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 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 value 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, Charolais 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.
Calving Ease EBVs (%) are based on calving difficulty scores,
birth weights and gestation length information.
More positive EBVs are favourable and indicate easier calving.
- CE % Dir = Direct Calving Ease - The EBV for direct calving ease indicates the
influence of the sire on calving ease in purebred females calving at two years
of age.
- CE % Daughters = Daughters' Calving Ease - The EBV for
daughters' calving ease indicates how easily that sire's daughters will calve
at two years of age.
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 650 days.
Eye Muscle Area
EBV (sq cm) indicates genetic
differences in eye muscle area at the 12/13th rib site of a 300kg 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 an indicator of the genetic
differences between animals in fat depth at the p8 rump site in a standard 300kg
steer 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.
Rib Fat EBV (mm) is an indicator of the genetic
differences between animals in fat depth at the 12/13th rib site in a standard 300kg
steer carcase. More positive or more negative
Rib Fat EBVs may be more favourable, depending on your breeding goals relating
to the finishing ability of your animals.
Retail Beef Yield
EBV (%) indicates genetic differences between
animals for retail yield percentage in a standard 300kg steer carcase. Sires with larger EBVs are expected to
produce progeny with higher yielding carcases.
Intramuscular Fat
EBV (%) is an estimate of the genetic difference
in the percentage of intramuscular fat (marbling) at the 12/13th rib site in a
300 kg steer carcase. Depending on
market targets, larger more positive values are generally more favourable.
Index values are reported as EBVs,
in units of relative earning capacity ($’s) for a given market. They reflect both the short-term profit
generated by a sire through the sale of his progeny, and the longer-term profit
generated by his daughters in a self-replacing cow herd. A selection index combines the EBVs with
economic information (costs and returns) for specific market and production
systems to rank animals based on relative profit values. Note that different types of animals can give
similar profit values, so consideration should be given to both the index and
the component EBVs when selecting animals for a particular production
system. More information is available on
selecting animals using a selection index.
The Index values are derived using BreedObject technology. More information is available from the BreedObject web site.
Charolais selection indices are
calculated for two standard market specifications – Domestic Terminal and
Northern Maternal - and are designed to optimise profit outcomes from
commercial production systems. More
information is available on Charolais Selection Indices.
Domestic Terminal
Index ($) - Estimates the
genetic differences between animals in net profitability per cow joined for a
typical commercial herd where Charolais bulls are joined with a British breed
cow base (e.g. Angus) targeting the domestic trade. This index assumes all progeny will be
marketed with steers finished in the feedlot for 90 days and weighing 450 kg
(250 kg HSCW and 7 mm P8 fat depth) when marketed at 12 months. Heifers will be in the feedlot for 75 days and
weigh 430 kg (230 kg HSCW and 9 mm P8 fat depth) at 12 months. In response to industry feedback, positive
emphasis has been placed on finishing ability.
Northern Maternal
Index ($) - Estimates
the genetic differences between animals in net profitability per cow joined for
a typical commercial herd where Charolais bulls are joined with Bos indicus cows
in Northern Australia targeting the grass fed Jap Ox market. Selected heifers are retained for breeding and
so maternal traits are of importance. Steers
target 650 kg live weight (360 kg HSCW and 12 mm P8 fat depth) and heifers 630
kg (340 kg HSCW and 14 mm P8 fat depth), at 26 months of age. In response to industry feedback; positive
emphasis has been placed on finishing ability.
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.
More information on accuracy is available from the BREEDPLAN Help Centre.
More information is available from the BREEDPLAN web site or by contacting the Charolais Association or Charolais BREEDPLAN.
Acknowledgments and Disclaimer
BREEDPLAN results are calculated using the
beef genetic evaluation analytical software developed by the Animal Genetics and
Breeding Unit and Meat & Livestock
Australia Limited.
Information analysed in BREEDPLAN
evaluations, including but not limited to pedigree, performance and DNA
information, is based on data supplied by clients and/or third parties. The Agricultural Business Research Institute (ABRI)
does not oversee or audit the collection of the data. Whilst every effort is made to ensure the
accuracy of the information, the ABRI, their officers and employees assume no
responsibility for its content, use or interpretation.
Estimated Breeding Values can only be
directly compared to other EBVs calculated in the same analysis.