Select Sires

SELECTIONS - Winter 2004
Using A Selection Index

by Charles Sattler, vice president, dairy progeny testing and genetic research

Chuck Sattler

With so much sire information available today it is a challenge to make good use of it in breeding decisions. However, with the understanding of a selection index you can turn this challenge into an opportunity that will allow you to zero in on the sires that will best meet your needs.

What is a Selection Index?

A selection index is a helpful tool that combines sire-summary information on several different traits to identify the bulls that provide the most combined improvement for all these traits.

Many people have heard of values like Type-Production Index (TPI™) in the Holstein breed and Jersey Performance Index (JPI™) in the Jersey breed. These are good examples of selection indexes. They help producers choose sires that have the best combination of traits to increase profitability. Other indexes that deserve consideration include Net Merit Dollars (NM$), Fluid Merit Dollars (FM$) or Cheese Merit Dollars (CM$). These values are calculated by the USDA and also are intended to help producers focus in on sire-summary traits that maximize profitability.

How Should You Use a Selection Index?

Everyone seems to have their own idea of how to breed for profitability. In order to use these selection indexes successfully, a producer needs to define which index best fits his or her operation. An initial step to selecting the appropriate index is to identify your milk market and then choose the index that best matches it. JPI naturally focuses on the value of milk used to manufacture cheese. TPI is based on milk values in multiple-component pricing markets. The difference between the USDA merit formulas is the value they assign to milk protein. Producers receiving little or no payment for protein in their milk should use the FM$ index. Those receiving a moderate payment for protein, such as prices that are received in multiple-component pricing markets, should focus on the NM$ index. Finally, those who receive a fairly high premium for protein in the milk, like those taking advantage of the cheese-yield pricing markets, should consider using the CM$ index when making their mating decisions.

Other Traits

The routinely available indexes also emphasize different non-production traits. TPI and JPI give a fairly strong emphasis to overall conformation. This is useful if a portion of your animals are sold for breeding stock. If your income is solely generated from the sale of milk, then the USDA merit formulas may be more appropriate. While all these indexes emphasize productive life and low somatic cell scores, the merit formulas emphasize these more strongly. Choose the index that includes those traits that are important to you.

Changes in the Formulas

In August 2003, the USDA merit formulas were revised to include the reproduction traits, such as Predicted Transmitting Abilities (PTAs) for daughter pregnancy rates and the calving-ease genetic evaluations. Producers need to keep in mind that the reliabilities of these traits are low, and including them in the USDA merit formulas is the best way to take advantage of the information in an appropriate way.

The new USDA formulas now allow producers to choose the merit index that best fits his or her milk market while feeling comfortable that important reproduction traits are included.

Information on all of these indexes is routinely available on A.I. organization Web sites, such as www.selectsires.com, and from A.I. sales representatives. If you are looking for more information on specific ways these indexes are being used or if you have questions pertaining to other selection indexes and want assistance in improving and reaching your breeding goals, please ask your local Select Sires representative for more information.

™TPI is a trademark of Holstein Association USA
™JPI is a trademark of the American Jersey Cattle Association

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