The concept of true breeding value has been discussed in other fact sheets in this series. A pig's true breeding value is never really known for any trait because it is not directly measurable. Therefore, some means of predicting or estimating breeding values for traits are required. Several methods that depend upon the available information can be used to calculate EBVs. All methods are based upon the concept of the deviation of an individual's or relative's records from their respective contemporary group averages and multiplying the deviation by a weighting factor.
P is the individual's record and P is the average of the individual's contemporary group.
Boar A has an adjusted backfat measurement of .65 inches and his contemporaries average .75 inches. This means that genetically he is leaner than his contemporaries by .04 inches. For traits such as number of pigs farrowed, there could be four or five records on each sow. Utilizing as many records as possible on each pig will also improve our ability to estimate breeding values. The sources of information contributing records to the estimate must be known.