title: Linking ileal digestible phosphorus and bone mineralization in broiler chickens fed diets supplemented with phytase and highly soluble calcium.
abstract: The objectives of this study were to determine the ileal digestibility of P in potassium phosphate, phytase-related ileal digestible P release, bone-mineralization-based ileal digestible P equivalency of phytase, and phytase-related efficiency of ileal digestible P utilization for bone mineralization in broiler chickens at 2 dietary concentrations of highly soluble Ca (HSC). Birds were sorted by BW at d 15 posthatch and assigned to 8 cages per diet with 8 birds per cage. Twelve diets were arranged in a 2 × 6 factorial of HSC at 5 or 6 g/kg and P supply treatment at 6 levels consisting of 4 added P levels (P from KH2PO4 added at 0, 0.7, 1.4, or 2.1 g/kg of diet) or 2 added phytase levels (500 or 1,000 phytase units). On d 24 posthatch, ileal digesta were collected for ileal P digestibility (IPD) determination and the left tibia was collected from the 4 heaviest birds in each cage for bone ash determination. Weight gain, G:F, and tibia ash were higher (P < 0.05) at 5 than at 6 g of HSC/kg. Added P from KH2PO4 or added phytase linearly increased (P < 0.001) weight gain, G:F, tibia ash, and IPD. The IPD of KH2PO4 derived from multiple linear regressions of digestible on total P intake for the diets without added phytase showed a reduction (P < 0.05) from 89.5 to 84.5% with increased HSC from 5 to 6 g/kg. Polynomial regressions of digestible P intake on phytase intake indicated that 1,000 units of added phytase released 1.701 or 1.561 g of digestible P in diets containing 5 or 6 g of added HSC/kg, respectively. Polynomial regressions of tibia ash on digestible P or phytase intake in diets containing 5 or 6 g of added HSC/kg at 1,000 phytase units gave digestible P equivalency of 1.487 or 1.448 g, respectively. Thus, phytase-related efficiency of ileal digestible P utilization for bone mineralization was 87.4 and 92.8% in diets containing 5 or 6 g of added HSC/kg, respectively.
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA. ladeola@purdue.edu
authors.forename: O
authors.initials: O
authors.lastname: Adeola
authors.forename: C L
authors.initials: CL
authors.lastname: Walk
mesh_terms: D010832:6-Phytase / Q000378:metabolism / Q000494:pharmacology*; D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002113:Calcification, Physiologic / Q000187:drug effects*; D002118:Calcium / Q000737:chemistry / Q000494:pharmacology; D002645:Chickens / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D004063:Digestion / Q000502:physiology*; D007082:Ileum / Q000502:physiology*; D008297:Male; D010758:Phosphorus / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010758:Phosphorus; D010832:6-Phytase; D002118:Calcium