Effects of endoxylanase addition to wheat-based diets on physico-chemical chyme conditions and mineral absorption in broilers

Four wheat cultivars, differing in in vitro viscosity and water-soluble arabinoxylan content, were added to a basal diet on a 50:50 weight basis. These wheat-based diets were fed to male broilers from 3 weeks of age, with and without the addition of 75 mg endoxylanase (70 000 EXU g−1 enzyme) per kg feed. The broilers were killed at 4.5 weeks of age, and the jejunal and ileal contents were sampled. The absorption of sodium, potassium, calcium, phosphorus, and magnesium was calculated, based on the contents of the last 10 cm of these intestinal segments, using Cr2O3 as a reference substance. The pH, osmolality and viscosity were measured in the remaining jejunal and ileal contents. Dietary addition of high viscosity wheats (HVW) resulted in higher intraluminal viscosities than on the low viscosity wheat (LVW) diets. The osmolality of the chyme supernatant of the birds fed the HVW diets declined less as the chyme moved from the jejunum into the ileum, compared with the LVW diets. This indicates a less efficient absorption of osmo-active soluble chyme components at higher intraluminal viscosities, as complex formation in the intestinal lumen could not account for this effect. Linear regression analysis revealed a clear negative relationship between the viscosity of the chyme supernatant and the absorption of dry matter and minerals in either one or both of the intestinal segments. Addition of endoxylanase lowered the viscosity of the chyme supernatant to similar levels on all wheat-based diets. Furthermore, it enhanced the apparent absorption of calcium, magnesium, sodium and potassium from the jejunal lumen. However, at the lower ileal level only magnesium absorption was improved by dietary endoxylanase addition.