EPDs - 

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How to read the results

EPD’s are an estimate of an animal's genetic worth for that particular trait. An EPD is expressed in the units of measure for that trait. EPD’s are based on a combination of performance information from an animal's pedigree, individual and progeny performance. EPD’s can be used to predict one animal's progeny performance compared to another's progeny. EPD’s can also be used to compare the genetic worth of one animal to the overall Brahman population average and distribution. Each calculated EPD has an associated accuracy value. 

An accuracy value calculated by the genetic analysis is a number between 0 and 1. Accuracy is a relative indicator of the confidence you can place in that particular EPD. The closer an accuracy is to one, the more reliable is the estimate.  

Accuracy ranges from 0-99% and indicates the probability of an EPD changing with the addition of more progeny data.  The magnitude of possible change decreases as accuracy increases.  Accuracy below 75% should be regarded as low, between 76-90% as medium and above 90% as high. 

An EPD with an accuracy of "P" is "Pedigree Estimate" and is simply the exact average of that animal's parents. 

Accuracy is based on the amount of performance information available on the animal and its close relatives - particularly the number of progeny analyzed.  Accuracy is also based on the heritability of the trait and the genetic correlations with other recorded traits.  Hence accuracy indicates the "confidence level" of the EPD.

Regn. No:  The Association Registration Number of the animal.

Name:  The registered name of the animal.

Maternal Birth Weight (MBW)

For any trait, including birth weight, the sire and dam each contribute half of the genes that affect that trait to any particular calf.  However, if a cow carries her own calf, she provides the environment (in her womb) in which the calf develops.  Of course, in addition to simply providing a place for the calf to develop, she provides the nutrients to the calf through the placenta.

 

One of the most important characteristics of Brahman and Brahman crossbred cows is that they typically do not allow the developing fetus to get too large, and consequently, they have minimal amounts of calving difficulty.

 

Therefore, although the sire and dam contribute equally to the genes carried by the calf, the cow (that is carrying her own calf) has an additional effect on the size of the calf at birth.  This additional effect is the maternal effect on birth weight.

 

The maternal birth weight EPD predicts differences in birth weight of the calves born to the daughters of different bulls, due to the maternal effect.

 

However, since each of the bull’s daughters receives half of their genes from him, they receive genes from him that directly affect birth weight as well as genes that affect her maternal effect.  Some of these may be the same genes (that is, some of the same genes that directly affect birth weight in his calves may also have maternal effects in his daughters). 

 

To fully understand birth weight EPDs, it is important to consider expected differences in calves out of the daughters of bulls that differ in both birth weight EPDs and maternal birth weight EPDs.

 

Bull

Birth weight EPD, lb

Maternal birth weight EPD, lb

A

0

–2

B

0

  0

C

3

  0

D

0

  0

E

3

  1

F

2

–1.5

 

1.    Comparison of bulls with the same birth weight EPD and different maternal birth weight EPD

 

However, first consider calves out of the daughters of bulls that have the same birth weight EPDs but have different maternal birth weight EPDs.  Bulls A and B both have birth weight EPDs of zero, but bull A’s maternal birth weight EPD is -2 lb. and bull B’s maternal birth weight EPD is zero.  If both of these bulls were originally bred to similar cows, and if groups of both of their daughters were bred to the same or similar bulls, the calves out of the daughters of bull B would be expected to weigh 2 lb. less at birth, on average, than those out of the daughters of bull B.

 

 

 

2.    Comparison of bulls with different birth weight EPD and the same maternal birth weight EPD

 

Now consider calves out of the daughters of bulls that have the same maternal birth weight EPDs but have different birth weight EPDs.  Bulls C and D both have maternal birth weight EPDs of zero, but bull C’s birth weight EPD is 3 lb. and bull D’s birth weight EPD is zero.  If both of these bulls were originally bred to similar cows, and if groups of both of their daughters were bred to the same or similar bulls, the calves out of the daughters of bull D would be expected to weigh 1.5 lb. less at birth, on average, than those out of the daughters of bull C.  The difference in their birth weight EPDs is halved because they are the grandsires of these calves, not the sires.

 

3.    Comparison of bulls with different birth weight EPD and different maternal birth weight EPD

 

For comparing bulls that differ in both birth weight EPDs and maternal birth weight EPDs, bull E has maternal birth weight EPD of 1 lb. and birth weight EPD of 3 lb. and bull F has maternal birth weight EPD of  -1.5 lb. and birth weight EPD of 2 lb. Again, if both of these bulls were originally bred to similar cows, and if groups of both of their daughters were bred to the same or similar bulls, the calves out of the daughters of bull F would be expected to weigh 3 lb. less at birth, on average, than those out of the daughters of bull E.  This difference is calculated by first calculating the “daughter birth weight effect” for both bulls.  This “daughter birth weight effect” is the maternal birth weight EPD plus half of the birth weight EPD.  For bull E the “daughter birth weight effect” is 1 + 1.5 = 2.5 lb.  For bull F it is -1.5 + 1 = -.5 lb.         

Birth Weight (BW) :
The BW EPD is an indicator of birth weight and calving ease.  Progeny sired by a bull with a BW EPD of 2.2 can be expected to weigh 3.2 lb. more at birth, on average, than progeny sired by a bull with an EPD of -1.0 lb. (2.2 minus -1.0 = 3.2 lb.) Birth weight is another indicator of calving ease. Larger BW EPDs usually, but not always, indicate more calving difficulty. 

Weaning Weight (WW) :
The WW EPD reflects pre-weaning growth potential. Measured from adjusted 205-day weight.  It is an indicator of direct genes for growth independent of milk production of the dam. Calves sired by a bull with a WW EPD of 30 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 10.0 = 20 lb.). 

Yearling Weight (YW) :
YW EPD for a sire with an EPD of 87 indicates that on average, his progeny should be 30 lb. above the average of progeny of a bull with an EPD of 57 lb. YW EPD reflects differences in the 365-day adjusted yearling weight for progeny. It is the best estimate of total growth.

Milk (MM) :
The MM EPD is a prediction of weaning weight differences due to milk and maternal ability of the dam. For a sire, the MM EPD predicts the maternal ability of his daughters expressed in pounds of calf weaned. MM EPD’s do not specifically predict pounds of milk produced, but pounds of calf weaned due to maternal production of the dam.  It predicts the difference in average weaning weight of sires’ daughters’ progeny due to milking ability. Daughters of a sire with a MM EPD of 14 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 over the entire lactation period.

Carcass Wt (WT) :
Carcass weight EPDs predict the difference in carcass weight (pounds) between bulls of interest. In the above example, Bull A should produce calves that have carcasses that are 10 pounds heavier than calves sired by Bull B. Carcass weight is an indicator of the total amount of retail product in a carcass, but a poor indicator of carcass composition (quality and cutability). 

Fat (FAT) :
The FAT EPD reflects differences in twelfth-rib fat thickness based on actual carcass measurements of harvested progeny. Sires with low, or negative, FAT EPDs are expected to produce leaner progeny than sires with higher EPDs. 

Ribeye Area (REA) :
REA EPDs reflect differences in ribeye area measures based on actual carcass measurements of harvested progeny. 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

Intramuscular Fat (IMF) :
IMF EPDs reflect differences in intramuscular fat (marbling score) based on actual carcass measurements of harvested progeny. Breeding cattle with higher IMF EPD’s should produce slaughter progeny with a higher degree of intramuscular fat and therefore higher quality grades.

Retail Product % :
Percent retail product EPDs predict differences in the yield of closely trimmed retail cuts from the carcass and are expressed on a percentage basis. Percent retail cuts is calculated from the same traits used in the USDA yield grade equation (carcass weight, ribeye area, fat thickness, and % kidney, pelvic, and heart fat). Sires with higher % retail product EPDs are expected to produce progeny with increased cutability and more desirable yield grades. In the above example, Bull A should sire slaughter progeny whose carcasses will have .8% more retail product than progeny of Bull B (+.5 vs. -.3 % retail product EPD). 

Tenderness :
The tenderness EPD is a combination of Warner-Bratzler Shear Force from harvest data and GeneSTAR DNA results for Tenderness. A lower value indicates more tender meat and is more desirable.

Docility :
Docility is expressed as a difference in weaning cattle temperment with a high value indicating more favorable docility. It predicts the average difference of progeny from a sire in comparison with another sire calves. Only groups with variation in disposition scores are used in EPD evaluation.


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