study were only bred at the preassigned fixed times, in practice breeding cows to detected estrus with the first 48 to 60 hours after the prostaglandin will likely add a few pregnancies and reduces hormone costs as these cows would not need the second GnRH injection. This approach way also be very complementary to implement in herds with good heat detection or tale chalk program.

An important qualifier of this study is that all cows received presynch injections of prostaglandin to make sure they were in the right stage of the estrus cycle to respond to the first GnRH. This will tend reduce the number of cows that display estrus early. Most of all to breed cows exclusively to fixed-time A.I. with no heat detection should not use the 72-Cosynch approach without also implementing the presynch program. It is also important that we do not interpret these data to say that the 72-hour Cosynch is better than the Ovsynch because Ovsynch was not truly evaluated. It simply says if we must keep events scheduled in 24-hour intervals, the 72-hour Cosynch appears to be the best of the three protocols we evaluated.

For more information on synchronization programs to simplify life on your dairy, contact your local Select Sires Reproductive Solutions™ specialists.

Thank you, Mel. That’s Mel DeJarnette, reproduction specialist at Select Sires.

™Reproductive Solutions is a trademark of Select Sires Inc.

Select Sires Inc., 11740 U.S. 42 North, Plain City, Ohio 43064 / Phone: (614) 873-4683 Fax: (614) 873-5751