Expected progeny difference
This article provides insufficient context for those unfamiliar with the subject.(June 2022) |
Expected progeny differences (EPD) are an evaluation of an
Types of EPDs
An example of a set of EPDs looks like the following chart. Each set of letters stands for a specific measurement with an accuracy reading and percent rank below it. Each EPD is compared to the breed average of a given year. The number given by the EPD is the amount above or below this given average.
CE | BW | WW | YW | MCE | Milk | MWW | Stay | CW | YG | Marb | Fat | REA | API | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
EPD | 8 | 1.8 | 44.5 | 84.3 | 4.4 | 3.4 | 25.6 | 18.2 | 15.4 | .09 | .02 | .00 | -.05 | 104.4 |
Acc | .32 | .75 | .72 | .68 | .18 | .31 | .32 | .11 | .52 | .33 | .32 | .43 | .29 | |
%Rank | 10 | 3 | 15 | 4 | 20 |
Growth EPDs
Growth EPDs measure the amount of weight a given offspring will gain due to the parent's genetics.
Birth weight measures how much above or below the breed's average an offspring will gain due to the parent. It does not necessarily predict the exact weight of all offspring, but instead gives a general prediction of how much extra or less weight an offspring will weigh compared to if it had been sired by another bull. High birth weight is the biggest cause of difficulty in calving, so having a bull with a low birth weight EPD is high beneficial.[1]
Weaning and yearling weight measure the amount of weight an offspring has gained by the time it is weaned and at the one year mark. Typically the weaning weight is measured at the 205-day mark and the yearling weight is taken at the 365-day mark. Typically a larger number is favored for both of these traits.[2]
Milk EPDs give an estimate for the maternal portion of the weaning weight that determined by
Reproductive EPDs
Scrotal circumference is an indicator of a bull's fertility. A larger circumference is preferred and is an indicator for his sons to have a larger scrotal circumference and his daughters to reach puberty sooner and therefore have calves sooner.[2]
Stayability is an indicator EPD of
Carcass EPDs
Use and accuracy
EPDs are used in both
To determine how accurate EPDs are for an individual, samples of all of a bull's offspring are looked at and compared to what their expected outcome should have been. The EPDs can then be changed based on the values that are gathered. The higher the accuracy rate, the closer most of the progeny will be to the EPD values listed. Accuracy is not an indicator of beneficial EPDs, but rather shows how close the EPD is to the true genetic potential of the animal.[2] The closer an accuracy value is to 1, the more accurate the EPDs can be thought to be. Other factors can affect the progeny as well, such as non genetic effects including feed, weather, environment, as well as random Mendelian sampling.
In addition to the EPD and accuracy shown in a chart, often the percent rank is also given. This shows what percentile the animal ranks for the given EPD. The higher the percentile, the better the EPD is for that characteristic. The better the EPDs for a given bull, the higher chance its progeny will have a given characteristic.[5]
References
- ^ a b Understanding Expected Progeny Differences (EPDs). Scott P. Greiner, Extension Animal Scientist, Virginia Tech.http://pubs.ext.vt.edu/400/400-804/400-804.html
- ^ a b c d e f Janice M. Rumph (7 June 2023). "Interpretation and Use of Expected Progeny Differences (EPD)" (PDF). Pfzer Animal Genetics.
- ^ a b c Understanding and using Expected Progeny Differences (EPDs). Brett Barham, PhD. Extension Livestock Specialist at University of Arkansas. http://www.uaex.edu/Other_Areas/publications/PDF/FSA-3068.pdf
- PMID 16478961.
- ^ Drennan M. J., McGee M. (2008). "Effect of beef sire expected progeny difference for carcass conformation on live animal muscularity scores and ultrasonic muscle and fat depths, and on carcass classification and composition of their progeny". Irish Journal of Agricultural & Food Research. 47 (2): 161–170.