THE NATIONAL BRITISH BELGIAN BLUE EVALUATION
what it does, how it works

Beef Value and Calving Value

EBVs are presented for each trait measured but they are also combined into two multi-trait selection indexes, the Beef Value and the Calving Value. Economic weightings relevant to current market conditions are used to ensure each trait is given the appropriate amount of emphasis in the indexes.

Beef Value

The Beef Value ranks animals on their estimated overall genetic merit for growth and carcase traits. The goal of the index is to improve net returns by improving carcase weight, fat and conformation scores and each of these traits is assigned an economic value based on current UK commercial carcase pricing structures. The economic values for carcase weight and carcase fat score are adjusted for anticipated correlated responses in feed intake to account for feed costs.

Since it is difficult to directly measure carcase weight, fat and conformation (the goal traits) in the live animal, all of the direct trait EBVs, which can be accurately measured, are used to predict the genetic merit of the animal for the goal traits. The growth and carcase trait EBVs contribute the most to the calculations:

200-day growth, 400-day growth, muscle depth, muscling score and fat depth

It is possible to use EBVs for these traits to predict overall genetic merit because they are correlated with the goal traits. For example:

• high positive 400-day growth EBVs are associated with higher carcase weights so will increase the Beef Value
  
  
• high positive muscling score and muscle depth EBVs are associated with better conformation so will increase the Beef Value
  
  
• high positive backfat depth EBVs are associated with fatter carcases so will reduce the Beef Value

The Beef Value also takes account of the heritability of each trait, which is the degree to which each trait is inherited by the next generation, and correlations between traits.

Heritability and correlation estimates have been derived from UK data as well as from an extensive review of world literature carried out by SAC.

When using the Beef Value it should be remembered that only half of an animal's genetic merit for Beef Value will be passed on to its progeny. Hence the expected financial benefit in the offspring is one half of the sire's Beef Value plus one half of the dam's Beef Value.

Calving Value

In addition to the Beef Value users of Signet's Beefbreeder also have access to a second multi-trait selection index - the Calving Value. The goal of this index is to improve net returns via genetic improvement of gestation length and calving ease.

The EBVs for gestation length and calving ease are used to calculate the Calving Value but all the other traits - in particular birth weight - already contribute indirectly because of the correlations between traits. For example, high birth weight EBVs tend to be associated with more difficult calvings so will reduce the Calving Value.

The Calving Value is a terminal sire selection index. It tells us what the effect will be of using a particular bull on the ease with which his progeny are born. A bull with a high Calving Value should sire calves which are born easily and have shorter gestation lengths resulting in reduced calving costs for the producer.

A high Calving Value for a cow relates to her ability to produce bulls which, when used as sires, will produce progeny which calve easily.

Implications of having two indexes

Having two indexes provides users of the scheme with additional flexibility. The economic importance of the various traits differs substantially across breeds and production systems and the new Calving Value allows trade-offs to be made between the amount of selection pressure placed on calving traits and that placed on growth and carcase traits.