Cattle breeders who look at Estimated Breeding Values (EBVs) are now confronted with up to 18 different EBVs which describe the genetic merit of an animal. Some of these traits are complementary (eg, liveweight and carcase weight) and some are antagonistic (eg, marbling and retail yield).

How can you possibly make a decision on which is the best bull for your production system? What weighting should you put on each trait?

Fortunately we have a very clever computer program which can do all of these calculations for you, provided you tell it what market you are targeting. It is called BREEDOBJECT and it calculates $indexes.

To calculate these $indexes it takes into account:

• The economic importance of each trait for that market

• The heritability of each trait

• The genetic complementarity or antagonism between the traits

You may think this is new technology. It is not. The poultry, pig and dairy industries have been using it for many years.

The relative importance of each trait for a range of markets is shown below:

1. Japanese B3 market



Not surprisingly, marbling score is the most important trait. However, note that weaning rate, liveweight, dressing percentage and meat yield are also important.

2. Domestic Market Terminal Sire



The index for a Terminal Sire for the Domestic Market is much simpler because all female progeny are slaughtered so maternal traits such as milk production and days to calving are not relevant.

400-Day Weight and retail beef yield are the most important with direct calving ease also important. Fat depth has a small importance.

3. Self-Replacing Limousin herd producing Steers

Note the big differences from the terminal sire example. The maternal traits, days to calving and maternal calving ease are now very important as well as direct calving ease (size and shape of the calf).

Note that even in a self replacing herd, milk is not as important as some would expect. Marbling has no importance for this market.

Most of the bulls produced by most Limousin breeders are for use as terminal sires.

However some commercial breeders keep Limousin X females and even higher content Limousin females. It is also important to have a functional and fertile Limousin stud herd. My advice is to use the self-replacing index for selection of sires for your herd.

If your bull buyers are interested you can provide both terminal sire and self-replacing herd indexes for your sale bulls.

In fact they are already available on our website www.limousin.com.au.

You can also use the website to sort and select available AI Sires on the index that suits your production system.

As well as sorting on an index you can impose other restrictions such as a maximum birthweight, a minimum docility and colour or horn status.

The example below lists AI sires selected for a self-replacing herd with a maximum birthweight of +3.0 kgs and a maximum docility EBV of +2 and sorted on the self-replacing herd index.

At this stage docility is not included in the indexes because its genetic relationship with the other traits and economic value has not yet been established. At this stage it needs to be used as an independent trait by setting a minimum acceptable value.