EPD EXAM STUDY GUIDE
EPD - Answers - -Expected progeny differences
-a valuable tool to aid purebred and commercial producers in the selection of potential
breeding stock
-the measure of predicted genetic merit in beef cattle
PTA - Answers - for dairy cattle (Predicted Transmitting Ability)
What is the role of purebred breeders? - Answers - to improve the genetic quality of the
seedstock cattle they produce to sell to the commercial beef producers
What can EPDs do? - Answers - Can indicate the genetic value of one specific animal
compared to another specific animal of the same breed, regardless of the age or
location of the herd
How are EPDs calculated? - Answers - using performance record information, with a
complex algebraic formula in the National Cattle Evaluation Computing Centers at the
University of Georgia and Iowa State University
Accuracy (Acc) - Answers - The reliability that can be placed on an EPD. Accuracy
expresses the reliability of the EPD and is presented as a number between .01 and .99
The amount of change expected will be decreased the closer the Acc. is to 1.0
Birth Weight (BW) - Answers - The birth weights of a bull's/cow's progeny when
compared to the breed average, in pounds. The lower the value the lighter the calf at
birth and the lower the likelihood of a difficult birth.
Weaning Weight (WW) - Answers - The adjusted weaning weights of a bull's/cow's
progeny when compared to the breed average, in pounds. Is calculated from the weight
of progeny taken between 80 and 300 days of age. Values are adjusted to 205 days and
for age of dam
Yearling Weight (YW) - Answers - The adjusted yearling weights of a bull's/cow's
progeny when compared to the breed average, in pounds. Is calculated from the weight
of progeny taken between 301 and 450 days of age, adjusted to 365 days and for age
of dam. This EPD is the best single estimate of a sire's genetic merit for yearling weight
Scrotal Circumference (SC) - Answers - The adjusted yearling scrotal circumferences of
a bull's/cow's progeny when compared to the breed average, in centimeters. is
calculated from measurements of scrotal size in yearling bulls, adjusted to 365 days.
Scrotal circumference is a good indicator of puberty, fertility and semen quality/quantity.
Increased scrotal size will also result in decreased age of puberty in daughters and
greater lifetime production. Positive EPD values indicate larger scrotal circumference
, Milk - Answers - 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. For sires, this EPD indicates the effect of the daughter's
milking ability, inherited from the sire, on the weaning and yearling weights of her
calves. For dams, it indicates her own milking ability
Total Maternal (TM) - Answers - 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 maternal 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) - Answers - 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) - Answers - 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. Is calculated from carcass weight data from the progeny of
sires, adjusted to 450 days of age. Positive values indicate heavier carcass weights at
the standard age of 450 days
Marbling Score (MB) - Answers - 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) - Answers - 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) - Answers - -the 12th rib fat heritability has been estimated to be
.25 traits, from the Angus carcass database.
EPD - Answers - -Expected progeny differences
-a valuable tool to aid purebred and commercial producers in the selection of potential
breeding stock
-the measure of predicted genetic merit in beef cattle
PTA - Answers - for dairy cattle (Predicted Transmitting Ability)
What is the role of purebred breeders? - Answers - to improve the genetic quality of the
seedstock cattle they produce to sell to the commercial beef producers
What can EPDs do? - Answers - Can indicate the genetic value of one specific animal
compared to another specific animal of the same breed, regardless of the age or
location of the herd
How are EPDs calculated? - Answers - using performance record information, with a
complex algebraic formula in the National Cattle Evaluation Computing Centers at the
University of Georgia and Iowa State University
Accuracy (Acc) - Answers - The reliability that can be placed on an EPD. Accuracy
expresses the reliability of the EPD and is presented as a number between .01 and .99
The amount of change expected will be decreased the closer the Acc. is to 1.0
Birth Weight (BW) - Answers - The birth weights of a bull's/cow's progeny when
compared to the breed average, in pounds. The lower the value the lighter the calf at
birth and the lower the likelihood of a difficult birth.
Weaning Weight (WW) - Answers - The adjusted weaning weights of a bull's/cow's
progeny when compared to the breed average, in pounds. Is calculated from the weight
of progeny taken between 80 and 300 days of age. Values are adjusted to 205 days and
for age of dam
Yearling Weight (YW) - Answers - The adjusted yearling weights of a bull's/cow's
progeny when compared to the breed average, in pounds. Is calculated from the weight
of progeny taken between 301 and 450 days of age, adjusted to 365 days and for age
of dam. This EPD is the best single estimate of a sire's genetic merit for yearling weight
Scrotal Circumference (SC) - Answers - The adjusted yearling scrotal circumferences of
a bull's/cow's progeny when compared to the breed average, in centimeters. is
calculated from measurements of scrotal size in yearling bulls, adjusted to 365 days.
Scrotal circumference is a good indicator of puberty, fertility and semen quality/quantity.
Increased scrotal size will also result in decreased age of puberty in daughters and
greater lifetime production. Positive EPD values indicate larger scrotal circumference
, Milk - Answers - 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. For sires, this EPD indicates the effect of the daughter's
milking ability, inherited from the sire, on the weaning and yearling weights of her
calves. For dams, it indicates her own milking ability
Total Maternal (TM) - Answers - 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 maternal 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) - Answers - 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) - Answers - 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. Is calculated from carcass weight data from the progeny of
sires, adjusted to 450 days of age. Positive values indicate heavier carcass weights at
the standard age of 450 days
Marbling Score (MB) - Answers - 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) - Answers - 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) - Answers - -the 12th rib fat heritability has been estimated to be
.25 traits, from the Angus carcass database.
