Take a stroll down memory lane and recall how many EPDs you had to contend with back in the day when they were a relatively new management tool. Only four or five, right? – birth weight, weaning weight, yearling weight, carcass and milk.
Nowadays, you have 15 or more EPDs to sort through as you try to make bull-buying decisions. “We’ve got a lot of data to make selection decisions on. At times, I would argue it’s a tad bit overwhelming,” says Mark Enns, Colorado State University geneticist.
But not all is lost. So, before you spend so much time longing for the good old days that you forget to bid, Enns has a few suggestions.
“Our perspective in the past has been that more EPDs for more traits allow us to better characterize the genetic potential of animals,” Enns says. “That’s not always the case because often, with this ever-increasing list of traits, we have several EPDs that are related to the same thing we’re interested in improving.”
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For example, a birth weight EPD and a calving ease EPD. They’re getting at the same thing, Enns says, and because of the mathematical calculations used to calculate EPDs, he says you can make a less accurate decision by using both of them rather than using the one that’s economically relevant.
Enns defines an economically relevant trait as one that affects the bottom line in some way. “If we change it and it increases our cost, decreases our cost or changes our income, that’s an economically relevant trait.”
The other trait, then, is called an indicator trait. ”Those are the things that are typically easy to measure that allow us to add accuracy to our EPDs,” he says.
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“So from the standpoint of calving ease, we measure birth weight because it’s related to whether we have to assist a calf being born. So birth weight is an indicator trait.” Calving ease, on the other hand, is the economically relevant trait. Birth weight doesn’t explain everything, he says. It’s an important component of whether or not a cow calves unassisted, but it’s not the only one.
“The other thing you’ve got to remember is that the more things you select for, the slower your rate of progress of any one of those.” So by ignoring the indicator traits and focusing on the economically relevant traits, you can lessen the confusion and make faster progress. “So there’s a balancing act we need to apply to make the most rapid progress we can in the traits that really influence our profitability.”