EPD's are a measure of the expected differences in performance of a sire's/dam's progeny when compared to the average progeny of all sires/dams evaluated within the same breed. This prediction is based on actual performance, progeny performance and relatives' performance.
The Expected Progeny Differences (EPDs) of all the cattle on this site are listed beneath the pedigree information. These values are expressed in plus (+) or minus (-) units of measure for the trait. For example, birth weight (BW), weaning weight (WW) and yearling weight (YW) EPDs are given in plus or minus pounds. Maternal Milk (MILK) EPD's are expressed as pounds of weaning weight.
Angus Carcass EPDs are used to give breeders the EPDs necessary to select for directional change in body composition (percent retail product) and/or quality (marbling) in progeny carcasses.
ACCURACY (Acc): The reliability that can be placed on an EPD. The amount of change expected will be decreased the closer the Acc. is to 1.0.
BIRTH WEIGHT (BW): The birth weights of a bull's/cow's progeny when compared to the breed average, in pounds.
YEARLING WEIGHT (YW): The adjusted yearling weights of a bull's/cow's progeny when compared to the breed average, in pounds.
WEANING WEIGHT (WW): The adjusted weaning weights of a bull's/cow's progeny when compared to the breed average, in pounds.
SCROTAL CIRCUMFERENCE (SC): The adjusted yearling scrotal circumferences of a bull's/cow's progeny when compared to the breed average, in centimeters.
MILK: A measure of the amount of pre-weaning performance gained by calves which can be attributed to the milking ability of a bull's/cow's daughters. The EPD is expressed in pounds of calf.
TOTAL MATERNAL (TM): The expected overall difference (lb) in weaning weight of calves out of a bull's daughters compared to calves from daughters of a bull with a zero EPD for total maternal. The total materanl EPD is a measure of both growth and milking ability and is an indication of the size of calf a bull's daughter will wean. The maternal milk EPD is combined with half of the weaning growth EPD to produce the total maternal EPD. This is a prediction of the total genetic influence that a sire will have on his daughter's progeny.
YEARLING GAIN (YG): The yearling gain indicates the ability of his calves to grow between 205 days of age (weaning) and 365 days of age (yearling)
CARCASS WEIGHT (CW): carcass weight is a good predictor of total retail product. In general, carcass weight is not a good predictor of percent retail product. Selecting sires/dams with the higher EPD for carcass weight will result in progeny carcasses that produce more total retail product at constant fat and age end points. An industry target weight range for carcasses would be between 650 and 850 pounds. As with any trait, you need to be cautious of selecting for extremes unless these are necessary for you program.
MARBLING SCORE (MB): The marbling score EPD can be used to select sires/dams that will produce progeny with more marbling at a constant fat and age end point. The higher the marbling score EPD, the higher the amount of intramuscular fat in the ribeye. It should be noted that the genetic correlation between the marbling score and external backfat at the 12th rib is nearly zero. This means that breeders can select for increased, external fat when taking animals to an age-constant end point.
RIBEYE AREA (REA): The cross-sectional area of the longissimus dorsi muscle (ribeye area) at the 12th rib has been shown to account for a significant amount of variation in percent retail product at a constant carcass weight end point. This means that given two sires/dams with the higher EPD for ribeye area will have progeny that yield higher percentages of retail product. Do not use the ratio of ribeye area EPD to carcass weight EPD as a selection index nor as an indicator of differences in percent retail product or muscling.
FAT THICKNESS (FAT): the 12th rib fat thickness heritablility has been estimated to be .25 traits, from the Angus carcass database.
PERCENT RETAIL PRODUCT (%RP): This EPD is expressed in percent, combining traditional carcass traitshot carcass weight, fat thickness, ribeye area and kidney-pelvic-heart fat. The formula for percent retail product is heavily influenced by fat thickness.
Additional facts to remember about EPDs are:
EPDs are the best overall prediction of progeny performance and are useful tools that aid in selection.
EPDs can be used to compare bulls/cows from different herds.
EPDs cannot be used to compare bulls/cows of different breeds.
EPD's on non-parent bulls/cows allow valid comparisons before progeny records are available.
EPDs on non-parents are calculated using pedigree information and individual records, if available.
A pedigree estimated EPD (PE) is the average of two parental EPD values (½ sire, ½ dam)
EPDs are useful tools when planning breeding programs. Attention should be paid to the heritability and correlations of the traits a breeder wants to improve upon within the herd. Some traits are more heritable than others resulting in swift progress being made in comparison to other less heritable traits. Also, many traits are correlated meaning that the expression of one trait is related to the expression of another trait. The correlation between traits can be either positive or negative and close attention should be paid to these relationships, when developing selection criteria in a breeding program.
Trait Heritability Range Level
reproductive less than 0.20 low
growth 0.20 0.40 moderate
carcass greater than 0.40 high
Understanding the heritability and the effects of correlation between traits will aid in developing a genetic selection program that will optimize improvement on desired traits while minimizing undesirable side effects.
How To Use EPDs in Sire Selection
Each individual breeder must set his own selection goals, based on the needs of his operation, the situation for that trait in his herd, and his production environment.
It would be easier if we could assume that the highest EPDs are the best. Unfortunately, it isn't that simple. Like most decisions, using EPDs for sire selection involves tradeoffs. For example, bulls with high growth EPDs may sire calves with a higher birth weight as well. And there may be other impacts on your operation to consider.
For example, when breeding heifers it is desirable to produce calves with lower birth weights, so a breeder may want to pay special attention to birth weight EPDs of prospective bulls. If all calves were sold as feeders, the milk EPD would generally not rate much attention. Yearling weight will be important if you want to ensure finished steers in the appropriate weight range.
It should also be kept in mind that reaction to selection can differ from trait to trait. This is because some traits have higher heritability than others, and are more easily passed to offspring. For instance growth traits such as weaning weight respond faster to selection, than reproductive traits such as age at first calving.
A balance of traits is required, and the perfect balance for you will depend on your climatic, nutritional and economic environment, as well as the management goals you have set for your herd.
One way to select for several traits are to set minimum and maximum acceptable levels for each trait, and then choose sires that meet criteria. Another method would be rank all sires, on each trait, then develop a weighted index which ranks each bull from one (most desirable) to five for each trait. The bull with the lowest total score would be your first choice.
Producer 1 is looking for a sire that can be used on heifers; he wants a bull that will produce low birth weights and he wants to keep some heifer calves as replacements. Growth performance is not his first priority. The sire that fits his needs is sire D. He has a low birth weight EPD and above-average milk EPD.
Producer 2 has a sound-breeding program; he is looking for a sire that will maintain performance and milking ability. He will select a bull that will increase growth performance and milk while maintaining calving ease. Sire B is his choice.
Producer 3 has a herd of above-average-frame cows and is not planning on keeping heifers as replacements. She is looking for a bull that will give her the most profit at weaning. Sire A will give her the best result in weaning weight. If heifers are kept as replacements, they will, on average, be inferior for maternal milk.
Producer 4 wants to maintain his calving performance and growth performance but would like tom increase the milking ability in his females. Sire C is his choice.