by: Wes Ishmael

“Selection indices, to me, are the most valuable tool we have to help us make more right decisions and fewer mistakes,” says Donnell Brown of R.A. Brown Ranch at Throckmorton, Texas. “That doesn't mean they're perfect; we still need to look at the animal visually, make sure the structure is right and all of those things, but we believe they help us make more right decisions than wrong ones.”

That says a mouthful when you understand that Brown's family has been building seedstock and running commercial cattle for generations, focusing along the way on how to more accurately select cattle for specific genetic ability.

Selection indexes and the idea behind them are straightforward. In simple terms, rather than select for a variety of traits that affect a production area, like maternal ability or carcass ability, as examples, utilize a single index value that incorporates the relevant traits, weighted for relative economic importance.

In other words, rather than select for improvement in independent traits or establish threshold values—ignoring the economic relevance in both cases—use an index that focuses on overall profitability related to a specific area of economic importance.

“In its simplest form, the selection index defines an animal's economic merit as a parent in terms of a mathematical function; an animal's EPDs are weighted by their respective economic value,” explains Bob Weaber, Extension beef cattle specialist at Kansas State University, in his insightful fact sheet, Beef Cattle Economic Selection Indices. “Traits that have larger impacts on profit or the production goal have larger economic weights associated with them. The index is simply computed as a sum of EPDs weighted by the relative economic value.”

“Even though EPDs give cattlemen a great tool for making genetic change in production traits, they ignore economic considerations,” explain authors of The Power of Economic Selection Indices to Make Genetic Change in Profitability, which was presented at the recent annual meeting of the Beef Improvement Federation (BIF). “It has been up to the individual cattleman to determine the economic impact of each trait and try to formulate that information into a multi-trait selection scheme. Without an organized, systematic approach to this complicated endeavor, the results are likely less than desirable. Unfortunately, this has led to an overemphasis on selection for increased outputs without due consideration to the traits affecting costs.”

Brown coauthored the aforementioned paper presented at BIF this year, and was part of a panel with coauthors, Larry Keenan, director of breed improvement for the Red Angus Association of American and Darrh Bullock, a professor specializing in beef cattle genetics at the University of Kentucky.

Although the idea of selection indices has been around for decades, at least, increased focus and availability of them for beef cattle selection is relatively recent. Depending on the breed in question, you can find a variety of selection indexes today.

In general terms, most beef cattle selection indexes available today are geared toward fed cattle and carcass performance, maternal performance or a blending of the two.

For example, the American Angus Association provides indexes for Weaned Calf Value ($W), Feedlot Value ($F), Grid Value ($G), Beef Value ($B) and Maintenance Energy ($EN). The Red Angus Association of America offers the HerdBuilder and GridMaster indexes. The American Simmental Association produces the All Purpose Index and the Terminal Index. You get the idea.

Each one includes specific traits weighted for specific economic values.

“Indexes are the Cliffs Notes that combine lots of multi-trait data and do it relative to production and marketing system,” Brown says.

Moreover, according to Weaber, selection indexes provide a more efficient selection strategy than other forms. He explains other commonly used forms of selection include sequential selection and the use of independent culling levels. With the former, selection pressure is applied to one trait at a time until achieving the desired level. In the latter, minimum and maximum threshold values are established for each selection trait.

Chart Objectives First

More than anything, making progress with selection indexes requires first knowing where you want to go.

“There is no use doing any selection, whatever tools we use, if you don't have a roadmap in front of you, what we call breeding objectives based on your management, how you're going to market cattle in the future and your environment,” Bullock told the BIF crowd.

“The first key to successfully implementing an effective breeding program utilizing selection indices is to develop and define your breeding objectives,” emphasize authors in the BIF paper. “Selection causes change to the herd; most are intentional, but some are consequences. It is critical to know what traits are important to your management and marketing scheme, but also how selection for those traits affects other traits of economic importance. For example, if a selection scheme was implemented to maximize calf weaning weights and replacements are to be retained, it might be tempting to select for maximum weaning weight direct and weaning weight milk EPDs. The result of this system would be large weaned calves, but there may be other consequences. Because of genetic correlations, this mating scheme would also result in large, heavy-milking cows that require greater nutritional demands; if those demands are not met then reproductive failure is a likely result.”

This reality means understanding the focus of individual selection indexes, what traits are accounted for and to what degree. As important is understanding what traits are not addressed in the index.

“Selection indices do a great job of economically balancing the traits that are included in the index, but there may be traits of economic/convenience/quality of life value to your cattle business that are not in the index of choice,” say authors of the BIF paper. “When this occurs, you need to use the index in tandem with the additional trait(s) of importance. A good example would be selecting for improved temperament in conjunction with improved carcass traits. In this scenario, it would be beneficial to select based on a combination of the Terminal Index and the Docility EPD.”

The BIF panel also emphasized that selection indexes remain robust in the face of changing market conditions.

“Even if market signals change significantly, corn prices go up and cattle prices go down, it's amazing to see how consistent and robust these indexes are at selecting the cattle that do more things right,” Brown says.

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