Across-Breed EPD Adjustment Factors
Expected Progeny Differences published by one breed are inherently not comparable to those published by another breed. This is due to several factors including differences in arbitrary base adjustments used by each breed and differences in selection intensity for a specific trait in one breed compared to another. Consequently, producers who wish to compare bulls of different breeds must utilize across-breed adjustment factors.
Breed association collaborations are underway that represent the opportunity to directly compare bulls of different breeds in the future. International Genetic Solutions (IGS) represents a partnership between 12 beef breed associations. Consequently, each participating breed association benefits from data contributed by partner breed associations enabling even more accurate EPDs when pedigree ties exist between breeds. These pedigree ties are evident when one thinks of SimAngus, LimFlex, Balancer, and Red Angus, as examples.
Currently the US Meat Animal Research Center (USMARC) calculates across-breed adjustment factors for 18 breeds for four or more traits including: birth weight, weaning weight, yearling weight, maternal milk, marbling score, ribeye area, and fat thickness. Producers can use these additive adjustment factors to adjust EPD to a common Angus base. Across-breed adjustments are updated annually to capture differences in base changes, genetic trends, and the addition of more data generated in the Germplasm Evaluation Project at USMARC. Each year new across-breed adjustment factors are released at the Beef Improvement Federation (BIF) meeting. Current across-breed adjustment factors can be found on the BIF homepage.
As an example, to compare a Limousin or LimFlex bull’s EPDs directly to an Angus bull’s EPDs bull buyers need to use the following adjustment factors to add to the Limousin or LimFlex bull’s EPDs:
- 3.0 (birth weight),
- -17 (weaning weight),
- -42 (yearling weight),
- -8.8 (milk),
- -0.6 (marbling),
- 0.98 (ribeye area), and
- -13.4 (carcass weight).
If a Limousin bull has a Milk EPD of 30, his Milk EPD on an Angus base would be 21.2 (30 – 8.8).
For bull buyers wishing to directly compare bulls of different breeds this exercise is critical. To make this exercise easier, online across-breed EPD calculators are available the eBEEF.org homepage under the Tools section.
Nebraska Extension Beef Genetics Specialist