Expected Progeny Differences Epds in Beef Cattle

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Expected Progeny Differences (EPDs) in Beef Cattle1

nineteen October 2006

By Hansen, G.R., Assistant Professor of Beast Scientific discipline, Academy of Florida, NFREC Marianna, and Riley, D.G, Enquiry Geneticist, Subtropical Agriculture Enquiry Station Brookesville.

Table of Contents

Await Progeny Departure
Genetic Trends
Average Breed EPDs
Accuracy
Practise EPDs Work?
Using EPDs
Contemporary Grouping
Percentile Ranking
Summary
Product Traits

Expected Progeny Differences (EPDs) were developed to provide cattle producers with an effective tool to evaluate prospective breeding stock. As the name implies, EPDs predict the performance of future offspring from an individual fauna. More specifically, EPDs predict the genetic transmitting ability of an individual as a parent. Using EPDs tin can increment the rate of genetic progress in a selection program. National Cattle Evaluation (NCE) models include:

Operation records of the individual, parents, progeny, and relatives

Contemporary group adjustment for ecology and management grouping effects

Calculations incorporating genetic relationships (correlations) between traits.

Adjustment for differences in relative merit of a contemporary grouping

Adjustment for genetic merit of females/males mated to individual breeding animals (elimination of bias due to an animate being being bred to individuals that are superior or inferior in terms of genetic merit).

Adjustments for genetic trend.

Look Progeny Departure

An EPD is a prediction, based on current information, of one-half the breeding value of the fauna that is predicted to exist passed on to its potential progeny. EPDs are used to evaluate the genetic merit of individuals when used in a breeding plan. Equally an example, the difference in EPDs between two bulls is an estimation of deviation in performance of their progeny provided they were bred to cows of equal merit and their progeny were subject to the same environmental atmospheric condition. Although the statistical models used to summate EPDs are cumbersome and require big computational systems, the end issue is a unmarried value that allows for the direct comparison of animals inside a brood. Some basic principles must exist followed in club for EPDs to be used wisely in a genetic selection program.

Showtime, EPDs are specific to a breed and analysis date. Do not compare individuals from ane brood to some other breed unless using a cross-brood EPD adjustment factors. Second, do non compare EPDs that were generated in prior sire summaries to EPDs generated in a current summary because EPD values will modify between analyses. Third, keep in listen EPDs are predictions based on averages. Reiterating from above, if two bulls are bred to cows of equal genetic merit and are subject to the same environmental conditions, so their progeny on average would exist expected to differ for the selected trait according to the difference in the EPD values. Using weaning weight as the instance, progeny from bull A with a weaning weight EPD of +40 lbs and balderdash B with a +30 lbs, so bull As progeny on boilerplate would be expected to be 10 lbs heavier at weaning than bull Bs progeny. Using weaning weight as an case, if bull A with a weaning weight EPD of + 40 lbs and bull B with a + 30 lbs where mated to cows of equal genetic merit, nosotros would expect bull A's progeny on boilerplate to exist 10 lbs heavier at weaning than bull B'south progeny. Consider the EPDs for the bulls in Table i.

Table ane. Growth Trait EPDs for Two Bulls.

When the two bulls are compared, nosotros would expect calves from bull A to counterbalance 4 lbs more at birth, and to be 12 lbs heavier at weaning and 18 lbs heavier as yearlings. This does not hateful that bull A would increment birth weight 5.6 lbs, add 44 lbs at weaning and or add 96 pounds at yearling within a herd. These changes would depend on the boilerplate EPD (production) within the producer's herd. For instance, if the average EPD in the producers herd for nativity weight was 4.0 lbs, then bull A would be expected to increase birth weight past +1.6 lbs within this particular herd. Nevertheless, it is hard to calculate an accurate average herd EPD because animals with various accuracy values would be included in the calculation.

Genetic Trends

Over time, EPDs within breed associations' National Cattle Evaluation's change as producers emphasize unlike traits in order to build upon strengths or weaknesses that are inherent in a breed. This type of selection results in genetic trends being established from year to year. For example, breeds that have big birth weights would have a goal to reduce nascency weight inside their herds, making the genetic trend for birth weight negative. Breeds with low growth rates would select for increased growth thereby causing the genetic trend for growth traits to be positive. Genetic trend is important because it indicates which direction the breed is moving in for various traits.

Genetic trend can be best illustrated in an example from the Hereford Breed Association (Table 2). Notice that average birth weight EPD increased from 1975 to 2000 by 4.2 lbs merely birth weight remained the same from 2000 to 2005, indicating that nativity weight has leveled off and is being maintained at current EPD levels in the Hereford brood. On the other hand, EPDs for weaning weight, yearling weight, milk and scrotal circumference accept increased 31.6 lbs, 56.7 lbs, 12.8 lbs and 1.5cm, respectively. This demonstrates that breeders are selecting animals that will increment EPDs in these traits. Genetic trends are available for all of the major brood associations and should exist used to determine if a specific breed is moving in a manner consequent with producers' goals.

Table 2. Hereford Genetic Trend past Nascency Year.

Boilerplate Breed EPDs

All EPDs are reported relative to a base population. Each breed's base year is arbitrary. Nigh bases are obtained by forcing the EPDs for all animals in a detail year to sum to zero. Therefore, EPDs reported on animals built-in in the current yr are relative to average genetic merit of animals born in the base of operations year. Breed associations publish the current average breed EPDs with each assay to assist producers in determining the merit of immature animals in the breed. An animal with a 0.0 EPD would not necessarily be at the current breed average. Tabular array iii lists current average breed EPDs for several breeds. Find that an Angus born in 2006 with a nativity EPD of +2.3 would be average for birth weight EPD, while a bull with a 0.0 EPD would be beneath the current average. Livestock producers should become familiar with current breed EPD averages for the breeds that they utilize in their breeding programs.

Tabular array three. Electric current Brood Average EPDs of Active Sires (2005-2006).

Accuracy

While EPDs are the all-time estimates of an creature'due south genetic transmitting ability, in that location is nevertheless margin for error or a possible alter associated with the estimates. Accuracy values are published with an EPD to help signal the corporeality of adventure an individual will take when using an animate being in a breeding plan. Accuracies reported in National Cattle Evaluations are correlations and range from cipher to 1 with larger values indicating less risk of an EPD changing as boosted data is included in the assay. Accurateness is a reflection of the number and distribution of progeny per sire along with how much pedigree information is available. Accuracy values give us an indication of how close our estimates are to an animals truthful genetic value. Tabular array 4 shows how much an EPD for a Charolais sire could peradventure change equally more than information (private performance and future progeny) is included in the National Cattle Evaluations.

Tabular array 4. Possible Change in EPD Values at Different Accuracy Levels (AICA Spring 2005).

Accuracy values(ACCs) are extremely useful to breeders in determining the reliability of an EPD. Notice that as ACC level increases, the possible modify value decreases. Still, an EPD tin change from twelvemonth to year even though it may have a high level of accuracy. The indicate to remember is that the expected change of an EPD with a high accuracy value is correspondingly less than that of an EPD with a lower accurateness value.

The possible change of identical EPDs, given dissimilar levels of accuracy can be seen in the post-obit example of two Charolais bulls. Two sires have yearling weight EPD of +30, simply differ as to accuracy value. Figure 1 illustrates the possible range within which the true genetic value is. Sire A has an accurateness of .40 with a possible alter value of 23 lbs, and sire B has an accurateness of .fourscore with a possible change value of 8.5 lbs.

Accuracy values assistance determine the corporeality of risk associated with genetic repeatability, simply they are not foolproof. The tabular array in a higher place shows the possible alter values of an EPD with a given accuracy value (ACC). Approximately 70 percentage of the fourth dimension the EPD should non deviate outside of these parameters. In other words, the true value should fall within the EPD ± one possible modify value.

Even though both sires have an EPD of +thirty lbs for yearling weight, sire B has a college reliability that his true genetic value is within the narrower range of 21.5 lbs to 38.v lbs (30 ± 8.5) while sire A's true genetic value is within a larger range from 7 to 53 lbs (30 ± 23).

The accuracy of a given EPD tin can help make up one's mind the amount of risk a breeder is willing to take when making breeding decisions. Let u.s. compare the sires in the example over again. Which sire is more desirable for your breeding program? The sire with the high accuracy is more than predictable, only the amount of genetic change that tin can be made is correspondingly express as well. Sire A has the same yearling EPD, but his true genetic value may exist across that of Sire B. Therefore Sire A could possibly increase the amount of genetic progress made, but he is also more than of a risk considering his truthful genetic value falls within a wider range.

Cattle producers should use EPDs to decide which individuals to use and should utilise accuracy values to determine how extensively an individual should be used in a convenance program. Bulls with low accuracies should be used on a express basis while bulls with high accuracies can be used every bit deemed necessary. Tabular array 5 summarizes accuracy values in relation to associated risk. Bulls with accuracy values of less than .xl are considered high chance because their EPDs accept a loftier probability of changing equally more data is included in the analysis. On the other hand, bulls with accuracy values greater than .fourscore take a low probability of changing considering large quantities of information were included in the calculation of the EPDs.

Table 5. Levels of Accuracy and Associated Risk.

Do EPDs Work?

Numerous studies take verified that selection using EPDs produces beneficial effects, particularly with weight traits. Researchers in Georgia selected bulls within the top one percentile for yearling weight EPD over a six-year period. Heifers from these sires were returned to herd and their performance was compared to a control group. At the finish of the study, 70 % of the base cows had been replaced past the selected heifers. Progeny for the selected heifers was 95 lbs heavier at yearling compared to control fauna progeny. They too were 68 lbs heavier at weaning, yearling hip acme increased 2.four inches and birth weight as well increased 6.8 pounds. Results of this written report indicate out that it is imperative to know the genetic correlations that exist between traits as a correlated selection response in a related trait tin atomic number 82 to problems. Researchers in Virginia found similar results when comparison two sire groups with average differences in EPD of ii.ii lbs for nascency, 9.nine for weaning and 13.ix for yearling. Differences in progeny performance were four.7 at birth, 16 lbs at weaning, and 26 lbs at yearling.

In a large purebred operation in Texas, bulls were ranked according to EPD value and actual performance for several traits. Only bulls with loftier EPD accuracy values (80%) were included in the data set. Notice that in almost all cases the bulls ranked the aforementioned when comparing actual performance averages to EPD values (Table half dozen). Using the same data, predicted differences using EPDs were compared to bodily performance differences (Table 7). In all comparisons actual performance was close to the predicted operation divergence.

Table 6. Rank Comparison of EPD and Actual Performance.

Table seven. Predicted Difference VS. Actual Operation Difference of Two High Accuracy EPD Bulls (>ninety%) Mated to Cows of Similar Genetic Merit.

Several other studies have verified that selection using EPD is the most accurate and quickest mode to brand genetic change in a beefiness cattle operation. However, common sense must be used when using EPDs in a beef cattle operation to reach optimum results.

Using EPDs

Using EPDs in a beef cattle functioning tin can best be illustrated with an case. Suppose six cattle producers are identifying sires to use in their breeding programs. The production objectives for each producer are listed in Tabular array eight. Bulls available to meet the production objectives are quantified in Table ix.

Selection/ Goals	CED	BW	WW	YM	MM	SC	Fat	REA	Imf
1. Maximize growth with no replacements kept (terminal cross).	none	none	maximise	maximise	none	none	none	none	none
2. Meliorate growth maintain milk	none	none	maximise	maximise	15-20	none	none	none	none
3. Inseminate yearling heifers/minimize dystocia while maintaining growth.	>3.0	<0.8	30-38	threescore-65	fifteen-20	none	none	none	none
4. Ameliorate weaning weight while property moo-cow mature size now levels. Post-weaning growth is acceptable. Calves sold at weaning. Cows maintain adequate condition with trivial supplementation.	none	none	38-42	sixty-70	25+	none	none	none	none
five. Meliorate carcass quality along with increased growth potential of offspring.	none	none	xl+	60+	none	none	none	none	0.15+
6. Save replacement heifers and decrease age of puberty inside the herd. Current levels of production for calving ease, weaning and post-weaning gain are acceptable	>0.3	<3.7	38+	65+	25+	>0.7	none	none	none

Table eight. Matching EPDs to Production Goals

Table 9. EPDs for Prospective Sires.

Producer 1 would benefit most from growth potential as long as other production traits practise not become excessive. Milk production is irrelevant since all calves volition be sold to slaughter. Bull A would be the most probable choice.

Producer two would consider bull D as his/her nearly likely choice.

Producer 3 would consider bulls B or C depending on the size and maturity of the heifers that will be inseminated. Bull C would be the nearly likely bull to utilize in pocket-sized-framed, early-maturing heifers, while balderdash B could be used in moderate to large-framed heifers.

Producer four would benefit most from milk production. Cows are currently maintaining adequate status and dogie functioning is acceptable. Bull E would exist the virtually logical choice.

Producer 5 would consider a bull that combines growth rate with carcass quality. Bull D is above average for growth and carcass quality, which would make him the logical selection.

Producer 6 would consider Bull B or E. Which bull to use would depend on the feed resources bachelor to the producer. If feed resources are limited, then bull B would exist the virtually likely choice. Withal, if cows are able to maintain to a higher place average condition on the available resources, and so balderdash E would exist the most probable selection.

Most all breed associations have computer sire sorts that allow producers to set independent culling levels (ICLs) for the various traits of interest. In one case the ICLs are determined, the producer can search the brood's database for bulls matching the criteria. Sires matching the ICLs are identified and the producer can then select which sires he/she wishes to use. Using ICLs for five traits generated the information in Table ten. Searching for sires using an ICL allows producers to quickly identify bulls that will come across their product goals. Producers should evaluate the bulls that the search returns to insure that calves from these sires volition exist functional in their herds.

Table ten. Contained Culling Levels for V traits and EPDs for Three Sires That Match Those Levels

Gimmicky Grouping

A contemporary group is a fix of animals that accept been similarly managed, are of the same historic period and gender, and were exposed to the same environmental conditions, assuasive each animal an equal opportunity to perform. This is the best way to account for ecology effects leaving the remaining differences amongst animals to be genetic. Proper contemporary group is crucial for genetic evaluation. Improper grouping of contemporaries is the number ane mistake in NCEs. Any brute that has been removed (temporally or permanently) or treated differently from the rest of the group needs to be eliminated from the contemporary grouping to insure bias is not introduced. The following guidelines should be used to insure correct contemporary group.

Contemporary Group:

Include but animals of the same gender. Heifers, bulls and steers should have their own contemporary group.

Two animals are required to course a contemporary grouping, however at least 10 animals are needed to form a useful contemporary group. Larger contemporary groups volition generate more than valuable information for breeders.

Insure that all animals within a gimmicky group were built-in in a 90 -mean solar day period. Group in smaller time periods (30 days) is advisable if sufficient numbers of calves are available to form a contemporary grouping.

Animals weighed more three days apart should be split into different contemporary groups.

Artificial and natural service sired calves should be grouped separate from embryo transfer calves. Calves from registered cows and commercial cows should be grouped separately.

Percentile Ranking

Breed associations publish percentile ranks for EPD values within a given brood. This allows producers to determine acceptable minimum and maximum levels for each trait in his selection program. Once production goals and objectives are established, then advisable sires can be selected using EPDs from the percentile rank to match each targeted trait. For Case, a bull with a -2.4 birth weight EPD would rank in the top ane% of all the active sires. Table 11 lists percentile breakdown for active sires in the Angus breed.

Table 11. Percentile Breakdown Current Sires (Angus 2006)

Summary

When selecting breeds and animals within breeds, consideration needs to be given to where animals will be raised and marketed. Market participation is becoming as much a function of the equation in today's beef manufacture every bit the surroundings. Knowing how to optimize resources for your particular herd with regards to environmental constraints, while targeting animals that will be able to compete in the marketplace volition be crucial to surviving in the beef cattle industry. Target your market and then piece of work backwards to place the right animals. To summarize how to use EPDs in your breeding plan, consider the post-obit points:

1. Know where your cow herd is in relation to your targets, while understanding that your cow herd withal has to produce in your environment. Keeping accurate records will help to identify what are the strengths and weaknesses of your cow herd.
   
2. Identify the point in the production chain where offspring will exist marketed. Different market end points will determine breeding objectives. Producers selling calves at weaning will use different sires than those selling at yearling or slaughter stop points.
   
3. Identify the breeds and animals inside those breeds (primarily bulls) that will movement the moo-cow herd in the right direction to optimize production within the environment. Producers must be realistic and practical to insure selection of the correct type of animals.
   
4. Insure that EPDs are used in the manner they were intended to exist used. Compare EPDs for the same sire summary or analysis. Realize that EPDs are estimates and will change equally new information becomes bachelor. Avert animals with extremely high or low EPDs for the traits that yous are selecting for. Remember to use common sense when using EPDs. They are tools which when used properly tin aid producers in reaching their product goals.
   

Production Traits

All breed associations generate nascence weight (BW), weaning weight (WW), yearling weight (YW) and milk EPDs. From here almost all of the breeds diverge with respect to what EPDs are generated. Listed beneath are descriptions of each EPD.

Four traits are routinely reported by brood associations that conduct National Cattle Evaluation analyses:

BW (Nascency Weight) - The birth weight of a sire'southward progeny when compared to the brood average, in pounds.

WW (Weaning Weight)- Weaning weight in pounds adjusted to 205 days excluding maternal effects (evaluated every bit milk).

YW (Yearling Weight) - Yearling weight in pounds adapted to 365 days excluding maternal effects.

Milk - A mensurate of the pre-weaning performance, pounds of calf attributed to the milking ability of a sire's daughters. The use of the term milk is inaccurate considering the trait measures all maternal furnishings of which milk is the major , but not the but, factor.

Traits reported by various breed associations include:

CE (Calving Ease) The ease with which a sire's calves are built-in. Expressed in a pct of unassisted births. Larger positive numbers indicate greater calving ease. Determined largely by the weight of the calf. (Gelbvieh and Simmental)
CED (Calving Ease Directly) Predicts calving ease of a sire when mated to heifers. Expressed as the difference in percentage of unassisted births, with a college value indicating increased calving ease in first-calf heifers. (Angus, Charolais, Gelbvieh, Hereford, Limousin and Red Angus)
CEM, MCE (Calving Ease Maternal, Maternal Calving Ease) Predicts calving ease in a sire's first-dogie daughters in comparison to other sires included in the evaluation. Expressed equally the difference of unassisted nativity in unlike sires' daughters when calving as first-calf heifers. (Angus, Charolais, Gelbvieh, Limousin and Simmental.)
CETM (Calving Ease Total Maternal) Describes differences in percent probability of a sire's daughter calving unassisted. (Red Angus and Hereford.)
CW (Carcass Weight) The adapted carcass weight of a sire's progeny expressed in pounds. (Angus, Brahman, Brangus, Charolais, Gelbvieh, Hereford, Limousin, Scarlet Angus, Simbrah and Simmental.)
Doc (Docility) Measure out of an fauna'southward temperament, nervousness and flightiness when handled. (Limousin.)
Fatty (Fat Thickness) Backfat thickness measured over the ribeye at the 12th/13th rib. Used every bit a predictor of total trunk fat being the major gene in calculating yield class. (Angus, Brahman, Brangus, Charolais, Gelbvieh, Red Angus, Simbrah and Simmental.)
GL (Gestation Length) The interval from conception to parturition measured in days. (Gelbvieh.)
HPG (Heifer Pregnancy) Describes the departure in per centum probability of female person progeny conceiving every bit two-year-olds. (Blood-red Angus.)
International monetary fund (Intramuscular Fat) Reflects differences in 365 twenty-four hour period adjusted intramuscular fatty measured over the 12th and 13th rib in live cattle using ultrasound. (Angus, Charolais [included in marbling EPD] Limousin and Hereford.)
ME (Maintenance Energy) Differences in mature cow maintenance energy requirements based on megacalories expended per month. (Red Angus.)
MARB, MB (Marbling) 365-24-hour interval adjusted marbling score measured in USDA marbling degrees. Primary cistron in USDA quality grades. (Angus, Brahman, Brangus, Charolais, Gelbvieh, Limousin, Red Angus, Simbrah and Simmental.)
MH (Mature Height)-Measured in inches-is a predictor of the difference in mature height when comparing daughters of ii sires. (Angus).
MW (Mature Weight) Measured in pounds A predictor of the departure in mature weight when comparing daughters of ii sires. (Angus.)
G &One thousand, TM, MWW (Milk and Growth, Total Maternal, Maternal Weaning Weight) Measure of a sire's power to transmit milk production and growth charge per unit through his daughters. It predicts the total weaning (direct and maternal) that will be displayed in his daughters offspring. It is calculated by summing half of the weaning weight EPD with the milk EPD ([1/ii WWEPD] + MWW EPD). Can exist calculated for all breeds participating in NCE.
REA, RE (Ribeye Area) Rib middle area measured in square inches between the 12th/13th rib and adjusted to 365 days. A good predictor of full amount of muscle in the carcass and highly related to carcass weight. (Angus, Braham, Brangus, Charolais, Gelbvieh, Limousin, Red Angus, Simbrah and Simmental.)
%RP (Pct Retail Production) Predicts the divergence in pounds of saleable retail product between different sire's progeny. (Brahman.)
SC, SCR (Scrotal Circumference) Predictor of sperm-producing tissue as measured in centimeters. Scrotal circumference is highly related to age at puberty in male person and female progeny. (Angus, Brangus, Beefmaster, Charolais, Gelbvieh, Hereford and Limousin.)
SHR (Shear Strength) A predictor of meat tenderness measured in pounds of force required to shear a steak. (Brahman and Simmental.)
STAY, ST (Stayability) Predicts the probability that a sire's daughters will remain in the herd until at least vi years of age. This measures a moo-cow's ability to remain in the cow herd, thereby involving reproductive efficiency, structural soundness, easy keeping ability equally well and growth parameters in her offspring. (Gelbvieh, Limousin, Red Angus and Simmental.)
UFAT (Scan Fatty, Ultrasound Fat) Backfat thickness measured over the ribeye at the twelfth/13th rib using ultrasound imaging (Angus, Brangus, Charolais and Hereford.)
YG (Yield Course) Expressed as a deviation of yield form units where negative values are desirable. As an example, a bull with a -.50 YG EPD would be expected to sire calves ½ of yield lower (better) than a bull with a 0 YG EPD. (Limousin, Simbrah and Simmental.)

EPD Accuracy Value

EPDs that are calculated between sire summary analyses are given a value of interim or pedigree estimates depending on how much information is incorporated into the calculation of the EPD. Registration papers usually have these types of accuracies associated with EPDs printed on the document.

I (Interim EPD Accuracy) Accuracy value given to an EPD that was calculated using an individual's functioning information and/or the EPDs of its parents and relatives.

P, PE (Pedigree Estimate) Accuracy value given to an EPD that was calculated summing the parents' EPDs and so dividing by two (PE EPD = (EPDs +[EPDd]/2).

Apr 2006

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