Background
The
Australian Wagyu Association (AWA) has been proactive in getting a genetic
evaluation for Wagyu animals. The AWA
sees genetic evaluation as a major step in breed development. While there is only limited data available at
present, the AWA is hopeful that a trial analysis will be a stepping stone to achieve
this aim.
For
the October 2009 analysis, there were eleven herds that had submitted
performance data. The analysis included
approximately 2400 gestation length records, 7500 birth weights, 8700 animals
with a weaning and/or later weight, 1000 bulls with a scrotal measurement and
3200 animals scanned for carcase traits. From a genetic evaluation perspective,
this is considered a small data set and should be considered as being a preliminary
analysis for the breed.
The EBVs
reported for the “carcase traits” are explained in detail
below. It should be noted that there was
no abattoir carcase data used in this trial analysis. While the AWA and its
members are strongly focused on the abattoir carcase information, there was
very little available that was useful for a genetic evaluation. As such, only live animal ultrasound scan data
has been used to calculate the carcase EBVs.
The
AWA is looking to build a database of Wagyu infused animals that have been
performance recorded for a range of traits, including weights from birth to
slaughter, live animal ultrasound scans, abattoir carcase and fertility
information. If you would like to
participate in this project, please contact the AWA direct.
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 positive or negative 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 the breed 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.
EBVs
are potentially available for a range of traits covering fertility, calving
ease, milking ability, growth, carcase merit and docility. The EBVs
available for Wagyu are outlined below. 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 (AI date) 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 potentially
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.
Eye Muscle Area EBV (sq cm) is calculated from measurements from live
animal ultrasound scans only at this stage. The scan is adjusted to a standard 500
days of age. This EBV estimates genetic
differences in scanned eye muscle area at the 12/13th rib site of a 500 day old
animal. More positive EBVs indicate larger eye muscles for animals with similar
400/600 day weight EBVs. That is, as
animals get bigger, we expect their EMAs to increase
as well. Hence, for animals with similar
growth EBVs, more positive EMA EBVs indicate more muscling. Sires with relatively higher Eye Muscle Area
EBVs are expected to produce better muscled and higher percentage yielding
progeny at the same 400/600 day weight EBV than will sires with lower Eye
Muscle Area EBVs.
Rib Fat and Rump Fat EBVs (mm) are calculated from measurements of
subcutaneous fat depth scanned at the 12/13 rib site and the P8 rump site (from
live animal ultrasound scans) and are adjusted to a standard 500 days of age.
These EBVs are indicators of the genetic differences in fat distribution on a 500
day old animal. Sires with low, or negative, fat EBVs are expected to
produce leaner progeny at 500 days than will sires with higher EBVs.
Intramuscular Fat EBV (%) is an estimate of the
genetic difference in the percentage of scanned intramuscular fat (marbling) at
the 12/13th rib site in a 500 day old animal. Larger more positive values are
more favourable Due to technical
limitations of the current ultrasound scanning equipment and the techniques to
analyse the ultrasound images, live animal scanning is limited to animals that
have less than 8% intra muscular fat – which is roughly equivalent to a
marble score 2 in AusMEAT terminology. As such, there is likely to be observed
differences between an early feedlot scan and later marble scores from the
carcase when slaughtered 200 or more days later. Research has shown that there is a reasonable
relationship between scan data and carcase measures for other cattle
breeds. However, this relationship has
not yet been determined for Wagyu infused cattle. The AWA is looking at running trials to
estimate this relationship for Wagyu infused cattle.
Wagyu
selection indexes are currently under development and will be available soon.
Indexes
are reported as an EBV, 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 retained for breeding in a sustainable cow herd. Both costs, including feeding, and returns from throughout
the production system are accounted for.
The
Indexes are derived using BreedObject
technology. For more information on this technology, go to the BreedObject
web site.
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 Australian
Wagyu Association or Wagyu BREEDPLAN.