In many breeding programs trait recording is expensive and therefore the number of animals from which traits are recorded is rather small in relation to the whole population of animals. Then, the genetic improvement is realized with a limited number of animals in which the selection is practiced. Subsequently, selected animals are used to disseminate the genetic improvement realized in the recorded population into the whole population. The selection of a limited number of animals, the multiplication in the next generation with a much larger number of animals and the production of the “production” animals in very large numbers in the final generation, leads to a pyramidal structure of such a breeding and production program. Besides, the pyramidal structure will allow to apply crossbreeding (hybridization), which can fully utilize the advantages of heterosis.
The dissemination of the selection response depends of the structure of the breeding programs. In commercial pigs and poultry programs, selection takes place in the top of the breeding program. In the pure lines in the top genomic selection is applied. Via a few “multiplying generations” the selection response obtained in the top is disseminated into the animals producing meat or eggs.