The World's source for Bovine Genetics
SELECTIONS - Winter 2005
Adjust Your Selection Standards in 2005


by Chuck Sattler, vice president, genetic programs

Chuck SattlerAlthough the February 2005 base change for dairy sire evaluations will result in lowered trait values on all bulls, this change reflects using a more current genetic base as a standard of comparison. This routine update of the genetic base provides a good opportunity to review your current sire selection standards.

Maintaining reasonable standards is important in many things, and it is certainly true with sire selection.

The standard used for publishing genetic evaluations is called the genetic base. This base is routinely updated to keep the evaluations current with the genetic level of the national herd.

With the February 2005 release of genetic evaluations, the genetic base for nearly all of the traits evaluated has been updated.

These adjustments cause published PTA values for A.I. sires to be lower. Since genetic improvement is being made in many areas, when the genetic base is updated, the genetic standard of comparison becomes higher, causing the published values to go down. Don’t let these lower values alarm you. The base adjustments do not change the ranking of sires. The evaluation for every animal is adjusted by the same amount. However, the magnitude of sire evaluations has changed. For example, a sire that was +2,000 PTA milk in November 2004 will have a PTA for milk near +1,400 in February 2005. A bull with a +1.50 Udder Composite in November will now be about +1.15 for Udder Composite in February.

Table 1: Evaluation changes expected from the Feb. 2005 genetic base adjustments.


For those of you that have established specific standards for the sires used in your herd, now is a good time to review those standards. Table 1 shows how the genetic base update will impact each trait. As you can see, requiring bulls to be +1,500 for milk will be much more restrictive now than it was back in November. The same thing goes for type traits, Productive Life (PL) and Daughter Pregnancy Rate (DPR). Again, now is a good time to review those standards to make sure you are selecting bulls that will improve your herd yet still allow some options for corrective mating and pedigree diversity.

The routine update of the genetic base is also a convenient time to implement other evaluation modifications. The most significant of these will be the new genetic base definitions used for Somatic Cell Score (SCS) and DPR. From this point forward, the genetic base for SCS evaluations is 3.00 for all breeds. This was done to help make SCS evaluations more stable from run to run and to make it easier to know where a bull ranks. The genetic base for DPR has been switched from a sire base to a cow base. The new base definitions for SCS and DPR will cause some fairly large changes in evaluations for these traits. It also means that the base change values in these traits are a combination of the genetic change over the previous five years as well as the impact of the new base definitions.

Updated TPI Formula

The Holstein Association’s Type-Production Index (TPI™) also has been revised. DPR, Daughter Calving Ease and the linear type trait Dairy Form are now included in the TPI formula. The addition of these three traits will improve the ranking of those A.I. sires that transmit good cow fertility and easy calving with some slight discrimination of those with daughters that tend to get too sharp and thin.

Table 2: Percentage of emphasis on each trait in the new Holstein TPI.


These changes to the TPI formula make it more useful for producers that breed registered as well as commercial cattle. Production traits receive half of the emphasis. The other 50 percent is dedicated to those sires that improve health and fitness traits. Table 2 shows the emphasis placed on each trait in the new TPI formula.

Many of the revisions to TPI are consistent with recent revisions to USDA’s Lifetime Net Merit (NM$) formula. The key difference is that TPI places more emphasis on overall type as well as udder composite and feet and legs composite. For those with an interest in maintaining sound type conformation, the new TPI is an excellent tool for improving the overall production and longevity in your herd.

The February 2005 genetic evaluations continue to be good indicators of which bulls offer the most genetic improvement. The published values are lower but this just simply reflects the change of using a more current genetic base as a standard of comparison. This routine update of the genetic base every five years provides a good opportunity to review your current sire selection standards.



™TPI is a trademark of Holstein Association USA

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