Page 9 - Atahua Angus Sale 2021 ebook

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 ($’s) for a given market. They reflect
both the short-term profit generated by a sire through the sale of his progeny, and the longer-term profit
generated by his daughters in a self-replacing cow herd. More information is available on selecting animals
using a selection index. The Index values are derived using BreedObject technology
Self-Replacing Index ($) - Estimates genetic differences between animals in net profitability per cow joined
for a self-replacing commercial herd, targeting the production of grass finished steers. Steers are assumed
marketed at 525 kg live weight (280 kg carcase weight and 10 mm fat depth) at 16 months of age.

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.
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:
For further information please contact NZ Angus or TACE.
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