Select Sires

Calving Ease and Reproduction
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired Aug. 8, 2002
With Chuck Sattler,
vice president dairy progeny testing and genetic research,
Select Sires Inc.

Today’s Reproductive Moment is with Chuck Sattler, Select Sires vice-president of dairy progeny testing and genetic research, and today, Chuck, we’re talking about improving reproduction by reducing calving problems.

Well that’s right Bill, and a key step in getting cows bred back is making sure they get through calving time with minimal problems. Calving difficulty is mainly a problem in first-calf heifers. First-calf heifers are two to three times more likely to experience a difficult calving, and this is according to data collected by the National Association of Animal Breeders. Efforts to minimize calving problems need to focus on first-calf heifers.

So what genetic evaluations of calving ease are most helpful to consider?

Well the A.I industry has sponsored genetic evaluations for rating sires on how difficult their calves are born for more than 20 years. The calving-ease evaluations we publish are expressed as the percent of difficult births in heifers that can be expected when a particular bull is used as a service sire. Because of the way these are expressed, the lower values on bulls are better. The average rate of calving difficulty in heifers is between eight and nine percent, so the typical calving-ease evaluations we see on the bulls are between 8 and 9 percent as well. So really the best strategy is to avoid using the real problem-calving bulls on heifers; bulls with calving-ease evaluations of 10 and higher. And this will allow us to take advantage of the calving-ease information and still allow opportunities to select for other important traits.

Is the industry planning to release a more specific calving-ease measure soon?

Yes, that’s right. With the August sire summaries, new information will be published that will help identify which bulls sire cows that deliver calves easily, and common sense tells us both the cow and the calf have a role in determining how easy or difficult the calving will be. And the new evaluations will allow us to evaluate how easily the calf is born, as well as the cow’s ability to deliver that calf. So next week we will have two values on calving ease published. One will be called service-sire calving ease, and this will be the same value the as the calving-ease values we’ve seen published for the past 20 years. The new values will be called daughter calving ease, and will indicate the ability of a sire’s daughters to deliver calves easily when they reach calving age. The new trait will be expressed on the same scale as the traditional calving-ease values. Reliability will be a little bit lower, because the genetic control of this trait is lower and we don’t have as much data to use in the evaluations to get our estimates. The new evaluation should provide us with more accurate genetic information to help us manage this issue of calving difficulty. The bottom line in all of this is that we have genetic information available to help us avoid calving difficulties and allow cows to be in good reproductive shape ready to resume cycling and become pregnant.

Copyright 1996-2002 Select Sires Inc. Last updated 26-Aug-2002.

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