Select Sires

SELECTIONS - Summer 2006
Stillbirth Evaluations to be Released by NAAB and USDA

by Chuck Sattler, vice president of genetic programs

One of the most valuable products your dairy herd produces is heifer calves. One tool that can help you make more of this valuable product is gender SELECTed™ semen.

Another new tool that is in development could also help you make gradual, sustained improvement in this area. Researchers at NAAB and USDA are putting the final touches on a genetic evaluation that rates Holstein and Brown Swiss A.I. sires based on their genetic ability to produce live calves. The new evaluations are scheduled for release in August 2006.

The release of these evaluations is part of a larger effort among genetics researchers to improve the health and fitness of dairy cattle. For some time, research studies have indicated an increasing rate of stillborn calves. Stillbirths are mainly a problem in first-calf heifers. Currently about 13 percent of Holstein calves from first-calf heifers are reported as being born dead or die within 48 hours. About 5 percent of calves from later lactation cows are born dead. These values indicate there is room for improvement in this area from both genetic and management standpoints.

The stillbirth genetic evaluations will be conducted much like the current calving ease evaluations. Data used in the evaluation is farmer-recorded data that is supplied at the time of calving. Producers have the options of recording a 1 = calf born alive, 2 = calf born dead or 3 = calf born alive but died within 48 hours of birth. The data is then accumulated through the NAAB calving ease data requests and summarized to provide genetic rankings of sires.

Like calving ease, stillbirth sire evaluations will be presented in two values; one value indicating the genetic merit of that sire as a service sire (SS SB) and the other value indicating how well his daughters do at delivering live calves (Dtr. SB). As in all genetic evaluations, the focus should be on the ranking of sires and the differences in their evaluations. A bull at 10 percent SS SB would be expected to have 5 percent fewer stillborn calves when used as a service sire than a bull with an evaluation of 15 percent SS SB.

Unlike calving ease, the most important genetic factor influencing the birth of a live calf is the maternal ability of the cow delivering the calf. Daughter stillbirth evaluations have a higher heritability value than the SS SB evaluations and there appears to be more genetic variation in the Dtr. SB trait. Dtr. SB should receive more attention than SS SB in selection decisions.

Reliability for stillbirth evaluations will be an issue. Heritability values for these traits are low. The heritability of Dtr. SB is 6.5 percent and for SS SB it is 3 percent. These values are among the lowest of any of the traits for which genetic evaluations are available. Also, stillbirth records are currently captured and stored by only one of the DHI computing centers. So, only a portion of Program for Genetic Advancement™ (PGA™) herds are contributing data to these genetic evaluations. Reliability values for first-crop A.I. sires will range from 40 to 55 for both traits.

™gender SELECTed, Program for Genetic Advancement and PGA are trademarks of Select Sires Inc.

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