Practice risk management when evaluating EPDs
All producers should be striving to purchase bulls that are as predictable as possible for the economically important traits desired. To accomplish this, EPDs (expected progeny differences) are the best tool available, but even they can vary widely on their predictability depending on accuracy. However, in bull sale catalogs, accuracies for the differing traits are rarely printed, so commercial producers must look for practices that a seedstock producer is utilizing that will enhance accuracy. This includes genomics, large contemporary groups and ultrasound.
Accuracies should be looked upon as a form of risk management. The higher the accuracy of an EPD, the surer you can be that the EPD printed is as close to its true value as possible. That is why if you breed to a high accuracy A.I. sire, you can be assured the bull will sire calves right in line with its EPDs. On the other hand, a yearling bull with no practices to enhance accuracies carries considerably more risk that its true genetic value may be different than the EPDs printed in the sale catalog.
Genomics are probably the most vastly undervalued tool to raise the reliability and precision of a genetic prediction. On average, genomic testing is like having a 12-15 progeny test on a bull before it ever has a calf, which is essentially a year’s calf crop for a yearling bull. So if you want to buy a calving ease bull you will either gain this knowledge the hard way by breeding your heifers and waiting for the results of that first calf crop or by purchasing a bull from a seedstock producer who supplies you with genomically-enhanced EP- Ds. The answer to that should be obvious in that it will pay dividends to buy the bulls with genomicallyenhanced EPDs.
Another thing that genomics provide is improved reliability on traits that are difficult to measure like reproduction, including stayability and heifer pregnancy. Reproduction is by far the most economically important trait, so all the information you can gain early on, the better off you will be.
The basics of formation of an EPD is the trait deviations within a contemporary group. Without an animal being in a contemporary group, measurements for the trait such as calving ease scores, weights and ultrasound data add no information to EPDs. Instead, the EPDs listed in a sale catalog will literally be half the sire’s EPDs added to half the dam’s. These are called interim or parental EPDs, and they are very low in accuracy. Therefore, it is important to make sure an animal was raised in a contemporary group (similar age, same management, etc.), and the data was actually collected for the various traits. The larger the contemporary group, the better. As an informed buyer, do not be afraid to ask a seedstock supplier if an animal was in a contemporary group or not and the size of the contemporary group.
The best quality EPDs from a reliability standpoint will come from animals raised in large equal opportunity contemporary groups in which all the data is collected and submitted to the breed association. Be very wary of choosing animals based on actual weights and measures; the environment can have a large impact on these values. The part of a trait value that is the result of environment, such as feeding practices, weather, etc., is not heritable, so traits such as actual birth weights can be very misleading. For example, parity of the cow, weather conditions and feeding can all have a drastic impact on actual birthweights, so the deviations within the contemporary group and their impact on the eventual EPDs is what counts.
One of the tried and true methods of increasing the accuracy of carcass EPDs is taking ultrasound measurements for a contemporary group. This includes backfat, rib-eye area and intramuscular fat. The nice thing about ultrasound is the contemporary group deviations can be used on ET calves to improve the reliability of an animal’s EPDs. This is not true for the weight traits since ET calves are out of surrogate mothers, which affect their values. The exception to this is if the donor dam was a registered cow, then the breed association can account for dam effects.
When purchasing a new herd sire, all producers should be looking to avoid risk by purchasing animals with the highest accuracy EPDs possible. This includes the seedstock producer raising their cattle in contemporary groups, measuring all the traits possible including ultrasound, and making the investment in genomically-enhanced EPDs. It is worth a premium to a commercial producer to purchase bulls from seedstock providers who offer these risk mediating tools assuring the EPDs on the sires they are selling are as close to the true genetic value as possible. — Dr. Bob Hough [Dr. Bob Hough has served as the Executive Vice President of the Red Angus Association of American and more recently as Executive Vice President of the North American Limousin Foundation from 2009 to early 2011. He is now a consultant, freelance writer and semiretired.]