Abstract
Starch chemistry affects enzymatic digestion of starch and thereby starch availability for microbial fermentation. The effect of starch chemistry on post-ileal nutrient flow and microbial activity was studied in 8 ileal-cannulated pigs (29.4 kg BW) each fed 4 diets containing 70% purified starch (amylose content, < 5, 20, 28 and 63%; reflected by in vitro maximal digestion rate; 1.06, 0.73, 0.38, and 0.22%/min, respectively). Amylose content and in vitro digestion rate of starch quadratically affected (P < 0.001) post-ileal starch flow (4.1, 3.7, 4.1 and 405 mg/g starch fed; respectively, for low to high amylose and rapid to slow digestion rate), fecal total SCFA (10.5, 9.6, 16.2 and 28.7 μmol/g of DM fed) and butyrate concentration (1.1, 1.0, 2.5, and 2.9 μmol/g of DM fed), and fecal bifidobacteria (5.6, 5.2, 5.1, and 6.6 log rDNA gene copies/g). Gene copy numbers of the Lactobacillus group, Enterococcus, Streptpcoccus, Enterobacteriaceae, Bacteroides-Prevotella-Porphyrmona and Clostridial clusters I, IV and XIV in ileal digesta and feces did not differ (P < 0.05) among starches. In conclusion, starch with high amylose and low in vitro digestibility increased post-ileal nutrient flow and microbial fermentation, and selectively promoted growth of bifidobacteria in the distal gut. Substantial changes of starch chemistry (≥45% amylose and ≤0.34%/min in vitro digestion rate) were required to alter the post-ileal variables in pigs. Grant Funding Source: ALMA, Provimi, Alberta Pulse Growers
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