Expected Progeny Differences (EPDs) provide the best means of comparing genetic merit of animals within the breed. For each trait evaluated, the EPD incorporates the animals within the breed. For each trait evaluated, the EPD incorporates the animal's individual and progeny performance with progeny performance information from other relatives. By utilizing national sire evaluation information, the evaluation also utilizes information from related traits and accounts, in part, for differences in the genetic merit of herdmates as well as genetic trends within the breed. Each trait evaluation predicts expected progeny performance relative to a fixed breed average - hence the term "Expected Progeny Difference." The key word is "difference". The EPD itself does not imply "good" or "bad" performance, only whether the performance of progeny is expected to be above or below that of progeny from average parents. Breeders should, on an individual basis, decide what is best for them by considering what traits are important to their program, their current herd performance, and the degree of change desired.
Accuracy (acc): A measure of certainty regarding the EPD evaluation for a performance trait. Accuracy is reported as a decimal number between zero and one; larger values indicate greater accuracy and more certainty that the EPD will not change significantly as additional progeny information is obtained. Accuracy values of less than .20 are typical for non-parent bulls. Birth Weight EPD (BW): The expected difference in average birth weight (lbs.) of progeny. Birth weight reflects prenatal growth potential and may also be used as an indicator of calving ease. Calving Ease (CE): The ease with which a bull's calves are born to first-calf heifers. When comparing two bulls, the larger EPD indicates a higher percent of unassisted births for calves sired by this bull. Weaning Weight EPD (WW): The expected difference in average weaning weight (lbs.) of calves. The evaluation reflects genetic influence on pre-weaning growth rate. Yearling Weight EPD (YW): The expected difference in average yearling weight (lbs.) of progeny. The evaluation reflects genetic influence on pre-weaning and post-weaning growth rate. Maternal Milk EPD (Milk): The expected difference in average weaning weight (lbs.) of daughter's calves, which is attributed to milking ability. In other words, is a predictor of a sire's genetic merit for milk and mothering ability as expressed in his daughters. Carcass Weight (CW): The expected difference, expressed in pounds, in the hot carcass weight of a sire's progeny at a given end point compared to progeny of an average sire. Marbling EPD (Mrb): The expected difference, expressed as a fraction, in a subjective USDA marbling score of a sire's progeny at a given end point compared to progeny of an average sire. Ribeye Area EPD (RE): The expected difference, expressed in square inches, in ribeye area of a sire's progeny at a given end point. Fat Thickness EPD (Fat): The expected difference, expressed in inches, in external fat thickness at the 12th-13th ribs of a sire's progeny at a given end point compared to progeny of an average sire. Percent Retail Product EPD (Fat): The expected difference in pounds of salable retail product of a given sire's progeny compared to the progeny of an average sire.
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