Using indexes to guide bull buying decisions

BROOKINGS – Today’s cattle ranchers may experience information overload when trying to make genetic purchasing decisions.

“There is an abundance of information available to ranchers to help make genetic decisions. The number of traits for which we have Expected Progeny Differences (EPDs) has increased to include carcass traits as well as traits such as stayability and disposition. All that information doesn’t make the selection task easy,” said Warren Rusche, SDSU Extension Cow/Calf Field Specialist. “It can be a bit like picking your 20 favorite George Strait songs; some hard decisions need to be made.”

He adds that one challenge when using EPDs is balancing between different traits and what kind of trade-offs cattle producers can afford to make.

“Perhaps there are two bulls you’re considering; one offers excellent growth performance and acceptable carcass traits, the other just meets your target for growth but the bull’s marbling EPD is exceptional. Traditional trait EPDs don’t do a very good job of telling us which one of these two bulls will be more profitable to own,” he said.

EPDs also don’t address costs.

“We all know that selecting for more growth and more maternal milk in the sires of our replacements can increase our weaning weights,” Rusche said.

Cattle producers also know that those higher producing cows require more nutrients – and that costs money. In this situation, Rusche says producers could use a tool that evaluates the value of the outputs and also considers input costs. Fortunately those kinds of tools are becoming more available in the form of selection indexes.

Selection indexes, Rusche explains, use the trait EPDs in an economic model to put a dollar value on an individual bull. He refers to a graph and shares an example.

“For example, the Angus Association publishes a Weaned Calf Value ($W) index that considers birth weight, weaning weight, maternal milk and mature cow weight,” he said, referencing Table 1. “The model considers how changes in those traits might affect percent calf crop and weaning weights, and also considers what might happen to feed costs over time using real world prices for both cattle and feed.”

When using selection indexes, Rusche says cattle producers still need to use their common sense.

“We could have a case where a bull might be undesirable for one trait, but so superior for one or two that he still ranks very high on an index,” he said. “A rancher might want to set some minimum or maximum values for some traits to make sure that the bull will “fit” in their system.”

Also, Rusche explains that these indexes are set up using a one-size fits all approach that may not exactly work in every cattle producer’s situation.

To learn more, visit iGrow.org, or contact your local SDSU Extension Regional Center and visit with an SDSU Cow/Calf Field Specialist.