The purpose of breeding is to make the chicken gene homozygous, the production traits tend to be consistent, and the production performance indicators continue to improve. High yield commercial hybrid chickens can be produced through breeding. There are two conventional breeding methods, inbreeding method and closed group family selection method.
1、 Inbreeding method
The inbreeding method is used to cultivate new varieties. The result of inbreeding will reduce the egg production, viability and fecundity of chickens. However, through hybridization between inbred lines, obvious heterosis will be generated. In order to select the best cross combination, inbreeding method must establish a large number of inbred lines, so it requires a lot of chicken houses and funds.
2、 Selection of closed group families
Blocking breeding method will not bring harm to production, and is now widely used. If there are too few closed lines, inbreeding will inevitably occur after several generations of breeding.
In order to avoid inbreeding, 5~7 lineages should be established in each line to form 5~7 small lines. In each generation of breeding, the cock of one small line mates with the hen of another small line. 20%~40% hens and 2%~3% cocks are selected for breeding in each generation. When selecting hens to stay, both the performance of the family and its own performance level should be considered. When selecting roosters to stay, both the performance of the family and that of the siblings should be considered. The more families, the greater the selection pressure, and the faster the genetic progress.
