Select Sires

What's Your Voluntary Waiting Period? And Why?
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired Oct. 28, 2004
With Mel DeJarnette,
reproductive specialist,
Select Sires Inc.

After calving, cows require time to complete regular uterine involution before they can be expected to rebreed. With us is Mel DeJarnette from Select Sires. Mel, over the years there has been a trend toward shorter and shorter voluntary waiting periods and many herds routinely breed cows as early as 40 days after calving. What has caused this to occur and is this really more profitable dairy management?

That’s a great question. The voluntary waiting period receives a lot of attention because it is the easiest component of the calving interval for us to change. Gestation is the biggest part of a calving interval, and we have no control over that. Changing heat detection and conception rates, which influence our calving interval, is inherently problematic. Simply changing the voluntary waiting period, with the hopes that the cows that can conceive early will average out with the cows that can conceive late is really a pretty easy procedure to implement. However, in a herd with poor reproductive performance, it is usually mathematically impossible to obtain the desired calving interval simply by shortening the voluntary waiting period. With low conception rates and low estrus detection, this often means we would have to start breeding cows at or even before they calve in order to obtain our calving interval and we know that is not possible. Additionally, a shorter voluntary waiting period may actually backfire and result in reduced, rather than improved, measures in reproductive performance. This is because; first, conception rates are typically lower at the shorter voluntary waiting period because of incomplete uterine involution and second, once a cow is inseminated we have now closed the door on what we can do to her until she either returns to estrus or is diagnosed open. Open cows will likely average at least another 30 or 40-days in milk at rebreeding if we bred them too early.

A recent study used Ovsynch® to compare the effects of a 50-day versus a 70-day voluntary waiting period in low-producing cows and a 70 versus 90-day voluntary waiting period in high-producing cows. Now, although the shorter voluntary waiting period generated some pregnancies earlier in both groups, the cumulative percentage of cows pregnant at 100-days in milk was greater for the group with the longer voluntary waiting period due to the higher first service conception rates at the later voluntary waiting period.

Many producers likely began their shift to the shorter voluntary waiting period before the development of Ovsynch in efforts to compensate for those cows that were greater than 100-days in milk and first breeding. But, now with the systematic implementation of Ovsynch, 100 percent of the cows can be bred at any predetermined time we choose and there is really no reason for any cow in the herd to exceed 100-days in milk at first breeding. So growing research is indicating 70-days or more in milk is the optimum target interval for Ovsynch® A.I. breedings. That is not to say that a herd owner would totally ignore standing heats prior to 60 to 70-days. As we are going to the trouble and expense to synchronize cows with Ovsynch®, we want to make sure it is not implemented too early and wasted on cows not ready to conceive. Herds with voluntary waiting periods with less than 60-days should periodically evaluate the actual levels of success being achieved and make sure it is a profitable management decision. In some herds it may actually be more profitable not to be too aggressive and to move to a slightly longer voluntary waiting period.

Thanks Mel, that is Select Sires’ Mel Dejarnette.

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