Have you ever picked up a sale or semen book and looked at expected progeny differences (EPDs) between breeds? Can those EPDs be compared apples to apples, or not? The answer is, no, at least not without using appropriate adjustment factors. 

For several decades EPDs have been powerful genetic selection tools that have assisted cattle breeders in making genetic change in their herds. 

The National Cattle Evaluation (NCE) uses data submitted by members through the Angus Herd Improvement Records (AHIR®) to calculate EPDs, which predict the average performance differences in the future progeny of other animals. Seedstock and commercial breeders alike have taken advantage of EPDs to make informed selection decisions for their herds. 

While EPDs are the best genetic selection tool, they can only be directly compared to those calculated from the same genetic evaluation.  

This presents a challenge for producers who want to compare EPDs on animals of different breeds, because each breed uses different evaluations and performance data, which means EPDs are not directly comparable across breeds. 

For commercial customers considering bulls from more than one breed, they must be able to compare EPDs from different breeds to find the best fit for their herd’s breeding objectives. 

For this reason, the U.S. Meat Animal Research Center (USMARC) began publishing across-breed adjustment factors in 1993.  

Across-breed adjustment factors 

Since the 1970s, researchers at USMARC have been studying differences between beef breeds most commonly used in the United States through the Germplasm Evaluation (GPE) program. This program’s overall objective is to characterize a wide variety of breeds for economic traits, such as growth, efficiency and carcass quality.  

The GPE program utilizes a herd of commercial females with known pedigrees who are bred to prominent, high-accuracy sires from the most widely used breeds in the industry. The resulting calves are raised within the same environment and their performance carefully recorded throughout their lifetime. 

By raising calves sired by multiple breeds in the same environment, the performance of the calves can be estimated and the differences in performance adjusted for the EPDs of the sires that were used. This results in adjustment factors that can be used to adjust EPDs from those respective breeds and allows for comparisons of EPDs across breeds.   

The across-breed adjustment factors are calculated and published annually. Since not all breeds publish the same EPDs, adjustment factors are calculated for growth and carcass traits, which are common to most breeds. The most recent release included adjustment factors for 18 different breeds for eight traits (Table 1). These adjustment factors themselves should only be applied to EPDs of the respective breed to make comparisons, and should never be directly compared to each other in an attempt to select a potential breed for a breeding program.  

Table. 1: 2024 adjustment factors to add to EPD values of respective breeds to estimate across-breed EPDs.