title: The interplay of dietary nutrient level and varying calcium to phosphorus ratios on efficacy of a bacterial phytase: 2. Ileal and total tract nutrient utilization.
abstract: A 14-d broiler experiment was conducted to assess the effects of 2 dietary variables on efficacy of a bacterial 6-phytase from Citobacter braakii on nutrient and phytate P (PP) utilization. Diets were formulated with or without nutrient matrix values (matrix) for phytase as negative control (NC) or positive control (PC), respectively, and with 2 Ca:total P (tP) levels (2:1 or 2.5:1). The diets were supplemented with 0, 1,000, or 2,000 phytase units (FYT)/kg of diet, thus producing a 2 × 2 × 3 factorial arrangement. Excreta were collected on d 19 to 21 and ileal digesta on d 21. There was no 3-way interaction on digestibility of any nutrient. There was matrix × phytase (P < 0.01) interaction for Ca and DM digestibility and Ca:tP × phytase interaction (P < 0.05) for acid hydrolyzed fat and Ca and P digestibility. Prececal flow of Mn, Zn, and Na was greater (P < 0.05) in NC diets, whereas phytase increased (P < 0.05) prececal flow of Mg, Fe, Mn, and Zn but decreased (P < 0.05) prececal Na flow. Total tract PP disappearance and total tract Ca retention increased (P < 0.05) with phytase supplementation in diets with 2:1 Ca:tP, whereas there was no effect of phytase supplementation on PP disappearance or Ca retention in diets with 2.5:1 Ca:tP. Total P and Ca retention were reduced (P < 0.05) in PC and NC diets when Ca:tP increased to 2.5:1, but the depression was more pronounced in the NC diet. In addition, PP disappearance decreased (P < 0.05) with increasing Ca:tP in the PC diets, but there was no effect of widening Ca:tP on PP disappearance in NC diets. It was concluded from the current study that the effect of phytase supplementation on P utilization is reduced when diets contain adequate P as exemplified in the PC diets and that the negative impact of wide Ca:tP is more pronounced in diets with phytase matrix allowance as exemplified in the NC diets.
authors.affiliation: Avian Science Research Centre, Scotland's Rural College, Auchincruive, Ayr, KA6 5HW, United Kingdom oluyinka.olukosi@sruc.ac.uk.
authors.forename: O A
authors.initials: OA
authors.lastname: Olukosi
authors.affiliation: DSM Nutritional Products Ltd., CH-4002 Basel, Switzerland.
authors.forename: F
authors.initials: F
authors.lastname: Fru-Nji
mesh_terms: D010832:6-Phytase / Q000378:metabolism*; D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002113:Calcification, Physiologic / Q000187:drug effects*; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000494:pharmacology*; D002645:Chickens; D004032:Diet / Q000662:veterinary; D007082:Ileum / Q000378:metabolism*; D016226:Phosphorus, Dietary / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D002136:Calcium, Dietary; D016226:Phosphorus, Dietary; D010832:6-Phytase
keywords: broiler; calcium:phosphorus; nutrient utilization; phytase matrix