Garfield County Cooperative Extension

Will Cattle Selection Indexes Make You Money?

Rick Nelson Extension Educator, Ag/4-H

When a beef producer starts the search for a new bull study the indexes. Beef cattle selection indexes have been developed and released by animal scientists and breed associations to aid in genetic decisions that will directly affect ranch profits. With selection indexes development and release beef producers have several questions.

What are selection indexes?

A selection index is a multi-trait selection tool that calculates a monetary value for a combination of genetic influences on or within a production system. Within their computations, performance and cost of production factors are considered and combined to evaluate beef cattle. Previously, EPDs (Expected Progeny Differences) were used for animal comparisons with each EPD focused on a single production trait such as birth weight, weaning weight, or yearling weight. The first wide spread application of multiple trait selection soon followed the release of EPDs when producers began to simultaneously select for low birth weight and high yearling weight proclaiming the procedure as “curve bending”. This has led some beef cattle producers to think extreme EPD values are ideal, forgetting that many traits and relationships between traits can greatly influence profits. Most producers have found that many combinations and levels of production traits can maximize profits.

How do selection indexes work?

Through the use of selection indexes, producers will influence several traits simultaneously using one selection value. More specifically, selection indexes are multiple regression equations. The dollar value (equation solution) equals a sum of weighted traits. For the process to work correctly, the regression model must include the correct traits and weight each of them properly. Successful models produce answers that are easy to apply even though their development is complex. Use of selection indexes began in the 1940’s. Iowa State University researchers developed the early theory and mechanics. From that point, selection indexes have evolved to assist genetic selection in several species of livestock. Because of complications involving data collection and cost information, the cattle industry has been slow to bring selection indexes into daily practice.

In the meantime, many producers used single trait and independent culling levels to make genetic decisions. Independent culling levels place a threshold value on one or more traits to separate potential individuals into acceptable and non-acceptable candidates. Single trait selection would allow for the greatest genetic progress for a single trait but often has adverse effects on non-selected production traits. In comparison, indexes allow the candidates to be sorted without a threshold for any particular trait but result in positive overall profit potential.

Which selection index do I use?

Cow/calf operators must first define goals for their own operations. They must discover the profit centers in their production system. The profit centers will then define the best index to use. Most selection indexes have been given names that readily identify their application to cattle producers. Several indexes are available from beef breed associations that are unique to each particular association. Presently it is impossible to compare between the breeds because they do not share their databases or their modeling techniques. Selection indexes are another tool in the box similar to EPDs.

Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Oklahoma Cooperative Extension Service is implied.


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