Understanding EPDs

Expected Progeny Differences (EPDs)

Expected Progeny Differences (EPDs) are used to compare the genetic merit of cattle for specific traits, and can aid in making selection decisions for desired traits in the herd. An EPD helps to predict the difference in performance of the future offspring of a parent. They are based on data from the animal’s pedigree, performance, and performance of its relatives and offspring. It is important to remember that the performance of an animal is determined both by genetics and environment, and EPDs help to predict differences due to genes passed from parents to offspring. When additional DNA information is available (testing through a 100K panel), accuracy of EPDs is improved. By combining performance, progeny data, as well as pedigree and genomic results, we can best estimate an animal’s genetic value as a parent.

Another fundamental concept of interpreting EPDs is to recognize that EPDs serve to rank animals. By comparing an animal’s EPD for a given trait to the average EPD of all animals, one can determine if the animal is above or below average. By familiarizing yourself with percentile rankings, you can determine the degree to which an animal is above or below average for a given trait. The Limousin and Lim-Flex percentile ranks are available on the Digital Beef registry platform on the left hand menu under Cattle Evaluation.

Calving Ease Direct (CED) and Calving Ease Maternal (CEM)

The Limousin breed has an excellent reputation for calving ease and associated calf vigor and survivability. But even low levels of calving difficulty can mean increased veterinary and labor costs, calf death loss, susceptibility to disease, mortality, delayed return to estrus, and lower conception rates. Higher calving ease EPDs are favored and indicate genetics for greater chances of unassisted births. The calving ease direct (CED) EPD is important for choosing which sires to breed to first calf heifers to produce calves that are born easily. The calving ease maternal (CEM) EPD is indicative of greater calving ease in bulls’ two-year-old daughters

CED

Sire A	14
Sire B	7
Breed Average	10

Sire B is expected to have 6.66% less assisted births than sire A when bred to two-year-old heifers.

CEM

Sire A	10
Sire B	4
Breed Average	6

Sire B is expected to have 8.5% less assisted births on his first-calf heifer daughters than sire A.

Birth Weight (BW)

Birth weight has been identified as the single most influential factor contributing to calving difficulty. Birth weight is used in the calculation of Calving Ease Direct. Lower birth weight EPDs indicate lighter progeny birth weights, which generally should translate into less potential for calving problems.

Sire A	-1.4
Sire B	2.6
Breed Average	1.4

Bull B has an expected birth weight that would be four pounds heavier on average than Bull A.

Weaning Weight (WW) and Yearling Weight (YW)

Since feeder cattle are marketed by the pound, heavier calves will return more $ than lighter weight calves. Weaning and yearling weight EPDs are expressed as the added pounds of weaning and yearling weight of offspring expected, due to genes for growth passed down from sire and dam. Pounds at weaning is most indicative of profit, but looking at YW as well as carcass traits will aid in selection. Selling high quality calves at weaning that will perform well to yearling age and into the feedlot will help to raise high-value, profitable calves.

	WW EPD	YW EPD
Bull A	72	110
Bull B	83	131
Difference	11	21

Bull B would be expected to produce calves that are 11lbs heavier, on average, than Bull A at weaning. If the producer elects to sell calves at weaning, Bull B’s calves would pay more. If not selling at weaning, the producer may want to look at the YW EPD, in which case Bull B would also be the more appropriate choice.

Average Daily Gain (ADG)

The ADG EPD estimate the genetic potential of a parent to transmit traits related to growth rate to its offspring. A higher ADG EPD indicates a greater genetic potential for faster growth.

Milking Ability (MK)

A sire’s milk EPD is expressed as the additional pounds of weaning weight of calves (grandprogeny of the sire) from daughters due to genes passed on from milk and mothering ability from the sire to his daughters. Determining the optimum range in milk EPDs which is most appropriate for any given situation and the amount of emphasis that should be given to this trait depends on a number of different factors including environment and management practices. A higher milk EPD in a female would typically indicate higher maintenance (feed) costs.

Total Maternal (TM)

The TM EPD is reflected as a formula (index), as the Milk EPD + half of the WW EPD. By combining the growth and milk information, this can be used to predict the weaning weight performance from a sire’s daughters. Since this is an index, there is no accuracy reported. A larger TM value indicates a female that returns comparatively higher weaning weights on her calves.

Scrotal Circumference (SC)

Measured in centimeters, SC predicts the difference of scrotal circumference of an animal’s male offspring at a year old. Older age at puberty has been linked to lower conception rates and later calving dates in females, a reduction in the quality and quantity of semen produced by bulls, and poor performance in several other measures of reproduction and fertility. SC has been found to be a good indicator of age at puberty, and is a highly heritable trait favorable to selection. SC is especially important to consider in herds where heifers will be retained. Keep in mind, a favorable SC is not a replacement for a breeding soundness exam!

Stayability (ST)

ST predicts the genetic difference in terms of probably that a female will stay productive in the herd until age six. These are calculated from calving and pedigree information. ST is one of the best measures to compare a bull’s ability to produce females with reproductive longevity, and helps producers sort out genetic differences from environmental differences.

Docility (DOC)

EPDs for docility help to predict cattle temperament, with a higher value indicating calmer behavior, and lower values suggesting more nervous or aggressive tendencies. It is important that offspring are scored as 1 (docile) or 2 (restless) as opposed to 3,4 5, or 6 (nervous to very aggressive). Docility directly affects how easily animals can be handled, managed, and processed.

Yield Grade (YG)

USDA yield grades estimate beef carcass cutability, which is defined as the combined yield of closely trimmed, boneless retail cuts. Yield grades range from 1 through 5, with lower values being more favorable, indicating great yield of lean beef from the carcass.

Carcass Weight (CW)

CW EPDs expressed in pounds are a predictor of the differences in hot carcass weight.

Ribeye Area (REA)

REA EPDs expressed in pounds are a predictor of the differences in ribeye area.

Marbling (MB)

MB EPDs are expressed as differences in intramuscular fat in the ribeye.

Fat Thickness (FT)

FT EPDs are expressed in inches and predict the differences in external fat measured between the 12th and 13th rib.

Dry Matter Intake (DMI)

DMI EPD is expressed in difference in pounds of daily dry matter intake. A lower EPD is representative of genetic potential for progeny to consume less feed.

Accuracy

Accuracy is a measure of reliability associated with an EPD and provides us with a level of confidence for the genetic merit of an animal. Bulls with accuracy values closer to one are considered proven sires.

Heritability

Heritability helps to measure the importance of both hereditary and environmental influences on the development of a specific trait. Heritability of reproductive traits is lower and carcass is higher, with growth more in the middle. Improvement in low heritability traits can be achieved with crossbreeding (hybrid vigor). The lower the heritability of a traits, the greater response from heterosis.

$MPI

In this production scenario, Limousin bulls are mated to Angus-based cows with replacement heifers retained from the calf crop and surplus calves marketed at weaning. EPDs weighted in this index are Calving Ease Direct and Maternal, Weaning Weight, Milk, Mature Weight, Dry Matter Intake, and Stayability. Mature weight is the primary driver and represents the significant cost of maintenance energy requirement in the cow-calf sector. Weaning Weight and Milk (expressed in pounds of calf weaning weight) represent the principal revenue stream. Stayability helps account for differences in replacement costs in the system and the effect of heifer retention on revenue streams. This index should be used by commercial cattlemen whose production scenario includes marketing calves at weaning and retaining replacements from the herd. Figure 1 reports the relative emphasis of traits included in $MPI. Marginal Economic Values for $MPI are determined by parameters in the iGENDEC program and simply multiplied by each EPD trait and then added up for a total $ value on each animal in the herdbook.

$IPI

The production scenario for $IPI includes mating Limousin sires to Angus-based cows with retention of replacements from the herd and all other calves fed out and marketed on a value-based grid that rewards quality and yield. IPI balances both maternal and terminal selection criteria by combining replacement female retention from the herd with carcass endpoint for marketed surplus heifers and all steers. Due to the challenges faced by commercial cattlemen in this production scenario, $IPI incorporates the largest and most diverse set of EPDs, including carcass traits as the primary revenue drivers, along with cow Mature Weight, Stayability, and Dry Matter Intake as cost drivers. Figure 2 reports the relative emphasis of traits included in $IPI. Marginal Economic Values for $IPI are determined by parameters in the iGENDEC program and simply multiplied by each EPD trait and then added up for a total $ value on each animal in the herdbook.

$TPI

Terminal Profit Index, constructed to identify terminal sires that produce the highest profit potential fed cattle. The index is reported in dollars and represents expected differences in profit per mating. $TPI places positive economic weight on post-weaning gain. Dry matter intake is also included, and combined traits explain differences in feed conversion. The parameters of this index include the most recent 10 years of reported fed cattle and grid pricing, Kansas State University reported feedlot cattle performance, and NALF production data.

$G

Dollar gain is an index to reflect an animal’s feed conversion capability, and identify animals that are superior in feed efficiency.

Mature Weight

Body weight of cows adjusted to six years of age at body condition score 5. MWT is reported in pounds and is computed from a genetic model that leverages information from weaning weight, post-weaning gain, and mature weights of cows. Reported weights are adjusted for both age at observation and for body condition. Body weights of cows 2 to 12 years of age are utilized in the evaluation so producers can report data at any age for the evaluation. Preferably, cows should be evaluated at or shortly following weaning, as that’s a convenient time for many producers to process cows. Weight collected at other times in the production cycle are acceptable. Producers should measure full contemporary groups on the same day as the observation date, which helps form the contemporary group.

Cow Energy Requirement – Yearly (CERY)

Mature body weight, lactation potential, and birth weight are primary predictors of energy requirements. Mature Weight, Milk, and Birth Weight EPD are utilized to inform prediction equations from beef cow nutrition research to estimate differences in energy requirement over a production year. The CERY EPD is reported in pounds of Total Digestible Nutrients (TDN) required for an age 6 cow.