Effect of diets containing enzyme supplements and microwave-treated or untreated wheat on inositol phosphates in the small intestine of broilers

Abstract

The objective was to study the effect of diets containing microwave-treated wheat and supplemental enzymes on myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP6) hydrolysis and the presence of inositol phosphate isomers (InsPs) in the small intestine of broilers. We assigned 16-day-old broilers to 48 pens of 15 broilers each (n=8 pens per treatment) in a 2×3 factorial arrangement of treatments. Birds were fed a wheat-soybean meal diet that was low in phosphorus (4.8g/kg dry matter) and that contained either microwave-treated (BDTW) or untreated (BDUTW) ground wheat. Diets were used without an enzyme supplement or after supplementation with an E. coli-derived phytase, alone or in combination with a xylanase. On d 23, samples of digesta from the duodenum/jejunum and lower ileum were pooled per segment on a pen basis, freeze-dried, and analyzed for P, InsPs, and the marker TiO2. Statistical significance was evaluated by a two-way analysis of variance. Microwaving affected dietary intrinsic phytase activity (BDUTW: 623U/kg; BDTW: 121U/kg). Interactions between microwave treatment and enzyme supplementation were found for InsP6 hydrolysis (P=0.048) and P net absorption (P=0.004) in the ileum. In both segments, InsP6 hydrolysis (duodenum/jejunum: P=0.004, ileum: P=0.002) and P net absorption (P≤0.001) were significantly increased by supplementation of phytase, but no further increments were caused by supplemental xylanase. The significant interaction on InsP6 hydrolysis in the ileum was due to a higher InsP6 hydrolysis for BDTW (78%) than for BDUTW (69%) in the absence of supplemental phytase. In birds that were fed the phytase-supplemented diets, microwave treatment of wheat had no effect on InsP6 hydrolysis. The significant interaction on P net absorption in the ileum was due to reduced P net absorption by microwave treatment in the presence but not absence of supplemental phytase. Broilers and their gut microbiota have a high potential to hydrolyze InsP6 in the intestine. Microwaving may have disrupted wheat aleurone structures in ways that increased accessibility of InsP6 and may have encouraged higher levels of activity among specific phytases of microbial or endogenous mucosal origin in the lower small intestine. Accumulation of InsP3 in the duodenum/jejunum for microwave-treated diets suggested that such treatment reduces the effectiveness of the phosphatases that further degrade InsP3 (P=0.004).