Effect of xylanases on ileal viscosity, intestinal fiber modification, and apparent ileal fiber and nutrient digestibility of rye and wheat in growing pigs
H. N. Lærke, S. Arent, S. Dalsgaard and K. E. Bach Knudsen
Two experiments were performed to study the effect of xylanase on ileal extract viscosity, in vivo fiber solubilization and degradation, and apparent ileal digestibility (AID) of fiber constituents, OM, CP, starch, and crude fat in rye and wheat in ileal-cannulated pigs. In Exp. 1, coarse rye without (NX) or with addition of xylanase from Aspergillus niger (AN), Bacillus subtilis (BS), or Trichoderma reesei (TR) was fed to 8 ileal-cannulated barrows (initial BW 30.9 ± 0.3 kg) for 1 wk each according to a double 4 × 4 Latin square design. In Exp. 2, fine rye, fine wheat, and coarse wheat with or without a combination of xylanase from Bacillus subtilis and Trichoderma reesei were fed to 6 ileal-cannulated barrows (initial BW 33.6 ± 0.5 kg) for 1 wk according to a 6 × 6 Latin square design with a 2 × 3 factorial arrangement of enzyme and cereal matrix. Chromic oxide (0.2%) was used as an inert marker. Ileal effluent was collected for 8 h on d 5 and 7 and pooled for analysis. In Exp. 1, TR reduced intestinal viscosity of pigs fed rye from 9.3 mPa•s in the control diet (NX) to 6.0 mPa•s (P < 0.001), whereas AN and BS had no effect. None of the enzymes changed the concentration of total arabinoxylan, high-molecular-weight arabinoxylan (HMW-AX), or arabinoxylan oligosaccharides (AXOS) in the liquid phase of digesta. In Exp. 2, the enzyme combination reduced intestinal viscosity for all 3 cereal matrices (P < 0.05), but the viscosity was much higher with fine rye (7.6 mPa•s) than with fine and coarse wheat (<1.7 mPa•s). Simultaneously, the total concentration of arabinoxylan in the liquid phase of digesta increased by 82.4% in fine wheat (P < 0.002) and by 45.9% in coarse wheat (P < 0.006), and AXOS increased 16-fold with enzyme addition. Similar effects of enzyme were not seen with rye. The concentration of xylooligosaccharides in the liquid phase of digesta increased with enzyme addition, but for xylose, it was only significant for wheat, for which it increased 3.9-fold (P < 0.001). None of the xylanases affected AID of arabinoxylan of rye in Exp. 1. In Exp. 2, the enzyme combination increased AID of arabinoxylan by 91% to 107% (P < 0.001) across cereal matrices. Enzyme addition did not affect AID of nutrients in any of the experiments except for a higher starch and crude fat digestibility of fine wheat with enzyme addition (P < 0.012) in Exp. 2. Collectively, the results suggest that xylanase is more efficient in degrading arabinoxylan from wheat than from rye.
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