Multi-breed Stayability EPDs: Here’s what you need to know

1.) Multi-breed stayability: The new stayability EPD is calculated for all cattle in the database (not just for purebred and fullblood Simmental).  As stayability is a very important economically relevant trait for female production, the ability to have stayability calculations on all cattle will improve the prediction of the All Purpose Index across all cattle in the ASA database.

2.) Direct incorporation of genomic data:  Because BOLT was used to calculate the Stayability EPD, the evaluation used the DNA markers, pedigree information, and phenotypic data simultaneously in the prediction of the stayability EPD.  Previously molecular breeding values (MBVs) were calculated from the genomic information and those MBVs were blended separately into the EPD prediction.  The new direct method (called Single Step) of including DNA markers not only improves the genomically enhanced EPD for the genotyped animal but also uses this information in the EPD calculations of relatives.

3.) Better prediction of accuracy:  The BOLT software calculates a true accuracy of the EPD rather than an approximation of accuracy.  With the limitations of the old software and computer memory, calculating true accuracy was not an option as the system of equations was too large and cumbersome to manipulate  In addition, the method of approximation tended to inflate accuracy values.  What does this mean to breeders? In most cases, animals will have a decrease in reported accuracy for stayability but this reported accuracy will be the true accuracy for the EPD. True accuracy values help producers better manage risk associated with bull selection.

4.) Change in base: With all the changes made to the stayabiltiy evaluation, the base for stayability has changed for purebred and fullblood Simmental.  All cattle in the IGS collective will be on the same base and comparable directly with each other. Breeders will see movement in stayability EPD from previous evaluations, not only because of changes to methodology but also because of a base change. However, changing the base does not affect the ranking of cattle; it simply shifts all EPDs up or down by the same increment.

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