2.1.3 Selection and mating and dissemination of genetic gain

Fifth, given the estimated breeding values of sires and dams, the actual selection of parents has to take place (step 5). The parents with a higher than average estimated breeding value will cumulatively improve the breeding goal traits in the next generations. When for example a group of dairy sires with the highest breeding value for milk yield is selected as sires for the next generation, their daughters and offspring in later generations will produce more milk than the present generation of dairy cows. Proper selection of parents will give a positive selection response in the next generations. Selection creates progress in breeding goal traits. After the selection of the parents another choice has to be made: which sire should be mated to which dam? The choice can be made e.g. on base of the pedigree information available or on the traits of the sires and the dams.

Dissemination of genetic gain

Sixth, in many breeding schemes the number of animals from which traits are recorded is rather small in relation to the population of animals used for human purposes. 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 and via a few “multiplying generations” the selection response obtained in the top is disseminated to the animals producing meat or eggs are bred. In cattle breeding artificial reproduction techniques, in particular artificial insemination techniques, give the opportunity to produce high numbers of offspring, disseminating the genes of the superior animals widely. Selection of a small number of animals may have a large impact on the traits of a population. Within the commercial breeding schemes e.g. for poultry and pigs specialized lines are crossed. These lines each are selected for specific traits and crossed in the multiplying phases to obtain crossbred progeny with the breeding goal traits by combining the traits of each of the lines.