Investigations of the importance for breeding of maternal lines in a Saxonian dairy cattle population - 2nd communication: Results of the estimation of individual effects

The inclusion of random line effects into the estimation of breeding values is not practicable. However, a conversion of the random effects into fixed effects and their combination with additive genetic effects is a potential approach that can be used to estimate breeding values. Fixed effects are h elpful to rank the best animals within large maternal lines or to distingui sh maternal lines from each other. Therefore, maternal lines with mothers o f sires exhibit better breeding values and higher fixed line effects. Chang es in ranking according to breeding values are more common if maternal effe cts are included into the estimation in comparison to models that do not in clude these effects. The cause for changes in ranking and their influence o n the estimation of breeding values needs to be determined in future studie s. Moreover, line effects need to be distinguished from maternal effects by using advanced methods. Molecular biological methods could help to explain differences between maternal lines for milk performance and secondary trai ts.