Page 5 - Tawanui, Aywon, Te Kupe Sale 2021 ebook

The absolute value of any EBV is not critical, but rather the differences
Understanding the EBVs, in EBVs between animals. Particular animals should be viewed as being
Selection Indices and Accuracy “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
EBVs conditions, they can only be used to compare animals analysed within the
An animal’s breeding value is its genetic merit, half of which will be passed same analysis. Consequently, TRANSTASMAN ANGUS CATTLE EVALUATION
on to its progeny. While we will never know the exact breeding value, for (TACE) EBVs cannot be validly compared with EBVs for any other breed.
performance traits it is possible to make good estimates. These estimates
are called Estimated Breeding Values (EBVs). 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
In the calculation of EBVs, the performance of individual animals within a traits that must be considered during selection of functional animals. In
contemporary group is directly compared to the average of other animals all situations, EBVs should be used in conjunction with visual assessment
in that group. A contemporary group consists of animals of the same sex for other traits of importance (such as structural soundness, temperament,
and age class within a herd, run under the same management conditions fertility etc). A recommended practice is to firstly select breeding stock
and treated equally. Indirect comparisons are made between animals based on EBVs and to then select from this group to ensure that the final
reared in different contemporary groups, through the use of pedigree selections are otherwise acceptable.
links between the groups.
EBVs are published for a range of traits covering fertility, calving ease,
EBVs are expressed in the units of measurement for each particular trait. milking ability, growth, carcase merit and feed efficiency. When using
They are shown as + ive or - ive differences between an individual animal’s EBVs to assist in selection decisions it is important to achieve a balance
genetics difference and the genetic base to which the animal is compared. between the different groups of traits and to place emphasis on those
For example, a bull with an EBV of +50 kg for 600-Day Weight is estimated traits that are important to the particular herd, markets and environment.
to have genetic merit 50 kg above the breed base of 0 kg. Since the breed One of the advantages of having a comprehensive range of EBVs is that it
base is set to an historical benchmark, the average EBVs of animals in each is possible to avoid extremes in particular traits and select for animals with
year drop has changed over time as a result of genetic progress within the balanced overall performance.
breed.
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