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Interpreting New Zealand Angus Selection Indexes

There are currently three different selection indexes calculated for New Zealand Angus animals. These are:

  • Self Replacing Index
  • AngusPure Index
  • Heifer/Dairy Terminal Index

Each selection index describes a different production/market scenario and relates to a typical commercial herd using Angus bulls. Producers are advised to use the selection index that most closely aligns to their production system. Each selection indexes is focussed on efficient beef production, including maternal traits where appropriate. In addition, each selection index targets the following specifications.

Self Replacing Index (SRI) - Estimates the genetic differences between animals in net profitability per cow joined in an example self-replacing commercial herd that targets the production of grass finished steers. Steers are assumed marketed at approximately 480 kg live weight (265 kg carcase weight and 7 mm fat depth) at approximately 16 months of age. Selected heifers are retained for breeding and the balance marketed at approximately 16 months weighing 415 kg (230 kg carcase weight and 8 mm fat depth). As some daughters are retained, maternal traits are also of importance.

AngusPure Index (API) - Estimates the genetic differences between animals in net profitability per cow joined in an example self-replacing commercial Angus herd that targets the production of grass finished steers for the AngusPure programme. Steers are assumed marketed at approximately 530 kg live weight (290 kg carcase weight and 10 mm fat depth) at approximately 20 months of age. Selected heifers are retained for breeding and the balance marketed at approximately 20 months weighing 450 kg (240 kg carcase weight and 10 mm fat depth). A significant premium for carcase quality was assumed and, as some daughters are retained, maternal traits are also of importance.

Heifer/Dairy Terminal Index (HDT) - 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.

All selection indexes are reported as an EBV, in units of net profit per cow mated ($) for a given production/market scenario. 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 (where applicable).

All selection index values have been derived using BreedObject technology. More detailed information regarding each selection index is provided in the downloadable document.