Diets containing different
starch types can affect enzymatic digestion of
starch and thereby
starch availability for microbial fermentation in the gut. However, the role of
starch chemistry in nutrient digestion and flow and microbial profile has been poorly explained. Eight ileal-cannulated pigs (29.4 ± 0.9 kg
body weight) were 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) in a replicated 4 × 4 Latin square. Ileal and fecal
starch output, postileal crude
protein yield, fecal total SCFA and total
butyrate content, and gene copies of Bifidobacterium spp. in feces were higher (P < 0.05) when pigs consumed the slowly digestible
starch diet than the remaining 3
starch diets. The in vitro
starch digestion rate had a negative, nonlinear relationship with ileal
starch flow (R(2) = 0.98; P < 0.001). Ileal
starch flow was positively related to Bifidobacterium spp. (R(2) = 0.27; P < 0.01), Lactobacillus group (R(2) = 0.22; P < 0.01), and total
butyrate content (R(2) = 0.46; P < 0.01) but was not related to Enterobacteriaceae (R(2) < 0.00; P = 0.92). In conclusion,
starch with high
amylose content and low in vitro digestibility increased postileal nutrient flow and microbial fermentation and selectively promoted Bifidobacterium spp. in the distal gut.