Ranchers use a multitude of tools to make decisions to improve their herd genetics. One of the pieces of that is known as Expected Progeny Differences or EPDs. EPDs predict the likelihood of the parents to pass on certain genetic traits to its offspring. EPDs are calculated by using data submitted to each breed association. Ranchers record actual birth weight, weaning weights, and many more pieces of information, and that data is submitted to the breed association. The data and performance are also submitted for progeny and relatives. All of this data makes up the EPD. Breed associations keep large databases of all these submissions and compile the data to give the EPD. They are then expressed as a unit of measure for the trait, either plus or minus. Most EPDs are comprised of two numbers. For example, a Weaning Weight EPD of 23, would mean that this bull would produce offspring that would be 23 pounds heavier than the breed average at weaning. The EPD is normally also attached to an accuracy measure. This measure ranges from 0-1, and as the number approaches 1, the more accurate the EPD is. Accuracy is influenced by how many records went into that EPD. The more data submitted, the more accurate it is.
Ranchers are also able to do genomic testing. Genomic testing has evolved in recent years. It now includes “high-throughput” testing, which means that thousands of markers, or single nucleotide polymorphisms (SNPs) can be read from the animal’s DNA. All that producers need to submit to get these DNA tests is a drop of blood or hair follicles. The most common DNA test done on cattle reads about 50,000 DNA markers or SNPs. Genomic testing is a tremendous advantage for producers because many economically important traits like calving ease, feed efficiency, tenderness, dry matter intake, and more are controlled by many genes as opposed to a single gene like hide color. This means that these tests can make predictions about the genetic merit of an animal at a younger age than traditional EPDs. Under traditional EPDs, some of these would not be accurate until the animal has had ten offspring. Complex tests such as these can cost the producer about $80 per animal, but for many producers that cost is well worth it for the information it provides.
EPDs are able to be used for almost any trait you could imagine. A rancher who sells their calf crop at weaning might consider birth weight, calving ease, weaning weight, and yearling weight. As I talked two weeks ago, producers who save replacement heifers might look at these traits, but also some additional traits. We might also look at milk production, heifer pregnancy, stayability, maintenance energy, mature height, and scrotal circumference. Interesting fact, scrotal circumference is positively correlated with puberty and fertility in the bulls’ daughters.
EPDs are calculated within a certain cattle breed. It allows us to compare one animal to another based on the breed average. Some breeds have created cross breed analysis charts that allow us to compare between two breeds. You might have already thought about this, but some of these traits are influenced by the animal’s environment. For example, weather, elevation, and more can play into how fast an animal grows. In order to help manage these effects, breed associations ask ranchers to separate their calves into contemporary groups. Contemporary groups separate animals based on sex, age, and the environmental conditions they were raised in. This allows the breed association to compare data based on animals that had equal opportunity to perform.
Breed associations also publish a percentile ranking of any EPD they track. For example, you could look and see that a bull you might purchase is in the top 1% of all active bulls in that breed for weaning weight.
Why on earth should you care about this? You should care because this is directly tied to producing a better, more efficient end product. The more we improve our cattle genetics, the more sustainable we can be as ranchers. The United States beef business has increased its efficiency dramatically. In the 1970s, 140 million head of cattle were needed to meet demand. Now, only 90 million cows meet that demand. How? By utilizing genetic selection tools like EPD to produce a more efficient cow.
All these genetic selections also give you a better-quality product. We can look at EPDs to increase ribeye area, marbling, and more meat quality traits. We are able to bring the consumer a better tasting steak by utilizing these complete genetic and lineage-based data sources.