Influence of different bone meal particle size induced calcium specific appetite on performance and egg quality parameters of layer chickens†

The effects of free choice feeding of bone meal (BM) of different particle sizes on performance and egg quality traits of layer chickens were assessed. A total of 128 Hy-line White layers (56 wks old, BW +/- SD: 1500 +/- 18 g) were assigned randomly into 16 cages of 8 birds each. Four dietary treatments based on BM particle sizes (Layer Diet/Control; Layer diet + 1-2 mm BM; Layer diet + 2-3 mm BM; Layer diet + 3-4 mm BM) were choice fed for five weeks. Dry matter (DM), calcium (Ca), total phosphorus (TP), ash content, particle size distribution and in vitro solubility of BM were tested. The birds' performance and external and inernal egg quality traits were examined over a 5 wk period. The DM, Ca, TP and ash content of BM were 893, 79, 44 and 476 g/kg, respectively. The geometric mean diameter (GMD) and the geometric standard deviation (GSD) of BM were 1.7 and 1.6 mm, respectively. In vitro solubility of 1-2 mm, 2-3 mm and 3-4 mm BM particles were 56.3, 47.5 and 39.8%, respectively. Bone meal, when choice fed, increased BM intake, Ca intake, and laying percentage, and reduced damaged egg percentage. Birds fed with BM having 2-3 mm particles performed best in improving the performance and egg quality. Bone meal significantly (p < 0.05) improved the egg shell thickness with maximum thickness recorded from birds fed with BM of 2-3 mm particle size. BM with 2-3 and 3-4 mm particles improved (p < 0.05) shell ratio and unit surface shell weight. The present study concluded that feeding with BM with 2-3 mm particle size is the best to improve the overall performance and egg quality traits of layer chickens.