title: Hydrolysis of phytate and formation of inositol phosphate isomers without or with supplemented phytases in different segments of the digestive tract of broilers.
abstract: The objective was to characterise degradation of myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP6) and formation of inositol phosphate (InsP) isomers in different segments of the broiler digestive tract. Influence of an Aspergillus niger (PhyA) and two Escherichia coli-derived (PhyE1 and PhyE2) phytases was also investigated. A total of 600 16-d-old broilers were allocated to forty floor pens (ten pens per treatment). Low-P (5·2 g/kg DM) maize-soyabean meal-based diets were fed without (basal diet; BD) or with a phytase added. On day 25, digesta from different digestive tract segments were pooled per segment on a pen-basis, freeze-dried and analysed for P, InsP isomers and the marker TiO2. InsP6 degradation until the lower ileum (74 %) in BD-fed birds showed a high potential of broilers and their gut microbiota to hydrolyse InsP6 in low-P diets. Different InsP patterns in different gut segments suggested the involvement of phosphatases of different origin. Supplemented phytases increased InsP6 hydrolysis in the crop (P < 0·01) but not in the lower ileum. Measurements in the crop and proventriculus/gizzard confirmed published in vitro degradation pathways of 3- and 6-phytases for the first time. In the intestinal segments, specifically formed InsP4-5 isomers of supplemented phytases were still present, indicating further activity of these enzymes. Myo-inositol tetrakisphosphate (InsP4) accumulation differed between PhyE1 and PhyE2 compared with PhyA in the anterior segments of the gut (P < 0·01). Thus, the hydrolytic cleavage of the first phosphate group is not the only limiting step in phytate degradation in broilers.
authors.affiliation: Institut für Tierernährung, Universität Hohenheim , 70599 Stuttgart , Germany.
authors.forename: Ellen
authors.initials: E
authors.lastname: Zeller
authors.affiliation: Institut für Tierernährung, Universität Hohenheim , 70599 Stuttgart , Germany.
authors.forename: Margit
authors.initials: M
authors.lastname: Schollenberger
authors.affiliation: AB Vista Feed Ingredients , 64293 Darmstadt , Germany.
authors.forename: Imke
authors.initials: I
authors.lastname: Kühn
authors.affiliation: Institut für Tierernährung, Universität Hohenheim , 70599 Stuttgart , Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Rodehutscord
keywords: BD, basal diet; Broilers; Inositol phosphate isomers; InsP, inositol phosphate; InsP3, myo-inositol trisphosphate; InsP4, myo-inositol tetrakisphosphate; InsP5, myo-inositol pentakisphosphate; InsP6, myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate); PhyA, Aspergillus-derived phytase Finase® P; PhyE1, Escherichia coli-derived phytase Quantum®; PhyE2, E. coli-derived phytase Quantum® Blue; Phytases; Phytate hydrolysis; tP, total P