EPD Info

Guide to the American Gelbvieh Association Expected Progeny Differences (EPDs)

Expected progeny differences (EPDs) can be used to predict the average performance of a bull’s offspring compared to other calves in their contemporary group (a contemporary group being calves that were born in the same calving season, in the same year, herd, sex, and were managed similarly). EPDs are measured in the units of the trait, and show the differences in performance between animals. For example, if Bull A has a weaning weight EPD of 80, and Bull B in the same herd has a weaning weight EPD of 70, then bull A’s calves would be expected to be 10 pounds heavier at weaning than those of bull B.

It is important to remember that this number is just a prediction of performance. Actual performance depends on many factors such as environment, management, etc. This being said, an EPD is by far the most reliable indicator of an animal’s genetic merit due to the amount of information incorporated into the calculation.

The American Gelbvieh Association uses all available information to predict an animal’s EPD. This information includes: individual performance, pedigree, progeny and grand progeny performance, plus available genomic information. All this information is combined into one easy to use number for selected traits that helps breeders make genetic improvement in their herd.

Spring 2017 EPDs Released

The AGA released its Spring 2017 Genetic Evaluation run at 10:15 a.m. on January 2, 2017. As part of this run, the AGA included multiple updates to the blending equations used for incorporating genomic data into the EPDs received from the multi-breed International Genetic Solutions evaluation. Breeders can expect to see some changes in the values of genomic-enhanced EPDs (GE-EPDs) as a result of these updates, mostly on young animals without progeny. Average change in GE-EPD value depends on the trait and animal. For example marbling, a trait where drift was most evident in GE-EPDs prior to the update, experienced an average change of -.37 across roughly 12,000 animals with GE-EPDs in the AGA database due to the update.
As the AGA participates in re-training to further update our genomic equations, breeders can expect to see moderate incremental changes in their EPDs over the coming months. The progress made over time to genetic evaluation and to EPDs is astounding. EPDs that describe Gelbvieh and Balancer® cattle are more accurate than they have ever been and we continue to learn more about genetic evaluation as time goes on. Updates to the EPD blending equations are a result of the need to stay current in genetic prediction. These updates are very timely as we prepare for more frequent genetic evaluation runs in the spring and summer of 2017 in the single-step analysis through the BOLT system. The multiple evaluations per year will result in smaller incremental change per run than we see now in biannual evaluations.
Below are Spring 2017 breed average EPDs as well as summary documents including percentile rank.
AGA members are encouraged to call the AGA office at 303-465-2333 or email kario@gelbvieh.org with any questions you may have regarding the current or future national cattle evaluations.

EPDs_Breed Averages_spring 2017_for real

Spring 2017 Summary

Accuracy

In an EPD listing, an accuracy number is often published below its corresponding EPD. Accuracy is defined as the strength of the relationship between a prediction (EPD) and a sire’s true genetic value. In other words, accuracy is an indicator of the reliability of an EPD. Accuracy is improved by the number of records reported for an animal and with genomic information. For example, a three year old bull with 90 calves would have EPDs of higher accuracy than a virgin yearling bull. Accuracies range from zero to one, with numbers closer to one being more accurate.

EPD Definitions

Listed below are the definitions of American Gelbvieh Association EPDs and the units in which they are published. The EPDs with an asterisk (*) next to the name are available to members only.

Maternal traits

Calving ease direct (CED): Percent of unassisted births of a bull’s calves when he is used on heifers. A higher number is favorable, meaning better calving ease. This EPD can be vital to a rancher looking to decrease the amount of calves pulled in his herd.

Milk (Milk): The genetic ability of a sire’s daughters to produce milk expressed in pounds of weaning weight.

Calving ease maternal (CEM): Represented as percent of unassisted births in a sire’s first-calving daughters. A higher number represents more favorable calving ease. This EPD is important to a rancher’s bottom line because it predicts which animals produce daughters with a genetic pre-disposition to calve unassisted as heifers.

Heifer pregnancy (HP): Predicts the probability that a bull’s daughters will become pregnant as first-calf heifers in a regular breeding season, expressed as a percent. A higher value of this EPD is favorable, meaning that a higher percentage of a sire’s daughters get pregnant as first calf heifers compared to other sires in his contemporary group.

30-month pregnancy (Pg30): Predicts the probability that a bull’s daughters will become pregnant and calve at three years of age, given that they calved as first-calf heifers. This EPD is expressed as a percent, again, with a higher number being more favorable meaning a higher percentage of a sire’s daughters will calve at three years of age, given they calved as first-calf heifers.

Stayability (ST): Predicts the genetic difference, in terms of percent probability, that a bull’s daughters will stay productive within a herd to at least six year of age. The stayability EPD is one of the best measures currently available to compare a bull’s ability to produce females with reproductive longevity.

Growth traits

Birth weight (BW): Predicts the difference, in pounds, for birth weight of the calf.

Weaning weight (WW): Predicts the difference, in pounds, for weaning weight (adjusted to age of dam and a standard 205 days of age). This is an indicator of growth from birth to weaning.

Yearling weight (YW): Predicts the expected difference, in pounds, for yearling weight (adjusted to a standard 365 days of age). This is an indicator of growth from birth to yearling.

*Mature weight EPD (MW): Predicts the average difference in pounds of mature weight of a sire’s progeny compared to their contemporaries.

Carcass traits

Yield grade (YG): Differences in yield grade score, which is a predictor of percent retail product. Smaller values suggest that progeny will have a better lean to fat ratio.

Carcass weight (CW): Differences in pounds of hot carcass weight, adjusted to an industry standard age endpoint.

Ribeye area (REA): Differences in ribeye area in inches between the 12th and 13th rib. Greater ribeye areas are preferable.

Marbling (MB): Predicts the differences in the degree of marbling within the ribeye as expressed in marbling score units. Greater marbling numbers are preferable and are an indicator of higher carcass quality grades.

Fat (FT): Differences for fat thickness, in inches, for a carcass over the 12th rib, smaller numbers of fat thickness are preferable as excess fat can be detrimental to yield grade.

Efficiency traits

Dry matter intake (DMI): Represents the average daily dry matter intake per day consumed in pounds. A negative, or lesser value, is more favorable. For example, Bull A has a DMI EPD of .15 and Bull B has a DMI EPD of -.20, so the progeny of Bull B consume, on average, .35 pound less dry matter per day than progeny from Bull A.

*Average daily gain (ADG): Difference in average daily gain in pounds based on an animal’s performance during a feed intake test period.

*Residual feed intake (RFI): Defined as the difference between an animal’s actual daily feed intake and its predicted daily intake based on growth rate and body size. Animals with a positive RFI value are deemed more inefficient because they consume more than expected while animals with a negative RFI value are considered more efficient because they consume less than expected.

Indexes

Indexes are tools that allow producers to select for several EPDs at once, making selections more efficient than selecting on one trait at a time. Indexes weigh traits based on their importance to a producer’s bottom line by using a trait’s economic and genetic value. Indexes are a good way to put selection emphasis on traits that are economically relevant.

Total maternal (TM): An index that combines growth and milk information as a prediction of the weaning weight performance of calves from a sire’s daughters. As an index, this value is not reported with an accompanying accuracy. A greater TM value means a mother that returns comparatively higher weaning weights on her calves. TM Index = MK EPD + ½ WW EPD.

$Cow: Represents the genetic value in dollars of profit of an animal when retained as a replacement female relative to other animals in the herd. A higher number represents more profitable genetics for maternal productivity. $Cow will serve producers in selecting bulls that will sire daughters with stayability and reproductive efficiency as well as other traits that lead to profitability in a production system, such as milk, calving ease, moderate mature weight and the ability of calves to gain. A female’s genetics also influence the performance of her calves in the feedlot and at slaughter, so traits such as feed efficiency and carcass value are also included in $Cow.

Efficiency profit index (EPI): An economic selection index developed to aid producers in selecting for more feed efficient cattle that still have acceptable amounts of gain. The EPI provides slight negative pressure on intake, while keeping gain at a constant value. By selecting on this index, producers will be able to find those animals that gain the same amount as their contemporaries while eating less.

FPI: An economic selection index designed to aid producers in selecting sires whose progeny will perform in the feedlot and are sold on a grade and yield standpoint. Well ranking sires for FPI have higher marbling and carcass weight than their contemporaries. As a terminal index, little emphasis is put on maternal traits such as stayability and calving ease.

Across-Breed EPD Adjustment Factors

Table 1 below allows for bulls of different breeds to be compared on the same EPD scale by adding the appropriate adjustment factor to the EPDs produced in the most recent genetic evaluations for the 18 breeds in the table. These factors were first calculated by the U.S. Meat Animal Research Center (MARC) in Clay Center, Nebraska in 1993. They are currently updated annually at the Beef Improvement Federation annual meeting.

Across-breed EPDs (AB-EPDs) are very useful for commercial producers when purchasing bulls of more than one breed for a crossbreeding program.

Genomic Enhanced EPDs: Add Reliability to Your Tools for Genetic Improvement

In these challenging times in the beef business, we know that Gelbvieh breeders are always looking for more tools to make their management decisions more efficient and accurate. Beginning in 2011 with the inception on the Genomic Pioneers Project, the American Gelbvieh Association starting work toward yet another tool that made the EPDs produced in the NCE even more useful to producers.

The American Gelbvieh Association first incorporated genomic information into the summer 2013 genetic evaluation. Dr. Dorian Garrick of Iowa State University reported that a Gelbvieh/Balancer® specific panel of DNA markers can be used to develop genomic-enhanced EPDs (GE EPDs). The combination of database information and genomic data resulted in EPDs that roll the accuracy of a DNA test and the information of individual, pedigree, and progeny performance into one, easy to use number.

Using GE EPDs can help your operation in three ways:
1. Increasing accuracy
2. Reducing risk by reducing possible change
3. Increasing rate of genetic change
Increasing accuracy
On young animals without individual or progeny performance records, genetic merit is estimated in the form of an EPD calculated by taking the average breeding value of its parents (VanEenennaam, 2009). This results in an EPD with a low accuracy calculation. The addition of genomic data to an EPD calculation is comparable to adding another source of information, like progeny or pedigree records. Specifically on lowly heritable traits, such as reproduction, genomic data has the potential to greatly increase the accuracy of an EPD prediction.

Reducing Risk
EPD estimates on an animal increase in accuracy over time as observations on an animal’s own performance and that of its descendants are added to the calculation. It follows that EPDs on young animals with very little accuracy have the possibility to change a great deal over time. Possible change is another measure of accuracy that indicates the amount of future change in an EPD prediction (Bourdon, 2000). This possible change can add risk when producers use young animals in their breeding herds, because the true merit of the genetics those animals will pass to their offspring is basically unknown. GE EPDs help to reduce the amount of error between the difference in an animal’s true genetic merit and its predicted genetic merit (in other words, an EPD). Confidence in an animal’s EPDs earlier in life means that producers can more reliably predict the performance outcomes of using unproven animals in their breeding herd.

Increasing rate of genetic change
The rate of genetic change in an operation is dependent on four factors:
1. accuracy of selection
2. selection intensity
3. genetic variation
4. generation interval

GE EPDs affect two factors in this equation: accuracy of selection and generation interval. We have already discussed how genomic data improves accuracy by adding another piece of information to EPD calculations. DNA information is also valuable because it can be collected at birth or soon after and added to an animal’s EPD calculation right away, which gives producers a better idea about that animal’s genetic merit at a younger age. Using this genomic enhanced information as a culling tool can help breeders decrease the generation interval in their herds, thereby speeding the rate of genetic change. This is a benefit to producers because it will allow more progress in their breeding goals in a shorter amount of time.

Just a few notes
-Genomic information is not a replacement for phenotypic information on an animal. Remember, genomic data is just another source of information to make an animal’s EPD estimations more accurate. Phenotypes such as birth weight, weaning weight, and calving ease are still needed to make the equation we use to predict GE EPDs as accurate as possible.
For more information on GE EPDs, call the office at 303-465-2333.

References
Bourdon, 2000. Understanding Animal Breeding. Prentice Hall. Upper Saddle River, NJ 07458.
Van Eenennaam, A. 2009. Marker Assisted Selection. University of California Extension.