Xylanase solubilization of corn and wheat arabinoxylans in mixed growing pig diets subjected to upper gut in-vitro digestion and in ileal digesta

Abstract Text: The objective of the present studies was to evaluate the efficacy of xylanase on solubilizing arabinoxylans (AX) in corn and wheat. In study 1, a corn (40% corn distillers dried grains with solubles–DDGs) and wheat based (5% wheat bran and 18% wheat midds) diet were formulated for growing pigs supplemented with or without 8,000XU/kg xylanase. Triplicate samples of the diets were subjected to a two stage sequential in-vitro digestion simulating porcine gastric and small intestine conditions. A sample (10mL) of small intestine effluents was freeze dried and subjected to analysis of non-starch polysaccharides (NSP). There was no interaction (P>0.05) between xylanase and diet type on the ratio of soluble to insoluble AX (RAX) and soluble to insoluble NSP (RNSP). The main effects were such that wheat diets had a higher ratio of RAX than corn diets (36.8 vs. 18.9%; P=0.001). Xylanase increased RAX (32.4 vs. 22.4%; P=0.03) and RNSP (75.1 vs. 52.6%; P=0.03). In study 2, ileal digesta samples obtained from growing pigs (32.4kg BW) fed 96% corn (n=5) or wheat (n=5) DDGS based diets (with 1.5% glycerol and 1% calcium carbonate) for 7 days were used to test dose response of xylanase on the release of soluble AX. Statistical analysis for both studies was conducted using the GLM procedure of SAS. The total NSP and AX concentrations in corn DDGs ileal samples were 378 and 174g/kg, respectively and the corresponding values in wheat DDGS ileal digesta were 291 and 117g/kg. The samples were subjected to a 2 (corn or wheat DDGS) x 3 (0, 2,000 or 20,000XU/kg) factorial design in-vitro incubation experiment. Briefly, 100mg of sample was mixed with buffer (pH=6) with or without xylanase and incubated for 2 h in a microplate shaker (1140rpm) at 40°C. The solution was then centrifuged at 3,000 rpm, 20°C for 10 min and the supernatant submitted for soluble AX analysis. There was no interaction (P=0.357) between DDGS type and xylanase on the concentration of soluble AX. The main effects of the diet (P<0.01) were such that wheat DDGS samples had twice the concentration of soluble AX relative to corn DDGS. Xylanase (P<0.01) increased the release of soluble AX in a linear manner. Specifically, the concentration of soluble AX was 5,027, 5,919 and 6,968µg/mL in the control, 2,000 and 20,000XU, respectively. Our results illustrate clearly that supplemental xylanase solubilized AX independent of cereal source in the diet and in the digesta matrices.

Keywords: xylanase, cereal arabinoxylans, solubilization