The ingredient and nutrient composition of the experimental diets are presented in Table 1. Three of the four experimental feeding regimens were based on alternative supplementary Ca sources to that of limestone. The Ca source treatments were limestone (LMS), LMS with meat and bone meal (MBM), LMS with oyster shell meal (OSM) and LMS with MBM + OSM combination, respectively. For the first treatment, the hens received a basal diet with only ground limestone as a control without MBM and OSM. MBM was supplemented at a 4% inclusion level, replacing dicalcium phosphate (DCP) in treatment two. Since MBM is also rich in both P and Ca, it substituted dietary supplemental DCP according to a least-cost formulation programme. The hens in the third treatment received this diet with 2% OSM replacing 2.4% limestone in the basal diet (0.25 OSM + 0.75 LMS). The hens in the fourth treatment were fed 4% MBM + 2% OSM (combination approach).