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EPDs provide valuable tool to cattlemen

Expected progeny differences are calculations of the genetic traits of an individual animal that will be passed on to its progeny.
Carol Ryan Dumas

Capital Press

Published on February 5, 2018 11:02AM

Capital Press File
Cattle graze in eastern Oregon. A genetics expert says Expected Progeny Differences — or EPD — calculations can help ranchers choose cattle for the traits they need in their herd.

Capital Press File Cattle graze in eastern Oregon. A genetics expert says Expected Progeny Differences — or EPD — calculations can help ranchers choose cattle for the traits they need in their herd.

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Expected progeny differences — or EPD — calculations have been used in the beef industry for decades to produce genetic changes through breeding that enhance desirable traits in cattle.

Yet there is a perception among producers that they aren’t an effective tool. To inform that perspective, the National Cattlemen’s Beef Association recently hosted a webinar on EDPs.

EDP is an estimate of the genetic merit of future progeny of an individual animal based on that animal’s pedigree, its own performance and the performance of its progeny, said Alison Van Eenennaam, a genomics and biotechnology researcher at the University of California-Davis.

An animal’s own performance is combined and properly weighted — for the contemporary group it’s in and any environmental impacts that might have affected it — along with the performance of its relatives and all genetic relationships to generate an EPD, she said.

“EPDs are the best estimate we have of how a bull or cow’s future progeny will perform on average compared to another bull or cow or the herd average for a given trait,” she said.

Many producers mistakenly place emphasis on raw measurements or adjusted phenotypes rather than the EDP, which already incorporates that information.

“It’s been shown that selection based on EPD, or what’s going to be passed on to the animal, is about five to nine times more accurate than selection based on index performance or ratios,” she said.

Basically, selection based on raw phenotype, such as actual weights or corrected weights, is not a measurement of the genetic potential of the animal. Those data include environmental influences, such as herd, year, season and management, she said.

“That can really impact that number, but it’s not something that’s transmitted to the progeny. So that’s why it’s really important to focus selection only on the EPD itself,” she said.

EPDs are calculated for several traits, such as those related to growth attributes of offspring, maternal characteristics and carcass and gain characteristics, she said.

It allows for the comparison of animals within a breed for their genetic potential as parents for a given trait.

One way to get a feel for whether an animal’s EDP is high or low for a particular breed is to look at EDP percentile rank tables for the breed, she said.

Depending on what a producer is selecting for, he might want to put a lot of selection emphasis on improving a particular trait, choosing an animal that’s high in the breed average for that EDP. On the other hand, he might be happy with another trait and want to stay at the breed average for that EDP, she said.

The overall message on using EPDs is “to match the genetics to your environment and what your overall breeding objectives and goals are,” she said.

The webinar was the first in a series of four to help producers better utilize genetics in beef production. It is available for viewing on NCBA’s website at beefusa.org under “Producer Education.”



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