The aims of the present study were therefore to evaluate the impact of selection according to AMEn on excretion traits, especially N and P excretion, until birds reach a commercial BW and to estimate its indirect impact on growth, body composition, meat quality, and bone strength. The evolution of the gastrointestinal tract morphology with age was also studied to understand the mechanisms involved in differences between lines. The line used at the beginning of the selection experiment to create the D+ and D- lines was also included in the comparison to evaluate the potential practical improvement that can be expected from selection on digestibility. It is of note that this reference line (RL) has been selected for commercial purposes after the beginning of the selection experiment and is not properly a control line.