Page 9 - Brackenfield Angus Catalogue ebook
P. 9

EBVS EXPLAINED


      UNDERSTANDING THE EBVS,
      SELECTION INDEXES AND ACCURACY EBVS
      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
 Brackenfield Angus        “above or below breed average” for a particular trait.
      Whilst EBVs provide the best basis for the comparison of the genetic
 3 May 2021
      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.


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