WEST LAFAYETTE, Ind. — Expected progeny differences, or
EPDs, can help beef producers evaluate bulls when looking to improve their
cattle herds, but they shouldn’t focus on just one trait, a Purdue Extension
beef specialist said.
Instead, producers should look at deficiencies in their
herds, whether it’s milk production, dystocia, poor carcass quality or slow
growth, and then start looking at the EPDs that would make the largest economic
“If you single-trait select for any one trait, you’ll take
your herd in the wrong direction,” Ron Lemenager said.
When searching for a new bull, producers commonly first
examine the EPD for birth weight because it can be a predictor of dystocia, or
problems with calving. But selecting a bull with an ultralight birth weight EPD
might not solve that problem.
“There’s a genetic correlation between birth weight and all
of the growth rates,” Lemenager said. “If you select for light birth weight,
you’re probably going to end up with light weaning weights, light yearling
weights and a slower-growth rate kind of cattle.”
He prefers comparing bulls by their calving ease EPDs rather
than birth weight because it considers birth weight, calf shape and other
Calving ease is expressed in two ways by most breed
associations. Direct calving ease predicts how easy the calves from a particular
bull will be to deliver, and maternal calving ease predicts how easy the
daughters of that bull are going to calve.
Another popular EPD for producers looking to improve their
herds is milk production, because higher milk production leads to higher weaning
Lemenager said it’s important for producers to consider what
higher milk production means for individual cow energy requirements.
For example, a 1,300-pound cow producing 30 pounds of milk a
day has a 30 percent higher energy requirement than that same size cow producing
15 pounds of milk. Lemenager said that works out to an additional 9.5 pounds of
good-quality hay or 5.75 pounds of grain-based supplement per day.
“It’s a pretty expensive proposition if you have to
supplement those cows to maintain body condition, weight and rebreed rate,” he
said. “If you’re comfortable with the cow condition and rebreed rate with
minimal supplementation, chances are you’re pretty close to the level of milk
that you need. If cows are thin and failing to conceive, maybe you’ve got too
much milk in your cows for the environment they’re working in.”
Dollar index EPDs, composite EPDs that combine several
traits into a single value, can help producers narrow down their
“They’re a great way to scan through some bulls to sort out
what kind of bull will work for a particular situation,” Lemenager said.
“However, realize that these indexes are multi-trait numbers.”
Producers still should look at the individual EPDs that make
up the index to make sure the bull will fit their herd situation.
EPDs should only be used to compare bulls of the same breed.
The U.S. Department of Agriculture’s Meat Animal Research Center generates and
updates an across breed EPD table each year to help compare bulls of different
breeds. For more information visit www.marc.usda.gov.