When evaluating bull choices for a breeding program, producers should look at several expected progeny differences, or EPDs, to develop a well-rounded herd.
Ron Lemenager, a Purdue Extension beef specialist, says the first step is to look at deficiencies in the current herd and select for EPDs that make the most economic sense.
"If you single-trait select for any one trait, you'll take your herd in the wrong direction," Lemenager notes. Specifically, there are three top EPDs he suggests considering before making your next big bull decision: calving ease, milk production and dollar index.
First, Lemenager says when searching for a new bull, producers gravitate towards birth weight because it can be a predictor of problems with calving.
But birth weight EPD might not be the correct factor to look at. Instead, Lemenager says looking at calving ease EPD is a better choice.
"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."
Instead, he explains that calving ease EPD in contrast, considers birth weight, calf shape and other factors. 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.
Second, Lemenager stresses that milk production is important, because it can dictate what's needed for individual cow energy requirements.
For example, a 1,300-pound cow producing 30 pounds of milk a day has a 30% 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."
Finally, Lemenager suggests narrowing choices by using the dollar index EPDs. These allow producers to scan through some bulls to sort out what bull will work for a particular situation.
As a composite number, however, he points out that dollar index EPDs are multi-trait numbers, and therefore producers should still 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. However, the U.S. Department of Agriculture's Meat Animal Research Center provides an across-breed EPD table each year to help compare bulls of different breeds.
For more information visit www.marc.usda.gov.