Expected Progeny Differences (EPDs)

Excerpts from “Cattleman’s Handbook for Expected Progeny Differences”
-by James S. Brinks

Identifying the genetic worth of animals allows cattlemen to more quickly genetically engineer the type of cow herd and progeny that fit their ranch resources, market, and overall goals. The computation of EPD values allows for the most accurate evaluation of the genetic worth of cattle for many economically important traits. Although the theory is complex and the computations are difficult, the results are relatively easy to interpret and use.

Most breed associations publish sire summaries that list EPD values of sires for may traits. EPD values are also calculated for dams and young animals. This increased accuracy in identifying the genetic worth of animals along with their subsequent use in selection programs should speed up the attainment of the breeder’s pre-set goals. It allows the breeder to obtain optimum values for the cow herd in terms of growth, mature size, and milk production level, or to change traits in the desired direction. For commercial cattlemen, an optimum breeding program should aid in obtaining optimum production and maximum profit.

Breeding value is the genetic value of an animal as a parent.

Expected progeny difference is the difference in performance that is expected from future progeny of a parent compared to the expected performance of future progeny of all other parents evaluated in the analysis when bred to mates of equal value. The EPD value is one-half the breeding value, since a parent passes on only a sample half of its genes to its progeny. These EPD values are reported as plus and minus deviations from a zero base point in units of the trait.

Maternal EPD relates to those traits that are maternally influenced and expressed only by the female, e.g. milk production. Both the sire and dam transmit genes for maternal traits to their female progeny.

Total Maternal EPD is calculated for traits that are both directly and maternally determined, such as weaning weight.

Interim EPD calculated for young animals from EPD values of its sire and dam plus its own performance and contemporary group information for the trait. It is an estimate of future progeny performance since these young animals have not yet produced progeny.

Pedigree EPD estimated as the average of the sire and dam EPDs or EPD young animal = _ EPD sire + _ EPD dam. This may be a useful guide when making specific matings, or when purchasing bulls that only have EPD information on parents or grandparents.

Accuracy value is calculated for each parent EPD and is a measure of reliability of the EPD value. Accuracy values depend on the amount and distribution of information.

Contemporary Groups ­ Cattle performance should be compared within groups of cattle of the same breed, born in the same year/season, at the same location (herd), of the same sex, and managed alike from birth until the time of measurement (same feeding regime, date of measurement, etc.). The percent of breed is also included for those breeds that are in the process of grading up, e.g. 50%, 75%, 88%, 100% groups; this grouping varies with the breed. Age restrictions are usually included for weaning weight and yearling weight. Age range for weaning weight recommended at 160 ­ 250 days and for yearling weight 330 ­ 400 days for cattle to be in the same contemporary group.

EPD Base Point is determined by the EPD values of the foundation animals in the analysis. Foundation animals are those without a parent or parents pedigree(s) in the analysis. The base point would change with new analyses if new animals without parents in the previous analyses were added (i.e. breeds that are grading up to purebred status or when new animals are added to the data set and their parents were not included in previous analyses).

The most important information is the difference between EPD values, not the absolute value.

Before one can use EPDs effectively, one must determine the direction of the breeding program and establish goals. Seedstock producers need to establish goals that will fulfill the needs of their clients.

Consumers are asking for leaner beef while maintaining quality and tenderness. Feedlots emphasize growth and efficiency. Developing a cow herd compatible with availability and cost of feed resources should be a primary goal of commercial cattlemen.

Percentile Charts (as explained in 2003 ASA Sire Summary) can be utilized to compare an individual to the entire group of Salers cattle. You may wish to see where a specific sire in this listing ranks within the population of sires in the breed. The bull you want to compare has a +25 WW EPD. You would look under the WW EPD column in the Sires A (Top 50) listing and find that he is in the top 25% of the top 50 sires for that trait. A dam would reference the Top 50 Dams listing.