Increasing Dietary Amylose Reduces Rate of Starch Digestion and Stimulates Microbial Fermentation in Weaned Pigs

Abstract

Abstract Objectives Starch with increasing ratio of amylose to amylopectin decreases ileal starch digestibility in pigs. Microbes in the large intestine ferment undigested starch and produce short-chain fatty acids (SCFA). The benefits of SCFA in modulating gut health stimulated interest in dietary strategies to increase microbial carbohydrate fermentation and digesta SCFA in pigs and humans. We studied effects of increasing dietary amylose on SCFA and the expression of transporters of glucose (sodium-glucose cotransporter 1, SGLT1) and SCFA (monocarboxylic acid transporter 1, MCT1; sodium-coupled monocarboxylate transporter, SMCT), and sweet taste receptor type 1, member 3 (T1R3) along the intestine of weaned pigs. Methods Weaned pigs (n = 32; 8.4 kg) were allocated to 1 of 4 diets containing 67% purified starch with 0, 20, 35, or 70% amylose in randomized complete blocks. On day 21, 47-day-old pigs were euthanized to collect digesta for SCFA and intestinal tissue for molecular analyses. Results Ileal starch digestibility was 44% lower and hindgut starch fermentation was 14% greater in pigs fed 70% amylose (P < 0.05). Increasing dietary amylose increased (P < 0.05) acetate and total SCFA in the cecum, butyrate in proximal and mid colon, and propionate and valerate throughout the colon. Increasing dietary amylose downregulated (P < 0.001) SGLT1 and T1R3 in the jejunum and upregulated (P < 0.001) MCT1 in the ileum. Ileal starch digestibility was inversely associated with MCT1 expression in the ileum (R2 = 0.41, P < 0.05). In the cecum, 35% amylose downregulated expressions of MCT1 and SMCT (R2 = 0.64, P < 0.001). Both 35 and 70% amylose regulated SMCT expression down in proximal colon (P < 0.001) but up in mid colon (P < 0.001). Weak associations (R2 = 0.20, P < 0.05) existed between SMCT and butyrate and valerate in mid colon. Conclusions Increasing dietary amylose in weaned pigs decreased ileal starch digestion and stimulated hindgut starch fermentation thereby increasing digesta total SCFA in cecum and colon. Consequently, expression of SCFA transporters was increased in the ileum supporting the conversion by dietary amylose of the pig from starch digester into starch fermenter. Funding Sources Swine Innovation Porc, Alberta Pork, and Discovery Grant of Natural Sciences and Engineering Research Council of Canada.