Estimation of genetic gains in populations with overlapping generations

A technique for estimating genetic improvement from an “internal genetic control” was developed for populations which fulfil the following requirements: (1) The population can be divided into distinct subpopulations (e.g. sire families or inbred lines) with several sets of offspring such as hatches or litters produced during the life‐span of each subpopulation. (2) The replacement of subpopulations or breeders in the selection programme takes place more or less continuously to provide overlapping generations. (3) The effect of ageing of the parents on progeny performance can be measured.

The genetic change in such populations independent of environmental time trends can be estimated directly from the breeding data without any need for a separate control population.

The technique was applied to a practical meat‐type poultry breeding operation to yield an estimated annual genetic improvement of 100 g body weight for each bird at 9 weeks of age.