Page 12 - Waimara Angus Catalogue ebook

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 three different selection indexes calculated for New Zealand Angus
animals. These are Self-Replacing, AngusPure and Heifer/Dairy Terminal. 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 ($’s) for a given market.
They reflect both the short-term profit generated by a sire through the sale of his progeny,
and the longer-term profit generated by his daughters in a self-replacing cow herd. More
information is available on selecting animals using a selection index.
The Index values are derived using BreedObject technology. More information is available from
the BreedObject web site.
SELF-REPLACING INDEX ($) - 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 ($) – Estimates genetic differences between animals in net profitability
per cow joined for a self-replacing commercial Angus herd, targeting the production of grass
finished steers for the AngusPure programme. Steers are assumed marketed at 525 kg live
weight (280 kg carcase weight and 10 mm fat depth) at 18 months of age with a significant
premium paid for marbling.
HEIFER/DAIRY TERMINAL INDEX ($) – Estimates the genetic differences between animals
in net profitability per female joined in an example herd where all progeny are marketed. All
progeny are marketed at approximately 510 kg live weight (280 kg carcase weight and 7 mm fat
depth) at approximately 24 months of age.
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 Indices.
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:
See the Table overleaf. 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.
10 Waimãra Angus