Indeed, considerably higher levels of dietary Ca levels (4% or more) have been suggested by breeders of modern layer breeds during the older age phases in order to compensate for higher Ca requirements. In spite of this, limited reports are available, re-defining the availability of alternative dietary Ca sources to limestone. Therefore, in the present study, MBM and OSM, either alone or in combination, partly replaced limestone or dicalcium phosphate in order to evaluate the influences of these feeding regimens on performance and egg quality of laying hens during the entire second production phase.