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Bull Genetics, How to Read, & Understand, EPD (Expected Progeny Differences) in Cattle

Jesse Lefevre from Chama NM gave a presentation on Bull Genetics, How to Read, & Understand, EPD (Expected ProgenyDifferences) in Cattle

EPDs can be quite intimidating and confusing for the novice cattle person, but, once you understand what EPDs are and know how to read them, they simply become a highly useful tool in determining how to choose the next best herd sire or purebred cows for your operation.

EPDs are numbers that predict the genetic quality of future offspring or progeny of a particular bull, cow or heifer. It is a method that helps a cattle producer, seedstock (purebred) or commercial, to determine whether that particular bull, cow or heifer is sufficient to produce the desired calves needed to either help improve the genetic quality of a breeding herd, or to sell to the meat market. However, this tool is considered to be most difficult part of breeding cattle because it involves reading, interpreting and understanding the various numbers and abbreviations that are present for a particular animal of interest.

 

EPD-1Calving Ease – Direct (CE)

CE EPD is based on calving ease scores and birth weights and is measured on a percentage. CE EPD indicates the influence of the sire on calving ease in females calving at 2 years of age. For example, if sire A has a CE EPD of 6 and sire B has a CE EPD of -2, then you would expect on average if comparably mated, sire A’s calves would be born with an 8% more likely chance of being unassisted when compared to sire B’s calves.

 

Birth Weight (BW)

BW EPD is an indicator trait for calving ease and is measured in pounds. For example, if sire A has a BW EPD of 3.6 and sire B has a BW EPD of 0.6, then you would expect on average if comparably mated, sire A’s calves would come 3 lb. heavier at birth when compared to sire B’s calves. Larger BW EPDs usually, but not always, indicate more calving difficulty. The figure in parentheses found after each EPD is an accuracy value or reliability of the EPD.

Weaning Weight (WW)

EPD-2WW EPD is an estimate of pre-weaning growth that is measured in pounds. For example, if sire A has a WW EPD of 60 and sire B has a WW EPD of 40, then you would expect on average if comparably mated, sire A’s calves would weigh 20 lb. heavier at weaning when compared to sire B’s calves.

Yearling Weight (YW) YW EPD is an estimate of post-weaning growth that is measured in pounds. For example, if sire A has a YW EPD of 100 and sire B has a YW EPD of 70, then you would expect on average if comparably mated, sire A’s calves would weigh 30 lb. heavier at a year of age when compared to sire B’s calves.

Maternal Milk (MM)

The milking ability of a sire’s daughters is expressed in pounds of calf weaned. It predicts the difference in average weaning weights of sires’ daughters’ progeny due to milking ability. Daughters of the sire with a +14 MM EPD should produce progeny with 205-day weights averaging 24 lb. more (as a result of greater milk production) than daughters of a bull with a MM EPD of -10 lb. (14 minus -10.0 = 24 lb.). This difference in weaning weight is due to total milk production during the entire lactation.

Maternal Milk & Growth (M&G)

Maternal Milk & Growth reflects what the sire is expected to transmit to his daughters for a combination of growth genetics through weaning and genetics for milking ability. It is an estimate of daughters’ progeny weaning weight. A bull with a 29 lb. M&G EPD should sire daughters with progeny weaning weights averaging 19 lb. heavier than progeny of a bull’s daughters with a M&G EPD of 10 lb. (29 minus 10 = 19 lb.). It is equal to one-half the sire’s weaning weight EPD, plus all of his MM EPD. No accuracy is associated with this since it is simply a mathematical combination of two other EPDs. It is sometimes referred to as “total maternal” or “combined maternal.”

Maternal Calving Ease (MCE)

MCE EPD predicts how easily a sires daughters will calve at 2 years of age and is measured on a percentage. For example, if sire A has a MCE EPD of 7 and sire B has a CE EPD of -3, then you would expect on average if comparably mated, sire A’s daughters would calve with a 10% more likely chance of being unassisted when compared to sire B’s daughters.

Mature Cow Weight (MCW) The MCW EPD was designed to help breeders select sires that will either increase or decrease mature size of cows in the herd. The trait was developed after years of cow weight data collection and the EPD relates directly to the maintenance requirements of a cow herd. An example of how the MCW EPD allows breeders to compare sires: If sire A has a MCW EPD of 100 and sire B has an EPD of 85, then you would expect the females of sire A, if mated to similar cows, to be 15 lb. heavier at mature size.

Udder suspension (UDDR) Scores range from 9 (very tight) to 1 (very pendulous) and represent assessments of udder support. Weak udder suspension results in pendulous udders that make it difficult for a calf to nurse. Weak suspension in the udder indicates a lack of support in the ligament that ties the udder to the cow’s body wall. Over time, weakness in this ligament will allow the udder to hang down too far from the body and may subject the udder to serious problems and increased potential for injury.

UDDR EPDs are reported on the scoring scale. Differences in sire EPDs predict the difference expected in the sires’ daughters’ udder characteristics when managed in the same environment. For example, if sire A has a UDDR EPD of 0.4, and sire B has a UDDR EPD of -0.1, the difference in the values is 0.5, or one-half of a score. If daughters of sires A and B are raised and managed in the same environment, you would expect half a score better udder suspension in daughters of sire A, compared to sire B.

Teat size (TEAT) Scores range from 9 (very small) to 1 (very large, balloon shaped) and are subjective assessments of the teat length and circumference. Oversized teats are difficult for newborn calves to nurse, and the calf may not receive adequate colostrum. This could lead to a higher incidence of scours or decreased immunity levels in the newborn calf.

TEAT EPDs are reported on the scoring scale. Differences in sire EPDs predict the difference expected in the sires’ daughters’ udder characteristics when managed in the same environment. For example, if sire A has a teat size EPD of 0.4, and sire B has a teat size EPD of -0.1, the difference in the values is 0.5, or one-half of a score. If daughters of sires A and B are raised and managed in the same environment, you would expect half a score smaller teat size in daughters of sire A, compared to sire B.

EPD-3Scrotal Circumference (SC)

Measured in centimeters and adjusted to 365 days of age, SC EPD is the best estimate of fertility. It is related to the bull’s own semen quantity and quality, and is also associated with age at puberty of sons and daughters. Larger SC EPDs suggest younger age at puberty. Yearling sons of a sire wth a .7 SC EPD should have yearling scrotal circumference measurements that average 0.7 centimeters (cm) larger than progeny by a bull with an EPD of 0.0 cm. In the Hereford genetic analysis, a multiple-trait model was used for scrotal circumference. Weaning weight was used as a predictor variable to increase the prediction accuracy of SC EPDs. Therefore, an animal with a weaning weight EPD should also have a SC EPD.

Carcass Weight (CW) Carcass weight is a beneficial trait when considering the impact that pounds have relative to end product value. At the same age constant endpoint, sires with higher values for carcass weight will add more pounds of hot carcass weight compared to sires with lower values for carcass weight. For example, if sire A has a CW EPD of 84 and sire B has a CW EPD 64, then you would expect the progeny of sire A, if harvested at the same age constant endpoint, to have a 20-lb. advantage in terms of hot carcass weight.

Rib Fat (FAT) The FAT EPD reflects differences in adjusted 365-day, 12th-rib fat thickness based on carcass measurements of harvested cattle. Sires with low, or negative FAT EPDs are expected to produce leaner progeny than sires with higher EPDs. Ultrasound measures are also incorporated into this trait and have been shown to be highly correlated with the performance of slaughter progeny. All data is expressed on a carcass scale.

Ribeye Area (REA)

REA EPDs reflect differences in an adjusted 365-day ribeye area measurement based on carcass measurements of harvested cattle. Sires with relatively higher REA EPDs are expected to produce better-muscled and higher percentage yielding slaughter progeny than will sires with lower REA EPDs. Ultrasound measurements are also incorporated into this trait and have been shown to be highly correlated with the performance of slaughter progeny. All data is expressed on a carcass scale.

Marbling (MARB)

MARB EPDs reflect differences in an adjusted 365-day marbling score (intramuscular fat, [IMF]) based on carcass measurements of harvested cattle. Breeding cattle with higher MARB EPDs should produce slaughter progeny with a higher degree of IMF and therefore higher quality grades. Ultrasound measurements are also incorporated into this trait and have been shown to be highly correlated with the performance of slaughter progeny. All data is expressed on a carcass scale.