The activities of these commercial breeding
companies are characterized by the following
features:
Pedigree selection occurs in the nucleus
only.
• Selection is strictly within specialized lines
(or breeds). These lines are designated as
sire and dam lines and are selected with
different intensities. In poultry bred for
meat and in pigs, male lines are selected for
growth and lean meat production, while
female lines are selected for reproduction.
New lines are constantly developed either
by crossing between existing lines or by
further selection in a given direction.
• The final product is a cross between two or
more pure-bred lines.