An animal's breeding value is its
genetic merit, half of which will be passed on to its progeny. While we will never know the exact breeding
value, for performance traits it is possible to make good estimates. These estimates are called Estimated Breeding
Values (EBVs).
In the calculation of EBVs, the
performance of individual animals within a contemporary group is directly
compared to the average of other animals in that group. A contemporary group consists of animals of
the same sex and age class within a herd, run under the same management conditions
and treated equally. Indirect
comparisons are made between animals reared in different contemporary groups, through the use of pedigree links between the groups.
EBVs are expressed in the units of
measurement for each particular trait.
They are shown as + ive or - ive differences between an individual animal's genetics
difference and the genetic base to which the animal is compared. For example, a bull with an EBV of +50 kg for
600-Day Weight is estimated to have genetic merit 50 kg above a base of 0
kg. Since the breed base is set to an
historical benchmark, the average EBVs of animals in each year drop has changed
over time as a result of genetic progress within the
breed.
The absolute value of any EBV is
not critical, but rather the differences in EBVs between animals. Particular animals
should be viewed as being "above or below breed average" for a
particular trait.
Whilst EBVs provide the best basis
for the comparison of the genetic merit of animals reared in different
environments and management conditions, they can only be used to compare
animals analysed within the same analysis.
Consequently, Wagyu BREEDPLAN EBVs cannot be validly compared with EBVs
for any other breed.
Although EBVs provide an estimate of an animal’s
genetic merit for a range of production traits, they do not provide information
for all of the traits that must be considered during
selection of functional animals. In all situations,
EBVs should be used in conjunction with visual assessment for other traits of
importance (such as structural soundness, temperament, fertility etc). A recommended practice is to firstly select
breeding stock based on EBVs and to then select from this group to ensure that
the final selections are otherwise acceptable.
EBVs are published for a range of
traits covering fertility, calving ease, milking ability, growth, carcase merit
and docility. When using EBVs to assist
in selection decisions it is important to achieve a balance between the
different groups of traits and to place emphasis on those traits that are
important to the particular herd, markets and
environment. One of the advantages of
having a comprehensive range of EBVs is that it is possible to avoid extremes
in particular traits and select for animals with balanced overall performance.
Gestation Length
EBV (days) is an estimate
of the time from conception to the birth of the calf and is based on Artificial
Insemination and hand mating records.
Lower (negative) Gestation Length EBVs indicate shorter gestation length
and therefore easier calving and increased growth after birth.
Birth Weight EBV (kg) is based on the measured birth weight of progeny, adjusted for dam
age. The lower the value the lighter the
calf at birth and the lower the likelihood of a difficult birth. This is particularly important when selecting
sires for use over heifers.
200-Day Growth EBV (kg) is calculated from the weight of
progeny taken between 80 and 300 days of age.
Values are adjusted to 200 days and for age of dam. This EBV is the best single estimate of an
animal's genetic merit for growth to early ages.
400-Day Weight EBV (kg) is calculated from the weight of
progeny taken between 301 and 500 days of age, adjusted to 400 days and for age
of dam. This EBV is the best single
estimate of an animal's genetic merit for yearling weight.
600-Day Weight EBV (kg) is calculated from the weight of
progeny taken between 501 and 900 days of age, adjusted to 600 days and for age
of dam. This EBV is the best single
estimate of an animal's genetic merit for growth beyond yearling age.
Mature Cow Weight
EBV (kg) is based on the cow weight when the
calf is weighed for weaning, adjusted to 5 years of age. This EBV is an estimate of the genetic
difference in cow weight at 5 years of age and is an indicator of growth at
later ages and potential feed maintenance requirements of the females in the
breeding herd. Steer breeders wishing to
grow animals out to a larger weight may also use the Mature Cow Weight EBV.
Milk EBV (kg) is an estimate of an animal's milking ability. For sires, this EBV indicates the effect of
the daughter's milking ability, inherited from the sire, on the 200-day weights
of her calves. For dams, it indicates her
milking ability.
Scrotal Size EBV (cm) is calculated from the circumference of the scrotum taken between
300 and 700 days of age and adjusted to 400 days of age. This EBV is an estimate of an animal's
genetic merit for scrotal size. There is
also a small negative correlation with age of puberty in female progeny and
therefore selection for increased scrotal size will result in reduced age at
calving of female progeny.
Carcase Weight EBV (kg) is based on abattoir carcase records and is an indicator of the
genetic differences in carcase weight at the standard age of 990 days.
Eye Muscle Area
EBV (sq cm) is calculated
from measurements from live animal ultrasound scans and from abattoir carcase
data, adjusted to a standard 420kg carcase.
This EBV estimates genetic differences in eye muscle area at the 12/13th
rib site of a 420kg dressed carcase.
More positive EBVs indicate better muscling on animals. Sires with relatively higher Eye Muscle Area
EBVs are expected to produce better muscled and higher percentage yielding
progeny at the same carcase weight than will sires with lower Eye Muscle Area
EBVs.
Rump Fat EBV (mm) is calculated from measurements of
subcutaneous fat depth at the P8 rump site (from live animal ultrasound scans
and from abattoir carcases) and is adjusted to a standard 420kg carcase. This EBV is an indicator of the genetic
differences in fat distribution on a standard 420kg carcase. Sires with low, or negative, fat EBV are
expected to produce leaner progeny at any particular carcase
weight than will sires with higher EBVs.
Retail Beef Yield
EBV (%) indicates genetic differences between
animals for retail yield percentage in a standard 420kg carcase. Sires with larger EBVs are expected to
produce progeny with higher yielding carcases.
Marble Score EBV (Aus-Meat Marble Score) is an estimate of the genetic difference in the Aus-Meat Marble Score in a 420kg carcase. Larger more positive values are
favourable.
Marble Fineness
EBV (Camera Marbling Fineness Index) is an estimate of the genetic difference in the Marbling Fineness Index
as measured by the Japanese Digital Image Camera. Sires with higher EBVs are expected to
produce progeny with higher Marbling Fineness Index.
Index values are reported as EBVs,
in units of relative earning capacity ($’s) for a given market. They reflect both the short-term profit
generated by a sire through the sale of his progeny, and the longer-term profit
generated by his daughters in a self-replacing cow herd. A selection index combines the EBVs with
economic information (costs and returns) for specific market and production
systems to rank animals based on relative profit values. Note that different types of animals can give
similar profit values, so consideration should be given to both the index and
the component EBVs when selecting animals for a particular production
system. More information is available on
selecting animals using a selection index.
The Index values are derived using BreedObject technology. More information is available from the BreedObject web site.
Wagyu selection indices are
calculated for three standard market specifications and are designed to
optimise profit outcomes from commercial self-replacing, fullblood terminal and
F1 terminal production systems. More
information is available on Wagyu Selection Indices.
Wagyu Breeders Index ($) – The Wagyu Breeder Index (WBI) can be used to
select Fullblood bulls that will produce females with high genetic merit for
growth and breed average slaughter progeny
for marbling. The WBI is suited to
commercial producers who rely on low-input, grass-based
production systems to produce steer progeny for high feedlot entry weight and
high growth daughters.
Heifers are retained for breeding
and therefore
maternal traits are of importance.
Steers are assumed to be slaughtered at 32 months after 550 days
of feedlot finishing targeting 460kg carcases with breed average Marble Score.
Self-replacing Index ($) – The Self-replacing Index (SRI) Index can
be used to select Fullblood bulls that will produce females with moderate
genetic merit for growth and above breed average slaughter progeny for marbling
(targeting marble score higher than 8).
The SRI is suited to commercial producers who provide supplementary
feeding on grass-based production systems to produce steer progeny of average
feedlot entry weight and moderate growth daughters. Heifers are retained for breeding and
therefore maternal traits are of importance.
Steers are assumed to be slaughtered at 32 months after 550 days of
feedlot finishing targeting 435kg carcases with above average Marble Score –
higher than 8.
Fullblood Terminal Index ($) – The Fullblood Terminal Index (FTI) has
increased weighting on the Marble Score EBV and can be used to select bulls for the production
of profitable slaughter animals where no progeny are
retained for breeding. The FTI is suited
to commercial producers
of Fullblood cattle who provide supplementary feeding to grass-based production system
before feedlot entry. The FTI targets to produce steer
and heifer progeny of average feedlot entry weight and Marble Score
significantly higher than 8.
F1 Terminal Index ($) – The F1 Terminal Index (F1 Index) has
predominant weighting on the Marble Score EBV and can be used to select bulls
for the production of profitable slaughter animals from cross-breeding
where no progeny are retained for breeding.
The F1 Index is suited
to commercial producers of crossbred slaughter cattle using Fullblood bulls and
non-Wagyu
females. The F1 Index targets average carcase
weight for steer progeny of 420kg and 387kg for heifers with above average F1
Marble Score (higher than 6) based on high marbling genetic merit of the
sire.
Accuracy (%) is based on the amount of performance information available on the
animal and its close relatives - particularly the number of progeny
analysed. 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 EBV.
The higher the accuracy value the lower the likelihood of change in the
animal's EBV as more information is analysed for that animal or its
relatives. Even though an EBV with a low
accuracy may change in the future, it is still the best estimate of an animal's
genetic merit for that trait. As more
information becomes available, an EBV is just as likely to increase in value,
as it is to decrease.
Accuracy values range from
0-99%. The following guide is given for
interpreting accuracy:
|
Accuracy range
|
Interpretation |
|
less than 50% |
Low accuracy. EBVs are preliminary and could change
substantially as more performance information becomes available. |
|
50-74% |
Medium accuracy, usually based on the
animal's own records and pedigree. |
|
75-90% |
Medium-high accuracy. Some progeny information included. EBVs may change with addition of more
progeny data. |
|
more than 90% |
High accuracy estimate
of the animal's true breeding value. |
As
a rule, animals should be compared on EBVs regardless of accuracy. However, where two animals have similar EBVs
the one with higher accuracy could be the safer choice, assuming other factors are equal.
For further information please
contact the Wagyu Association or Wagyu BREEDPLAN.