True ileal digestibility of phosphorus from dicalcium phosphate in diets for broilers

Abstract

The objective of this study was to determine the true ileal digestibility coefficient of phosphorus (TIDCP) of three dicalcium phosphates of different origins in diets for broilers using the regression method. The experimental design was completely randomized in a 3 × 2 + 1 factorial scheme with three dicalcium phosphates (DCP1, DCP2 and DCP3), two inclusion values (0.75 and 1.5 g/kg of P), and a basal diet. The seven diets were formulated based on corn and soybean meal: one (basal) diet lacked dicalcium phosphate, and six diets contained a concentration gradient of the test ingredients. Each test ingredient had two inclusion values of 0.75 and 1.5 g/kg of P. Titanium dioxide was added to the experimental diets at 5 g/kg as an indigestible indicator. A total of 252 Cobb 500 male broilers, 19 days old (average weight ± SD, 806 ± 29 g) were housed in metabolic cages and assigned to the seven test diets. On the 22nd day of life, all birds were euthanized, and the ileal contents were collected. The apparent digestibility of the diets was influenced by dicalcium phosphate source (P < 0.05), with greater P digestibility birds that received diets with the inclusion of DCP2. P digestibility was unaffected (P > 0.05) by increasing dietary concentrations of P. The TIDCP of DCP1, DCP2 and DCP3 was determined, by the regression method, to be 0.3639, 0.4897 and 0.3553, respectively. The endogenous P losses estimated by the regression method for DCP1, DCP2, and DCP3 were 0.66, 0.27 and 0.76 g/kg DM, respectively. In despite of differences in diet digestibility, there were no differences between TIDCP values (P > 0.05), as determined by covariance analysis. The use of a medium value of P digestibility for different sources of dicalcium phosphates can lead to errors or the use of large safety margins in the formulation of broiler diet.