INVESTIGATIONS ON POPULATION-STRUCTURE AN D BREEDING VALUE ESTIMATIONIN MIXED-MODELS IN POULTRY

Based on a Monte-Carlo study in a multi-trait mixed model we investiga ted the influence of different population structures (4; 8; 16 pens) o n genetic gain, genetic variance and inbreeding coefficient (populatio n size approximately 500 females; 500 replications; 12 generations). T he reduction of the pen number leads to an important increase of the g enetic gain and inbreeding coefficient as well as smaller genetic vari ances. Furthermore, we checked the value of additional information fro m all relationships and performances in this model (100 replications). The inclusion of the relationship and performance information of the last 4 generations leads also to an considerable surplus of the select ion gain. Compared to a model, which uses only the last generation dat a, for the aggregate genotype [1b.v.(egg number) +3*b.v.(feed conv.)] in the 12th generation we found: a) males: +11.6%; +23.6%; +24.9% b) females: +1.1%; +1.7%; +3.5% for 4, 8, 16 pens resp.