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Why use an index?

Selection indexes help you to select sheep which match the breeding objective.

To make selection more efficient, ASBVs for several traits are combined to give a single value. Indexes work well because they:

  • Place emphasis on traits – weighting depending on economic value.
  • Take into account correlations – get the ideal balance between traits.
  • Enable gain across many traits.

The index reflects the performance of the sheep relative to the breeding objective of the index.

What are other methods of selection?

Index selection is the superior method for selecting animals. It takes into account the whole picture and allows you to more efficiently breed sheep. There are other techniques that breeders may use that are not as efficient as index selection. These are:

Mass Selection
Selecting animals based on raw data without taking account of environment or pedigree. Works okay for highly heritable traits such as fibre diameter. It is more inaccurate than using ASBVs and has slower genetic gain.

Pedigree Selection
Making selection based on superior relatives. Only works for closely related animals such as sire or dams. It does not take into account the heritability of traits.

Independent culling levels
Using ASBVs but looking at individual traits and keeping animals that are above your set culling levels.

Tandem selection
Seeking to improve a group of particular traits in the flock before moving onto the other traits.