title: Phosphorus digestibility response of broiler chickens to dietary calcium-to-phosphorus ratios.
abstract: This study was conducted to evaluate the true digestibility of P in soybean meal (SBM) for broiler chickens fed diets with different dietary calcium-to-phosphorus ratios (Ca:P) using the regression method. The experiment used a 4 × 3 factorial arrangement with 12 diets formulated to contain combinations of 4 levels of dietary Ca:P: 0.8, 1.2, 1.6, or 2.0 and 3 levels of SBM: 31.0, 44.0, or 57.0%. A total of 576 male Ross 708 broilers were allocated to 12 dietary treatments with 8 cages (6 birds per cage) per treatment from d 15 to 22 posthatching, and the BW between groups were similar. Chromic dioxide was used as an indigestible marker to calculate P digestibility and retention. The results showed that BW gain and feed efficiency were increased (linear, P < 0.01), and prececal DM digestibility and DM retention were decreased (linear, P < 0.01) with graded SBM in diets for each Ca:P. Decreasing linear (P < 0.01) relationships were observed for apparent prececal P digestibility and total tract P retention with increased dietary SBM levels. The prececal and excreta P output increased (linear, P < 0.01; quadratic, P < 0.05) as increasing levels of SBM were added to the experimental diets. True prececal P digestibility in SBM was greater (P < 0.05) for birds fed a diet with Ca:P of 0.8 compared with those fed higher Ca:P, but there was no difference among the Ca:P ratios between 1.2 and 2.0. However, the total tract retention of P from SBM was not affected by Ca:P between 0.8 and 2.0. In conclusion, results of the present experiment demonstrated that prececal digestibility of P in SBM was not affected by Ca:P ratio between 1.2 and 2.0; and there was no difference in total tract retention of P from SBM among the Ca:P ratios between 0.8 and 2.0 in broiler chickens.
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Liu
authors.forename: D W
authors.initials: DW
authors.lastname: Chen
authors.forename: O
authors.initials: O
authors.lastname: Adeola
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002136:Calcium, Dietary / Q000378:metabolism*; D002645:Chickens / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D004063:Digestion / Q000502:physiology*; D010758:Phosphorus / Q000378:metabolism*; D016226:Phosphorus, Dietary / Q000378:metabolism*
chemical_list: D002136:Calcium, Dietary; D016226:Phosphorus, Dietary; D010758:Phosphorus