What is an Estimated Breeding Value?
Estimated Breeding Values(EBVs) are predictions of an animal's genetic merit, based upon available performance information on the individual and it's relatives.
The EBV of an animal is calculated by comparing the performance of that animal with the average performance of the group of animals(contemporary group)that animal has been running with. A contemporary group is one containing animals of the same age group and sex, within a herd, which are given exactly the same opportunity to perform.
Before calculating an EBV, certain adjustments need to be made to the raw information to remove inequalities created by differences due, for example, to date of birth, age of dam.
Calculation of a simple within herd EBV
The adjusted 400 day weight for animal X is 380 kgs., compared with the average for its contemporary group of 350 kgs. There is no information on its relatives. The heritability for 400 day weight is 0.3 or 30%. ie. 30% of the measured performance difference between animals is the result of genetic influences and will be passed on to the progeny.
Animal X's 400 day wt. EBV= (adjusted wt. of X - average adjusted wt.of the group) x heritability for 400 day wt.
=(380 kgs. – 350 kgs.) x 0.3 kgs. = 30 x 0.3 kgs. = 9 kgs.
This is the simplest form of an EBV using information on the animal's own performance. Modern genetic evaluation systems use information on relatives and the effects of related traits to make the EBV more accurate.