Page 9 - Sudeley Angus ebook
P. 9

Estimated Breeding Values

                       (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 “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,
      TRANSTASMAN ANGUS CATTLE EVALUATION 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
      SUDELEY GENETICS SHEEP & CATTLE COMPANY       9
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