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a system of pedigree breeding used for domestic breeds of agricultural animals. Linebreeding is based on the rational use in a number of generations of the valuable qualities of individuals of outstanding merit (see [in genetics]).
To establish a line, a foundation sire is selected from individuals of the greatest merit; selection is based on an evaluation of the progeny. The best females are mated with the sire, yielding offspring of the desired type and merit. From these offspring, the best sires are identified and, from them, a continuer of the line is selected (based on a progeny evaluation). The male offspring of this sire are evaluated according to their own offspring, and a new continuer of the line is selected from among them. This process is continued for three to six generations.
To increase the hereditary influence of the foundation sire, somewhat distantly related individuals are sometimes mated (see). Valuable dams (through their offspring) are also important in linebreeding; the gene pool of the line is marked by greater homozygosity. Breeding with female families is being conducted to ensure the matching of the best dams with the sire. Line crosses between the most successfully combined lines are also used.
Linebreeding furthers the differentiation of a breed into genetically nonidentical groups, as a result of which a complex structure of the breed is established and maintained and continual improvement of the breed is ensured. Linebreeding was first used in the 18th century in horse breeding (in Russia, the Orlov Trotter). Russian scientists, such as E. A. Bogdanov and D. A. Kislovskii, have contributed greatly to the development of the breeding systems.
Linebreeding in poultry farming differs slightly from the system described above. Inbred lines are established through purposeful selection over three to five generations within the flock (within closed populations). Hybrid poultry are produced by crossing the inbred lines, which are systematically tested for combining ability.
N. A. KRAVCHENKO