Page 5 - Ranui Angus Sale Catalogue eBook

TACE EBV’s

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
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, TACE 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 feed efficiency. 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.
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