Producer Application Committee:
Selection for Traits Without EPDs
Tips to select animals for traits not measured in the National Cattle Evaluation.
by Kasey Brown, associate editor, Angus Journal®
OKLAHOMA CITY (June 13, 2013) — Not all traits have measurements in a national cattle evaluation (NCE), which results in expected progeny differences (EPDs). Yet those traits may still be important to your operation’s selection strategy, said Dan Moser, Kansas State University, to attendees of the 45th Annual Beef Improvement Federation Research Symposium and Convention in Oklahoma City, Okla., June 12-15. Moser addressed the Producer Application Committee breakout session Thursday afternoon.
Dan Moser
There are a few reasons why a relevant trait isn’t included in NCE, Moser explained. Some traits have to be subjectively measured, and breed associations may not collect data for certain traits. For instance, he said, docility isn’t measured by every association, and it’s a trait that has to be measured subjectively.
Moser noted that niche traits aren’t included in NCE, nor are those with questionable indicators. Traits not related to profitability also are not included.
“Any time you make a selection decision, you are basing that on your estimation of the individual’s progeny difference,” Moser said. When making selection decisions based on traits for which there are no EPDs, it is important to consider what goes into calculating an EPD.
For instance, EPD selection starts with accurate, objective measurement of the phenotype. Measurement error lowers the accuracy of selection.
EPD selection compares animals’ phenotypes to those of other animals in the same contemporary group and accounts for environmental differences between groups.
EPDs account for heritability of a trait. Highly heritable traits, like carcass traits and mature size, respond well to phenotypic selection. Conversely, female reproductive rate and survival are low in heritability and are thus difficult to change without progeny testing. Rate of growth is moderately heritable, he added.
EPDs combine data from the animal, its ancestors and its progeny. They account for the level of genetic competition and for non-random mating. Some EPDs incorporate genomic information.
Moser said it’s important to understand the relationship between your trait of interest and profit.
EPD selection starts with accurate, objective measurement of the phenotype, but when EPDs are available, they are the most powerful tool available for selection, said Moser. “Mental adjustment” of EPDs, which are used when EPDs aren’t available, for visual characteristics and actual data introduces bias and lowers the rate of genetic progress.
Ultimately, traits without EPDs can be selected for, but selection is more difficult and genetic change is slower. Traits without EPDs are more difficult to improve through this method of selection, though the good news is that it is also more difficult to bring in problems.
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