Understanding $Index Values

Click here for a comprehensive list of answers to Frequently Asked Questions about Breedplan

$Index Values are calculated using selection indexes derived using BREEDOBJECT software, developed by the Animal Genetics and Breeding Unit (see acknowledgements).

In an ideal situation it would be desirable to select animals for breeding that excel in all traits.But, in reality it is always necessary to make some compromises in balancing the strengths and weaknesses among the animals available for selection. A selection index is a formal method of combining Estimated Breeding Values (EBVs) for different traits into a single $Index Value.

BREEDOBJECT uses estimates of the genetic relationships between EBVs and the various traits in the breeding objective for each example to determine a set of index weighting factors to apply to each EBV.The individual EBVs are multiplied by these weighting factors and summed to produce an overall $Index Value for each animal.The weighting factors take account of the relative economic importance of the traits in the breeding objective and the capacity to change them through selection on EBVs.

Variation in $Index Values between sires indicate differences in the expected net profitability per cow joined.

The composition of any selection index is sensitive to the assumptions used in the BREEDOBJECT analysis.

$Index Values have been calculated for different production systems and markets as described below. For each $Index, typical production parameters, prices and production costs were assumed for a beef enterprise operating in the past three years. It was also assumed that the enterprise obtains benefits from improved carcase performance (eg. via retained ownership to slaughter) in addition to improved herd productivity. In addition, it was assumed that feed was a limiting resource for a large part of the year and any increase in herd feed requirements has a cost. In the self-replacing herd cases an average calving rate of 85% was assumed, with a moderate concern for calving difficulty.

Japanese B3 Index

Suitable for a self-replacing commercial herd in temperate Australia targeting the production of steers for the long-fed export markets that value marbling (eg. Japanese B3 market).

The relative emphasis on each EBV for the Japanese B3 Index is shown in Figure1.

Click here to view the distribution of $Index values among the latest calf drop for the Japanese B3 Index.

Figure 1. Percentage emphasis on each EBV in the Japanese B3 Index.

CAAB™ Index

Suitable for a self-replacing commercial herd in temperate Australia, targeting the production of steers for the Certified Australian Angus Beef™ program.

The relative emphasis on each EBV for the CAAB™ Index is shown in Figure2.

Click here to view the distribution of $Index values among the latest calf drop for the CAAB™ Index.

Figure 2. Percentage emphasis on each EBV in the CAAB™ Index.

Domestic Supermarket Index

Suitable for a self-replacing commercial herd in temperate Australia targeting grass-finished production for the domestic supermarket trade with no marbling requirement.

The relative emphasis on each EBV for the Domestic Supermarket Index is shown in Figure 3.

Click here to view the distribution of $Index values among the latest calf drop for the Domestic Supermarket Index.

Figure 3. Percentage emphasis on each EBV in the Supermarket Index.

Northern Terminal Index

Suitable for a commercial crossbred herd in northern Australia using Angus sires over tropically adapted cows to produce terminal progeny to be grain fed for the Japanese B2 market.

The relative emphasis on each economic trait for the Northern Terminal Index is shown in Figure 4.

Click here to view the distribution of $Index values among the latest calf drop for the Northern Terminal Index.

Figure 4. Percentage emphasis on each EBV in the Northern Terminal Index.

$Index Percentile Values

When using $Index values to assist in selection of animals it is often useful to consider the figures relative to the values for other animals in the whole Angus population. The percentile band table for $Index Values for all calves born in a specific year is a useful guide to the relative ranking of any animal compared to the reverence year's total calf drop. For example, an animal with a CAAB™ $Index Value of +$72 is in the highest 10% of the breed for the CAAB™ selection index (i.e. relative to the specific calf drop). Similarly, an animal with a Domestic Supermarket $Index Value of +$20 is the lowest 1% of the breed for the Domestic Supermarket index.

Click here to view the percentile table for $Index values for the latest drop of calves.

Develop your own customised selection index

BREEDOBJECT can be used to establish customised selection indexes for particular situations. A questionnaire needs to be completed to provide information on production costs, performance levels and market targets.This information is used to derive the relative economic values of different traits, and the index weighting factors to be applied to the EBVs for potential candidate animals for selection.

Contact Carel Teseling (Ph 02 67723011) or Bob Dent (Ph 02 6732 5877) for more information.

Acknowledgements:
The BREEDOBJECT program was developed by the Animal Genetics and Breeding Unit (AGBU), a joint institute of NSW Agriculture and The University of New England. Ongoing research and development at AGBU is supported by funding provided by Meat and Livestock Australia. The assistance of Dr S. Barwick in the development of the indexes described above is gratefully acknowledged.