Page 64 - Rangatira Angus Catalogue 2021 ebook

with relatively higher EMA EBVs are expected to produce better-muscled and higher Accuracy
percentage yielding progeny at the same carcase weight than will sires with lower EMA
EBVs. Accuracy (%) is based on the amount of performance information available on the
animal and its close relatives - particularly the number of progeny analysed. Accuracy
Rib Fat and Rump Fat EBVs (mm) are calculated from measurements of subcutaneous is also based on the heritability of the trait and the genetic correlations with other
fat depth at the 12/13-rib site and the P8 rump site (from live animal ultrasound scans recorded traits. Hence accuracy indicates the “confidence level” of the EBV. The higher
and from abattoir carcases) and are adjusted to a standard 400 kg carcase. These EBVs the accuracy value the lower the likelihood of change in the animal’s EBV as more
are indicators of the genetic differences in fat distribution on a standard 400 kg carcase. information is analysed for that animal or its relatives. Even though an EBV with a low
Sires with low, or negative, fat EBVs are expected to produce leaner progeny at any accuracy may change in the future, it is still the best estimate of an animal’s genetic
particular carcase weight than will sires with higher EBVs. merit for that trait. As more information becomes available, an EBV is just as likely to
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 Accuracy range Interpretation
produce progeny with higher yielding carcases. less than 50% EBV should be considered as a preliminary estimate.
Intramuscular Fat EBV (%) is an estimate of the genetic difference in the percentage It could change substantially as more performance
of intramuscular fat at the 12/13th rib site in a 400 kg carcase. Depending on market information becomes available.
targets, larger more positive values are generally more favourable.
50-74% Medium accuracy, usually based on the animal’s own
Docility EBV (%) is an estimate of the genetic differences between animals in records and pedigree. Still subject to substantial changes
temperament. Docility EBVs are expressed as differences in the percentage of progeny with more information, particularly when the performance of
that will be scored with acceptable temperament (ie. either “docile” or “restless”). progeny are analysed.
Selection Indices 75-90% Medium - high accuracy and includes some progeny
There are currently two different selection indexes calculated for New Zealand Angus information. Becoming a more reliable indicator of the
animals. These are Self-Replacing and AngusPure. Each selection index describes a animal’s value as a parent.
different production/market scenario and relates to a typical commercial herd in New
Zealand that is targeting the following specifications. more than 90% High accuracy estimate of the animal’s true breeding
value. It is unlikely that the EBV will change much with the
Index values are reported as EBVs, in units of relative earning capacity ($’s) for a given addition of more progeny data.
market. They reflect both the short-term profit generated by a sire through the sale of his
progeny, and the longer-term profit generated by his daughters in a self-replacing cow increase in value, as it is to decrease.
herd. More information is available on selecting animals using a selection index. Accuracy values range from 0-99%. The following guide is given for interpreting
The Index values are derived using BreedObject technology. More information is accuracy:
available from the BreedObject web site.
As a rule, animals should be compared on EBVs regardless of accuracy. However,
Self-Replacing Index ($) - Estimates genetic differences between animals in net where two animals have similar EBVs the one with higher accuracy could be the safer
profitability per cow joined for a self-replacing commercial herd, targeting the production choice, assuming other factors are equal.
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. For further information please contact NZ Angus or BREEDPLAN.
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 Indices.

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