Genetic progress
Genetic improvement per generation is determined by three factors:
It requires genetic variation in order to select only the best.
In order to select only the best, breeders must decide which candidates are the best. Confidence on this ranking depends on accuracy of estimated breeding values of candidates.
The extent to which selection will results in genetic improvement depends on the intensity of selection.
We can summarize genetic improvement per generation by the following equation:
Because herd owners are usually interested in genetic progress per year, a fourth factor is quite important in determining the rate of genetic improvement. Genetic progress per generation divided by the number of years per generation gives genetic progress per year. Thus generation interval is important. The generation interval is the average time between birth of an animal and birth of its replacement.
We can therefore write:
