Multi-trait selection indexes combine expected progeny differences (EPDs) for several traits into a single economic value aimed at simplifying selection decisions. The index values are interpreted like EPDs; the difference in $Value between two bulls is the expected difference in average dollar value of their progeny when the bulls are bred to similar cows. Economic assumptions from “typical” beef production methods are used in calculating the indexes. All indexes are expressed in dollars per head.
• More $$$ is always better; higher index values are more desired, but only if your environment and management can handle the potential increase in inputs. Proceed with caution!
• $Indexes are not comparable between breeds, even if both breeds participate in the same multi-breed genetic evaluation (i.e., both breed’s EPDs have the same base). However, some breed indexes have the same general production goal in mind even though the indexes are calculated independently.
• Indexes are calculated from EPD values, so they are only updated and change when EPDs change. Also, if an EPD required in the index is not available (N/A) for lack of data submitted (Example: Carcass/Ultrasound data or Calving Ease records on young bull calves), the $Index will also be N/A.
• Phenotype is still extremely important to include in your selection program. Bulls with identical $Values can have drastically different composition, structure, frame size, etc.
$Values can be sorted into a few distinct categories based on the main goal of the index: Calving Ease, Maternal Strength, Growth and/or Carcass Performance, etc. Some $Values have utility in a number of different management schemes.
The complete five-page publication, with information on Angus, Hereford, Shorthorn, Red Angus, Simmental & SimAngus, Gelbvieh, Charolais, and Limousin is available on the Iowa Beef Center website, www.iowabeefcenter.org. — Iowa State University Extension
