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SELECTIONS - Summer 2003
Daughter Pregnancy Rates


In February, the U.S. Department of Agriculture released preliminary predicted transmitted abilities (PTA) for daughter pregnancy rate (DPR). DPR values are expressed as percentages. For example, a bull with a PTA DPR of +1.0 is expected to have 1 percent more pregnant daughters with each breeding cycle than a bull with a PTA DPR of 0. Another interpretation is that for each 1 percent increase in the PTA DPR, on average the bulls’ daughters would have four fewer days open each lactation.

According to industry experts, approximately 96 percent of reproductive success is dependent on management and environmental factors. DPR is an attempt to measure the genetic components of reproduction.

Practically speaking, what does this mean for producers?

Calculating The Numbers
DPR is calculated by using days-open information based on DHI records during each of a cow’s first five lactations, dating back to 1960. Values range from -3.3 to +2.8, and average -0.2. About 65 percent of current bulls have negative values, and reliabilities for first-crop sires range from 50 to 60 percent.

Like many fertility traits, DPR has a low heritability of 3.7 percent. To put this into perspective, this compares with 30 percent for production traits.

Using DPR
Because of the preliminary nature of this information, neither Holstein Association USA nor the American Jersey Cattle Association has published DPR PTAs in their official sire-summaries or pedigrees, and are not including them in performance indicies. In addition, geneticists have concerns about how well this new trait accurately measures genetic differences in cow fertility.

According to Chuck Sattler, vice president, genetic research and dairy progeny testing, Select Sires, if a producer consistently breeds 100 percent A.I. and uses only sires that are positive for PTA DPR, and if DPR does indicate true fertility differences, then it might be possible to reduce days open by four days (1 percent DPR) in seven years. However, that same producer likely will lower standards for production, type, inbreeding and other economically important traits.

Industry experts advise producers who use DPR as a selection criteria to do so only as a secondary consideration.

Key Points To Remember When Using DPR adapted from New Evaluations Offer a Genetic Approach to Improving Cow Fertility, by Dr. Kent Weigel and Dr. Paul VanRaden
  • Producers who use DPR as a selection criterion should make it a secondary consideration.
  • When using PTAs for DPR, be sure to consider their reliabilities.
  • Reliabilities will be low for bulls that have only first-crop daughters and evaluations may change significantly as information is added.
  • Many high-ranking bulls for milk, fat and protein will have negative evaluations for DPR.
  • DPR, a measure of female fertility, is not the same as estimated relative conception rate (ERCR), a measure of male fertility.










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