True ileal phosphorus digestibility of monocalcium phosphate, monodicalcium phosphate and dicalcium phosphate for broiler chickens

This study was conducted to determine the true ileal phosphorus (P) digestibility of monocalcium phosphate (MCP), monodicalcium phosphate (MDCP) and dicalcium phosphate from bones (DCP) for broiler chickens using the regression method. A corn-soy basal diet was formulated to contain 2.5 g/kg total P. Each test ingredient was then included at three levels to the basal diet to achieve graded concentrations of total P (3.0, 3.5 and 4.0 g/kg, respectively). The calcium (Ca):P ratio was maintained at 1.35-1.40:1 by the addition of limestone. Titanium dioxide (3 g/kg) was included in all diets as an indigestible marker. Day-old male broiler chicks were fed a commercial broiler starter diet from 1 to 20 days of age. On day 21, birds were individually weighed and assigned to 60 cages (6 birds/cage) and the 10 experimental diets (basal diet and 9 diets with 3 inclusion levels of each test ingredient) were then randomly allocated to 6 replicate cages each. The birds were fed the experimental diets ad libitum for 8 days. On day 29, all birds were euthanized and ileal digesta were collected from the posterior half of the ileum. True P digestibility of MCP, MDCP and DCP were calculated by the linear regression analysis. True P digestibility of MCP, MDCP and DCP were determined to be 64.6, 60.2 and 69.3%, respectively. The present results suggest that the P digestibility from two inorganic sources (MCP and MDCP) and one organic source (DCP from bones) were lower than the values of available P currently assumed in poultry feed formulations.