title: The presence of inositol phosphates in gastric pig digesta is affected by time after feeding a nonfermented or fermented liquid wheat- and barley-based diet.
abstract: The objective was to quantify the retention of digesta and evaluate the degradation of phytate or inositol hexakisphosphate (InsP(6)) and lower inositol phosphates (InsP₅, InsP₄, InsP₃, and InsP₂) in the stomach at different times after feeding pigs a fermented liquid diet with microbial phytase or a nonfermented diet with or without microbial phytase. Six barrows fitted with gastric cannulas were used. The experiment was a 3 × 3 Latin square with 3 pigs fed 3 diets during 3 wk in 2 replicates. Each experimental period lasted for 7 d, comprising 3 d of adaptation and 4 d of total collection of gastric digesta. For each pig, the digesta was collected once daily at 1, 2, 3, or 5 h after feeding the morning meal. A basal wheat- and barley-based diet was steam-pelleted at 90°C. The dietary treatments were a nonfermented basal diet (NF-BD), the NF-BD with microbial phytase (750 phytase units of phytase/kg, as-fed basis; NF-BD + phytase), and the NF-BD + phytase fermented for 17.5 h (F-BD + phytase). Gastric InsP₆-P was not detected at all in pigs fed F-BD + phytase because of complete InsP₆ degradation during fermentation of the feed before feeding. Gastric InsP₆-P decreased over time (P < 0.05) in pigs fed NF-BD and NF-BD + phytase. The decreases were 45, 54, 56, and 61 percentage points greater at 1, 2, 3, and 5 h, respectively, in pigs fed NF-BD + phytase compared with NF-BD. However, substantial amounts of InsP₆ still passed into the small intestine in pigs fed NF-BD + phytase, especially within the first hour (estimated to 17% of InsP₆-P intake). The accumulation of lower inositol phosphates in gastric digesta was very small for all treatments and at all times because of a rapid and almost complete degradation. In conclusion, phytase addition to the nonfermented diet increased the degradation of gastric InsP₆. However, considerable amounts of intact InsP₆ still passed into the small intestine because of a shortage of time for InsP₆ degradation in the stomach. Therefore, to increase the apparent digestibility of plant P in dry wheat- and barley-based diets, the development of phytases that can degrade InsP₆ effectively immediately after ingestion of the feed at an initial gastric pH from 6.5 to 5.0 is needed. Feeding F-BD + phytase compensated for the shortage of time because the InsP₆ degradation was completed during fermentation before feeding. The degradation of InsP₆ to InsP₅ is the bottleneck for plant P utilization in pigs because the degradation of the lower inositol phosphates is rapid and almost complete.
authors.affiliation: Aarhus University, Department of Animal Science, Research Centre Foulum, DK-8830 Tjele, Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Blaabjerg
authors.forename: H
authors.initials: H
authors.lastname: Jørgensen
authors.forename: A-H
authors.initials: AH
authors.lastname: Tauson
authors.forename: H D
authors.initials: HD
authors.lastname: Poulsen
mesh_terms: D010832:6-Phytase / Q000378:metabolism; D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004032:Diet / Q000662:veterinary; D004063:Digestion; D005285:Fermentation; D005766:Gastrointestinal Contents / Q000737:chemistry*; D001467:Hordeum / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007295:Inositol Phosphates / Q000737:chemistry*; D008297:Male; D013552:Swine / Q000502:physiology*; D013997:Time Factors; D014908:Triticum / Q000737:chemistry*
chemical_list: D007295:Inositol Phosphates; D010832:6-Phytase