Hereford 101

The American Hereford Association (AHA) measures 11 traits and calculates four profit ($) indexes. The Hereford Sire Summary, which is distributed each spring, provides breeders with a tremendous amount of information on a large population of Hereford sires. A comprehensive sort of Hereford sires can also be done online at

The current suite of Hereford expected progeny differences (EPDs) and $ indexes includes:

Calving Ease – Direct (CE)

CE EPDs are based on calving ease scores and birth weights. More positive EPDs are favorable and indicate easier calving. The EPD for direct calving ease indicates the influence of the sire on calving ease in purebred females calving at 2 years of age. In the sire summary, an EPD in a black box indicates that the bull is a trait leader.

Birth Weight (BW)

Progeny of the sire above can be expected to weigh an average of 3.2 lb. more at birth than progeny sired by a bull with an EPD of -1.0 lb. (2.2 minus – 1.0 = 3.2 lb.). Birth weight is an indicator of calving ease. 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. To learn more about how to use accuracy when evaluating EPDs please refer to the section “Accuracy and Confidence Range” in the Spring 2009 Sire Summary.

Weaning Weight (WW)

WW EPD reflects pre-weaning growth. Calves sired by a bull with a +30 WW EPD should have a 20 lb. advantage in 205-day adjusted weaning weight compared to calves sired by a bull with an EPD of +10 lb. (30 minus 10 = 20 lb.).

Yearling Weight (YW)

YW EPD reflects differences in the 365-day adjusted yearling weight for progeny. It is the best estimate of total growth.

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)

The MCE EPD indicates how easily a sire’s daughters will calve at 2 years of age when compared to the daughters of other sires.

Scrotal 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.

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.

Baldie Maternal Index (BMI$)

BMI$ is a maternally focused index that has a production system based on 1,000-Hereford x Angus females with a progeny harvest endpoint directed toward Certified Hereford Beef (CHB¨). This index is more critical of CE than the Brahman Influence Index (BII$) and also has significant weight on fertility. There is positive weight on WW and a slightly negative weight on YW, which promotes early growth and then a slow down on growth to keep mature size manageable. The emphasis of IMF is greater than the emphasis of REA. This is true because of the price difference of the Choice-Select spread and the fact that there is very little incentive to produce cattle better than a Yield Grade 3. This index is geared to service any commercial program that has British-cross cows.

Calving Ease Index (CEZ$)

This is a general purpose index that focuses on identifying bulls that can be used on heifers and then ultimately the calves will be marketed through the CHB program. As you might expect, CE and MCE carry significant weight in this index along with fertility. There is very little weight put on growth traits and less emphasis on carcass. Remember, this is a general index that is specifically designed to be used in a heifer program.

Brahman Influence Index (BII$)

BII$ is a maternally focused index that is based on a 1,000-head cow herd of Brahman x Hereford cows. The progeny for this index will be harvested in a commodity-based system since CHB does not accept Brahman-influenced cattle into the program. This index has less emphasis for CE than any of the other indexes. There is emphasis on both REA and IMF since the cattle will be harvested through a commodity market. The largest emphasis is in fertility, which is measured solely by SC at the present time. Obviously, the target for this index is the producers in the Southern regions of the U.S. where the bulls are typically sold to commercial cattlemen that have Brahman-influenced cow herds.

Certified Hereford Beef Index (CHB$)

This is a terminal sire index that is built on a production system where Hereford bulls sire calves for the CHB market. There is some pressure put on CE and then positive weight on both WW and YW. Remember that all offspring in this index are harvested, so they need to be born alive and then grow fast at all stages of life. Of course, we have much more emphasis on fat in this index, as we want the cattle to stay lean. There is also a significant weight on both REA and IMF with more emphasis again on IMF. This index would be used by producers who have a target of producing bulls for a terminal breeding program. It could be used heavily in the Midwest where bulls are used in rotational breeding programs to produce cattle in a retained ownership program or are simply sold to backgrounders. This is the only index that has no emphasis on fertility. Remember that nothing is retained in the herd.

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