Decoding Expected Progeny Differences

by Caitlin Richards, The Cattleman Magazine

Making buying decisions can be challenging and using expected progeny differences (EPDs) when buying herd sires may often seem to complicate the decision even more. EPDs have been around for a long time, but they are misunderstood and underutilized.

Tommy Perkins, Ph.D., executive vice president of the International Brangus Breeders Association (IBBA) and past executive vice president of Beefmaster Breeders United (BBU), could not agree more. He offers some decoding advice for producers to use in making herd selections, especially bull purchases.

“To put it simply, EPDs are a mathematical number that helps a breeder select between 2 animals,” Perkins says. “They are meant to be used to compare one animal to another animal within the same breed.”

In the case of IBBA, once a registered Brangus bull is purchased and the seller has transferred ownership to the buyer, the buyer receives the registration paper. At the bottom of the paper is where the buyer will find that animal’s EPDs. This might be the first time some buyers take a close look at the EPDs of the bull he or she just purchased. However, EPDs are where buying decisions start, not end. There are thousands of registered herd bull choices out there, and EPDs can help pare down the selection pool.

Define EPD

By definition, EPDs are predictions of how future progeny of each animal are expected to perform. The traits highlighted in EPDs can be categorized by production EPDs, maternal EPDs, and carcass EPDs.

Production EPDs include birth weight, weaning weight and yearling weight, as well as other important production traits. Calving ease and milk, along with other maternal traits, are considered maternal EPDs. Carcass EPDs are traits related to the animal’s carcass, such as intramuscular fat and ribeye area.

Each EPD is a unit of measurement for that trait, Perkins explains, that is plus or minus a value to the overall breed average for the given trait. For example, a +1 birth weight means that on average, that animal will produce calves that weigh 1 pound more at birth than the average of the breed population. If it is a -1, Perkins says it would go the other direction and that animal will produce calves that weigh 1 pound less at birth.

The process of calculating EPDs has become even more advanced in recent years, Perkins says, with the use of genomics. For years, only pedigree information was used. Today, genetic samples can also be taken to add value to EPDs. When analyzing EPDs on registration papers and sale catalogs look for a notation or symbol that will denote whether it is a genomic-enhanced EPD.

Genomic-enhanced EPDs will have noticeably higher accuracy values attached to each trait on young unproven animals. EPDs are not static and will change over time, as more pedigree or genomic information is included for an animal with each genetic evaluation.

Using EPDs

Being able to read EPDs is only the start to decoding them. Understanding how to use them in buying decisions is where a producer’s operation can really benefit.

“EPDs take out what I call the ‘love factor,’ where everybody falls in love with a phenotype,” Perkins says. “It takes all of that out of the equation and puts it back to the science of selecting animals to genetically move your operation forward.”

The number of EPDs available can be overwhelming to the point where using them gets thrown out altogether. Perkins even says it could easily be data overload for a producer. To make it simpler, Perkins advises ranchers to pay particular attention to 2 traits — weaning weight and calving ease direct.

“The most important thing you have to have is a live calf,” Perkins says. “So everyone needs to make sure to look at calving ease direct or birth weight to improve the odds of a live calf. We all sell calves at weaning, whether it’s a cull calf or if that’s when you market your crop. So weaning weight is going to be very important as well.”

Perkins advises bull buyers to consider scrotal circumference and, if available, mature weight (mature cow size). Scrotal circumference, Perkins explains, is an easy way to help build fertility in replacement heifers. A large scrotal circumference usually indicates earlier puberty in females, which equates to higher fertility.

“Not all breeds have a mature weight EPD, but it is a good one to factor in to prevent making cows too big for the environment,” Perkins says. “Evaluating mature weight determines whether or not the cattle will plateau once they reach yearling weight in order to keep them at a desirable mature-cow size.”

Minimizing the number of EPDs used to make buying decisions is best, Perkins says. He recommends starting with 1 breed and then selecting 4 or 5 EPDs that impact a producer’s most important traits or program objectives.

EPDs are best used within a breed, not between breeds, Perkins says. However, it is possible to compare them among other breeds using adjustment values to the EPD measurements. Across breeds, EPDs are determined by the United States Meat Animal Research Center (USMARC) and can be found online at beefimprovement.org.

“Your production goals plus your environment will help you decide which EPDs are most important to meet your breeding objectives,” Perkins says.

If a producer is selling calves at weaning, intramuscular fat may not be a trait that would be concentrated on as much as weaning weight. However, if the producer is retaining ownership and feeding the cattle out at the feedyard, intramuscular fat becomes more important because it is a major price determinant at the packing plant.

The same consideration should also be taken with the producer’s environment. Perkins warns producers to know their environment and factor it in when selecting EPDs to utilize in their selection decisions.

He explains that if a producer lives out in West Texas where grass is scarce, selecting a lower value for maternal milk is more logical, but if the producer is in Missouri with abundant grass, they can select a higher value for maternal milk.

“However, no matter what part of the country you are in or what your production goals are, you still have to worry about a live calf being produced and then selling it at an efficiently produced, heavy weaning weight. These 2 factors can never really be taken out of the equation.”

More to consider

Once the EPDs are selected, the comparing starts and buying decisions are made. When evaluating animals, Perkins cautions ranchers not to get hung up on the actual values. Instead, take a look at where the animal ranks within the breed

by using percentile rankings from the breeds sire summary.

Percentile rankings are listed as percentages so that animals can be evaluated by where their individual EPDs rank in the breed. A 10 percentile ranking for weaning weight means the animal ranks in the top tenth percentile ranking of that breed, whereas a 90 percentile ranking means the animal ranks in the bottom tenth percentile ranking for weaning weight.

“Let’s say I want to simultaneously improve calving ease and increase weaning weight,” Perkins says. “Then I want the cattle to be in the top 25 percent for that percentile ranking for both EPDs. All of the other traits I want to keep in moderation, but the main traits being selected for should be in the upper percentile.”

Perkins advises that being in the top 1 percent for a trait is not always the most desirable. For example, maternal milk may be best at the fiftieth percentile. It is important to keep all traits balanced and not to use extremes. Perkins warns that not doing so is one of the biggest mistakes a cattleman can make.

By concentrating solely on a single EPD, antagonistic relationships between traits can quickly become a problem. For instance, stressing a high weaning weight may push the limit on birth weight for the cattle.

“I always tell breeders pick 3 to 4 traits that you are interested in, make them all meet a 25 percentile level, and then anything else above and beyond that is just icing on the cake.”

Understanding EPDs and using them in buying decisions takes time and education. There are many resources out there to further understand EPDs, such as the Beef Improvement Federation guidelines and ebeef.org. Perkins says breed associations are willing and able to help all cattlemen understand, as well. So don’t be afraid to call.

“EPDs are often underutilized because people get overwhelmed with so many numbers, and they think it is difficult to understand,” Perkins explains. “Once they understand that it is comparing one number to another number, between 2 animals, it is so much simpler.”

This article was originally published in The Cattleman Magazine by Texas and Southwestern Cattle Raisers Association.

The original article may be found here: http://www.thecattlemanmagazine.com/archives/2016/10/feature_1016_decodingEPDs.html