Page 8 - Ranui Angus Sale Catalogue eBook
P. 8

AngusPure Index  ($)  –  Estimates  genetic  differences  between
      animals  in  net    profitability  per  cow  joined  for  a  self-replacing
      commercial Angus herd, targeting the production of grass finished
      steers for the AngusPure programme.  Steers are assumed marketed
      at 525 kg live weight (280 kg carcase weight and 10 mm fat depth)
      at 18 months of age with a significant premium paid for marbling.
      Note  that  $Index  values  for  individual  animals  are  sensitive  to
      the assumptions used in the BreedObject analysis to calculate the
      selection index.  More information is available on the weightings
      used in the New Zealand Angus Selection Indexes.
      Accuracy

      Accuracy (%) is based on the amount of performance information
      available on the animal and its close relatives - particularly the number
      of progeny analysed.  Accuracy is also based on the heritability of the
      trait and the genetic correlations with other recorded traits.  Hence
      accuracy indicates the “confidence level” of the EBV.  The higher the
      accuracy value the lower the likelihood of change in the animal’s
      EBV as more information is analysed for that animal or its relatives.
      Even though an EBV with a low accuracy may change in the future,
      it is still the best estimate of an animal’s genetic merit for that trait.
      As more information becomes available, an EBV is just as likely to
      increase in value, as it is to decrease.
      Accuracy values range from 0-99%.  The following guide is given for
      interpreting accuracy:

      Accuracy range  Interpretation
                    EBV should be considered as a preliminary
                    estimate.  It could change substantially as
        Less than 50%
                    more  performance  information  becomes
                    available.
                    Medium   accuracy,  usually  based  on
                    the animal’s own records and pedigree.
          50-74%    Still subject to substantial changes with
                    more information, particularly when the
                    performance of progeny are analysed.
                    Medium - high accuracy and includes some
                    progeny  information.    Becoming  a  more
          75-90%
                    reliable indicator of the animal’s value as a
                    parent.
                    High accuracy estimate of the animal’s true
                    breeding value.  It is unlikely that the EBV
       More than 90%
                    will change much with the addition of more
                    progeny data.
      As a rule, animals should be compared on EBVs regardless of
      accuracy.  However, where two animals have similar EBVs the one
      with higher accuracy could be the safer choice, assuming other
      factors are equal.
      For further information please contact NZ Angus or TACE.
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