Page 36 - Tapiri Angus 2021 Catalogue ebook

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