Page 9 - Brackenfield 2020
P. 9

Days to Calving EBV (days) indicates the fertility of the daughters
      of the sire. It is the time interval between the day when the female
      is first exposed to a bull in a paddock mating to the day when she
      subsequently calves. A negative EBV for days to calving indicates a
      shorter interval from bull-in date to calving and therefore higher
      fertility.
      Carcase Weight EBV (kg) is based on abattoir carcase records and
      is an indicator of the genetic differences in carcase weight at the
      standard age of 750 days.
      Eye Muscle Area EBV (sq cm) is calculated from measurements
      from live animal ultrasound scans and from abattoir carcase data,
      adjusted to a standard 400 kg carcase. This EBV estimates genetic
      differences in eye muscle area at the 12/13th rib site of a 400 kg
      dressed carcase. More positive EBVs indicate better muscling on
      animals. Sires with relatively higher EMA EBVs are expected to
      produce better-muscled and higher percentage yielding progeny
      at the same carcase weight than will sires with lower EMA EBVs.
      Rib  Fat and  Rump  Fat  EBVs (mm)  are calculated from
      measurements of subcutaneous fat depth at the 12/13-rib site
      and the P8 rump site (from live animal ultrasound scans and
      from abattoir carcases)  and  are  adjusted  to a  standard  400  kg
      carcase. These EBVs are indicators of the genetic differences in
      fat distribution on a standard 400 kg carcase. Sires with low, or
      negative, fat EBVs are expected to produce leaner progeny at any
      particular carcase weight than will sires with higher EBVs.
      Retail Beef Yield EBV (%) indicates genetic differences between
      animals for retail yield percentage in a standard 400 kg carcase.
      Sires with larger EBVs are expected to produce progeny with
      higher yielding carcases.
      Intramuscular Fat EBV (%) is an estimate of the genetic difference
      in the percentage of intramuscular fat at the 12/13th rib site in a
      400 kg carcase. Depending on market targets, larger more positive
      values are generally more favourable.
      Docility EBV (%) is an estimate of the genetic differences between
      animals in temperament. Docility EBVs are expressed as differences
      in the percentage of progeny that will be scored with acceptable
      temperament (ie. either “docile” or “restless”).
      SELECTION INDEXES
      There are currently two different selection indexes calculated
      for New Zealand Angus animals.  These are Self-Replacing and
      AngusPure. Each selection index describes a different production/
      market scenario and relates to a typical commercial herd in New
      Zealand that is targeting the following specifications.
      Index  values  are  reported  as  EBVs,  in  units  of  relative  earning
      capacity ($’s) for a given market. They reflect both the short-term
      profit generated by a sire through the sale of his progeny, and the
      longer-term profit generated by his daughters in a self-replacing
      cow herd. More information is available on selecting animals using
      a selection index.
      The Index values are derived using BreedObject technology. More

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