Understanding and Utilizing Expected Progeny Differences (EPDs)

What are EPDs?

Expected Progeny Differences, or EPDs, are statistical predictions used to estimate the genetic potential of an animal as a parent. EPDs are expressed as a difference between the expected performance of an animal’s progeny and the average performance of a different progeny across the breed. These estimates are generated through the collection of performance data, pedigree information, and, increasingly, genomic data.

For example, an Angus bull with a weaning weight EPD of +75 pounds indicates that his calves are expected to weigh 50 pounds more at weaning, on average, than calves from a bull with an EPD of +25 pounds for the same trait.

Breed associations continue to improve upon and make advances to the data they can provide producers in order to help them make the best decisions for their specific operation’s goals. The most recent research EPD for the Angus breed is Functional Longevity (FL). The purpose of this research EPD is to help further characterize relevant maternal traits with the goal of increasing the long-term success of profitability in cow-calf herds. Functional Longevity considers how long a sire’s daughter will stay in the herd and how many calves she will produce in her lifetime. The unit of this trait is the number of calves produced by the time the cow reaches six years of age. A higher EPD correlates on average to a higher number of calves produced (by six years of age), compared to a lower EPD.¹ Since Functional Longevity is still in the Research stage, you will not see it listed with the other EPDs that are updated weekly. Rather, it is shared periodically with the intent to gain feedback as a trait while collecting the vast amount of data needed before it is officially added as a trait to the Angus EPDs.

Challenges and Considerations When Using EPDs

While EPDs are powerful tools, they are not without limitations. Factors such as environmental influences and different management practices can affect the expression of traits. Therefore, it is crucial for cattlemen and cattlewomen to use EPDs in conjunction with visual appraisal, predictable pedigrees, and outliers amongst the individuals’ contemporary groups. The emphasis on specific traits can sometimes lead to unintended consequences. For example, selecting solely for rapid growth might inadvertently increase birth weights, leading to calving difficulties. This is why a balanced approach, considering all relevant traits, is essential.

EPDs are a tool to help enable cattle producers to predict and enhance desirable traits across generations. By understanding and utilizing EPDs, seedstock breeders and commercial cattle producers can continue to improve the quality, efficiency and longevity of their herds. As technology advances and more data gets turned into the different breed associations, the accuracy of EPDs will continue to increase.

Key Traits Measured by EPDs

Several key traits are measured by EPDs in cattle. Let’s take the Angus breed for example. These traits can be grouped into categories that relate to different aspects of cattle production. See the list below, where the traits are broken down into their respective categories for better understanding.

Production Traits

• Birth Weight (BW): Predicts the weight of a calf at birth.
• Calving Ease Direct (CED): Measures the likelihood of an unassisted birth in first-calf heifers. Higher CED EPDs are desirable for reducing calving difficulties.
• Weaning Weight (WW): Indicates the calf’s weight at weaning, around 205 days of age. A higher WW EPD suggests faster growth rates during the early life stages.
• Yearling Weight (YW): Reflects the calf’s weight at one year of age. Higher YW EPDs are associated with faster growth and larger mature sizes.
• Residual Average Daily Gain (RADG): Reflects the ability of an animal to gain weight efficiently. Higher RADG EPDs indicate better feed conversion and growth.
• Dry Matter Intake (DMI): Estimates the feed intake of an animal. Lower DMI EPDs are preferred for more efficient feed utilization.
• Yearling Height (YH): Expressed in inches, this EPD predicts a sire’s height at one year of age.
• Scrotal Circumference (SC): Reported in centimeters, this EPD predicts the adjusted scrotal circumference at one year of age.

 Maternal Traits

• Heifer Pregnancy (HP): Reported by percentage difference, this EPD shows the probability of a sire’s daughters becoming pregnant as yearlings during a normal breeding season.
• Milk: Expressed in pounds of weaning weight that is attributed to milk production. The higher the number, the “wetter” the udder.
• Calving Ease Maternal (CEM): Predicts the ease with which a cow’s daughters will calve. This trait is important for long-term herd management and cow longevity.

Management Traits

• Docility (DOC): The difference between cattle’s temperament - the higher number is better. We can all agree on that!
• Claw: Reported in units of claw-set score. The Lower the EPD, the better in terms of making a more symmetrically shaped and properly spaced front toes.
• Angle: Expressed in units of foot-angle score. The lower the EPD, the closer the foot angle is to 45 degrees at the pastern, with the proper amount of toe length and heal depth.

Carcass Traits

• Marbling (MARB): Predicts the amount of intramuscular fat, which contributes to meat tenderness and flavor. Higher MARB EPDs are desirable for producing high-quality beef.
• Ribeye Area (REA): Measures the size of the ribeye muscle, an indicator of overall muscling. Larger REA EPDs are typically sought after for better meat yield.
• Fat Thickness (FAT): Indicates the amount of external fat on a carcass. Lower FAT EPDs are often preferred to meet market demands for leaner beef.