Limousin breeders and bull buyers are now confronted by up to 18 different EBVs which describe the genetic merit of each animal for growth and fertility, carcase and docility.

It is not possible to put the correct emphasis on each EBV to come up with the most profitable animal for a given production system without some help.

We now have the tools to do this in the form of dollar indexes which are calculated for many animals in the breed and displayed as an option on the website.

These indexes take into account the economic weighting of each trait, its heritability and genetic correlation with other traits.

Three dollar indexes are available for Limousin:

Each of these indexes is based on the correct economic weighting for each trait which is relevant to that production system. For example, in the $ index for a terminal sire for the domestic market the EBVs for milk and days to calving are not relevant because daughters of the bull are not retained. However for a self replacing Limousin herd these traits are important.

Figure 1 shows the relative economic weighting on each trait for the two production systems.

(a) Terminal Sire for domestic Beef

(b) Self Replacing herd producing steers

For the terminal sire $ index 400 day weight and direct calving ease have the most importance with retail beef yield and fat depth also important.

In the self-replacing herd the female fertility trait days to calving is the most important with calving ease also important.

When using the $indexes to select AI sires or young bulls additional criteria can be imposed. For example, the EBV for docility is not incorporated in the index and can be used independently.

While the birthweight EBV is incorporated in the $ index a secondary criteria could be imposed to give some protection against a bad calving year. For example, a maximum birthweight of +3.0 could be imposed.

However the $ index approach allows some compromises to be made. If a sire has a very high $ index a slightly higher birthweight than 3.0 may be tolerated.

What does the $ index mean?

If there was a choice between two bulls to be used as terminal sires with $ indexes of +$30 and +$10 the value of each calf by the +$30 bull would be $10 greater than the value of the progeny of the +$10 bull (This is because only half the difference between the bulls is passed onto the progeny 30 - 10 / 2 = 10

For 30 calves each year over five years this amounts to $1500 difference in the value of the progeny of the two bulls.

For more information about the Breed Object program which calculates $ indexes, click here www.breedobject.com