A Guide to Angus Selection Indexes Ten selection indexes are published for animals within the TransTasman Angus Cattle Evaluation (TACE). The selection indexes cater for a range of different breeding systems, target markets and production systems, and include: Index Name
each animal to identify animals with genetics that are most aligned with the breeding objective for the given selection scenario.
Abbreviation
Angus Breeding Index
$A
Example Selection Index Calculation
Domestic Index
$D
Heavy Grain Index
$GN
Selection Index = b1T1 + b2T2 + b3T3 + …….. + bⁿTⁿ
Heavy Grass Index
$GS
Angus Breeding Low Feed Cost Index
$A-L
Domestic Low Feed Cost Index
$D-L
Heavy Grain Low Feed Cost Index
$GN-L
Heavy Grass Low Feed Cost Index
$GS-L
AngusPRO Index
$PRO
Angus Terminal Sire Index
What is a selection index?
$T
Selection indexes are utilised by livestock breeders of many species around the world and are considered an essential part of any modern livestock breeding program. Selection indexes aid in the selection of animals for use within a breeding program where there are several traits of economic or functional importance by providing an overall “score” of an animal’s genetic value. Selection indexes are derived for a specific breeding purpose and are calculated based on weightings placed on individual traits that are deemed to be important for that purpose. The selection indexes assist in making “balanced” selection decisions, taking into account the relevant attributes of
Where b = weighting placed on the trait T = trait
How are selection indexes calculated?
The selection indexes published within the TransTasman Angus Cattle Evaluation are economic selection indexes and are derived using BreedObject software, as developed by the Animal Genetics & Breeding Unit (AGBU) in Armidale, NSW. A range of different selection indexes are published, with each individual selection index reflecting differences in net profitability, being income minus expenses, in a defined breeding system, target market and production system. For the breeding system, target market and production system relevant to each respective selection index, the BreedObject software firstly calculates the net economic value of changing each trait in the breeding objective by one unit, independent of any change in other traits. The BreedObject software then links the economic value of the traits in the breeding objective with the Estimated Breeding Value (EBV) traits published in the TransTasman Angus Cattle Evaluation, and places appropriate emphasis on each EBV based on its relative economic importance in the defined breeding system, target market and production system.
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