The when: $ Indexes vs. EPDs

In bull selection, indexes and expected progeny differences (EPDs) are often used as an either/or type of question: “Do I use indexes when I select bulls, or do I stick with EPDs because our operation focuses on _____?” Without a doubt, the answer is always: “Use both.” Some still question the validity of indexes because they are still relatively new or don’t fit exactly what their operation sets out to accomplish; EPDs are more reliable because the numbers have simply been around longer. Whatever scenario you have talked yourself into – or out of – there’s a logical way through it.

Wall patrick
Southeast Iowa Beef Specialist / Iowa State University
Culbertson randie
Cow-Calf Extension Specialist / Iowa State University

Since indexes are designed to tie current economics to a series of EPDs all at the same time, they are a good place to start when viewing a sale catalog or beginning a search for your next bull battery. At this point, most breeds have indexes that can be classified into three basic categories: all-purpose, maternal or terminal. The most obvious question to ask yourself is, “Will replacement females be retained, or is breeding female revenue a significant source of income from this bull?” If the answer is no, simply focus on terminal and carcass indexes first. If the answer is yes, maternal indexes should become the priority. All-purpose indexes, as the name implies, simply try to keep a wide variety of economically relevant traits (ERTs) moving in the right direction.

Setting some basic boundaries on your index of choice is a logical next step. Maybe it’s as simple as eliminating the bulls that are below breed average. Setting the criteria too narrowly, like only “starring” the bulls in the top 20% of the breed, might leave you with a really short list. They could be all half-brothers, or a list that is simply out of your price range. Keep in mind, there are countless ways a set of bulls can all arrive at the same $ Index value.

Next, determine the EPD columns that are most important to you. If your operation runs in pretty tough country, then a Moderate Milk EPD could help trim your list. If the bull must cover heifers, the Calving Ease Direct (CED) EPD must be considered. If you retain ownership through the feedlot and chase grid premiums, the Marbling or Carcass Weight EPD should be considered. You get the idea.

At this point, it’s probably a good idea to grab a sale order, a data sheet and a cup of coffee. Are the bulls on your short list going to be in your price range? There’s nothing worse than doing all your homework only to find out you’re really good at finding the bulls everyone else is going to bid on too. The last step is the easiest: Head to the pens and study only the bulls on your list. Good feet, good growth and a good attitude are all a must. At the end of the day, most producers still won’t buy a bull they don’t like phenotypically. However, using indexes to move the herd in the right direction, followed by EPDs to ensure the operation’s goals are met, is a solid approach to navigate the process.


The what: Indexes defined

Simply put, an index is the economic merit of an animal as a parent. It provides a method to simultaneously select multiple economically relevant traits. Genetic selection should be made with the goal of overall improvement to production profitability, and that profitability is driven by not one, but a combination of traits. Reproductive rates, calf survivability and cow herd feed costs are just a few contributing factors to the final paycheck received when selling calves at weaning. Including all ERTs in a breeding objective is crucial, but recognize that each trait has a different economic importance and contributes at varying degrees. Trying to decide what traits should be included in your breeding objective from the wide array of available EPDs – and the amount of emphasis to place on each trait – is daunting. This is where indexes can provide a solution.

Economic indexes (commonly referred to as $ value indexes) are the summation of an animal’s economically relevant EPDs, where each EPD has its own economic contribution. The economic influence of these traits will dictate the magnitude of the contribution associated with each EPD. For example, Cow Longevity has a significant economic impact on a cow-calf operation. As a result, maternal indexes and all-purpose indexes will have a larger economic contribution for Cow Longevity. On the other hand, terminal indexes have large contributions placed on Marbling and Carcass Weight EPDs, but a negative economic contribution from Feed Intake.

Generalized indexes published by breed associations are designed for breedwide use and don’t account for breed differences or resource limitations. The realization of index values may vary depending on individual operations, but the ranking of bulls within an index should be similar. It is important to understand which EPDs are used in these indexes and to know your operation’s resource limitations when using indexes for selection decisions.