EPDs cannot be compared across breeds (one breed to another breed) without first making an adjustment that accounts for several factors. Each breed association maintains a separate database of pedigrees and performance records. They also typically conduct their own genetic evaluation. These separate populations and evaluations result in a different base (year in which the average EPD for animals born that year are forced to average zero). Further, each breed has different population parameters (means, variances, covariances, correlations, heritabilities, etc.) used in computation of their EPDs. So, published EPDs should only be used to compare bulls within a breed (Hereford to Hereford, Angus to Angus, etc.) and not across breeds (Hereford to Angus, Angus to Simmental, etc.) unless an adjustment is made.
Each year the Beef Improvement Federation publishes a table of adjustment factors to adjust EPDs of any one of 16 breeds to a standard which is usually the Angus breed because Angus are numerous, and most breeders have a rough idea of the Angus breed average EPDs. These adjustment factors are developed from data on all breeds of cattle located at the Meat Animal Research Center (MARC), Clay Center, Nebraska. Across-breed EPDs are computed by adding the appropriate breed and trait adjustment factor to the EPD of the animal whose EPD you want to compare on the Angus base. To compare animals from two different breeds, not including Angus, it is easiest to move both animals' EPD to the Angus base. You can usually find a copy of the Across-Breed EPD Adjustment Table in various breed magazines or Web sites. You may download a copy of the 2007 adjustment tables from the Beef Improvement Federation Conference Web site at: www.ars.usda.gov/sp2UserFiles/Place/54380000/GPE/AB_EPD2007News.pdf .
