True digestibility of phosphorus determined by regression method for rapeseed meal

One-hundred and forty-four male broiler chickens at 26 d old were employed to determine the ileal true phosphorus digestibility of a double zero rapeseed meal (RSM). The broiler chickens were reared together and received diets meeting nutrient recommendations from d 0 to 21. On d 21, the broiler chickens were weighed and allocated to three treatments (eight replicates and six broiler chickens per replicate) in a randomized complete block design. The three diets were maize starch and dextrose-based semi-purified diets in which RSM was added at the rates of 450, 560, and 670 g/kg as the sole source of P. All the broiler chickens were euthanized on d 26 and digesta from the distal ileum were collected for chemical analysis. Apparent ileal P digestibility tended to increase linearly (P=0.074) with increasing level of RSM in the diet. Intake of total and ileal digestible P, as well as total P output, increased linearly (P <0.01) with increasing dietary P supplied by RSM. Regression of P output against dietary P produced the regression equation: Y=0.575x+1.140Y=0.575x+1.140, with the estimate of true P indigestibility being 57.5%. Consequently the ileal true P digestibility for the RSM was calculated to be 43%. It was concluded that RSM can be substantial source of P, as well as protein and energy for broiler chickens.