Page 45 - Woodbank-Matariki ebook

Understanding
Hereford Selection Indexes

New Zealand Herefords currently report three different selection indexes.
These are the Hereford Prime Index, Beef Heifer Index and the Dairy Beef
Index. These Indices relate to typical commercial herds in New Zealand
targeting these specifications.
Index values are reported as EBVs, in units of relative earning capacity ($)
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. A selection index combines the
EBVs with economic information (costs and returns) for specific market and
production systems to rank animals based on relative profit values. Note
that different types of animals can give similar profit values, so consideration
should be given to both the index and the component EBVs when selecting
animals for a particular production system. More information is available
on selecting animals using a selection index. The Index values are derived
using BreedObject technology.
There are three breed-specific Indexes for Hereford cattle:
1. Hereford Prime Index
Estimates the genetic differences between animals in net profitability
per mixed age cow joined for a typical self-replacing commercial herd
where Hereford bulls are joined to either Hereford or other British
breed females and targeting the production of grass finished steers
for the Hereford Prime program. Selected heifers are retained for
breeding and so maternal traits are of importance. Steers target 550
kg live weight (300 kg carcase weight & 7 mm P8 fat) at 20 months
of age, and heifers 475 kg (260 kg carcase weight & 8 mm fat depth),
at 22 months of age.
2. Beef Heifer Index
Estimates the genetic differences between animals in net profitability
per yearling heifer joined for a typical self-replacing commercial herd
where Hereford bulls are joined to either Hereford or other British
breed heifers. Selected heifers are retained for breeding and so
maternal traits are of importance. Steers target 510 kg live weight
(280 kg HSCW and 7 mm P8 fat depth) and heifers 450 kg ( 250 kg
HSCW and 8 mm P8 fat depth) at 20 months of age.
3. Dairy Beef Index
Estimates the genetic differences between animals in net profitability
per mixed age dairy cow joined with all progeny destined for slaughter.
Steers and heifer progeny target 550 kg live weight (300 kg carcase
weight and 6 mm fat depth) at 24 months of age and at 475 kg live
weight (260 kg carcase weight and 7 mm fat depth) at 22 months,
respectively.
Note that $Index values for individual animals are sensitive to the
assumptions used in the BreedObject analysis to calculate the selection index.

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